GLSL image2D antialiasing

Question

Is it possible to set MSAA sampling for image2D? Can it be of multisampled type as texture2D in OpenGL? I am writing first pass not to a render buffer (or texture) but to image where I store several pixel copies of the same primitive but at different offsets.Then I blit it to the main window frame buffer.The output has a strong aliasing and I wonder if it's possible to make the first pass to use MSAA.

Answer 1

No, an image2D cannot be multisampled.

An image2DMS can however; indeed, it must. Remember: multisample textures represent a fundamentally different texture type from 2D textures. They're just as different from 2D textures as 3D textures are.

Answer 2

Yes, use glTexImage2DMultisample instead of glTexImage2D for your render-to-texture target.

In the shader that you use for blitting the texture to the screen, use a sampler2DMS instead of a sampler2D, and texelFetch instead of texture2D.

You'll have to call texelFetch several times, one per sample, and average yourself.