# OpenGL bit of a conversion problem

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i have recntly bought a few tutorials from www.gametutorials.com i am currently trying to convert the c++ direct3d water tutorial to vb.net , i have been trying for ages and can seem to find the problem , i have converted the code over word for word and still dosent work, so below i have posted the c++ and vb.net and i would be very gratefull if somebody could have a look at them and maybe point out some mistakes that i have made. c++ version water.h
#include "d3d_obj.h"
#include "d3d_texture.h"

/////////////
// Macros //
///////////

#define DEG2RAD(x) (x * (D3DX_PI / 180.0f)) // Converts degrees to radians
#define RAD2DEG(x) (x * (180.0f / D3DX_PI)) // Converts radians to degrees

#define F2I(x) ( (int)((x) + 0.5f) ) // Converts a float to int with proper rounding

////////////////
// Constants //
//////////////

const int kWaterTesselation = 32; // Number of rows X cols of tessellated quads in water
const int kWaveTableSize = 36; // Number of entries in the wave table

const float kWaterForce = 1.0f / 25.0f; // Controls the "choppiness" of the water (Range is 0.0f - 1.0f)
// 0.0f == Water is still
// 1.0f == Water is VERY choppy (so choppy it looks very bad)
const float kWaterWid = 30.0f; // Width of water (along X-axis)
const float kWaterHgt = 30.0f; // Height of water (along Z-axis)

class CWater
{
public:

CWater(); // Constructor

bool init(); // Initialize the water object
void process(); // Process the water object (apply sin() wave to Y value of verts)
void render(); // Render the water

~CWater(); // Deconstructor

private:

bool createGeometery(float width, float height, int tesselation);

CD3DTexture mTexture;
SVertex *mVerts;
WORD *mIndices;

int mVertCount;
int mIndexCount;
int mTesselation;

float mWaveTable[kWaveTableSize];
};

#endif


water.cpp

#include "water.h"

const CPos kWaterCen(0.0f, 0.0f, 0.0f); // Water is always centered at (0,0,0)

// Helper function for determining if a float is less than or equal to
// another float
inline bool ToleranceLE(float a, float b, float tolerance = 0.001f)
{
return ((a - tolerance) <= b);
}

// Constructor
CWater::CWater()
{
memset(mWaveTable, 0, sizeof(mWaveTable));

mVerts = NULL;
mIndices = NULL;

mVertCount = 0;
mIndexCount = 0;
mTesselation = 0;

// "texture" gets initialized by it's constructor
}

// Init the water object, returns true on success, false otherwise
bool CWater::init()
{
// Fill the wave table
float angInc = 360.0f / (float)kWaveTableSize;
float angle = 0.0f;

// Fill in the table with values of the sine function
for(int i = 0; i < kWaveTableSize; ++i)
{
angle += angInc;
}

if(!createGeometery(kWaterWid, kWaterHgt, kWaterTesselation))
return false;

}

// Process the water every frame
void CWater::process()
{
static int startIndex = 0;

int waveIndex = startIndex;
int vertIndex = 0;

// Loop through all rows of triangles
for(int i = 0; i <= mTesselation; ++i)
{
// Loop through all the columns of triangles
for(int j = 0; j <= mTesselation; ++j, ++vertIndex)
{
// Perturb each vertex
mVerts[vertIndex].y += mWaveTable[waveIndex] * kWaterForce;

if(++waveIndex == kWaveTableSize)
waveIndex = 0;
}

}

// Keep cycling thorough the mWaveTable
if(++startIndex == kWaveTableSize)
startIndex = 0;
}

// Render the water object as a triangle strip
void CWater::render()
{
bool b = g3D->setAlphaBlendMode(true); // Turn on alpha blending

mTexture.select(); // Select the water texture
g3D->render(mVerts, mVertCount, mIndices, mIndexCount); // Render the tessellated quad

g3D->setAlphaBlendMode(false); // Turn off alpha blending
}

// Creates a tesselated quad of (width x height) dimensions
// Number of triangles in quad is (tessAmt * tessAmt * 2)
bool CWater::createGeometery(float width, float height, int tessAmt)
{
if(width < 0.0f || height < 0.0f || tessAmt <= 0)
return false;

