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DarkDemon

OpenGL OpenGL Texture IDs.... help please :(

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Hello, I'm still rather at a novice level with Opengl and I've been hitting the same problem for awhile now. I have a proprietary 3Ds loader, and framework. Each of the objects in the scene have their own struct with information about it's structure and texture ID. I've been playing around / debugging for awhile and the texture I load is in never binded to the object and I'm not sure why. When I add break points I can see that glBindTexture(GL_TEXTURE_2D, contains the correct address for this texture ); The problem is it's never drawn, the raw texture is loaded and 2d textures are enabled. I'm using a set of arbitrary values for the tex co ords for now to ensure it's correctly displaying. The framework does read in the tex co ords but for the purposes of testing I've no need to use them yet. So the main problem is the texture is never loaded onto the model I select. I'm not entirely sure why either... I would appreciate any assistance. The project can be downloaded here: http://darkdemon.org/gl/spaceships.zip These are the offending classes, Ball.cpp, where objects are drawn and textures for that object are assigned
#include "ball.h"



void Ball::draw(){
    int l_index;
	glPushMatrix();
  	glTranslatef(x,y,z);

  	if (fileloaded){
    glScalef(0.01f,0.01f,0.01f);
    glRotatef(theta,1.0f,0.0f,0.0f);



	//Whether the object has a defined texture
	if(object.texture != NULL)
	{
	  glEnable(GL_TEXTURE_2D);
	  glBindTexture(GL_TEXTURE_2D,object.texture);
	}
	else
	{
      glDisable(GL_TEXTURE_2D);
	}

	glBegin(GL_TRIANGLES);


    for (l_index=0;l_index<object.polygons_qty;l_index++)
	{

        //----------------- FIRST VERTEX -----------------
        //TEX

		glTexCoord2f(-0.0f,0.0f); // -> arbitrary values to test to see if the texture is loading in

		// Coordinates of the first vertex
        glVertex3f( object.vertex[ object.polygon[l_index].a ].x,
                    object.vertex[ object.polygon[l_index].a ].y,
                    object.vertex[ object.polygon[l_index].a ].z); //Vertex definition

        //----------------- SECOND VERTEX -----------------
		//TEX

		glTexCoord2f(1.0f,0.0f); //-> arbitrary values to test to see if the texture is loading in

        // Coordinates of the second vertex
        glVertex3f( object.vertex[ object.polygon[l_index].b ].x,
                    object.vertex[ object.polygon[l_index].b ].y,
                    object.vertex[ object.polygon[l_index].b ].z);
        
        //----------------- THIRD VERTEX -----------------
		//TEX

		glTexCoord2f(1.0f,1.0f); //-> arbitrary values to test to see if the texture is loading in

        // Coordinates of the Third vertex
        glVertex3f( object.vertex[ object.polygon[l_index].c ].x,
                    object.vertex[ object.polygon[l_index].c ].y,
                    object.vertex[ object.polygon[l_index].c ].z);


		 
    }
	glEnd(); 
   
	//glutSwapBuffers();
  }

  glPopMatrix();
}


And Scene.cpp Where new objects are created and the texture id for an object generated
#include "scene.h"
#include "ball.h"

void Scene::initialise(){


    float startarray[4][6]={{9.0f,9.0f,0.0f,0.1f,-0.25f,0.0f},
                            {7.0f,9.0f,0.0f,0.05,-0.05f,0.0f},
                            {3.0f,9.0f,0.0f,0.01f,-0.02f,0.0f},
                            {0.0f,9.0f,0.0f,0.03f,-0.076f,0.0f}
    };
    nBalls=5;
    myBall=new Ball[nBalls];

	for(int i=0;i<nBalls;i++){
		myBall.initialise(0.0f,0.0f,0.0f);
	
	}

    for(int i=0;i<nBalls;i++){
        myBall.setx(startarray[0]);
        myBall.sety( startarray[1] );
		myBall.setz(startarray[2]  );

        myBall.setvx(startarray[3] );
        myBall.setvy(startarray[4] );
        myBall.setvz(startarray[5] );
       
		myBall.loadfile();
        myBall.setangle();
    }
  
	//setup a particular objects texture
	//generate new glutTextureID ready for binding for this object
	myBall[0].loadTexture("blue.raw");


