# OpenGL Surface plot for any data

This topic is 3098 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

## Recommended Posts

Hi all, I need to draw surface plot using OpenGL for the following data. X-Axis | Y-Axis | Z-Axis ========================= Jan-08 | 120.0 | 25.5 Feb-08 | 125.7 | 24.15 Mar-08 | 100.0 | 42.11 Apr-08 | 190.0 | 15.62 May-08 | 109.0 | 21.88 Jun-08 | 150.5 | 56.55 Jul-08 | 191.8 | 89.93 Aug-08 | 177.7 | 15.65 I searched in the web and found some samples all of which draw a sin function or exp functional data. But I need the surface plot for the above data. So, I am not able to figure out. Can anybody tell me an idea to do this. Thanks in advance, Regards, Srinu

##### Share on other sites
I don't have any experience with surface plots but AFAIK you need a function that takes two arguments to plot it as a 3D surface (with the arguments generally representing the X- and Z-Axis).

Your data just resembles a bunch of points, so the most natural way would be to connect them to a line (converting the months to numbers, like Jan = 1). If you need a surface you might draw a quad/two triangles between two adjacent datasets (where each dataset has 2 points - one specified by X,Y,Z and one with one coordinate set to 0), e.g. for Jan and Feb you could use the points:

X/Y/Z
1/120.0/0
1/120.0/25.5
2/125.7/0
2/125.7/24.15

Hope that helps.

##### Share on other sites
Hi Lord,
Thanks for the response. Your idea sounds like a good one. I am going to implement it to see whether it works. But, I am stuck at converting these coordinates to OpenGL coordinates. Could you please tell me how to do this?

Thanks,
Srinu

##### Share on other sites
I'm not sure where you're stuck, but you could just convert the months to January = 0.0, February = 1.0, March = 2.0 and so on (or use another scale, if you like). Then you alreay have the needed coordinates and just need to call glVertex3f(x,y,z) or - which would be better - put the coordinates into a VBO and render that.

##### Share on other sites
Thats ok. But OpenGL coords should be between -1 to 1, right? So, these coords must be converted to their equivalent opengl coords.
For example Take a 3d point - 1.0, 120.0, 25.5. We can not render this point in OpenGL window. It must be converted to OpenGL window coords. I am asking how to do this convertion?

Thanks,
Srinu

##### Share on other sites
For a 2 dimensional plot, you could make the vertical axis the Y & Z variables and the horizontal the X (time), then plot the data as vectors instead of points. Or you could do something more interesting, like use the Z data to be the diameter of a circle with the X variables on the horizontal and y be the vertical. Then if you scale the axes properly, you'd have circles of diameter Z centered at height Y and the proper time X which should be spaced not to overlap. Or you could represent one of the fields as color (X makes the most sense, having exact and regular values to easily correspond to a given color). I would look at some differential equation or vector field graphs to see techniques people use for graphic 3 dimensional data in 2 dimensional graphs if thats what you want, or you could make the graph 3D if you really want.

##### Share on other sites
Quote:
 Original post by srinivaz111Thats ok. But OpenGL coords should be between -1 to 1, right? So, these coords must be converted to their equivalent opengl coords. For example Take a 3d point - 1.0, 120.0, 25.5. We can not render this point in OpenGL window. It must be converted to OpenGL window coords. I am asking how to do this convertion?Thanks,Srinu

No, you use whatever coordinates you want and OpenGL will internally scale it.

##### Share on other sites
You can use any (reasonable) number for a OpenGL coordinate. However, to get it drawn to screen you have to setup your modelview and projection matrices properly.

If you don't want to do that you'd have to convert the coordinates to range [-1,1] for x and y and to [0,1] for z. This shouldn't be too hard (e.g. if months go from 0 to 11 you can set x to month * (2.0f/11.0f) - 1.0f).

However, I'd recommend using the matrices as they would allow you to use different viewing angles.

##### Share on other sites
not able to draw the plot using the method where I took 2 points for every coordinate. I got a weird graph. I am following the Contour plot method which involves defining a texture and drawing triangles and setting the texture to those triangles. Can anybody who knows the contour plot method please help me?
I am sending the code also. Please look into it.

This is the actual data for which I have to plot the graph

X-Axis | Y-Axis | Z-Axis
=========================
Jan-08 | 120.0 | 25.5
Feb-08 | 125.7 | 24.15
Mar-08 | 100.0 | 42.11
Apr-08 | 190.0 | 15.62
May-08 | 109.0 | 21.88
Jun-08 | 150.5 | 56.55
Jul-08 | 191.8 | 89.93
Aug-08 | 177.7 | 15.65

So, I have taken the following points table

float data[24][3] =
{
{1.0,120.0,0},
{1.0,120.0,0.5},
{1.0,120.0,25.5},
{2.0,125.7,0},
{2.0,125.7,0.5},
{2.0,125.7,24.15},
{3.0,100.0,0},
{3.0,100.0,0.5},
{3.0,100.0,42.11},
{4.0,190.0,0},
{4.0,190.0,0.5},
{4.0,190.0,15.62},
{5.0,109.0,0},
{5.0,109.0,0.5},
{5.0,109.0,21.88},
{6.0,150.5,0},
{6.0,150.5,0.5},
{6.0,150.5,56.55},
{7.0,191.8,0},
{7.0,191.8,0.5},
{7.0,191.8,89.93},
{8.0,177.7,0},
{8.0,177.7,0.5},
{8.0,177.7,15.65}

};

Here is the code:

void MyGraph::Generate3DData()
{
m_fWidth = 1.0f;
m_fStep = 0.05f;
int nSurface = 1;
int nVertex = nSurface + 1;

v3DVector tempVector;

for (int x=0; x<24; x+=3)
{
double ogl_x, ogl_y, ogl_z;
GetOpenGLCoords(data[x][0], data[x][1], data[x][2], &ogl_x, &ogl_y, &ogl_z);
tempVector.push_back(C3DVector(ogl_x, ogl_y, ogl_z));

GetOpenGLCoords(data[x+1][0], data[x+1][1], data[x+1][2], &ogl_x, &ogl_y, &ogl_z);
tempVector.push_back(C3DVector(ogl_x, ogl_y, ogl_z));

GetOpenGLCoords(data[x+2][0], data[x+2][1], data[x+2][2], &ogl_x, &ogl_y, &ogl_z);
tempVector.push_back(C3DVector(ogl_x, ogl_y, ogl_z));

m_vVertexNormal.push_back(tempVector);

tempVector.clear();
}

tempVector.clear();

/* int size = m_vVertexNormal.size();
std::vector<v3DVector>::iterator it;
for (it=m_vVertexNormal.begin(); it!=m_vVertexNormal.end(); it++)
{
v3DVector tVector = *it;
int vsize = tVector.size();
}
*/

// Surface Normal
for(int nX = 0; nX < 7; nX ++)
{
for(int nY(0); nY < 2; nY ++)
{
C3DVector temp3DVector(0, 0,0);
C3DVector point1 = m_vVertexNormal.at(nX).at(nY);
C3DVector point2 = m_vVertexNormal.at(nX+1).at(nY);
C3DVector point3 = m_vVertexNormal.at(nX+1).at(nY+1);