// Set tesselation amount
mTesselation = tessAmt;

// Calculate vertex count.  We know that we have (tesselation * tesselation * 2) triangles
// with 3 vertices per triangle.  So each row of vertices will contain "number of rows + 1"
// vertices and each column of vertices well contain "number of columns + 1" vertices.  This
// makes the total number of vertices equal the following equation
mVertCount = (mTesselation + 1) * (mTesselation + 1);

// Calculate index count.  We know that we'll have (tesselation * tesselation * 2) triangles
// and we have 3 vertices per triangle, thus the below equation
mIndexCount = mTesselation * mTesselation * 6;

// Allocate space for vertices and indices
mVerts = new SVertex[mVertCount];
mIndices = new WORD[mIndexCount];

if(mVerts == NULL || mIndices == NULL)
return false;

// Get the sub divided width and height of each triangle
float subDivideWid = width * (1.0f / (float)mTesselation);
float subDivideHgt = height * (1.0f / (float)mTesselation);

// Calculate the starting (x,y) and ending (x,y) of the quad
float startX = kWaterCen.x - (width / 2.0f);
float startY = kWaterCen.z - (height / 2.0f);
float endX = kWaterCen.x + (width / 2.0f);
float endY = kWaterCen.z + (height / 2.0f);

float uCoord = 0.0f; // Holds the current trinagle's U coordinate
float vCoord = 1.0f; // Holds the current triangle's V coordinate
float uvInc = 1.0f / (float)mTesselation; // Calculate the amount to add to each UV coordinate

int i = 0; // Index for all of for...loops

// Create all the vertices
for(float y = startY; ToleranceLE(y, endY); y += subDivideHgt)
{
for(float x = startX; ToleranceLE(x, endX); x += subDivideWid, ++i)
{
// Set the value for the current vert
mVerts.x = x;
mVerts.y = kWaterCen.y;
mVerts.z = y;
mVerts.u = uCoord;
mVerts.v = vCoord;
mVerts.color = D3DCOLOR_ARGB(128, 255, 255, 255);

uCoord += uvInc;
}

// Set UV for next row of vertices
uCoord = 0.0f;
vCoord -= uvInc;
}

// Make sure we calculatd the vertex count correctly
assert(mVertCount == i);

int indexValue = 0;
int nextRow = 0;

// Look at this sample 2 x 2 quad to understand the pattern used to fill in the indices
/*
6----7----8		Index count =  24
|\ 	 |\   |		Tesselation = 2
| \  | \  |
|  \ |  \ |		Pattern is:	0, 3, 1
|   \|   \|					1, 3, 4
3----4----5					1, 4, 2
|\ 	 |\   |					2, 4, 5
| \  | \  | 				3, 6, 4
|  \ |  \ |					4, 6, 7
|   \|   \|					4, 7, 5,
0----1----2					5, 7, 8
*/

// Create all the indices
for(i = 0; i < mIndexCount; i += 6)
{
mIndices = indexValue;
mIndices[i + 1] = indexValue + (mTesselation + 1);
mIndices[i + 2] = mIndices + 1;

indexValue++;

mIndices[i + 3] = indexValue;
mIndices[i + 4] = indexValue + mTesselation;
mIndices[i + 5] = mIndices[i + 4] + 1;

if(++nextRow == mTesselation)
{
indexValue++;
nextRow = 0;
}
}

return true;
}

// Free the memory
CWater::~CWater()
{
if(mVerts)
{
delete[] mVerts;
mVerts = NULL;
}

if(mIndices)
{
delete[] mIndices;
mIndices = NULL;
}
}


and here is my vb.net conversion

Public Class RealisticWater

Public Function Deg2Rad(ByVal X As Single) As Single
Return X * (PI / 180.0F) 'convert degrees to radian
End Function

Public Function Rad2Deg(ByVal x As Single) As Single
Return x * (180.0F / PI) 'converts radians to degrees
End Function