}
 
void Scene::spinballs(){
  for(int i=0;i<nBalls;i++){
      myBall.spin();
    }
}

void Scene::moveobjects(){
    for(int i=0;i<nBalls;i++){
      myBall.move();
    }
}

void Scene::render(){
  //glColor3f(1.0f,0.0f,0.0f);
//  glTranslatef(x,y,z);
  // glScalef(10.0f,10.0f,10.0f);
  //glutSolidCube(5.0);
  for(int i=0;i<nBalls;i++)
	  myBall.draw();

}

void Scene::cdetect(){
   
    for(int i=0;i<nBalls;i++){
      if((myBall.getx()<-10.0)||(myBall.getx()>10.0))
        myBall.setvx(myBall.getvx()*-1.0f);

      if((myBall.gety()<-10.0)||(myBall.gety()>10.0))
        myBall.setvy(myBall.getvy()*-1.0f);
    }

    for(int i=0;i<nBalls;i++){
	for(int j=i+1;j<nBalls;j++){
	    float tx=myBall.getx()-myBall[j].getx();
	    float ty=myBall.gety()-myBall[j].gety();
	    float tz=myBall.getz()-myBall[j].getz();

            float dist=sqrt(tx*tx+ty*ty+tz*tz);
            if(dist<0.9f){
                float temp=myBall.getvx();
                myBall.setvx(myBall[j].getvx());
                myBall[j].setvx(temp);
                temp=myBall.getvy();
                myBall.setvy(myBall[j].getvy());
                myBall[j].setvy(temp);
                temp=myBall.getvz();
                myBall.setvz(myBall[j].getvz());
                myBall[j].setvz(temp);
	    }
	}
    }
}


[Edited by - DarkDemon on December 16, 2008 8:40:15 AM]

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You made a few mistakes. First you need a valid render context when creating your textures. The second thing is, your data is stored as 24 bit RGB. So you need to change the lines:


unsigned char * data = (unsigned char*) malloc(512*512*3); // <--
fread(data,1,512*512*3,infile); // <-- raw file contains RGB data, not RGBA
fclose(infile);

// ...

glTexImage2D(GL_TEXTURE_2D,0,3,512,512,0,GL_RGB,GL_UNSIGNED_BYTE,data); // <-- changed 3 and GL_RGB


And one last thing. This'll not work...

if(object.texture != NULL)


...because most of your objects texturemembers aren't initialized correctly.

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Thanks David,

I have made those revisions so I can only assume the problem now is with the render context as the texture still doesn't get drawn, I'm not too sure on these though.. I assume that was setup in the viewer class...

Revised source

#include "ball.h"



void Ball::draw(){
int l_index;
glPushMatrix();
glTranslatef(x,y,z);

if (fileloaded){
glScalef(0.01f,0.01f,0.01f);
glRotatef(theta,1.0f,0.0f,0.0f);


glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D,object.texture);

glBegin(GL_TRIANGLES);


for (l_index=0;l_index<object.polygons_qty;l_index++)
{

//----------------- FIRST VERTEX -----------------
//TEX

glTexCoord2f(0.0f,1.0f); // -> arbitrary values to test to see if the texture is loading in

// Coordinates of the first vertex
glVertex3f( object.vertex[ object.polygon[l_index].a ].x,
object.vertex[ object.polygon[l_index].a ].y,
object.vertex[ object.polygon[l_index].a ].z); //Vertex definition

//----------------- SECOND VERTEX -----------------
//TEX

glTexCoord2f(1.0f,1.0f); //-> arbitrary values to test to see if the texture is loading in

// Coordinates of the second vertex
glVertex3f( object.vertex[ object.polygon[l_index].b ].x,
object.vertex[ object.polygon[l_index].b ].y,
object.vertex[ object.polygon[l_index].b ].z);

//----------------- THIRD VERTEX -----------------
//TEX

glTexCoord2f(0.0f,1.0f); //-> arbitrary values to test to see if the texture is loading in

// Coordinates of the Third vertex
glVertex3f( object.vertex[ object.polygon[l_index].c ].x,
object.vertex[ object.polygon[l_index].c ].y,
object.vertex[ object.polygon[l_index].c ].z);
}
glEnd();