CalculateNormal(point1, point2, point3, temp3DVector);

tempVector.push_back( temp3DVector );
}
m_vSurfaceNormal.push_back(tempVector);
tempVector.clear();
}

// Vertex Normal
for(nX = 0; nX < 7; nX ++)
for(int nY(0); nY < 2; nY ++)
{
m_vVertexNormal.at(nX).at(nY) += m_vSurfaceNormal.at(nX).at(nY);
m_vVertexNormal.at(nX+1).at(nY) += m_vSurfaceNormal.at(nX).at(nY);
m_vVertexNormal.at(nX).at(nY+1) += m_vSurfaceNormal.at(nX).at(nY);
m_vVertexNormal.at(nX+1).at(nY+1) += m_vSurfaceNormal.at(nX).at(nY);
}
for(nX = 0; nX < 8; nX ++)
for(int nY(0); nY < 3; nY ++)
m_vVertexNormal.at(nX).at(nY).Average();
}

BOOL MyGraph::CalculateNormal(C3DVector& fPoint1, C3DVector& fPoint2, C3DVector& fPoint3, C3DVector& fNormal)
{
float fx = (fPoint2.GetY()-fPoint1.GetY())*(fPoint3.GetZ()-fPoint2.GetZ())-
(fPoint3.GetY()-fPoint2.GetY())*(fPoint2.GetZ()-fPoint1.GetZ());

// (y2-y1)(z3-z2)-(y3-y2)(z2-z1)

float fy = (fPoint3.GetX()-fPoint2.GetX())*(fPoint2.GetZ()-fPoint1.GetZ())-
(fPoint2.GetX()-fPoint1.GetX())*(fPoint3.GetZ()-fPoint2.GetZ());

float fz = (fPoint2.GetX()-fPoint1.GetX())*(fPoint3.GetY()-fPoint2.GetY())-
(fPoint3.GetX()-fPoint2.GetX())*(fPoint2.GetY()-fPoint1.GetY());

float fd = (float) sqrt(fx*fx + fy*fy + fz*fz);

fNormal.SetVector(fx/fd, fy/fd, fz/fd);

return TRUE;
}

void MyGraph::GetOpenGLCoords(float x, float y, float z, double *ogl_x, double *ogl_y, double *ogl_z)
{

*ogl_x = x * (2.0/11.0) - 1.0;
*ogl_y = y * (2.0/191.8) - 1.0;
*ogl_z = z/89.93;
}

void MyGraph::CreateGraph3DList(UINT nList)
{
::glNewList(nList , GL_COMPILE);
for(int x=0, int nX(0); nX < m_vSurfaceNormal.size(); nX++, x+=2)
{
double ogl_x, ogl_y, ogl_z;
GetOpenGLCoords(data[x][0], data[x][1], data[x][2], &ogl_x, &ogl_y, &ogl_z);

float fx = ogl_x; //(nX*m_fStep - 1)*m_fWidth;

::glBegin(GL_TRIANGLE_STRIP);
for(int nY(0); nY < 3/*m_vSurfaceNormal.size()*/; nY++)
{
float fNormal[3];
m_vVertexNormal.at(nX).at(nY).GetVector(fNormal);
::glNormal3fv(fNormal);
float fy = ogl_y;//(nY*m_fStep - 1)*m_fWidth;
float fz = ogl_z;//GetZ(fx, fy);
::glTexCoord1f((fz+1)/2);
::glVertex3d(fx, fy, fz/2);

m_vVertexNormal.at(nX+1).at(nY).GetVector(fNormal);
::glNormal3fv(fNormal);

GetOpenGLCoords(data[x+1][0], data[x+1][1], data[x+1][2], &ogl_x, &ogl_y, &ogl_z);

float fx2 = ogl_x;//fx+m_fStep;
fz = ogl_z;//GetZ(fx2, fy);
::glTexCoord1f((fz+1)/2);
::glVertex3d(fx2, fy, fz/2);
}
::glEnd();
}
::glEndList();
}

Please look into it and show me a way to achieve it.

~Srinu

##### Share on other sites
First, please use the source tags

Quote:
 Original post by srinivaz111So, I have taken the following points tablefloat data[24][3] = { {1.0,120.0,0}, {1.0,120.0,0.5}, {1.0,120.0,25.5}, {2.0,125.7,0}, {2.0,125.7,0.5}, {2.0,125.7,24.15}, {3.0,100.0,0}, {3.0,100.0,0.5}, {3.0,100.0,42.11}, {4.0,190.0,0}, {4.0,190.0,0.5}, {4.0,190.0,15.62}, {5.0,109.0,0}, {5.0,109.0,0.5}, {5.0,109.0,21.88}, {6.0,150.5,0}, {6.0,150.5,0.5}, {6.0,150.5,56.55}, {7.0,191.8,0}, {7.0,191.8,0.5}, {7.0,191.8,89.93}, {8.0,177.7,0}, {8.0,177.7,0.5}, {8.0,177.7,15.65}};

I just skimmed over your code but looking at your data I can make a guess:

You draw the data as a triangle strip, so you get triangles like (in your coords):

{1.0,120.0,0}/{1.0,120.0,0.5}/{1.0,120.0,25.5} -- this basically is a line and wouldn't be rendered (degenerate triangle)
{1.0,120.0,0.5}/{1.0,120.0,25.5}/{2.0,125.7,0}
{1.0,120.0,25.5}/{2.0,125.7,0}/{2.0,125.7,0.5}
{2.0,125.7,0}/{2.0,125.7,0.5}/{2.0,125.7,24.15} -- this is a line, too
...

Why are those {..,..,0.5} point in there? If you remove them, the graph should look better.
If not, I maybe misunderstood you and a screenshot would help me to get a better impression on what your graph looks like.

##### Share on other sites
I have taken 3 points for each coordinate to draw a triangle. (As actually Contour plot drawing involves triangles). But I am really confused whether the 3 points are taken correctly or not?
And I think you understood the code. Please suggest if any changes can be done to the code. And can you please tell me how to attach files to posts (I am trying to send the scrrenshot of the plot I got, But not able to find the way to do that).

Thanks,
Srinu

##### Share on other sites
Well, take out the coords with z=0.5 and it should work with GL_TRIANGLE_STRIP.
If not, there might be another error in the code.

##### Share on other sites
Please look into the following code which draws the surface plot using contour method. Actually this code was written to take data in a random manner. I modified it to take the data from an array. I am not able to find the places where the required changes have to done for my data. Please help me.

