🔒 Locked

render to 3D texture

Started by blubberbert Aug 22, 2011 at 7:02 PM 0 replies 2.8k views

Original Post

Aug 22, 2011 at 7:02 PM

im working on a volumetric renderer and want to implement updating mechanisms to the volume (wich is represented as 3D texture)

i wanted to know wether and how rendering to 3D textures is possibly (there is glFramebufferTexture3D but i dont quite get the rest)

so normally(when rendering to 2D textures) i would bind a framebuffer with the target texture and in my fragment shader do something like:


 gl_FragData[0] = stuff.xyzw;

but since the fragment shader is run after the projection, coordinates should be 2d.
basically what im looking for is a way to write to a specific position in the 3D texture, lets say [0.43,0.5,0.7] without uploading the data from RAM
but instead writing it from a shader

blubberbert

Author

blubberbert

Aug 25, 2011 at 8:56 PM

ok so after many sleepless nights (and no replies here

)
i finally found out how to do it


 
 void buildFramebuffer()
 {
 renderTarget = new Texture3D(GL_RGB, GL_RGB8, GL_UNSIGNED_BYTE, GL_LINEAR, GL_CLAMP_TO_EDGE, 100,100,100,NULL);
 glGenFramebuffers(1, &framebuffer);
 glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);
 glFramebufferTexture3D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_3D, renderTarget->getId(), 0, 0);
 GLenum buffers[] = { GL_COLOR_ATTACHMENT0 };
 glDrawBuffers(1, buffers);
 glReadBuffer(GL_NONE);
 GLenum status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
 glBindFramebuffer(GL_FRAMEBUFFER, 0);
 printf("Framebuffer status: %s\n", status == GL_FRAMEBUFFER_COMPLETE?"OK":"ERROR");
 }
 
 void fillTarget()
 {
 glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);
 glPushAttrib(GL_VIEWPORT_BIT);
 glViewport(0,0,100,100);
 for(int i = 0; i < 100; i++)
 {
 glFramebufferTextureLayer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, renderTarget->getId(), 0, i);
 glClearColor(1.0f,(1.0f/100.0f)*((float)i),0.0f,1.0f);
 glClear(GL_COLOR_BUFFER_BIT);
 glMatrixMode(GL_MODELVIEW);
 glLoadIdentity();
 glTranslatef(0.0f,0.0f,-5.0f);
 glColor3f(0.0f, 1.0f, 1.0f);
 glBegin(GL_TRIANGLES);
 glVertex3f(-1.0f,0.0f,0.0f);
 glVertex3f( 0.0f,1.0f,0.0f);
 glVertex3f( 1.0f,0.0f,0.0f);
 glEnd();
 }
 glPopAttrib();
 glBindFramebuffer(GL_FRAMEBUFFER, 0);
 }
 
 void draw()
 {
 fillTarget();
 glClearColor(0.0f,0.0f,1.0f,1.0f);
 glClear(GL_COLOR_BUFFER_BIT);
 glEnable(GL_TEXTURE_3D);
 renderTarget->bind();
 glColor3f(1.0f,1.0f,1.0f);
 glBegin(GL_QUADS);
 glTexCoord3f(0.0f,0.0f,1.0f); glVertex3f(-1.0f, 1.0f,0.0f);
 glTexCoord3f(0.0f,1.0f,1.0f); glVertex3f(-1.0f,-1.0f,0.0f);
 glTexCoord3f(1.0f,1.0f,1.0f); glVertex3f( 1.0f,-1.0f,0.0f);
 glTexCoord3f(1.0f,0.0f,1.0f); glVertex3f( 1.0f, 1.0f,0.0f);
 glEnd();
 Texture3D::unbind();
 SDL_GL_SwapBuffers();
 }

just posting this here for the people facing similar problems

this code should render a blue background with a yellow quad in the center with a turquoise triangle in it
(the quad is yellow because the texcoords Z is 1 if it were 0 the quad would be red)
however if someone finds anything wrong with my code feel free to point any mistakes out (apart from every 2nd function call being deprecated)

Topic Locked

This topic has been locked by a moderator. New replies are not allowed.