Yes, any crash is a bug and we would appreciate bug reports at
developer.apple.com/bugreporter. Hitting send on the crash report also
reaches us but it is much better for us if you use bug reporter
because it goes directly into our system.
Thanks,
Troy
On Dec 13, 2007, at 6:24 AM, Alex Drinkwater wrote:
Hi Chris,
-
-- Christopher Wright <[EMAIL PROTECTED]> wrote:
1. Not all graphics hardware supports Sampler2D
input
to a vertex shader
Crashing probably isn't the Right Thing to do in
this case though :) A
simple "Not Supported" log message would suffice :)
That said, I
don't think this cause is the problem he's running
into, since, as you
mention, it works with still images.
No, you're right there. If your hardware won't support
Vertex Shader images, I think you get an error message
saying so, rather than a crash. It's still worth
bearing in mind though.
2. There's a but in QC that means only still
images
can be input to a vertex shader.
This isn't quite accurate. You can have animating
images (Plasma and
Flame Image, for example, work perfectly 100%) that
work. Similarly,
you can have a still image that gets statically
filtered (through a
Gaussian Blur, for example) and it'll crash it
Guaranteed, even though
it's not 'moving'. So it looks like it's more of a
GL/Core Image bug
than a moving image bug. Semantics, I know :)
Ah, no; semantics are good. Especially if they help
track down the cause of the problem. If this is a
low-level Core Image bug, I wonder if it will be fixed
with a future OS update. Don't imagine it's very high
up anyone's 'to do' list though. It would be nice to
know definitevely if it is a CI thing, or a QC
problem though. I was very disappointed when I hit
this issue myself,
There is a more universally-compatible way of
doing
something similar, using something called VBOs
(Vertex
Buffer Objects), but I'm not sure that method can
be
implemented in GLSL. You'd probably have to write
a
custom QC plugin using OpenGL commands.
This would work. Unfortunately, you lose the
possibility of having
the displacement take place in hardware though
(which might end up be
expensive for complex models)... but maybe I'm
mistaken on this
point? I'm pretty new to shaders.
I'm a complete GLSL/OpenGL newbie myself. From the
little reading I've done around this (and the even
smaller proportion of that reading I've actually
understood), it seems the VBO method is in fact very
fast, and can be made to run entirely on the GPU. I've
no real idea how to implement the method as a QC
plugin, however, or if it can be in a GLSL vertex
shader.
alx
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