OpenGL 16 bit stencil buffers?

Question

I am trying to create framebuffer with 4 colour attachments, a 16 bit depth buffer and a 16 bit stencil buffer. I need 16 bits for the stencil buffer because I store object ID's in them for object picking, and I have a lot more then 255 objects. I create two render buffers:

glBindRenderbuffer(GL_RENDERBUFFER, mID);
glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, width, height);

glBindRenderbuffer(GL_RENDERBUFFER, mID2);
glRenderbufferStorage(GL_RENDERBUFFER, GL_STENCIL_INDEX16, width, height);
glBindRenderbuffer(GL_RENDERBUFFER, 0);

I ask SDL to give me 16 bit stencils:

SDL_GL_SetAttribute(SDL_GL_STENCIL_SIZE, 16);

But when I bind the stencil render buffer to the framebuffer I get a framebuffer incomplete error. I know the wiki states that GL_STENCIL_INDEX16 is not required by the spec. Is it not possible to create 16 stencil buffers? Could I encode the object ID integers down to 8 bit values?

user_5577765 · Answer

A separate depth and stencil buffer attachment need not be supported.

See OpenGL 4.6 API Core Profile Specification - 9.4.3 Required Framebuffer Formats

[...] However, when both depth and stencil attachments are present, implementations are only required to support framebuffer objects where both attachments refer to the same image.

_{See also:
Unable to attach separate stencil buffer to FBO (packed depth+stencil is fine)
Framebuffer Object - Completeness Rules}

OpenGL 16 bit stencil buffers?

1 Answers