Ariff Jeff avatar image
Ariff Jeff asked ·

Potential bug: Cloner Multi-Instance and color_jitter unintended randomness?

Arnold core

To replicate problem:

1. Create a cloner and set it to multi-instance mode

2. Add some object as a child like a default cube

3. Add a standard surface shader to the cloner where a color_jitter node is connected to the standard_surface base color

4. color_jitter Input color parameter set to full saturation of any color

5. color_jitter Object drop-down: Hue Max parameter set to 1

6. Add a light to the scene

7. Start IPR

8. Watch cloner instances and scroll forward in timeline one frame at a time, nothing should happen.

9. Now scroll BACKWARDS in timeline one frame at a time. Cloner instances with their random colors should start flicking to different colors. They don't appear to return to original at any point. This must be a bug? It's like moving backwards in the timeline is the equivalent to changing the seed of the color_jitter node. Multi-instance mode on cloner appears to be the source of the problem.

Also there are some cases where scrolling backwards in the timeline in this context also causes the cloner instances except one to dissapear in the IPR and won't reappear until the IPR is restarted. This is hard to replicate though since it happens infrequently and randomly.


I was just working in another scene with a similar setup as above except I was working with a cloner in Instance mode as apposed to Multi-Instance and the same bug just occurred where the color on the cloner instances switched to other random colors. This only happened once when I scrolled back in the timeline but then I wasn't able reproduce it immediately after. So it seems that Instance mode is also susceptible to this bug but not nearly as frequently.

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Peter Horvath avatar image
Peter Horvath answered ·

This issue should exist only in the IPR. The color_jitter shader is based on the object name. When you move back on the timeline, the Cloner recreates the instances which are exported with a different name (with a different index in the name actually, to avoid any collision with existing objects). If you restart the IPR it builds the scene from scratch and should display the proper colors. Also you should see the proper colors rendering to the Picture Viewer. I'm not sure it can be easily fixed taking how the IPR operates at the moment.

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