# Calculate multiple objects as one

Hello!

I’m trying to make a white blood cell using SSS, translucency, and particles. But the problem is that the emitter is absorbing a lot of light from the particles so you can tell they are all separate. Is there a way to make Blender see them as one object? Or remove the faces between them without directly affecting the geometry? Thanks!

Hi !

Hmmmm… too bad the remesh modifier does not work on particles…

The question is, in the absence of a magic shader that would connect all these geometries together to form a whole and get rid of interpenetrating faces, how can we isolate said faces so they don’t show obviously on render ?

These faces share at least two features :

1. They show through another surface, that means a ray depth of at least two (not accounting for any bounce off the cell’s surface before that)
2. They show through another surface - that means you see them through transmission rays !

We’re going to make transmission rays that have a ray depth of more than two entirely transparent :

The less than math node here should make the transmission nature of the rays acts as a trigger between the two main shaders - your shader tree and the transparent one. The number in the divide math node is the number of bounces after which you’d like the transmission rays to disappear, in this case three bounces make it more likely that they’ve hit internal surfaces on their way to the camera lens (or to the light rather because that’s the way it goes, lens to light).

Try tweaking the SSS size, too ?

Whoa, I haven’t thought about it like that, thanks for all the info! I’m still tweaking things around, but currently this node set up produces some strange results:

I’m not sure what’s causing it, but I’ll keep trying some things out. What do you think?

EDIT: I got some interesting results using Transparent Depth instead of Ray Depth, but you can now also see the particles on the other side:

Ah, damn ! I thought this would be a good start already, but given the image you posted… I am surprised transparent depth even works somehow, because as far as I know it operates only on transparent BSDFs, and translucent and SSS BSDFs are something else. Unless your shader has some transparency component in it ?

It might be better to approach this not using shaders but geometry. Have you tried using a metaball as particle instance (instead of meshes) ? Gives you less freedom for the shape of the particles themselves but there is the “ellipsoid” metaball which seems quite fitting for your image, given a little randomness in size/orientation etc.

Right now I don’t see any other way to have these blobs merged together since the remesh modifier does not work with particles instances - unless… I assumed you were to render an animation but if you’re going for a still image you can always apply the particle system modifier, add a remesh modifier and render the result ?

I got the effect by the way, I’m not too sure how it was fixed, just adjusted the translucency and the SSS size like you suggested, and eventually it looked OK!

It looks pretty cool, but it lacks that “falloff effect” that you get on most microscopic pictures = darker on the front faces, brighter as the angle becomes grazing.