Why can't I render objects to texture properly using FBO?
- by Brett
Hello,
I'm trying to implement a simple program using 3 FBO's to render a scene to a texture and display a textured quad. I've successfully done this previously using fragment shaders before projecting to the textured quad but can't get it to work without a shader. What could be wrong?
First I set up my textures
glGenTextures(3, renderTextureID);
for (GLint i = 0; i < 3; i++)
{
glBindTexture(GL_TEXTURE_2D, renderTextureID[i]);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
// this may change with window size changes
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, fboWidth, fboHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE, 0);
}
Next some framebuffer state
glGenFramebuffersEXT(3, framebufferID);
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, framebufferID[0]);
glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, renderTextureID[0], 0);
GLenum fboStatus = glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT);
if(fboStatus != GL_FRAMEBUFFER_COMPLETE_EXT)
{
fprintf(stderr, "FBO Error!");
}
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, framebufferID[1]);
glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, renderTextureID[1], 0);
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, framebufferID[2]);
glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, renderTextureID[2], 0);
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
Then I render the scene
glViewport(0, 0, fboWidth, fboHeight);
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, framebufferID[0]);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
drawModels();
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
glBindTexture(GL_TEXTURE_2D, renderTextureID[0]);
glEnable(GL_SCISSOR_TEST);
glViewport(windowWidth/2, 0, fboWidth, fboHeight);
glScissor(windowWidth/2, 0, fboWidth, fboHeight);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glBegin(GL_QUADS);
glTexCoord2i(0, 0);
glVertex2f(-1.0f, -1.0f);
glTexCoord2i(1, 0);
glVertex2f(1.0f, -1.0f);
glTexCoord2i(1, 1);
glVertex2f(1.0f, 1.0f);
glTexCoord2i(0, 1);
glVertex2f(-1.0f, 1.0f);
glEnd();
glDisable(GL_SCISSOR_TEST);
glutSwapBuffers();
The result is a yellow square. Draw models draws yellow wireframe cubes if not using the FBO so the problem is not that. I've read a previous similar post that talks about using glTexParameterf after generating and binding textures but i've done this.
Thanks...