//Data:float data[16][3] ={	{1.0,120.0,0},	{1.0,120.0,25.5},	{2.0,125.7,0},	{2.0,125.7,24.15},	{3.0,100.0,0},	{3.0,100.0,42.11},	{4.0,190.0,0},	{4.0,190.0,15.62},	{5.0,109.0,0},	{5.0,109.0,21.88},	{6.0,150.5,0},	{6.0,150.5,56.55},	{7.0,191.8,0},	{7.0,191.8,89.93},	{8.0,177.7,0},	{8.0,177.7,15.65}};void Generate3DData(){  int nSurface = 3;  int nVertex = nSurface + 1;	    v3DVector tempVector;  int i = 0;	    // Vertex coordinates  for(int nX(0); nX < nVertex; nX ++)  {     for(int nY(0); nY < nVertex; nY ++)      {        float fx, fy, fz;        GetOpenGLCoords(data[0], data[1], data[2], &fx, &fy, &fz);        i++;	          tempVector.push_back( C3DVector(fx, fy, fz) );     }	       m_vVertexNormal.push_back(tempVector);     tempVector.clear();	    }	  tempVector.clear();	  	  // Surface Normal  for(nX = 0; nX < nSurface; nX ++)  {    for(int nY(0); nY < nSurface; nY ++)     {      C3DVector temp3DVector(0, 0,0);      CalculateNormal(m_vVertexNormal.at(nX).at(nY),  m_vVertexNormal.at(nX+1).at(nY),  m_vVertexNormal.at(nX+1).at(nY+1), temp3DVector);			        tempVector.push_back( temp3DVector );    }    m_vSurfaceNormal.push_back(tempVector);    tempVector.clear();  }	  // Vertex Normal  for(nX = 0; nX < nSurface; nX ++)    for(int nY(0); nY < nSurface; nY ++)     {			  m_vVertexNormal.at(nX).at(nY) +=  m_vSurfaceNormal.at(nX).at(nY);			  m_vVertexNormal.at(nX+1).at(nY) += m_vSurfaceNormal.at(nX).at(nY);			  m_vVertexNormal.at(nX).at(nY+1) += m_vSurfaceNormal.at(nX).at(nY);			  m_vVertexNormal.at(nX+1).at(nY+1) +=   m_vSurfaceNormal.at(nX).at(nY);    }  for(nX = 0; nX < nVertex; nX ++)    for(int nY(0); nY < nVertex; nY ++)       m_vVertexNormal.at(nX).at(nY).Average();}void CreateGraph3dList(){  int i = 0;  ::glNewList(nList , GL_COMPILE);  for(int nX(0); nX < m_vSurfaceNormal.size(); nX++)  {    ::glBegin(GL_TRIANGLE_STRIP);     for(int nY(0); nY < m_vSurfaceNormal.size(); nY++)     {        float fNormal[3];        m_vVertexNormal.at(nX).at(nY).GetVector(fNormal);        ::glNormal3fv(fNormal);        float fx, fy, fz;        GetOpenGLCoords(data[0], data[1], data[2], &fx, &fy, &fz);	::glTexCoord1f((fz+1)/2);	::glVertex3d(fx, fy, fz/2);				m_vVertexNormal.at(nX).at(nY+2).GetVector(fNormal);	::glNormal3fv(fNormal);	GetOpenGLCoords(data[i+2][0], data[i+2][1], data[i+2][2], &fx, &fy, &fz);	::glTexCoord1f((fz+1)/2);	::glVertex3d(fx, fy, fz/2);	i++;    }    ::glEnd();  }  ::glEndList();}void GetOpenGLCoords(float x, float y, float z, float *ogl_x, float *ogl_y, float *ogl_z){  *ogl_x = x * (2.0/8.0) - 1.0;  *ogl_y = y * (2.0/191.8) - 1.0;  *ogl_z = z/89.93;}

##### Share on other sites
The code seems to operate on a quadratic grid, i.e. you have the same number of vertices in x and y.

It then loops over the grid vertices column by column and sets the position according to the converted data. After that it iterates over the grid cells (called surfaces in the code) and calculates the normals per surface and per vertex.

The problem seems to be that your data does not form a quadratic grid, but rather a 8x2 grid.

You need to change the loops to accommodate for that, i.e. in the loops that iterate over the vertices set maxX=8 and maxY=2. For the loops iterating over the surfaces you have to use the same values decremented, i.e. 7/1.

That said, I'd recommend you carefully read the code and try to figure out what it does (especially which data it reads). It would certainly help you if you had some basic knowledge of 3D rendering concepts, but I guess it's more a matter of what data is to be read in your case.

Basically, you have to geometrically layout your data like this (using vertex indices):
1--3--5--7--9--..|\ |\ |\ |\ |\ || \| \| \| \| \|0--2--4--6--8--..

I assume you're not that fit in OpenGL, so I'll help you with the display list function. The data part will be your excercise [smile].

void CreateGraph3dList(){  int i = 0;  //create a new display list and store its id in nList  glNewList(nList , GL_COMPILE);  //begin drawing triangles - I don't use triangle strip because I think it's easier for you to understand   glBegin(GL_TRIANGLES);   //loop through the columns, maxCols would be 8 in your case  for(int col(0); col < maxCols; col++)   {    //assuming your data is laid out as described above you can now read the relevant data        //we'll use 2 triangles for each cell    glNormal3f(/*normal for index col * 2*/);    glVertex3f(/*position for index col * 2*/);    glNormal3f(/*normal for index col * 2 + 1*/);    glVertex3f(/*position for index col * 2 + 1*/);    glNormal3f(/*normal for index (col + 1) * 2*/);    glVertex3f(/*position for index (col + 1) * 2*/);    glNormal3f(/*normal for index col * 2 + 1*/);    glVertex3f(/*position for index col * 2 + 1*/);    glNormal3f(/*normal for index (col + 1) * 2*/);    glVertex3f(/*position for index (col + 1) * 2*/);        glNormal3f(/*normal for index (col + 1) * 2 + 1*/);    glVertex3f(/*position for index (col + 1) * 2 + 1*/);      }  //end triangle drawing  glEnd();  //end display list definition  glEndList();}

Another side note: reading the code I'm not sure whether the normal data is correctly set. I didn't check the normal calculation and thus assume it to be correct, but the normal is then added to the position, which doesn't seem correct (but I'm no expert in plots, so I'm not sure what exactly you want - maybe an image of what you'd expect would be helpful).

##### Share on other sites
Hi Lord,
Thank you for the explanation and the code.
I am trying to integrate this code in my application. But I think there has to be still more to do with this code. Actually I am trying to plot a surface from the X, Y and Z values which looks like the plot http://www.scribd.com/doc/17716693/Surface-Plot .
This plot is drawn for the values z = sin(3*x)*cos(3*y). So, Could you please tell me how to use this code to modify so that it draws a surface plot for my data.

Thanks,
Srinu

##### Share on other sites
Well, the plot in the link represents the value of z for x/y-pairs. Since z is a function of x and y you can calculate z at any point you want and thus get a value for every point on the grid.

The problem with your data is that it just represents some specific points in 3D, like so:
     y   o o| o     o   o|         o |  |  |  -----------------------x

Thus the first thing is to decide how to map all the other x/y pairs.

One solution (that we talked about above) would be to map the exact x values (1.0, 2.0, ...) and y-values from 0 to the value you provided to the z-value in your table. This would result in something like this:
     _y   / \__|  /| | |\ /|| | | | | | || | | | | | || | | | | | || | | | | | |-----------------------x

when seen from above (the z-value would represent different depths and would be interpolated between two months).

We already discussed most of the code you need to get this done. Take your data array and the draw method I posted above.

Keep in mind that in OpenGL y is up, so you might want to swap y and z (if z should represent the height).

Since lighting seems to be beyond your skill for now, you should stick to something easier, e.g. simple colors. Replace the glNormal3f(...) calls with glColor3f(...) and pass in a color that you calculate somehow (I guess you want to use z and/or y). Keep in mind that every channel has to be in range [0,1] so you might for example use shades of red and set r = z-value at the specified index / 100.0 . Or use something more complex (e.g. to use other colors, too). That's something I leave you to play with.