Public Function F2I(ByVal x As Single) As Integer
Return CType(x + 0.5F, Integer) 'converts  float to int with proper rounding
End Function

Private Const kWaterTesselation As Single = 32 ' number of row columns of teselation in water
Private Const kWaveTableSize As Single = 36 ' number of entries in the wav table
Private Const kWaterForce As Single = 0.1F / 25.0F ' // Controls the "choppiness" of the water (Range is 0.0f - 1.0f)
'// 0.0f == Water is still
'// 1.0f == Water is VERY choppy (so choppy it looks very bad)
Private Const kWaterWid As Single = 30.0F 'width of water along x axis
Private Const kWaterHgt As Single = 30.0F ' height of water along z axis

#Region "Water Vertex Structure"
Public Structure WVertex
Public x, y, z As Single
Public Color As Integer
Public u, v As Single
Public Const Format As VertexFormats = VertexFormats.Position Or VertexFormats.Diffuse Or (1 << VertexFormats.TextureCountShift)
'Public Const Format As VertexFormats = VertexFormats.Diffuse Or VertexFormats.Position Or (1 << VertexFormats.TextureCountShift)
End Structure
#End Region

Private mTexture As Direct3D.Texture
Private mVerts() As WVertex
Private mIndices() As Integer
Private mVertCount As Integer
Private mIndexCount As Integer
Private mTesselation As Single
Private mWaveTable(kWaveTableSize) As Single
Private kWaterCen As Vector3 = New Vector3(0, 0, 0) 'water is always cenetred at 0.0f
Private Dev As Direct3D.Device

Public Function ToleranceLE(ByVal a As Single, ByVal b As Single, Optional ByVal tolerance As Single = 0.001F) As Boolean
Return ((a - tolerance) <= b)
End Function

'// Constructor
Public Sub New(ByVal Device As Direct3D.Device, ByVal TexturePath As String)
Dev = Device
mVerts = Nothing
mIndices = Nothing
mVertCount = 0
mIndexCount = 0
mTesselation = 0
Init(TexturePath)
End Sub

'// Init the water object, returns true on success, false otherwise
Private Sub Init(ByVal TexturePath As String)
'// Fill the wave table
Dim anginc As Single = 360.0F / CType(kWaveTableSize, Single)
Dim angle As Single = 0.0F
Dim I As Integer

'// Fill in the table with values of the sine function
For I = 0 To kWaveTableSize - 1
angle += anginc
Next

CreateGeometery(kWaterWid, kWaterHgt, kWaterTesselation)

End Sub

'// Process the water every frame
Public Sub Process()
Static startIndex As Integer = 0
Dim waveIndex As Integer = startIndex
Dim vertIndex As Integer = 0
Dim i As Integer
Dim j As Integer

'// Loop through all rows of triangles
For i = 0 To mTesselation '- 1
'// Loop through all the columns of triangles
For j = 0 To mTesselation
'// Perturb each vertex
mVerts(vertIndex).y += mWaveTable(waveIndex) * kWaterForce
waveIndex = 0
End If
Next
Next

'// Keep cycling thorough the mWaveTable
startIndex = 0
End If
End Sub

Public Sub Process2()
Static startindex As Integer
Dim waveindex As Integer = startindex
Dim vertindex As Integer
Dim i As Integer
Dim j As Integer
'// Loop through all rows of triangles
For i = 0 To mTesselation
'// Loop through all the columns of triangles
For j = 0 To mTesselation
'// Perturb each vertex
mVerts(vertindex).y += mWaveTable(waveIndex) * kWaterForce
vertindex += 1
waveindex += 1
If waveindex = kWaveTableSize Then
waveindex = 0
End If
Next
Next
'// Keep cycling thorough the mWaveTable
startindex += 1
If startindex = kWaveTableSize Then
startindex = 0
End If
End Sub

