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cavetroll
10-31-2005, 12:44 PM
Sorry guys to bring up this issue again as it has been discussed beforehand.
But Iīm having a serious problem here that wasnīt discussed before.
I render out a beauty pass for our character that I later want to have mBlurred using the Reelsmart MotionVector node in shake.
To render out a mBlurPass Iīm assigning the lm2dmv shader to the character.
As suggested I use values of 0.5 for both shutter and shutterDelay to turn off the real motionBlur. Everything gets rendered otu fine. I also have an alphaChannel for the mBlur-images.
But now, when I use the vectorNode in shake, the blurPass and the beautyPass donīt match each other when there is fast movement going on. This is not about the normalization. I adjusted the factor to match my amount of pixelMovement. I really do get ugly blur artefacts because the images donīt match.
What can I do here. Even in maya, when I render a frame with noBlur and no lm2dmv-shader and the same frame with the shader, the two images donīt match. You can see it best in the alpha channel.
I suppose that this has to do with the blurSettings. Because in the viewport you can see the wireframe updating when it is calculatin the blur. You also can see the timeline going 0.80 to 1.20 for example. If I change the shutter and shutterDelay to very small values the mismatch is even bigger. Setting both to 0.5 and 0.5 should do the trick of matching the unblurred frame but it doesnīt.
What am I missing here.
Any help greatly appreciated.
Cheers, Tom.
cavetroll
10-31-2005, 02:21 PM
Another thing I recognized is the problem of different antialiasing between mayaRenderer and mentalRay. This small difference is responsible for getting ugly streaks or peaks on the edges of your blurred image....
zhenyang
10-31-2005, 04:31 PM
Hi, did you set Motion Back Offset to 0? It's under Motion Blur settings in Render Globals
cavetroll
10-31-2005, 05:38 PM
Just played around with the values and got the footage to match. I had to set shutter to a very low value like 0.001 and shutterDelay to the same. After doing that the pictures still didnīt match each other.
Yes, after I did set motion back to zero, the pictures did match each other. But this only works when shutter delay and shutter have those very small values. Setting them to zero will produce no mBlur.
But there still is the big problem with the antiAliasing and I donīt seem to get rid of that. Even when there is little blur I get those nasty streaks on the edges of objects, as reelsmart will blur not matching pixels, too.
I donīt think there is a chance to eliminate that? I think it is a technical problem of using two different renderers to get one matching image. Because if the AA values donīt match, you will always see streaks.
Anyway, I managed to minimize those streaks by using the mentalRay option "Pass surface color to alpha channel". Before that I used a surfaceShader with the lm2dmv connected to the outColor to have an alphaChannel with my vectorPass. And those blur results had really nasty streaks on the edges.
Not the perfect blurring result now, but I think I can live with that.
Anyone any more experiences with that problem...?
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