}

glPopMatrix();
}






Viewer class

#include "viewer.h"


Viewer::Viewer(){


WinName="";
BufType=GLUT_SINGLE;

for(int i=0;i<3;i++){
background=0.0f;
}

}

Viewer::~Viewer(){
return;
}

void Viewer::Init(int argc,char **argv){

eye[0]=0.0f;
eye[1]=0.5;
eye[2]=25.0;

aim[0]=0.0f;
aim[1]=0.0f;
aim[2]=0.0f;

upright[0]=0.0f;
upright[1]=1.0f;
upright[2]=0.0f;

glutInit(&argc,argv);

}

void Viewer::CreateWin(char *Name,int Width,int Height){
WinName=Name;
WinWidth=Width;
WinHeight=Height;
}

void Viewer::SetValue(myEnum PName,myEnum Type){

switch(PName){
case BUFFER:
if(Type==MDOUBLE)
BufType=GLUT_DOUBLE;
else
if(Type==SINGLE)
BufType=GLUT_SINGLE;
break;
case BACKCOLOUR:
break;
default:
break;
}
}


void Viewer::InitWorld(){
vrman=new WorldManager;
vrman->initialise();

}
void Viewer::InitCamera(){
mycamera=new camera(PERSPECTIVE);
mycamera->SetValue(MNEAR,5.0f);
mycamera->SetValue(YANGLE,45.0f);


mycamera->SetValuev(AIMAT, aim);
mycamera->SetValuev(UPDIRECTION, upright);
mycamera->SetValuev(POSITION, eye);

mycamera->SetValue(MFAR,33.0f);
mycamera->SetValue(HEIGHT,WinHeight);
mycamera->SetValue(ASPECT,1.0f);
}

void Viewer::SetCamera(float nvalue,float viewangle){
mycamera->SetValue(MNEAR, nvalue);
mycamera->SetValue(YANGLE, viewangle);

}

void Viewer::Show(){

GLInit();
glutMainLoop();

}


void Viewer::GLInit(){


glutInitDisplayMode(BufType |GLUT_RGB |GLUT_DEPTH);
glutInitWindowSize(WinWidth, WinHeight);
glutCreateWindow(WinName);
glutReshapeFunc(Reshape);
glutDisplayFunc(Display);
glutMouseFunc(Mouse);
glutIdleFunc(Idle);
glutKeyboardFunc(Keyboard);
glutSpecialFunc(SpecialKey);
// glEnable(GL_DEPTH_TEST);
glClearColor(0.0f,0.0f,0.0f,1.0f);

}


void Viewer::Display(){
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

vrman->exec_loop();

glFlush();
if(BufType==GLUT_DOUBLE){

glutSwapBuffers();
}


}

void Viewer::Reshape(int w,int h){

glViewport(0,0,(GLsizei)w,(GLsizei)h);
WinWidth=w;
WinHeight=h;
mycamera->SetValuev(POSITION,eye);
mycamera->SetValuev(AIMAT,aim);
mycamera->Render();

}

void Viewer::Mouse(int button,int state,int x,int y){

vrman->mouse(button,state,x,y);
Display();
}

void Viewer::Idle(){
vrman->idle();
Display();
}

void Viewer::Keyboard(unsigned char key,int x,int y){

switch(key){
case 0x14b:
case GLUT_KEY_UP:
eye[2]-=0.5;
aim[2]-=0.5;
break;
case GLUT_KEY_DOWN:
eye[2]+=0.5;
aim[2]+=0.5;
break;
case GLUT_KEY_LEFT:
eye[0]-=0.5;
aim[0]-=0.5;
break;
case GLUT_KEY_RIGHT:
eye[0]+=0.5;
aim[0]+=0.5;
break;
default:
vrman->keyboard((unsigned char)key,x,y);
break;
}