##### Share on other sites
Thanks Lord,
I implemented the procedure you explained. Its working fine. The plot is drawn correctly. But it has very sharp curves. Can it be made smoother like the one which I sent to you (Sinusoidal graph).

##### Share on other sites
Well, to smooth it you'd need more data or some algorithm to fit a curve onto your data.
Finding an algorithm is not that trivial and depends on what that data really means. One approach could be a moving average of the z values.

Then you'd need to subdivide the mesh by adding additional steps on x and/or y (e.g. month 1.0, 1.2, 1.4 etc.) and calculate the corresponding z for the new x/y pairs (for example by using the algorithm you used for the curve).

##### Share on other sites
Hi Lord,
Thanks a lot for the help you provided me so far. I am able to draw the plot correctly.
I am having a problem with colors. That is, I am drawing X, Y and Z axis(lines) with red, green and blue colors. But all these lines are being drawn with a single color. I mean whatever color I set using glColor(), the color is not getting set.
But it is getting set If i dont call the function glEnable(GL_TEXTURE_1D). Is there constraint as the color can not be set if we use textures?
I am suing the following gl initilizations.

glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);glEnable(GL_DEPTH_TEST);glDrawBuffer(GL_BACK);// Setup light 0GLfloat  fLightAmbient0[] = { 0.7f, 0.0f, 0.1f, 0.5f };GLfloat  fLightDiffuse0[] = { 0.1f, 0.3f, 0.7f, 0.5f };GLfloat	 fLightPosition0[] = { 10.0f, 10.0f, 10.0f, 1.0f };	glLightfv(GL_LIGHT0, GL_AMBIENT, fLightAmbient0);glLightfv(GL_LIGHT0, GL_DIFFUSE, fLightDiffuse0);glLightfv(GL_LIGHT0, GL_POSITION, fLightPosition0);	// Enable light 1::glEnable(GL_LIGHT0);// Setup light 1GLfloat  fLightAmbient1[] = { 0.1f, 0.3f, 0.5f, 0.5f };GLfloat  fLightDiffuse1[] = { 0.3f, 0.0f, 0.1f, 0.5f };GLfloat	 fLightPosition1[] = { -10.0f, 5.0f, -1.0f, 1.0f };::glLightfv(GL_LIGHT1, GL_AMBIENT, fLightAmbient1);::glLightfv(GL_LIGHT1, GL_DIFFUSE, fLightDiffuse1);::glLightfv(GL_LIGHT1, GL_POSITION, fLightPosition1);// Enable light 1::glEnable(GL_LIGHT1);// Enable lighting::glEnable(GL_LIGHTING);// Enable 1D texture ::glEnable(GL_TEXTURE_1D);::glShadeModel(GL_SMOOTH);  // Setup materialGLfloat materialSpecular[] = { 0.9f,  0.9f,  0.9f,  0.5f };GLfloat materialAmbDiff[] = { 0.6f, 0.6f, 0.6f, 0.5f };GLfloat materialShininess[1] = { 20.0f };::glMaterialfv( GL_FRONT, GL_SPECULAR, materialSpecular);::glMaterialfv( GL_FRONT, GL_AMBIENT_AND_DIFFUSE, 	materialAmbDiff);::glMaterialfv( GL_FRONT, GL_SHININESS, materialShininess);

The axis drawing code

void DrawAxis(){// draw carthesian axes  glBegin(GL_LINES);		       // red x axis	glColor3f(1.0f,0.0f,0.f);		glVertex3f(m_XMin,m_YMin,m_ZMin);	glVertex3f(m_XMax,m_YMin,m_ZMin);        // Draw 'X'	glVertex3f(0.2f,-0.9f,m_ZMin);	glVertex3f(0.23f,-0.96f,m_ZMin);	glVertex3f(0.2f,-0.96f,m_ZMin);	glVertex3f(0.23f,-0.9f,m_ZMin);        	// green y axis	glColor3f(0.0f, 1.0f, 0.0f);	glVertex3f(m_XMin,m_YMin,m_ZMin);	glVertex3f(m_XMin,m_YMax,m_ZMin);        // Draw 'Y'	glVertex3f(-0.9f, 0.0f, m_ZMin);	glVertex3f(-0.87f, -0.04f, m_ZMin);	glVertex3f(-0.84f, 0.0f, m_ZMin);	glVertex3f(-0.87f, -0.04f, m_ZMin);        glVertex3f(-0.87f, -0.04f, m_ZMin);	glVertex3f(-0.87f, -0.08f, m_ZMin);     	// blue z axis	glColor3f(0.f,0.f,1.f);	glVertex3f(m_XMin,m_YMin,m_ZMin);	glVertex3f(m_XMin,m_YMin,m_ZMax);        // Draw 'Z'	glVertex3f(m_XMin,-0.5f,0.2f);	glVertex3f(m_XMin,-0.5f,0.16f);	glVertex3f(m_XMin,-0.5f,0.16f);	glVertex3f(m_XMin,-0.55f,0.2f);        glVertex3f(m_XMin,-0.55f,0.2f);        glVertex3f(m_XMin,-0.55f,0.16f);  glEnd();}

Is there any mistake I am doing? Please guide me.

Thanks for the help.

Regards,
Srinu

##### Share on other sites
When you enable texturing the color will be modulated with the texture color by default.
I assume you don't use a texture for the plot and thus when the driver tried to read texels from the "texture" returns black. Now your colors are multiplied with black, which results in ... black [smile].

If you want to use a texture, e.g. for having a gradient, you have to bind a texture (which should be grey scale if you want to use vertex colors, too) and provide texture coords for your vertices.

If you don't want to use textures, just disable texturing when drawing your axes.

• 10
• 11
• 10
• 11
• 9
• ### Similar Content

• By EddieK
Hello. I'm trying to make an android game and I have come across a problem. I want to draw different map layers at different Z depths so that some of the tiles are drawn above the player while others are drawn under him. But there's an issue where the pixels with alpha drawn above the player. This is the code i'm using:
int setup(){ GLES20.glEnable(GLES20.GL_DEPTH_TEST); GLES20.glEnable(GL10.GL_ALPHA_TEST); GLES20.glEnable(GLES20.GL_TEXTURE_2D); } int render(){ GLES20.glClearColor(0, 0, 0, 0); GLES20.glClear(GLES20.GL_ALPHA_BITS); GLES20.glClear(GLES20.GL_COLOR_BUFFER_BIT); GLES20.glClear(GLES20.GL_DEPTH_BUFFER_BIT); GLES20.glBlendFunc(GLES20.GL_ONE, GL10.GL_ONE_MINUS_SRC_ALPHA); // do the binding of textures and drawing vertices } My vertex shader:
uniform mat4 MVPMatrix; // model-view-projection matrix uniform mat4 projectionMatrix; attribute vec4 position; attribute vec2 textureCoords; attribute vec4 color; attribute vec3 normal; varying vec4 outColor; varying vec2 outTexCoords; varying vec3 outNormal; void main() { outNormal = normal; outTexCoords = textureCoords; outColor = color; gl_Position = MVPMatrix * position; } My fragment shader:
precision highp float; uniform sampler2D texture; varying vec4 outColor; varying vec2 outTexCoords; varying vec3 outNormal; void main() { vec4 color = texture2D(texture, outTexCoords) * outColor; gl_FragColor = vec4(color.r,color.g,color.b,color.a);//color.a); } I have attached a picture of how it looks. You can see the black squares near the tree. These squares should be transparent as they are in the png image:

Its strange that in this picture instead of alpha or just black color it displays the grass texture beneath the player and the tree:

Any ideas on how to fix this?

