OpenGL multiple render target FBO with multisampling - requirements

Question

When creating a multisample FBO, do all attached target textures need to be multisample-textures?

Answer 1

Section 9.4.2 Whole Framebuffer Completeness of the spec states:

The framebuffer object bound to target is said to be framebuffer complete if all the following conditions are true:
[...]

• The value of RENDERBUFFER_SAMPLES is the same for all attached renderbuffers; the value of TEXTURE_SAMPLES is the same for all attached textures; and, if the attached images are a mix of renderbuffers and textures, the value of RENDERBUFFER_SAMPLES matches the value of TEXTURE_SAMPLES.

So yes, the number of samples has to be the same for all attached textures and renderbuffers.

Answer 2

I think so.

§ 9.2.3.1 Multisample Queries

The values of SAMPLE_BUFFERS and SAMPLES control whether and how multisampling is performed (...).

If a framebuffer object is not framebuffer complete (...), then the values of SAMPLE_BUFFERS and SAMPLES are undefined.

Otherwise, the value of SAMPLES is equal to the value of RENDERBUFFER_SAMPLES or TEXTURE_SAMPLES (depending on the type of the attached images), which must all have the same value.

(emphasis mine)