Display();
}

void Viewer::SpecialKey(int key, int x, int y){
switch(key){
case GLUT_KEY_F1:
upright[0]=0.0f;
upright[1]=0.0f;
upright[2]=-1.0f;
aim[0]=0.0f;
aim[1]=0.0f;
aim[2]=0.0f;
eye[0]=0.0f;
eye[1]=25.0f;
eye[2]=0.0f;
break;
case GLUT_KEY_F2:
upright[0]=0.0f;
upright[1]=1.0f;
upright[2]=0.0f;
aim[0]=0.0f;
aim[1]=0.0f;
aim[2]=0.0f;
eye[0]=0.0f;
eye[1]=0.5f;
eye[2]=25.0f;
break;
case GLUT_KEY_F12:
vrman->restart();
break;
case GLUT_KEY_UP:
eye[2]-=0.5;
aim[2]-=0.5;
break;
case GLUT_KEY_DOWN:
eye[2]+=0.5;
aim[2]+=0.5;
break;
case GLUT_KEY_LEFT:
eye[0]-=0.5;
aim[0]-=0.5;
break;
case GLUT_KEY_RIGHT:
eye[0]+=0.5;
aim[0]+=0.5;
break;
case GLUT_KEY_PAGE_UP:
eye[1]+=0.5;
aim[1]+=0.5;
break;
case GLUT_KEY_PAGE_DOWN:
eye[1]-=0.5;
aim[1]-=0.5;
break;
default:
vrman->keyboard((unsigned char)key,x,y);
break;
}
mycamera->SetValuev(UPDIRECTION,upright);
mycamera->SetValuev(POSITION,eye);
mycamera->SetValuev(AIMAT,aim);
mycamera->Render();
Display();
}





[Edited by - DarkDemon on December 16, 2008 8:59:39 AM]

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Thanks David,

I'm taking some guesses here, I tried this

http://msdn.microsoft.com/en-us/library/ms537549(VS.85).aspx


Viewer.cpp

void Viewer::Show(){

// create a rendering context
hglrc = wglCreateContext (hdc);

// make it the calling thread's current rendering context
wglMakeCurrent (hdc, hglrc);

GLInit();
glutMainLoop();
}




Still no texture is rendered, I'm probably doing it complely wrong I also read this http://www.nullterminator.net/opengl32.html but I couldn't implement it without messing it up. I've been unable to find any clear simple way to construct one.

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You already create a gl context in GLInit. Just call it before you create the textures (and don't call it twice ;)).

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Thanks David,

I've tried to move it.. still no luck.


Test.cpp
I tried moving ->Show which calls glutInt and the update but I got memory errors.


Viewer *myViewer=new Viewer;
myViewer->Init(argc,argv);
myViewer->InitWorld();
myViewer->SetValue(BUFFER,MDOUBLE);
myViewer->CreateWin("Further Programming 3D",1000,800);
myViewer->InitCamera();
myViewer->Show();







Viewer.cpp I got rid of the GLInit call from the show method, and moved it to InitWorld before everything is created. I get no errors but everything moves slow, and flashes.....

void Viewer::InitWorld(){
GLInit();
vrman=new WorldManager;
vrman->initialise();

}





I've also tried moving myViewer->InitWorld(); below myViewer->Show(); again I get memory problems.


I've also made GLInt public and called it like this


Viewer *myViewer=new Viewer;
myViewer->Init(argc,argv);

myViewer->SetValue(BUFFER,MDOUBLE);
myViewer->CreateWin("Further Programming 3D",1000,800);
myViewer->GLInit();
myViewer->InitWorld();
myViewer->InitCamera();
myViewer->Show();



Everything loaded correctly, but still no texture.

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The flashes are probably becauses you just use a single buffer. Ok... let's see what you can do:


Viewer *myViewer=new Viewer;
myViewer->Init(argc,argv);
myViewer->SetValue(BUFFER,MDOUBLE);
myViewer->CreateWin("Further Programming 3D Apps Assignment: By Adam Davis",1000,800);
myViewer->InitWorld(); // <-- Init the world AFTER creating the window + gl initialization
myViewer->InitCamera();

yViewer->Show();




void Viewer::CreateWin(char *Name,int Width,int Height){
WinName=Name;
WinWidth=Width;
WinHeight=Height;
GLInit(); // <-- Initialize GL after the windows properties are set
}




void Viewer::Show(){

//GLInit(); // <-- Don't initialize GL twice
glutMainLoop();

}



And the other stuff I mentioned before. Have fun! :)

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Thanks David for the help,

That stopped the flicker and the models move fine. Sadly though that annoying issue of the texture not being applied at all seems apparent.