• This article uses material originally posted on Diligent Graphics web site.
Introduction
Graphics APIs have come a long way from small set of basic commands allowing limited control of configurable stages of early 3D accelerators to very low-level programming interfaces exposing almost every aspect of the underlying graphics hardware. Next-generation APIs, Direct3D12 by Microsoft and Vulkan by Khronos are relatively new and have only started getting widespread adoption and support from hardware vendors, while Direct3D11 and OpenGL are still considered industry standard. New APIs can provide substantial performance and functional improvements, but may not be supported by older hardware. An application targeting wide range of platforms needs to support Direct3D11 and OpenGL. New APIs will not give any advantage when used with old paradigms. It is totally possible to add Direct3D12 support to an existing renderer by implementing Direct3D11 interface through Direct3D12, but this will give zero benefits. Instead, new approaches and rendering architectures that leverage flexibility provided by the next-generation APIs are expected to be developed.
There are at least four APIs (Direct3D11, Direct3D12, OpenGL/GLES, Vulkan, plus Apple's Metal for iOS and osX platforms) that a cross-platform 3D application may need to support. Writing separate code paths for all APIs is clearly not an option for any real-world application and the need for a cross-platform graphics abstraction layer is evident. The following is the list of requirements that I believe such layer needs to satisfy:
Lightweight abstractions: the API should be as close to the underlying native APIs as possible to allow an application leverage all available low-level functionality. In many cases this requirement is difficult to achieve because specific features exposed by different APIs may vary considerably. Low performance overhead: the abstraction layer needs to be efficient from performance point of view. If it introduces considerable amount of overhead, there is no point in using it. Convenience: the API needs to be convenient to use. It needs to assist developers in achieving their goals not limiting their control of the graphics hardware. Multithreading: ability to efficiently parallelize work is in the core of Direct3D12 and Vulkan and one of the main selling points of the new APIs. Support for multithreading in a cross-platform layer is a must. Extensibility: no matter how well the API is designed, it still introduces some level of abstraction. In some cases the most efficient way to implement certain functionality is to directly use native API. The abstraction layer needs to provide seamless interoperability with the underlying native APIs to provide a way for the app to add features that may be missing. Diligent Engine is designed to solve these problems. Its main goal is to take advantages of the next-generation APIs such as Direct3D12 and Vulkan, but at the same time provide support for older platforms via Direct3D11, OpenGL and OpenGLES. Diligent Engine exposes common C++ front-end for all supported platforms and provides interoperability with underlying native APIs. It also supports integration with Unity and is designed to be used as graphics subsystem in a standalone game engine, Unity native plugin or any other 3D application. Full source code is available for download at GitHub and is free to use.
Overview
Diligent Engine API takes some features from Direct3D11 and Direct3D12 as well as introduces new concepts to hide certain platform-specific details and make the system easy to use. It contains the following main components:
Render device (IRenderDevice  interface) is responsible for creating all other objects (textures, buffers, shaders, pipeline states, etc.).
Device context (IDeviceContext interface) is the main interface for recording rendering commands. Similar to Direct3D11, there are immediate context and deferred contexts (which in Direct3D11 implementation map directly to the corresponding context types). Immediate context combines command queue and command list recording functionality. It records commands and submits the command list for execution when it contains sufficient number of commands. Deferred contexts are designed to only record command lists that can be submitted for execution through the immediate context.
An alternative way to design the API would be to expose command queue and command lists directly. This approach however does not map well to Direct3D11 and OpenGL. Besides, some functionality (such as dynamic descriptor allocation) can be much more efficiently implemented when it is known that a command list is recorded by a certain deferred context from some thread.
The approach taken in the engine does not limit scalability as the application is expected to create one deferred context per thread, and internally every deferred context records a command list in lock-free fashion. At the same time this approach maps well to older APIs.
In current implementation, only one immediate context that uses default graphics command queue is created. To support multiple GPUs or multiple command queue types (compute, copy, etc.), it is natural to have one immediate contexts per queue. Cross-context synchronization utilities will be necessary.
Swap Chain (ISwapChain interface). Swap chain interface represents a chain of back buffers and is responsible for showing the final rendered image on the screen.
Render device, device contexts and swap chain are created during the engine initialization.
Resources (ITexture and IBuffer interfaces). There are two types of resources - textures and buffers. There are many different texture types (2D textures, 3D textures, texture array, cubmepas, etc.) that can all be represented by ITexture interface.
Resources Views (ITextureView and IBufferView interfaces). While textures and buffers are mere data containers, texture views and buffer views describe how the data should be interpreted. For instance, a 2D texture can be used as a render target for rendering commands or as a shader resource.
Pipeline State (IPipelineState interface). GPU pipeline contains many configurable stages (depth-stencil, rasterizer and blend states, different shader stage, etc.). Direct3D11 uses coarse-grain objects to set all stage parameters at once (for instance, a rasterizer object encompasses all rasterizer attributes), while OpenGL contains myriad functions to fine-grain control every individual attribute of every stage. Both methods do not map very well to modern graphics hardware that combines all states into one monolithic state under the hood. Direct3D12 directly exposes pipeline state object in the API, and Diligent Engine uses the same approach.
Shader Resource Binding (IShaderResourceBinding interface). Shaders are programs that run on the GPU. Shaders may access various resources (textures and buffers), and setting correspondence between shader variables and actual resources is called resource binding. Resource binding implementation varies considerably between different API. Diligent Engine introduces a new object called shader resource binding that encompasses all resources needed by all shaders in a certain pipeline state.
API Basics
Creating Resources
Device resources are created by the render device. The two main resource types are buffers, which represent linear memory, and textures, which use memory layouts optimized for fast filtering. Graphics APIs usually have a native object that represents linear buffer. Diligent Engine uses IBuffer interface as an abstraction for a native buffer. To create a buffer, one needs to populate BufferDesc structure and call IRenderDevice::CreateBuffer() method as in the following example:
