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View Full Version : Spinning light trick problem?

TSpyrison
12-15-2005, 09:51 AM
I知 trying to do an outside scene, with a distant light spinning for the "spinning light trick". 720 degrees spin from frame 0 to 1, and the light is pointing 5 degrees on its bank. and I知 running the PLD 9 pass AA.

What I知 getting in my shadow, is a 6 or 7 shadows that don稚 seem to blur into each other, but kind of move around each other. Definite shadow movement..

Example is here..

ingo
12-15-2005, 10:23 AM
Could it be that you forgot to switch motion blur on in the camera settings ? The best option is dithered motion blur.

TSpyrison
12-15-2005, 11:13 AM
yea, I had motion blur on..
Trying it now dithered, but it still has an "undulating" look in the shadows..

andy gee
06-30-2006, 08:06 AM
Maybe

i saw on a video that motion blur calculates passes so the higher the passes

done the better transition

andy gee

06-30-2006, 09:18 AM
I’m trying to do an outside scene, with a distant light spinning for the "spinning light trick". 720 degrees spin from frame 0 to 1, and the light is pointing 5 degrees on its bank. and I’m running the PLD 9 pass AA.

What I’m getting in my shadow, is a 6 or 7 shadows that don’t seem to blur into each other, but kind of move around each other. Definite shadow movement..

Example is here..

Try selecting both keys in the Graph Editor and setting their curve-type from TCB to "Linear," to make sure there's no chance of a curve in their movement.

Also, use this formula for the spin: 720-720/n, where "n" is the number of AA passes per frame. For 9-pass, non-dithered AA, it would be 720-720/9, which turns out to be 720-80 = 640. For 9-pass, dithered AA, there's 18 half-passes altogether, so it would be 720-720/18 = 720-40 = 680.

Third...did you import this light from a scene with a different Fps, or did you change the Fps in this scene recently? That always screws up my motion-blur-over-one-frame tricks, since the key that's supposed to be on frame 1 ends up on a fractional frame instead (like 0.75 or 1.33 instead of 1). The undulating behavior looks an awful lot like what happens when frame 1 of the spinner is not actually on frame 1. Try deleting the frame 1 key and recreating it on frame 1, just to make sure that it's not a fractional key problem.

Dave Jerrard
06-30-2006, 09:27 AM
Make sure the two keys in the graph are on frames 0 and 1 and that they're both set to Linear. Post behaviour should be set to Repeat. It kinda looks like you have it set to Linear as well, which would case the circular motion effect you see.

If you really want to get technical, the 'formula' for this is (360/MB)-(360/MB/P), where MB is motion blur as a decimal (50% is 0.5) and P is the number of render passes. If you're using Dithered Blur, this will be doubled, so High AA would go from 9 to 18 passes here. You can actually input this (with the correct values for MB and P inserted) into the Graph Editor for the Value at frame 1. In your case, you would enter (360/.5)-(360/.5/18), based on your statement that you were using PLD 9 and dithered, and assuming you haven't changed the default blur amount. This should give you a value of 680 degrees.

If that doesn't fix it then there's something else that's not set up right. :stumped:

He Who Has Been Spinning Lights For Over A Decade Now.