As a test in scene.cpp I call

myBall[0].loadTexture("blue.raw");

This should map the first object with a blue image but it doesn't work.

I did some debugging by adding break points to ensure that the image does get loaded. I also tested to ensure that inside draw glBindTexture(GL_TEXTURE_2D,object.texture); contains the correct address for the image, and it does which is something I can't understand. Everything is loaded in but it doesn't appear to be applied, I know the text co ords are just arb values but I would aspect to see least some of the blue from the image on the object.

- Again thanks again for the help it's been like hitting a brick wall.


#include "ball.h"



void Ball::draw(){
int l_index;
glPushMatrix();
glTranslatef(x,y,z);

if (fileloaded){
glScalef(0.01f,0.01f,0.01f);
glRotatef(theta,1.0f,0.0f,0.0f);

glEnable(GL_TEXTURE_2D);
glBindTexture(GL_TEXTURE_2D,object.texture);
glBegin(GL_TRIANGLES);


for (l_index=0;l_index<object.polygons_qty;l_index++)
{

//----------------- FIRST VERTEX -----------------
//TEX

glTexCoord2f(0.0f,1.0f); // -> arbitrary values to test to see if the texture is loading in

// Coordinates of the first vertex
glVertex3f( object.vertex[ object.polygon[l_index].a ].x,
object.vertex[ object.polygon[l_index].a ].y,
object.vertex[ object.polygon[l_index].a ].z); //Vertex definition

//----------------- SECOND VERTEX -----------------
//TEX

glTexCoord2f(1.0f,1.0f); //-> arbitrary values to test to see if the texture is loading in

// Coordinates of the second vertex
glVertex3f( object.vertex[ object.polygon[l_index].b ].x,
object.vertex[ object.polygon[l_index].b ].y,
object.vertex[ object.polygon[l_index].b ].z);

//----------------- THIRD VERTEX -----------------
//TEX

glTexCoord2f(0.0f,1.0f); //-> arbitrary values to test to see if the texture is loading in

// Coordinates of the Third vertex
glVertex3f( object.vertex[ object.polygon[l_index].c ].x,
object.vertex[ object.polygon[l_index].c ].y,
object.vertex[ object.polygon[l_index].c ].z);
}
glEnd();

}

glPopMatrix();
}





[Edited by - DarkDemon on December 16, 2008 8:52:05 AM]

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You forgot to set the minifying function. The GL expects GL_LINEAR_MIPMAP_NEAREST as default, and you end up with an uncomplete textureobject.

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      (here is the full shader source code if someone wants to take a look at it)
      Now, i suspect that the normals are the culprit.
      vec3 normal = ((uNormalViewMatrix*vec4(normalize(texture2D(sNormals, vTexcoord).rgb),1.0)).xyz); "sNormals" is a 2D texture which stores the normals in world space in a RGB FP16 buffer.
      Now i can't use the camera viewspace matrix to transform the normals into viewspace as the cameras position isn't set at (0,0,0), thus skewing the result.
      So what i did is to create a new viewmatrix specifically for this normal without the position at vec3(0,0,0);
      //"camera" is the camera which was used for rendering the normal buffer renderer.setUniform4m(ressources->shaderSSAO->getUniform("uNormalViewMatrix"), glmExt::createViewMatrix(glm::vec3(0,0,0),camera.getForward(),camera.getUp())//parameters are (position,forwardVector,upVector) ); Though i have the feeling this is the wrong approach. Is this right or is there a better/correct way of transforming a world space normal into viewspace?
    • By HawkDeath
      Hi,
      I'm trying mix two textures using own shader system, but I have a problem (I think) with uniforms.
      Code: https://github.com/HawkDeath/shader/tree/test
      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.


    • By norman784
      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
    • By Hashbrown
      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! 
    • By phil67rpg
      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.
      https://learnopengl.com/Advanced-Lighting/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?
    • By OneKaidou
      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?
       