'// Render the water object as a triangle strip
Public Sub Render()
Dev.RenderState.AlphaBlendEnable = True
Dev.RenderState.Lighting = False
Dev.VertexFormat = WVertex.Format
Dev.SetTexture(0, mTexture)
Dev.RenderState.CullMode = Cull.None
Dev.DrawIndexedUserPrimitives(PrimitiveType.TriangleStrip, 0, mIndexCount, mIndexCount / 3, mIndices, False, mVerts)
Dev.RenderState.Lighting = True
Dev.RenderState.AlphaBlendEnable = False
End Sub

'// Creates a tesselated quad of (width x height) dimensions
'// Number of triangles in quad is (tessAmt * tessAmt * 2)
Public Function createGeometery(ByVal width As Single, ByVal height As Single, ByVal tessAmt As Single) As Boolean

If width < 0.0F Or height < 0.0F Or tessAmt <= 0 Then Return False

'Set tesselation amount
mTesselation = tessAmt

' Calculate vertex count.  We know that we have (tesselation * tesselation * 2) triangles
' with 3 vertices per triangle.  So each row of vertices will contain "number of rows + 1"
' vertices and each column of vertices well contain "number of columns + 1" vertices.  This
' makes the total number of vertices equal the following equation
mVertCount = (mTesselation + 1) * (mTesselation + 1)

' Calculate index count.  We know that we'll have (tesselation * tesselation * 2) triangles
' and we have 3 vertices per triangle, thus the below equation
mIndexCount = mTesselation * mTesselation * 6

' Allocate space for vertices and indices
ReDim mVerts(mVertCount)
ReDim mIndices(mIndexCount)

'not sure how this could ever be true given the two lines above
'if mVerts = NULL or  mIndices == NULL Then Return False

' Get the sub divided width and height of each triangle
Dim subDivideWid As Single = width * (1 / mTesselation)
Dim subDivideHgt As Single = height * (1 / mTesselation)

Dim startx As Single
Dim starty As Single
Dim endx As Single
Dim endy As Single
Dim ucoord As Single
Dim vcoord As Single
Dim uvinc As Single

' Calculate the starting (x,y) and ending (x,y) of the quad
startx = kWaterCen.X - (width / 2.0F)
starty = kWaterCen.Z - (height / 2.0F)
endx = kWaterCen.X + (width / 2.0F)
endy = kWaterCen.Z + (height / 2.0F)

ucoord = 0.0F ' Holds the current trinagle's U coordinate
vcoord = 1.0F ' Holds the current triangle's V coordinate

uvinc = 1.0F / mTesselation ' Calculate the amount to add to each UV coordinate

Dim i As Integer = 0 ' Index for all of for...loops
Dim y As Single
Dim x As Single

' Create all the vertices
For y = starty To ToleranceLE(y, endy) Step subDivideHgt
For x = startx To ToleranceLE(x, endx) Step subDivideWid

' Set the value for the current vert
mVerts(i).x = x
mVerts(i).y = kWaterCen.Y
mVerts(i).z = y
mVerts(i).u = ucoord
mVerts(i).v = vcoord
mVerts(i).Color = Color.FromArgb(128, 255, 255, 255).ToArgb

ucoord += uvinc

i += 1

Next x

' Set UV for next row of vertices
ucoord = 0.0F
vcoord -= uvinc

Next y

' Make sure we calculatd the vertex count correctly
'If mVertCount <> i Then Throw New Exception("Vertex count does not equal " & i.ToString)

Dim indexValue As Integer = 0
Dim nextRow As Integer = 0

' Look at this sample 2 x 2 quad to understand the pattern used to fill in the indices
'6----7----8      Index count =  24
'|\     |\   |      Tesselation = 2
'| \  | \  |
'|  \ |  \ |      Pattern is:   0, 3, 1
'|   \|   \|               1, 3, 4
'3----4----5               1, 4, 2
'|\     |\   |               2, 4, 5
'| \  | \  |             3, 6, 4
'|  \ |  \ |               4, 6, 7
'|   \|   \|               4, 7, 5,
'0----1----2               5, 7, 8

