Object info random node gets reassigned every frame to particles

Support Materials and Textures
,
1

Hi! Not sure if I write this to the correct category but it’s both a partcile and a texturing problem as well. I have a point cloud simulation and I instanced a mesh on the points in geometry nodes. I set up a material with the object info random node that has 95% of the particles normal and 5% glows. For still frames works perfectly, but when I run the animation the randomness gets reassigned every frame and the glow jumps around between different points. I’ve tried every trick up my sleeve and I just can’t make it work. I want the same particles to glow from birth to death as the animation runs. Anyone has any idea how to achieve this? Is there a geo node point ID attribute that I have to play with or something like that? I’m not that good in geo nodes, it’s probably where the solution lies. Thanks! :slight_smile:

2

Are the index numbers changing over time? What does the Spreadsheet tell you?

Have you tired assigning IDs via the SetID node right after inputting the point cloud?

grafik
grafik3109×1542 1.12 MB

3

setID doesn’t really do anything helpful for me. Also the point cloud already has ID assigned. I think when the particles start to die, the IDs get shuffled around.

4

Thanks man! I think I’ve solved it. Set ID was the solution. You have to set ID just before the set material and use the point clouds generated ID as input. I will do some test, and report back if it’s a good solution.

image
image735×350 26.2 KB

5

Where does nx_id come from?

6

I’m playing around with NeXus for Blender. A simulation system made by Insydium for Blender now in Beta. When you export the simulation out you can assign the particle ID number to the alembic. So it’s generated by the NeXus addon.

7

Have you tried assigning a new id right after the node where the sim gets input into the node tree?

8

Yeah, I tried that but it didn’t help. Nothing changed.

9

Hmm… that is strange. Can you see what is going on with the ids in the spreadsheet?

10

Okay it didn’t help actually, just made some changes to the ID to behave differently but still not stable to points.

11

yeah so really strange from frame 126 to 127 IDs get f’ed up.

image
image104×547 3.38 KB

image

12

okay I managed to capture ID and have it stable the way you showed it, but the material still jumps around. The issue might be with the object info random node.

13

Hmm… in that case I would try to assign a random number in geonodes and then send it to shader nodes via attribute.
Perhaps the object info node does not use ID? It seems to use it in my tests, though… :face_with_raised_eyebrow:

14

I stabilized the nx_id attribute by overwriting it with newly assigned ID at the beginning, but still material jumps around. Damn :)) I’m really not sure what to do here.

15

Can you upload an example file?

16

Okay, I gave a restart to Blender, and seems like stabilizing all ID attributes have solved it. So basically set a new ID at the beginning and after that overwrite all other ID attributes in your point cloud with that.

17

Thanks a lot for your help!

18

Actually it doesn’t work again. Hmmm something really strange is happening no idea what.