BufferDesc BuffDesc; BufferDesc.Name = "Uniform buffer"; BuffDesc.BindFlags = BIND_UNIFORM_BUFFER; BuffDesc.Usage = USAGE_DYNAMIC; BuffDesc.uiSizeInBytes = sizeof(ShaderConstants); BuffDesc.CPUAccessFlags = CPU_ACCESS_WRITE; m_pDevice->CreateBuffer( BuffDesc, BufferData(), &m_pConstantBuffer ); While there is usually just one buffer object, different APIs use very different approaches to represent textures. For instance, in Direct3D11, there are ID3D11Texture1D, ID3D11Texture2D, and ID3D11Texture3D objects. In OpenGL, there is individual object for every texture dimension (1D, 2D, 3D, Cube), which may be a texture array, which may also be multisampled (i.e. GL_TEXTURE_2D_MULTISAMPLE_ARRAY). As a result there are nine different GL texture types that Diligent Engine may create under the hood. In Direct3D12, there is only one resource interface. Diligent Engine hides all these details in ITexture interface. There is only one  IRenderDevice::CreateTexture() method that is capable of creating all texture types. Dimension, format, array size and all other parameters are specified by the members of the TextureDesc structure:
TextureDesc TexDesc; TexDesc.Name = "My texture 2D"; TexDesc.Type = TEXTURE_TYPE_2D; TexDesc.Width = 1024; TexDesc.Height = 1024; TexDesc.Format = TEX_FORMAT_RGBA8_UNORM; TexDesc.Usage = USAGE_DEFAULT; TexDesc.BindFlags = BIND_SHADER_RESOURCE | BIND_RENDER_TARGET | BIND_UNORDERED_ACCESS; TexDesc.Name = "Sample 2D Texture"; m_pRenderDevice->CreateTexture( TexDesc, TextureData(), &m_pTestTex ); If native API supports multithreaded resource creation, textures and buffers can be created by multiple threads simultaneously.
Interoperability with native API provides access to the native buffer/texture objects and also allows creating Diligent Engine objects from native handles. It allows applications seamlessly integrate native API-specific code with Diligent Engine.
Next-generation APIs allow fine level-control over how resources are allocated. Diligent Engine does not currently expose this functionality, but it can be added by implementing IResourceAllocator interface that encapsulates specifics of resource allocation and providing this interface to CreateBuffer() or CreateTexture() methods. If null is provided, default allocator should be used.
Initializing the Pipeline State
As it was mentioned earlier, Diligent Engine follows next-gen APIs to configure the graphics/compute pipeline. One big Pipelines State Object (PSO) encompasses all required states (all shader stages, input layout description, depth stencil, rasterizer and blend state descriptions etc.). This approach maps directly to Direct3D12/Vulkan, but is also beneficial for older APIs as it eliminates pipeline misconfiguration errors. With many individual calls tweaking various GPU pipeline settings it is very easy to forget to set one of the states or assume the stage is already properly configured when in fact it is not. Using pipeline state object helps avoid these problems as all stages are configured at once.
While in earlier APIs shaders were bound separately, in the next-generation APIs as well as in Diligent Engine shaders are part of the pipeline state object. The biggest challenge when authoring shaders is that Direct3D and OpenGL/Vulkan use different shader languages (while Apple uses yet another language in their Metal API). Maintaining two versions of every shader is not an option for real applications and Diligent Engine implements shader source code converter that allows shaders authored in HLSL to be translated to GLSL. To create a shader, one needs to populate ShaderCreationAttribs structure. SourceLanguage member of this structure tells the system which language the shader is authored in:
SHADER_SOURCE_LANGUAGE_DEFAULT - The shader source language matches the underlying graphics API: HLSL for Direct3D11/Direct3D12 mode, and GLSL for OpenGL and OpenGLES modes. SHADER_SOURCE_LANGUAGE_HLSL - The shader source is in HLSL. For OpenGL and OpenGLES modes, the source code will be converted to GLSL. SHADER_SOURCE_LANGUAGE_GLSL - The shader source is in GLSL. There is currently no GLSL to HLSL converter, so this value should only be used for OpenGL and OpenGLES modes. There are two ways to provide the shader source code. The first way is to use Source member. The second way is to provide a file path in FilePath member. Since the engine is entirely decoupled from the platform and the host file system is platform-dependent, the structure exposes pShaderSourceStreamFactory member that is intended to provide the engine access to the file system. If FilePath is provided, shader source factory must also be provided. If the shader source contains any #include directives, the source stream factory will also be used to load these files. The engine provides default implementation for every supported platform that should be sufficient in most cases. Custom implementation can be provided when needed.
When sampling a texture in a shader, the texture sampler was traditionally specified as separate object that was bound to the pipeline at run time or set as part of the texture object itself. However, in most cases it is known beforehand what kind of sampler will be used in the shader. Next-generation APIs expose new type of sampler called static sampler that can be initialized directly in the pipeline state. Diligent Engine exposes this functionality: when creating a shader, textures can be assigned static samplers. If static sampler is assigned, it will always be used instead of the one initialized in the texture shader resource view. To initialize static samplers, prepare an array of StaticSamplerDesc structures and initialize StaticSamplers and NumStaticSamplers members. Static samplers are more efficient and it is highly recommended to use them whenever possible. On older APIs, static samplers are emulated via generic sampler objects.
The following is an example of shader initialization:
Creating the Pipeline State Object
After all required shaders are created, the rest of the fields of the PipelineStateDesc structure provide depth-stencil, rasterizer, and blend state descriptions, the number and format of render targets, input layout format, etc. For instance, rasterizer state can be described as follows:
PipelineStateDesc PSODesc; RasterizerStateDesc &RasterizerDesc = PSODesc.GraphicsPipeline.RasterizerDesc; RasterizerDesc.FillMode = FILL_MODE_SOLID; RasterizerDesc.CullMode = CULL_MODE_NONE; RasterizerDesc.FrontCounterClockwise = True; RasterizerDesc.ScissorEnable = True; RasterizerDesc.AntialiasedLineEnable = False; Depth-stencil and blend states are defined in a similar fashion.
Another important thing that pipeline state object encompasses is the input layout description that defines how inputs to the vertex shader, which is the very first shader stage, should be read from the memory. Input layout may define several vertex streams that contain values of different formats and sizes:
// Define input layout InputLayoutDesc &Layout = PSODesc.GraphicsPipeline.InputLayout; LayoutElement TextLayoutElems[] = {     LayoutElement( 0, 0, 3, VT_FLOAT32, False ),     LayoutElement( 1, 0, 4, VT_UINT8, True ),     LayoutElement( 2, 0, 2, VT_FLOAT32, False ), }; Layout.LayoutElements = TextLayoutElems; Layout.NumElements = _countof( TextLayoutElems ); Finally, pipeline state defines primitive topology type. When all required members are initialized, a pipeline state object can be created by IRenderDevice::CreatePipelineState() method:
// Define shader and primitive topology PSODesc.GraphicsPipeline.PrimitiveTopologyType = PRIMITIVE_TOPOLOGY_TYPE_TRIANGLE; PSODesc.GraphicsPipeline.pVS = pVertexShader; PSODesc.GraphicsPipeline.pPS = pPixelShader; PSODesc.Name = "My pipeline state"; m_pDev->CreatePipelineState(PSODesc, &m_pPSO); When PSO object is bound to the pipeline, the engine invokes all API-specific commands to set all states specified by the object. In case of Direct3D12 this maps directly to setting the D3D12 PSO object. In case of Direct3D11, this involves setting individual state objects (such as rasterizer and blend states), shaders, input layout etc. In case of OpenGL, this requires a number of fine-grain state tweaking calls. Diligent Engine keeps track of currently bound states and only calls functions to update these states that have actually changed.