' Create all the indices
For i = 0 To mIndexCount - 1 Step 6

mIndices(i) = indexValue
mIndices(i + 1) = indexValue + mTesselation + 1
mIndices(i + 2) = mIndices(i) + 1

indexValue += 1

mIndices(i + 3) = indexValue
mIndices(i + 4) = indexValue + mTesselation
mIndices(i + 5) = mIndices(i + 4) + 1

nextRow += 1

If nextRow = mTesselation Then
indexValue += 1
nextRow = 0
End If

Next i

Return True
End Function

Public Sub Dispose()
Erase mVerts
Erase mIndices
End Sub

End Class


plase any help will be very helpfull ive been trying for ages to get this working and i cant seem to see anything wrong. sorry i though i used the code tags already, i know im really sorry about all the code but the prob is i have gone trough it loadz of times and icant find the prob. the prob is it dosent render properly, but from what i can see its the vertice generation that causes the prob, i just for the life of me figure it out. and im not convberting opengl to MDX, its c++ MDX to vb.net MDX, which i have done loadz of times and should be almost identical, but i cant seem to find the problem. [Edited by - tuvd on May 17, 2006 6:25:36 AM]

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Also, alot of people that answer questions on these forums don't really have time to go through a whole bunch of code like that. A simple question with regards to conversion might be something like how do I convert ID3DXSprite to MDX or what is the MDX equavalent.

Stay cool.

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To debug I use RenderDocs, but I did not receive good results. In the first attachment is my result, in the second attachment is what should be.
PS. I base on this tutorial https://learnopengl.com/Getting-started/Textures.

• I'm having issues loading textures, as I'm clueless on how to handle / load images maybe I missing something, but the past few days I just google a lot to try to find a solution. Well theres two issues I think, one I'm using Kotlin Native (EAP) and OpenGL wrapper / STB image, so I'm not quite sure wheres the issue, if someone with more experience could give me some hints on how to solve this issue?
The code is here, if I'm not mistaken the workflow is pretty straight forward, stbi_load returns the pixels of the image (as char array or byte array) and you need to pass those pixels directly to glTexImage2D, so a I'm missing something here it seems.
Regards

• I've noticed in most post processing tutorials several shaders are used one after another: one for bloom, another for contrast, and so on. For example:
postprocessing.quad.bind() // Effect 1 effect1.shader.bind(); postprocessing.texture.bind(); postprocessing.quad.draw(); postprocessing.texture.unbind(); effect1.shader.unbind(); // Effect 2 effect2.shader.bind(); // ...and so on postprocessing.quad.unbind() Is this good practice, how many shaders can I bind and unbind before I hit performance issues? I'm afraid I don't know what the good practices are in open/webGL regarding binding and unbinding resources.
I'm guessing binding many shaders at post processing is okay since the scene has already been updated and I'm just working on a quad and texture at that moment. Or is it more optimal to put shader code in chunks and bind less frequently? I'd love to use several shaders at post though.
Another example of what I'm doing at the moment:
1) Loop through GameObjects, bind its phong shader (send color, shadow, spec, normal samplers), unbind all.
2) At post: bind post processor quad, and loop/bind through different shader effects, and so on ...
Thanks all!