      // [the following code includes all used gl* functions, other parts are due to readability partialy excluded] // glfw: initialize and configure // ------------------------------ glfwInit(); glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4); glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 4); glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE); // glfw window creation // -------------------- GLFWwindow* window = glfwCreateWindow(SCR_WIDTH, SCR_HEIGHT, "LearnOpenGL", NULL, NULL); if (window == NULL) { cout << "Failed to create GLFW window" << endl; glfwTerminate(); return -1; } glfwMakeContextCurrent(window); glfwSetFramebufferSizeCallback(window, framebuffer_size_callback); glfwSetCursorPosCallback(window, mouse_callback); glfwSetScrollCallback(window, scroll_callback); // tell GLFW to capture our mouse glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED); // glad: load all OpenGL function pointers // --------------------------------------- if (!gladLoadGLLoader((GLADloadproc)glfwGetProcAddress)) { cout << "Failed to initialize GLAD" << endl; return -1; } // ==================================================================================================== // window and functions are set up // ==================================================================================================== // configure global opengl state // ----------------------------- glEnable(GL_DEPTH_TEST); glEnable(GL_CULL_FACE); // build and compile our shader program [...] // set up vertex data (and buffer(s)) and configure vertex attributes [...] // shader configuration [...] // render loop // =========== while (!glfwWindowShouldClose(window)) { // input processing and fps calculation[...] // render // ------ glClearColor(0.1f, 0.1f, 0.1f, 1.0f); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); glDepthMask(GL_TRUE); //enable depth writing glDepthFunc(GL_LEQUAL); //avoid z-fighting //draw ambient component into color and depth buffer view = camera.GetViewMatrix(); projection = glm::perspective(glm::radians(camera.Zoom), (float)SCR_WIDTH / (float)SCR_HEIGHT, 0.1f, 100.0f); // setting up lighting shader for ambient pass [...] // render the cubes glBindVertexArray(cubeVAO); for (unsigned int i = 0; i < 10; i++) { //position cube [...] glDrawArrays(GL_TRIANGLES, 0, 36); } //------------------------------------------------------------------------------------------------------------------------ glDepthMask(GL_FALSE); //disable depth writing glEnable(GL_BLEND); glBlendFunc(GL_ONE, GL_ONE); //additive blending glEnable(GL_STENCIL_TEST); //setting up shadowShader and lightingShader [...] for (int light = 0; light < lightsused; light++) { glDepthFunc(GL_LESS); glClear(GL_STENCIL_BUFFER_BIT); //configure stencil ops for front- and backface to write according to z-fail glStencilOpSeparate(GL_FRONT, GL_KEEP, GL_DECR_WRAP, GL_KEEP); //-1 for front-facing glStencilOpSeparate(GL_BACK, GL_KEEP, GL_INCR_WRAP, GL_KEEP); //+1 for back-facing glStencilFunc(GL_ALWAYS, 0, GL_TRUE); //stencil test always passes if(hidevolumes) glColorMask(GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE); //disable writing to the color buffer glDisable(GL_CULL_FACE); glEnable(GL_DEPTH_CLAMP); //necessary to render SVs into infinity //draw SV------------------- shadowShader.use(); shadowShader.setInt("lightnr", light); int nr; if (onecaster) nr = 1; else nr = 10; for (int i = 0; i < nr; i++) { //position cube[...] glDrawArrays(GL_TRIANGLES, 0, 36); } //-------------------------- glDisable(GL_DEPTH_CLAMP); glEnable(GL_CULL_FACE); glStencilFunc(GL_EQUAL, 0, GL_TRUE); //stencil test passes for ==0 so only for non shadowed areas glStencilOp(GL_KEEP, GL_KEEP, GL_KEEP); //keep stencil values for illumination glColorMask(GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE); //enable writing to the color buffer glDepthFunc(GL_LEQUAL); //avoid z-fighting //draw diffuse and specular pass lightingShader.use(); lightingShader.setInt("lightnr", light); // render the cubes for (unsigned int i = 0; i < 10; i++) { //position cube[...] glDrawArrays(GL_TRIANGLES, 0, 36); } } glDisable(GL_BLEND); glDepthMask(GL_TRUE); //enable depth writing glDisable(GL_STENCIL_TEST); //------------------------------------------------------------------------------------------------------------------------ // also draw the lamp object(s) [...] // glfw: swap buffers and poll IO events (keys pressed/released, mouse moved etc.) // ------------------------------------------------------------------------------- glfwSwapBuffers(window); glfwP } // optional: de-allocate all resources once they've outlived their purpose: // ------------------------------------------------------------------------ glDeleteVertexArrays(1, &cubeVAO); glDeleteVertexArrays(1, &lightVAO); glDeleteBuffers(1, &VBO); // glfw: terminate, clearing all previously allocated GLFW resources. // ------------------------------------------------------------------ glfwTerminate(); return 0;  
