Hi,
By trial and error, I determined that the COLOR output of
my vertex program was being clamped to the range [0,1].
I would have expected that the clamping would occur only
on the output of the fragment program. I worked around
this by storing the value in TEXCOORD0 instead.
Where is this information documented? I couldn't find it
in the Cg Toolkit User's Manual.
I don't like this behavior, it seems too much like magic.
I understand why the fragment color output needs to be
clamped, but it doesn't seem necessary for the vertex
color output.
I think I read once that it is possible to create your own
custom semantics, but again I couldn't find this in the
User's Manual (maybe I read it in the Cg Tutorial book,
which I don't currently have access to). Is this true? If
I am imagining this, the rest of the paragraph does not
apply. Is it possible to create a custom semantic that
clamps the value passed from the vertex to the fragment
program? If not, this is an example of what I mean by magic:
an un-/poorly-documented exception to the core model of
the language/runtime that can only be achieved by hacking
the framework itself (not just by using the framework).
Maybe I'm missing something obvious about why this clamping
behavior is intuitive and/or necessary. If so, please
enlighten me.
Thank you,
Josh
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