• void collision(int v) { collision_bug_one(0.0f, 10.0f); glutPostRedisplay(); glutTimerFunc(1000, collision, 0); } void coll_sprite() { if (board[0][0] == 1) { collision(0); flag[0][0] = 1; } } void erase_sprite() { if (flag[0][0] == 1) { glColor3f(0.0f, 0.0f, 0.0f); glBegin(GL_POLYGON); glVertex3f(0.0f, 10.0f, 0.0f); glVertex3f(0.0f, 9.0f, 0.0f); glVertex3f(1.0f, 9.0f, 0.0f); glVertex3f(1.0f, 10.0f, 0.0f); glEnd(); } } I am using glutTimerFunc to wait a small amount of time to display a collision sprite before I black out the sprite. unfortunately my code only blacks out the said sprite without drawing the collision sprite, I have done a great deal of research on the glutTimerFunc and  animation.
• By Lewa
So, i stumbled upon the topic of gamma correction.
So from what i've been able to gather: (Please correct me if i'm wrong)
Old CRT monitors couldn't display color linearly, that's why gamma correction was nessecary. Modern LCD/LED monitors don't have this issue anymore but apply gamma correction anyway. (For compatibility reasons? Can this be disabled?) All games have to apply gamma correction? (unsure about that) All textures stored in file formats (.png for example) are essentially stored in SRGB color space (as what we see on the monitor is skewed due to gamma correction. So the pixel information is the same, the percieved colors are just wrong.) This makes textures loaded into the GL_RGB format non linear, thus all lighting calculations are wrong You have to always use the GL_SRGB format to gamma correct/linearise textures which are in SRGB format
Now, i'm kinda confused how to proceed with applying gamma correction in OpenGL.
First of, how can i check if my Monitor is applying gamma correction? I noticed in my monitor settings that my color format is set to "RGB" (can't modify it though.) I'm connected to my PC via a HDMI cable. I'm also using the full RGB range (0-255, not the 16 to ~240 range)

What i tried to do is to apply a gamma correction shader shown in the tutorial above which looks essentially like this: (it's a postprocess shader which is applied at the end of the renderpipeline)
vec3 gammaCorrection(vec3 color){ // gamma correction color = pow(color, vec3(1.0/2.2)); return color; } void main() { vec3 color; vec3 tex = texture2D(texture_diffuse, vTexcoord).rgb; color = gammaCorrection(tex); outputF = vec4(color,1.0f); } The results look like this:
No gamma correction:
With gamma correction:

The colors in the gamma corrected image look really wased out. (To the point that it's damn ugly. As if someone overlayed a white half transparent texture. I want the colors to pop.)
Do i have to change the textures from GL_RGB to GL_SRGB in order to gamma correct them in addition to applying the post process gamma correction shader? Do i have to do the same thing with all FBOs? Or is this washed out look the intended behaviour?

• Hi

I am trying to program shadow volumes and i stumbled upon an artifact which i can not find the cause for.
I generate the shadow volumes using a geometry shader with reversed extrusion (projecting the lightfacing triangles to infinity) and write the stencil buffer according to z-fail. The base of my code is the "lighting" chapter from learnopengl.com, where i extended the shader class to include geometry shader. I also modified the "lightingshader" to draw the ambient pass when "pass" is set to true and the diffuse/ specular pass when set to false. For easier testing i added a view controls to switch on/off the shadow volumes' color rendering or to change the cubes' position, i made the lightnumber controllable and changed the diffuse pass to render green for easier visualization of my problem.

The first picture shows the rendered scene for one point light, all cubes and the front cube's shadow volume is the only one created (intentional). Here, all is rendered as it should be with all lit areas green and all areas inside the shadow volume black (with the volume's sides blended over).

If i now turn on the shadow volumes for all the other cubes, we get a bit of a mess, but its also obvious that some areas that were in shadow before are now erroneously lit (for example the first cube to the right from the originaly shadow volumed cube). From my testing the areas erroneously lit are the ones where more than one shadow volume marks the area as shadowed.

To check if a wrong stencil buffer value caused this problem i decided to change the stencil function for the diffuse pass to only render if the stencil is equal to 2. As i repeated this approach with different values for the stencil function i found out that if i set the value equal to 1 or any other uneven value the lit and shadowed areas are inverted and if i set it to 0 or any other even value i get the results shown above.
This lead me to believe that the value and thus the stencil buffer values may be clamped to [0,1] which would also explain the artifact, because twice in shadow would equal in no shadow at all, but from what i found on the internet and from what i tested with
GLint stencilSize = 0; glGetFramebufferAttachmentParameteriv(GL_DRAW_FRAMEBUFFER, GL_STENCIL, GL_FRAMEBUFFER_ATTACHMENT_STENCIL_SIZE, &stencilSize); my stencilsize is 8 bit, which should be values within [0,255].
Does anyone know what might be the cause for this artifact or the confusing results with other stencil functions?

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