Direct3D11 and OpenGL utilize fine-grain resource binding models, where an application binds individual buffers and textures to certain shader or program resource binding slots. Direct3D12 uses a very different approach, where resource descriptors are grouped into tables, and an application can bind all resources in the table at once by setting the table in the command list. Resource binding model in Diligent Engine is designed to leverage this new method. It introduces a new object called shader resource binding that encapsulates all resource bindings required for all shaders in a certain pipeline state. It also introduces the classification of shader variables based on the frequency of expected change that helps the engine group them into tables under the hood:
Static variables (SHADER_VARIABLE_TYPE_STATIC) are variables that are expected to be set only once. They may not be changed once a resource is bound to the variable. Such variables are intended to hold global constants such as camera attributes or global light attributes constant buffers. Mutable variables (SHADER_VARIABLE_TYPE_MUTABLE) define resources that are expected to change on a per-material frequency. Examples may include diffuse textures, normal maps etc. Dynamic variables (SHADER_VARIABLE_TYPE_DYNAMIC) are expected to change frequently and randomly. Shader variable type must be specified during shader creation by populating an array of ShaderVariableDesc structures and initializing ShaderCreationAttribs::Desc::VariableDesc and ShaderCreationAttribs::Desc::NumVariables members (see example of shader creation above).
Static variables cannot be changed once a resource is bound to the variable. They are bound directly to the shader object. For instance, a shadow map texture is not expected to change after it is created, so it can be bound directly to the shader:
m_pPSO->CreateShaderResourceBinding(&m_pSRB); Note that an SRB is only compatible with the pipeline state it was created from. SRB object inherits all static bindings from shaders in the pipeline, but is not allowed to change them.
Mutable resources can only be set once for every instance of a shader resource binding. Such resources are intended to define specific material properties. For instance, a diffuse texture for a specific material is not expected to change once the material is defined and can be set right after the SRB object has been created:
m_pSRB->GetVariable(SHADER_TYPE_PIXEL, "tex2DDiffuse")->Set(pDiffuseTexSRV); In some cases it is necessary to bind a new resource to a variable every time a draw command is invoked. Such variables should be labeled as dynamic, which will allow setting them multiple times through the same SRB object:
m_pSRB->GetVariable(SHADER_TYPE_VERTEX, "cbRandomAttribs")->Set(pRandomAttrsCB); Under the hood, the engine pre-allocates descriptor tables for static and mutable resources when an SRB objcet is created. Space for dynamic resources is dynamically allocated at run time. Static and mutable resources are thus more efficient and should be used whenever possible.
As you can see, Diligent Engine does not expose low-level details of how resources are bound to shader variables. One reason for this is that these details are very different for various APIs. The other reason is that using low-level binding methods is extremely error-prone: it is very easy to forget to bind some resource, or bind incorrect resource such as bind a buffer to the variable that is in fact a texture, especially during shader development when everything changes fast. Diligent Engine instead relies on shader reflection system to automatically query the list of all shader variables. Grouping variables based on three types mentioned above allows the engine to create optimized layout and take heavy lifting of matching resources to API-specific resource location, register or descriptor in the table.
This post gives more details about the resource binding model in Diligent Engine.
Setting the Pipeline State and Committing Shader Resources
Before any draw or compute command can be invoked, the pipeline state needs to be bound to the context:
m_pContext->SetPipelineState(m_pPSO); Under the hood, the engine sets the internal PSO object in the command list or calls all the required native API functions to properly configure all pipeline stages.
The next step is to bind all required shader resources to the GPU pipeline, which is accomplished by IDeviceContext::CommitShaderResources() method:
m_pContext->CommitShaderResources(m_pSRB, COMMIT_SHADER_RESOURCES_FLAG_TRANSITION_RESOURCES); The method takes a pointer to the shader resource binding object and makes all resources the object holds available for the shaders. In the case of D3D12, this only requires setting appropriate descriptor tables in the command list. For older APIs, this typically requires setting all resources individually.
Next-generation APIs require the application to track the state of every resource and explicitly inform the system about all state transitions. For instance, if a texture was used as render target before, while the next draw command is going to use it as shader resource, a transition barrier needs to be executed. Diligent Engine does the heavy lifting of state tracking.  When CommitShaderResources() method is called with COMMIT_SHADER_RESOURCES_FLAG_TRANSITION_RESOURCES flag, the engine commits and transitions resources to correct states at the same time. Note that transitioning resources does introduce some overhead. The engine tracks state of every resource and it will not issue the barrier if the state is already correct. But checking resource state is an overhead that can sometimes be avoided. The engine provides IDeviceContext::TransitionShaderResources() method that only transitions resources:
m_pContext->TransitionShaderResources(m_pPSO, m_pSRB); In some scenarios it is more efficient to transition resources once and then only commit them.
Invoking Draw Command
The final step is to set states that are not part of the PSO, such as render targets, vertex and index buffers. Diligent Engine uses Direct3D11-syle API that is translated to other native API calls under the hood:
ITextureView *pRTVs[] = {m_pRTV}; m_pContext->SetRenderTargets(_countof( pRTVs ), pRTVs, m_pDSV); // Clear render target and depth buffer const float zero[4] = {0, 0, 0, 0}; m_pContext->ClearRenderTarget(nullptr, zero); m_pContext->ClearDepthStencil(nullptr, CLEAR_DEPTH_FLAG, 1.f); // Set vertex and index buffers IBuffer *buffer[] = {m_pVertexBuffer}; Uint32 offsets[] = {0}; Uint32 strides[] = {sizeof(MyVertex)}; m_pContext->SetVertexBuffers(0, 1, buffer, strides, offsets, SET_VERTEX_BUFFERS_FLAG_RESET); m_pContext->SetIndexBuffer(m_pIndexBuffer, 0); Different native APIs use various set of function to execute draw commands depending on command details (if the command is indexed, instanced or both, what offsets in the source buffers are used etc.). For instance, there are 5 draw commands in Direct3D11 and more than 9 commands in OpenGL with something like glDrawElementsInstancedBaseVertexBaseInstance not uncommon. Diligent Engine hides all details with single IDeviceContext::Draw() method that takes takes DrawAttribs structure as an argument. The structure members define all attributes required to perform the command (primitive topology, number of vertices or indices, if draw call is indexed or not, if draw call is instanced or not, if draw call is indirect or not, etc.). For example:
DrawAttribs attrs; attrs.IsIndexed = true; attrs.IndexType = VT_UINT16; attrs.NumIndices = 36; attrs.Topology = PRIMITIVE_TOPOLOGY_TRIANGLE_LIST; pContext->Draw(attrs); For compute commands, there is IDeviceContext::DispatchCompute() method that takes DispatchComputeAttribs structure that defines compute grid dimension.
Source Code
Full engine source code is available on GitHub and is free to use. The repository contains two samples, asteroids performance benchmark and example Unity project that uses Diligent Engine in native plugin.
AntTweakBar sample is Diligent Engine’s “Hello World” example.

