OpenGL fragment shader not writing to fbo color buffer
I'm having trouble writing from my fragment shader to a color buffer in the FBO. The idea is to draw to this texture, and then draw this texture into a quad. The thing is, the shader works when drawing to the default window buffer, since if I remove the FBO, the scene is displayed. And the texturing of the quad works too, I tried it with an imported texture, and it showed. All I'm getting is a black screen. What could have gone wrong? :(
Code for creating the FBO:
glGenFramebuffers(1, &fbo);
glBindFramebuffer(GL_FRAMEBUFFER, fbo);
glGenRenderbuffers(1, &depthbuff); //Add a depth renderbuffer for depth testing
glBindRenderbuffer(GL_RENDERBUFFER, depthbuff);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT, width, height);
glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depthbuff);
//Add the buffer to be drawn to and the buffer for the picking information
glGenTextures(1, &drawbuff);
glBindTexture(GL_TEXTURE_2D, drawbuff);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, 0);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, drawbuff, 0);
glGenTextures(1, &pickingbuff);
glBindTexture(GL_TEXTURE_2D, pickingbuff);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, 0);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT1, GL_TEXTURE_2D, pickingbuff, 0);
Code for rendering:
glBindFramebuffer(GL_FRAMEBUFFER, fbo);
GLenum buffers[] = { GL_COLOR_ATTACHMENT0, GL_COLOR_ATTACHMENT1 };
glDrawBuffers(2, buffers);
shader->bind(); //If the three lines above are removed, it draws correctly to the window
drawStuff();
Code for the quad:
quadshader->bind();
glEnable(GL_TEXTURE_2D);
int drawTexID = quadshader->uniformLocation("drawTex");
glActiveTexture(GL_TEXTURE0);
//glBindTexture(GL_TEXTURE_2D, anotherTexture); //This works. A texture imported from a TGA
glBindTexture(GL_TEXTURE_2D, drawbuff);
glUniform1i(drawTexID, 0);
drawQuad();
And lastly, the frag shader, I just set it to draw everything to a solid color:
void main(void) {
gl_FragData[0] = vec4(1.0, 1.0, 0.0, 1.0);
gl_FragData[1] = vec4(0.0, 1.0, 1.0, 1.0);
}
EDIT: If it is of any help, the whole thing is in a Qt GLWidget.
Are you careful to make sure that you're texture is not simultaneously bound to a sampler (glBindTexture), and a framebuffer? I believe the behavior is either an error or undefined if you try to write to a texture while it's bound to an active sampler, or if you try to sample a texture while it's attached to an active framebuffer.
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