Commen=
t # 7
on bug 10660=
1
from Yunchao He
#5, In GL 3.0. RGB32F is color-renderable for texture-only. It=
is not
color-renderable for renderbuffer. But we do use A TEXTURE with RGB32F as
color-attachment and then check the framebuffer attachment, it says framebu=
ffer
incomplete on Intel mesa driver. It is OK for Intel Windows GL driver and I=
ntel
MacOS GL driver. It's also OK for NVIDIA and AMD (Windows, MacOS, Linux, et=
c).
For this statement to check framebuffer completeness below:
"""
Required Framebuffer Formats
Implementations must support framebuffer objects with up to MAX COLOR
ATTACHMENTS color attachments, a depth attachment, and a stencil attachment.
Each color attachment may be in any of the required color formats for textu=
res
and renderbuffers described in sections 3.9.1 and 4.4.2.
"""
My understanding is that the color formats for a color attachment should be
color-renderable for a texture, or color-renderable for a renderbuffer. It =
is
not required that the color format should be color-renderable both for a
texture and a renderbuffer. If you attach a texture with a color-renderable
format, that format is not color-renderable for a renderbuffer (like RGB32F=
),
it doesn't matter. This is A TEXTURE, not a renderbuffer. There is no reason
that we need to go through renderbuffer's color-renderable formats for a
texture. In short, this statements says that color attachment should be
attached an image which is color-renderable, no matter it is a texture or a
renderbuffer.=20
In addition, why you say "GL_RGB32F is marked as color-renderable, but=
not
required to be renderable"? My understanding is that, a format is
color-renderable (or depth-renderable, or stencil renderable), it must be
renderable. But a color-renderable format for texture is not guaranteed to =
be
color-renderable for renderbuffer.=20
Let's discuss this issue from a different perspective. You know, for a text=
ure,
it has 2 main usage: 1) sample (or read) from a texture, 2) draw (or write)=
to
a texture. If a format is color-renderable for a texture, but we can't atta=
ch
it to a FB/FBO, I don't know how could we draw into this kind of texture. A=
s a
result, it makes no sense that we say it is color-renderable. So I think
attaching a color-renderable format to a fbo should be valid.=20
But for same other formats which is used only for sampling from a texture, =
it
can be not renderable. That formats can't be attached to a fbo and used as a
render target.=20
However, RGB32F is claimed as color-renderable in OpenGL. So texture with t=
his
format can be rendered into without error.=20
For a renderbuffer, It is mainly used to draw. We can't sample from a
renderbuffer (although we can call readpixel to read AFTER you draw somethi=
ng).
So all formats for a renderbuffer should be renderable (color-renderable,
depth-renderable, etc).=20=20
Please correct me if I am wrong. Any other comments are welcome too.