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Extraneous Thinking Particles With Physical Renderer Motion Blur

Thinking Particles Rendering

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#1 WShawn

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Posted 06 January 2012 - 04:05 PM

Revisiting a project I originally created in R12, I had to rerender some Thinking Particles, but I found that when I rendered those particles using "real" motion blur in the Physical Renderer, extraneous particles were being rendered, making the render unusable. Rendering the same scene with the Standard Renderer using Vector Motion Blur does not create extraneous particles.

Here's a link to a Quicktime showing the renders side-by-side:

http://www.marshall-...Comparisons.mov

The extraneous particles in the Physical Renderer appear briefly in the lower left of that frame. I seem to get a different result each time I render the scene that way (which isn't good, either.)

The guidelines for the Physical Renderer Motion Blur say to bake the dynamics in a scene, but, sadly, you can't bake Thinking Particles. So what does one do?

No extraneous particles are rendered with the Physical Renderer if Motion Blur is deactivated.

I also just found that I get extraneous particles when I use the Standard Renderer and Sub-Frame Motion Blur.

For now I'll make due with the Standard Renderer and Vector Motion Blur, but I'd like to know if this is a bug or if I'm missing a setting somewhere.

Thank you.

Shawn Marshall
Marshall Arts Motion Graphics

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#2 WShawn

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Posted 06 January 2012 - 07:57 PM

Well, this is frustrating. I'm now getting this problem when using the Standard Renderer with Vector Motion Blur. As I watch it render I can see it dropping particles where they shouldn't be, and then the post-process blur is added. If I turn off the Vector Motion Blur and render the same frame those extraneous particles aren't generated. If I make a hardware preview all of the Thinking Particle ticks are where they should be.

I've tried quitting and restarting my computer, but the problem persists.

Any thoughts or suggestions would be greatly appreciated.

Thanks.

Shawn Marshall
Marshall Arts Motion Graphics
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#3 baramdo

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Posted 06 January 2012 - 08:47 PM

Didn't try a render, but I opened your scene and when I pressed play those particles were in the scene. After it played though they were not generated the second or third time the scene played through.

If you are rendering into the picture viewer directly from the scene file try turning off all the tp emitters and playing forward a few frames. Then go back to your first preroll frame and turn on all the emitters. Then render. This should help clear any extraneous tp data.

#4 WShawn

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Posted 06 January 2012 - 10:08 PM

And now these particles are appearing with no motion blur of any kind enabled. Randomly. Sometimes they're generated, sometimes they're not. And now my Hardware Preview is showing these phantom particles that weren't there before. The scene has a 90 frame lead in to allow the particles to complete their journey along the two splines I'm using. If I play the animation with "All Frames" enabled these phantom particles don't appear. If I do a Hardware Preview now they do appear at the beginning of the animation, then disappear.

I've posted a side-by-side comparison showing this:

http://www.marshall-arts.net/Test/ThinkPartsPreviews.mov

The hardware preview on the left is timed to start when the screen capture preview hits frame 0. As you can see, there are no extraneous particles generated when I play every frame of the animation, but the phantom particles appear in the 0-100 hardware preview at the beginning.

I found that if I make a Hardware Preview with the Timeslider at -90 (where the project starts) I get 3 extraneous particles, though their positions don't match where they're rendered. If the Timeslider is at any other point it doesn't show phantom particles.

It's issues like these which precipitated my switch from Lightwave to C4D.
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#5 WShawn

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Posted 06 January 2012 - 11:03 PM

Thanks for the reply, Baramdo. Unfortunately, your suggestions didn't work for me. These particles that are being erroneously generated never correspond to any of the particle ticks when I step through every frame, frame-by-frame. They don't appear in a Hardware Preview unless the Timeslider is at -90 when I launch the preview. But they now always appear when I render with motion blur activated, regardless of whether it's Vector, sub frame or the Physical render.

I was under the impression that TP doesn't cache in any way. That's the big drawback. It had to calculate every particle on the fly, frame-by-frame. That's why you can't just scrub through the scene. You have to let TP calculate every frame. It's like turning on motion blur is corrupting that calculation upon render.

I've posted another screen grab. It shows the project as it renders a frame 0 with no motion blur (no extra particles), Vector Motion Blur (3 extra particles), and Sub-frame motion blur (2 visible extra particles).

http://www.marshall-arts.net/Test/DemoRendersREV.mov

Man, this is frustrating.
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#6 WShawn

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Posted 06 January 2012 - 11:30 PM

I opened up the scene in R12. When I render with the Vector Motion Blur it looks like I'm getting phantom particles, though they're in a different position than when rendered in R13. But when I render with Scene Motion Blur it all looks correct, so I'm rendering all 400 frames that way.
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#7 baramdo

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Posted 07 January 2012 - 11:00 AM

Another thing to try is copying the scene parts to another file. Whenever C4D is doing something that I absolutely know it shouldn't do that helps.

#8 motherwell

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Posted 20 March 2012 - 01:39 PM

I am getting this problem as well. When I use the physical render in the picture viewer - i.e. to render out a quicktime, most of my particles are missing and I have random particles showing up.

But if I render the current frame in the viewer (cmd-R) with the physical render everything looks normal.


If I use the standard render while in the picture viewer, it looks like everything is there.





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