hi there,
i'm stuck with a problem that really drives me nuts: i have a fairly complex 3d scene. my aim is to take a snapshot of a part of this scene via pix_snap2tex, render this texture on a rectangle that covers exactly the same area where the snapshot has been taken and do this over and over again to create trails of objects moving over this part of the scene. now, no matter what i do, the positions of the moving objects and their representations in the snapshots are always slightly off. as a result, the trails are not what they are supposed to be - they tend to vanish in the middle of the snapshot, instead of representing the motion of the moving objects. everything is perfectly fine when doing the same thing with just a single [rectangle 5.33333 4] filling the whole screen, so it works in principle. but i do need to have other parts of the scene visible as well ...
i guess that OpenGL's perspective calculations are kicking in here - is there any way of preventing this? i extensively played around to get this straight: among other things, i tried [ortho], another attempt was to make the single rectangle partly transparent with [alpha], but none of these ideas worked.
i greatly appreciate any help -
thank you, thoralf.
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hi thorolf,
now, no matter what i do, the positions of the moving objects and their representations in the snapshots are always slightly off.
i know the problem and it was also mentioned/discussed in an exchange on the gem-dev list in august or september, search under motion blur. fact is that the trails and motionblur only work "exact" when the gemwin is rectangular and the snap and the square where the texture is glued onto has the same size then the gemwin. why - i dont know - and was also back then not answerd.
best
erich
as a result, the trails are not
what they are supposed to be - they tend to vanish in the middle of the snapshot, instead of representing the motion of the moving objects. everything is perfectly fine when doing the same thing with just a single [rectangle 5.33333 4] filling the whole screen, so it works in principle. but i do need to have other parts of the scene visible as well ...
i guess that OpenGL's perspective calculations are kicking in here - is there any way of preventing this? i extensively played around to get this straight: among other things, i tried [ortho], another attempt was to make the single rectangle partly transparent with [alpha], but none of these ideas worked.
i greatly appreciate any help -
thank you, thoralf.
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hi erich,
--- Erich Berger eb@randomseed.org wrote:
why - i dont know - and was also back then not answerd.
thank you ... i got it to work by grabbing the whole gemwin with pix_snap rather than pix_snap2tex, applying an pix_alpha to make any black pixels in the snapshot transparent and texturing on a full-screen rectangle afterwards. however, due to its high ressource consumption, this workaround is almost good for nothing :-(
with kind regards, thoralf.
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hi,
just realised that anti-aliasing settings also tend to interfere with feedback: enabling any sort of anti-aliasing via |FSAA x( fscks up clean feedback on my geforce 5700 with the 1.0.8776 driver blob.
with kind regards, thoralf.
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-
Erich Berger -
Thoralf Schulze