PFlow, particle age map and motion blur problem.

[davius3d]

Hey guys.

Let me try to explain the best I can. I'm rendering some smoke with pflow the old school way (i.e. with facing particles, gradient ramps and particle age map).

All works fine, the particles fade away (opacity diminishes) driven by the particle age map. The problem arises if I turn on motion blur (either on Max's physical camera or Vray's camera, created through maxscript).

With Motion Blur ON, they go slowly fading as they are supposed to, but on the last couple of frames, they pop up to 100% opacity again, like the particle age was reset. The problem is even more pronounced if you increase the motion blur effect (like going from 1/50 sec to 1/25 sec).

It seems that, when sampling the motion blur, VRay has to take into account what happens before and after the current frame and while looking at "the future", instead of finding that the particles are dead, it cycles through and suddenly the particles display as they are on the beginning of their lifespan.

Hope I was clear. If needed I can provide files to show the issue. It's kind of a show stopper in a current job I'm doing now.

Cheers!

[davius3d]

So, some findings:

1 - It only appears on the last particles of an emitter. I mean, if you set your pflow to emit from 0 to 10, this will only happen on the particles which were born near frame 10 at the last frames of their age (set on a delete operator). So, following this example, let's say you emit particles from 0 to 10, and set a delete operator on age mode, and set the age to 10 too. This means you'll see the bug at frames 18, 19, 20.

2 - This also happens on Scanline (If you set the motion blur type for "object", not "image". But this bug does NOT shows up on Mental Ray. Weird huh?!

[jrandom]

Try Bercon Maps

[davius3d]

Thanks for the suggestion John! Did try bercon with gradient and the result is the same of the standard Particle Age map....