    • By Green_Baron
      Hi,
      i am self teaching me graphics and oo programming and came upon this:
      My Window class creates an input handler instance, the glfw user pointer is redirected to that object and methods there do the input handling for keyboard and mouse. That works. Now as part of the input handling i have an orbiting camera that is controlled by mouse movement. GLFW_CURSOR_DISABLED is set as proposed in the glfw manual. The manual says that in this case the cursor is automagically reset to the window's center. But if i don't reset it manually with glfwSetCursorPos( center ) mouse values seem to add up until the scene is locked up.
      Here are some code snippets, mostly standard from tutorials:
      // EventHandler m_eventHandler = new EventHandler( this, glm::vec3( 0.0f, 5.0f, 0.0f ), glm::vec3( 0.0f, 1.0f, 0.0f ) ); glfwSetWindowUserPointer( m_window, m_eventHandler ); m_eventHandler->setCallbacks(); Creation of the input handler during window creation. For now, the camera is part of the input handler, hence the two vectors (position, up-vector).  In future i'll take that functionally out into an own class that inherits from the event handler.
      void EventHandler::setCallbacks() { glfwSetCursorPosCallback( m_window->getWindow(), cursorPosCallback ); glfwSetKeyCallback( m_window->getWindow(), keyCallback ); glfwSetScrollCallback( m_window->getWindow(), scrollCallback ); glfwSetMouseButtonCallback( m_window->getWindow(), mouseButtonCallback ); } Set callbacks in the input handler.
      // static void EventHandler::cursorPosCallback( GLFWwindow *w, double x, double y ) { EventHandler *c = reinterpret_cast<EventHandler *>( glfwGetWindowUserPointer( w ) ); c->onMouseMove( (float)x, (float)y ); } Example for the cursor pos callback redirection to a class method.
      // virtual void EventHandler::onMouseMove( float x, float y ) { if( x != 0 || y != 0 ) { // @todo cursor should be set automatically, according to doc if( m_window->isCursorDisabled() ) glfwSetCursorPos( m_window->getWindow(), m_center.x, m_center.y ); // switch up/down because its more intuitive m_yaw += m_mouseSensitivity * ( m_center.x - x ); m_pitch += m_mouseSensitivity * ( m_center.y - y ); // to avoid locking if( m_pitch > 89.0f ) m_pitch = 89.0f; if( m_pitch < -89.0f ) m_pitch = -89.0f; // Update Front, Right and Up Vectors updateCameraVectors(); } } // onMouseMove() Mouse movement processor method. The interesting part is the manual reset of the mouse position that made the thing work ...
      // straight line distance between the camera and look at point, here (0,0,0) float distance = glm::length( m_target - m_position ); // Calculate the camera position using the distance and angles float camX = distance * -std::sin( glm::radians( m_yaw ) ) * std::cos( glm::radians( m_pitch) ); float camY = distance * -std::sin( glm::radians( m_pitch) ); float camZ = -distance * std::cos( glm::radians( m_yaw ) ) * std::cos( glm::radians( m_pitch) ); // Set the camera position and perspective vectors m_position = glm::vec3( camX, camY, camZ ); m_front = glm::vec3( 0.0, 0.0, 0.0 ) - m_position; m_up = m_worldUp; m_right = glm::normalize( glm::cross( m_front, m_worldUp ) ); glm::lookAt( m_position, m_front, m_up ); Orbiting camera vectors calculation in updateCameraVectors().
      Now, for my understanding, as the glfw manual explicitly states that if cursor is disabled then it is reset to the center, but my code only works if it is reset manually, i fear i am doing something wrong. It is not world moving (only if there is a world to render :-)), but somehow i am curious what i am missing.
       
      I am not a professional programmer, just a hobbyist, so it may well be that i got something principally wrong :-)
      And thanks for any hints and so ...
       
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