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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