Atmospheric scattering sample is a more advanced example. It demonstrates how Diligent Engine can be used to implement various rendering tasks: loading textures from files, using complex shaders, rendering to multiple render targets, using compute shaders and unordered access views, etc.

Asteroids performance benchmark is based on this demo developed by Intel. It renders 50,000 unique textured asteroids and allows comparing performance of Direct3D11 and Direct3D12 implementations. Every asteroid is a combination of one of 1000 unique meshes and one of 10 unique textures.

Finally, there is an example project that shows how Diligent Engine can be integrated with Unity.

Future Work
The engine is under active development. It currently supports Windows desktop, Universal Windows and Android platforms. Direct3D11, Direct3D12, OpenGL/GLES backends are now feature complete. Vulkan backend is coming next, and support for more platforms is planned.
• By reenigne
For those that don't know me. I am the individual who's two videos are listed here under setup for https://wiki.libsdl.org/Tutorials
I also run grhmedia.com where I host the projects and code for the tutorials I have online.
Recently, I received a notice from youtube they will be implementing their new policy in protecting video content as of which I won't be monetized till I meat there required number of viewers and views each month.

Frankly, I'm pretty sick of youtube. I put up a video and someone else learns from it and puts up another video and because of the way youtube does their placement they end up with more views.
Even guys that clearly post false information such as one individual who said GLEW 2.0 was broken because he didn't know how to compile it. He in short didn't know how to modify the script he used because he didn't understand make files and how the requirements of the compiler and library changes needed some different flags.

At the end of the month when they implement this I will take down the content and host on my own server purely and it will be a paid system and or patreon.

I get my videos may be a bit dry, I generally figure people are there to learn how to do something and I rather not waste their time.
I used to also help people for free even those coming from the other videos. That won't be the case any more. I used to just take anyone emails and work with them my email is posted on the site.

I don't expect to get the required number of subscribers in that time or increased views. Even if I did well it wouldn't take care of each reoccurring month.
I figure this is simpler and I don't plan on putting some sort of exorbitant fee for a monthly subscription or the like.
I was thinking on the lines of a few dollars 1,2, and 3 and the larger subscription gets you assistance with the content in the tutorials if needed that month.
Maybe another fee if it is related but not directly in the content.
The fees would serve to cut down on the number of people who ask for help and maybe encourage some of the people to actually pay attention to what is said rather than do their own thing. That actually turns out to be 90% of the issues. I spent 6 hours helping one individual last week I must have asked him 20 times did you do exactly like I said in the video even pointed directly to the section. When he finally sent me a copy of the what he entered I knew then and there he had not. I circled it and I pointed out that wasn't what I said to do in the video. I didn't tell him what was wrong and how I knew that way he would go back and actually follow what it said to do. He then reported it worked. Yea, no kidding following directions works. But hey isn't alone and well its part of the learning process.

So the point of this isn't to be a gripe session. I'm just looking for a bit of feed back. Do you think the fees are unreasonable?
Should I keep the youtube channel and do just the fees with patreon or do you think locking the content to my site and require a subscription is an idea.

I'm just looking at the fact it is unrealistic to think youtube/google will actually get stuff right or that youtube viewers will actually bother to start looking for more accurate videos.

• i got error 1282 in my code.
sf::ContextSettings settings; settings.majorVersion = 4; settings.minorVersion = 5; settings.attributeFlags = settings.Core; sf::Window window; window.create(sf::VideoMode(1600, 900), "Texture Unit Rectangle", sf::Style::Close, settings); window.setActive(true); window.setVerticalSyncEnabled(true); glewInit(); GLuint shaderProgram = createShaderProgram("FX/Rectangle.vss", "FX/Rectangle.fss"); float vertex[] = { -0.5f,0.5f,0.0f, 0.0f,0.0f, -0.5f,-0.5f,0.0f, 0.0f,1.0f, 0.5f,0.5f,0.0f, 1.0f,0.0f, 0.5,-0.5f,0.0f, 1.0f,1.0f, }; GLuint indices[] = { 0,1,2, 1,2,3, }; GLuint vao; glGenVertexArrays(1, &vao); glBindVertexArray(vao); GLuint vbo; glGenBuffers(1, &vbo); glBindBuffer(GL_ARRAY_BUFFER, vbo); glBufferData(GL_ARRAY_BUFFER, sizeof(vertex), vertex, GL_STATIC_DRAW); GLuint ebo; glGenBuffers(1, &ebo); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo); glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices,GL_STATIC_DRAW); glVertexAttribPointer(0, 3, GL_FLOAT, false, sizeof(float) * 5, (void*)0); glEnableVertexAttribArray(0); glVertexAttribPointer(1, 2, GL_FLOAT, false, sizeof(float) * 5, (void*)(sizeof(float) * 3)); glEnableVertexAttribArray(1); GLuint texture[2]; glGenTextures(2, texture); glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, texture[0]); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); sf::Image* imageOne = new sf::Image; bool isImageOneLoaded = imageOne->loadFromFile("Texture/container.jpg"); if (isImageOneLoaded) { glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, imageOne->getSize().x, imageOne->getSize().y, 0, GL_RGBA, GL_UNSIGNED_BYTE, imageOne->getPixelsPtr()); glGenerateMipmap(GL_TEXTURE_2D); } delete imageOne; glActiveTexture(GL_TEXTURE1); glBindTexture(GL_TEXTURE_2D, texture[1]); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); sf::Image* imageTwo = new sf::Image; bool isImageTwoLoaded = imageTwo->loadFromFile("Texture/awesomeface.png"); if (isImageTwoLoaded) { glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, imageTwo->getSize().x, imageTwo->getSize().y, 0, GL_RGBA, GL_UNSIGNED_BYTE, imageTwo->getPixelsPtr()); glGenerateMipmap(GL_TEXTURE_2D); } delete imageTwo; glUniform1i(glGetUniformLocation(shaderProgram, "inTextureOne"), 0); glUniform1i(glGetUniformLocation(shaderProgram, "inTextureTwo"), 1); GLenum error = glGetError(); std::cout << error << std::endl; sf::Event event; bool isRunning = true; while (isRunning) { while (window.pollEvent(event)) { if (event.type == event.Closed) { isRunning = false; } } glClear(GL_COLOR_BUFFER_BIT); if (isImageOneLoaded && isImageTwoLoaded) { glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, texture[0]); glActiveTexture(GL_TEXTURE1); glBindTexture(GL_TEXTURE_2D, texture[1]); glUseProgram(shaderProgram); } glBindVertexArray(vao); glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, nullptr); glBindVertexArray(0); window.display(); } glDeleteVertexArrays(1, &vao); glDeleteBuffers(1, &vbo); glDeleteBuffers(1, &ebo); glDeleteProgram(shaderProgram); glDeleteTextures(2,texture); return 0; } and this is the vertex shader
#version 450 core layout(location=0) in vec3 inPos; layout(location=1) in vec2 inTexCoord; out vec2 TexCoord; void main() { gl_Position=vec4(inPos,1.0); TexCoord=inTexCoord; } and the fragment shader
#version 450 core in vec2 TexCoord; uniform sampler2D inTextureOne; uniform sampler2D inTextureTwo; out vec4 FragmentColor; void main() { FragmentColor=mix(texture(inTextureOne,TexCoord),texture(inTextureTwo,TexCoord),0.2); } I was expecting awesomeface.png on top of container.jpg

• By khawk
We've just released all of the source code for the NeHe OpenGL lessons on our Github page at https://github.com/gamedev-net/nehe-opengl. code - 43 total platforms, configurations, and languages are included.
Now operated by GameDev.net, NeHe is located at http://nehe.gamedev.net where it has been a valuable resource for developers wanting to learn OpenGL and graphics programming.

View full story