pbuffers / depth_component internalForma

[execom_rt]

This is the continuation of this answered post (http://lists.apple.com/archives/mac-opengl/2004/Mar/msg00162.html) .

How works PBuffers with AGL and GL_DEPTH_COMPONENT?

It seems that creating PBuffer with GL_DEPTH_COMPONENT returns no error on ATI video cards although this feature (rendering to depth possible) is not possible on thoses video cards ?

Do we have to check the ATI vendor string and check for ATI or it is a safer way to do that ?
Or just consider that GL_DEPTH_COMPONENT with PBuffer is unsupported and use glRead method ?

Another question, how to create floating point depth texture ?

Is GL_LUMINANCE_FLOAT32_APPLE as internal format is sufficient ? Then which parameters to pass to aglChoosePixelFormat ? AGL_RGBA ?

Thanks;