Hi people,
you've probably seem this already, but I thought it might be useful to
paste the error message from the console log for the crashes I've been
experiencing attempting to use Vertex Displacement Mapping in Quartz
Composer.
07/11/2007 00:22:25
[0x0-0x50050].com.apple.QuartzComposer.editor[561] Error:
MPEG2Decompressor[0x1c85d5a0]: bad picture_coding_type (number =3D 0,
size =3D 4)
07/11/2007 00:23:28 com.apple.launchd[83]
([0x0-0x50050].com.apple.QuartzComposer.editor[561]) Exited
abnormally: Bus error
Maybe this throws some light on the issue.
I'd love to find a workaround for this. VDM is such a powerful
technique, opening up all sorts of avenues for creating and distorting
geometry, that it would be a real shame if we can't get it to work on
moving images, or at least filtered static images. It seems like any
process in QC, be it a custom CoreImage filter, one of the builtin FX
patches, or even nesting the movie in a Render in Image patch, results
in a crash when the image goes into the Vertex Shader of the GLSL patch.
This section from the tutorial I was following may be significant,
since it seems to relate to the input image format:
To achieve vertex displacement mapping, there are two main constraints:
• The displacement map must be in floating point format. In OpenGL
terms, that means an internal pixel format that is set to
GL_RGBA_FLOAT32_ATI (valid on ATI as well as on nVidia).
• The displacement map must not be filtered: no linear or trilinear
filtering. Nearest mode is the only one accepted.
Thus once the displacement map is loaded in floating point format with
nearest filtering, displacement mapping becomes really simple as shown
in the following vertex / pixel shader:
Could this be the solution, or at least suggest a solution?
Incidentally, the instructions I've been following are from this page:
http://www.ozone3d.net/tutorials/vertex_displacement_mapping_p03.php
There may be some other information there of relevance to someone more
3D math-literate than myself.
Sorry to keep hassling you all about this one, but I just think it
would be so good to be able to get this to work.
alx
http://www.toneburst.net
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