OpenGL FBO Rendering

Question

I'm getting some artifacts when I try to use a colour attachment on an FBO. I'm saving my first pass as a texture, then passing it as an input to an anti-aliasing shader. The result is, as below, some weird noise and an enforced black background. The AA is applied fine.

GL.BindFramebuffer(FramebufferTarget.FramebufferExt, _hndFBO);
GL.BindTexture(TextureTarget.Texture2D, 0);
GL.DrawBuffer((DrawBufferMode) FramebufferAttachment.ColorAttachment0Ext);
GL.PushAttrib(AttribMask.ViewportBit);
GL.Viewport(0, 0, _intWidth, _intHeight);
//Do rendering here
GL.PopAttrib();
GL.BindFramebuffer(FramebufferTarget.FramebufferExt, 0);
GL.DrawBuffer(DrawBufferMode.Back);

Any ideas? Need more code?

Answer 1

Are you clearing the back buffer before you render to it each frame?

I'm assuming magenta is "transparent" in the first picture. If so, the parts of the back-buffer where there is no terrain are not affected. Residual data could very well account for what you are seeing.