Add sample motion blur to cycles?

General Forums Blender and CG Discussions
#1

Sample motion blur make more sens in cycles then in BI. The render samples can be distributed over the motion blur samples (if every motion blur sample is given it’s own seed). So a 4000 samples render with 200 motion blurs samples will render 20 samples for each motion blur sample.

We still need to build the BHT for each motion blur sample - but the actual render need not cost any extra (in contrast to BI where a sufficient number of motion blur samples get insanely expensive).

With sufficient motion blur samples that is the best method, think reflections in a fast moving train, motion blur on shadows, moving object passing behind each other, or any other indirect effect that just works with motion blur samples but need hard extra work with other methods.

#2

One of Brecht’s top priorities for Mango and Cycles is 3d motion blur, according to the mango blog.

To that I say, “F**K YEAH!”

#3

When that day comes…
http://i.imgur.com/mrM3j.gif

#4

There is a method floating around somewhere here on the forums to do this manually in Blender using frame stepping, some simple math, and the compositor, and it works pretty well. That said, it would be much, MUCH easier to do this is the seed value were able to be animated in a simple way, but as far as I know it stays locked even if you set keyframes.

#5

There is a method floating around somewhere here on the forums to do this manually in Blender using frame stepping, some simple math, and the compositor, and it works pretty well. That said, it would be much, MUCH easier to do this is the seed value were able to be animated in a simple way, but as far as I know it stays locked even if you set keyframes.

The seed is completely animatable already; I tried it.

However, if an object is moving and the scene is being rebuilt between samples, wouldn’t the noise pattern change regardless of what the random seed is?

#6

I was curious, so I tested it myself.

Here’s 7 frames of the same scene, but with an animated seed:
http://i.imgur.com/hS9ZX.gif

Here’s the same 7 frames, but with the object moving slightly while the seed is unchanged:
http://i.imgur.com/CPOZS.gif

It seems that I was wrong; if you didn’t change seeds between motion blur samples, you would pay an opportunity cost in quality.

#7

I seen speed vectors and vector blur coming - but I sure hope for sample motion blur to.

Rocketman: I say it looks like You where right, changing seed works.

I wonder if enough is exposed to implement sample motion blur in a python add-on? And if that can give sane speed? Speed vice the merging of ~200 renders worry a bit.

If we in python can sett seed and render at a fraction of a frame it should be doable in python I think.

#8

This will be nice. I’m finally getting some cool results with the Painting With Polygons technique, but I want to do it with Cycles if possible. I thought it would be utterly prohibitive until now.

#9

Changing seed works, but as far as I know it doesn’t currently work when you enable time remapping, which is needed to get the stepped motion blur effect.

#10

Seed works with time remapping alright, tried it some time ago when that topic was hot. You just have to add enough change to it because when you do time remap, seed must change between remapped frames also. For example if you have an animation with 100 frames and you animate seed from 0 to 100 and then do remap to 5000 frames you get seed change in every 50 frames which obviously isn’t what you need. Seed change in this case should be at least from 0 to 5000 between the original 100 frames.