Flickering whn adding more particles

Krakatoa for 3ds Max
1

Hi guys,

Im rendering out a sand sequence in Krakatoa. I had 32 partitions, equaling about 250,000 particles and did not have any issues. I recently added another 96 partitions (about 2.5 mill particles) and am now getting flickering in the lighting.

Im using depthmaps for matting and have 6 lights in there with shadow maps on.

Ill upload a mov of the problem, I just have to find some web space!



Jordan Walsh



Lead VFX artist

Zero One Animation

2

here is the mov:



krakatoa_flickering.mov



Jordan Walsh



Lead VFX artist

Zero One Animation

3

Hi Jordan,



I cannot tell what it causing it from simply looking at the MOV file, so I would suggest debugging this by removing various factors to see where the problem is. Find two frames that show the flickering very clearly and render those to compare whether the changes you are making affect the result:


  1. Try switching off the Use Depth Maps option and see if it changes anything.


  2. Try disabling all lights but one and render again the two frames. Do they still flicker? Try each light separately to see if there is one of them that is causing it.


  3. Try changing the shadow map size settings of the light(s).


  4. Try turning off the “Cast Shadows” Property of your matte object(s) to see whether the geometry is causing the flickering, or the particles self-shadowing.



    Once you have a better idea about the possible cause, we can try to find a possible solution.
4

Another possibility is numerical underflow in either the density or the lighting channels. The way to fix that would be to go to the channels rollout, and switch Density, Lighting, or both to 32 bit precision from their default 16 bit precision. This will require more memory, but may be necessary with your settings.



Another way to avoid underflow would be to increase the density, but that will obviously change the look of the render as well.



-Mark

5

Thanks for the ideas. I tried shadows off, different lights etc, but the thing that fixed it was changing the sorting method to Radix or standard sort rather than FF Threaded. (I forgot to say im on 1.0.1!). So with 1.1 would this issue occur as there is only one sorting method, or is more robust?



Jordan Walsh



Lead VFX artist

Zero One Animation

6

Thanks for the ideas. I tried

shadows off, different lights

etc, but the thing that fixed

it was changing the sorting

method to Radix or standard

sort rather than FF Threaded.

(I forgot to say im on

1.0.1!). So with 1.1 would

this issue occur as there is

only one sorting method, or is

more robust?





Interesting. It would be very helpful if you could try rendering the same scene in 1.1 and see if it shows the same problem when using multiple threads. You still have the option to force a single thread in 1.1, so you would still have a workaround, but if there is a bug in the multi-threaded sorting, we should look into fixing it!

7

Ill do that Bobo, we are finishing the job up next week, so after then I’ll be upgrading. I’ll try it then.





Jordan Walsh



Lead VFX artist

Zero One Animation

8

Ok, I have just installed 1.1 and on the multi threaded mode it seems fine. no flickering!! :slight_smile:

9

:smiley: :smiley: :smiley:
Good to hear. We should add this to the list of bug fixes in 1.1 :wink: