Intermediate or edge/face particle creation?

[josemendez]

Look how regularly spaced all the vertices are on these models, they're designed to work well with Obi.

They're designed for good deformation, be it using Obi or otherwise (skeletal skinning, procedural shape modifiers, blend shapes, or any other kind of deformation).

The problem is that real game assets aren't usually built like this, they're optimised and vertex density varies from one part of the model to another.

Real game assets that are intended to deform *are* built like this, simply because it's impossible to deform them otherwise. Models are made of triangles and it's mathematically impossible to bend a single triangle, so you need many. Once you want part of a model to deform in any meaningful way you need to add more triangles and hence, more vertices.

This is why game characters have more edge loops & vertices around joints (shoulders, elbows, knees, etc): so that they can be deformed properly by the skeleton:

   

If you had to deform any part of the character and not just the joints, you'd place edge loops everywhere and end up with homogeneous vertex density. Of course, most pre-made game assets you can find online aren't designed with deformation in mind: vertex distribution is "optimized" for visuals only.

As a result, the surface blueprints generated can have big gaps and the particles won't be able to connect properly using distance. That's why I was thinking that either intermediate particles need to be created or there needs to be a much better way of connecting particles to neighbours than using distance.

What's the point of adding and connecting more particles, if there's no vertices to be deformed by them? Take for instance Unity's built-in capsule shape:


  Captura de pantalla 2021-06-02 a las 9.16.52.png (Size: 61.02 KB / Downloads: 22)

If you wanted to bend it 90º (I used Blender's deform modifier here) this is what you'd get:


  Captura de pantalla 2021-06-02 a las 9.17.12.png (Size: 87.45 KB / Downloads: 22)

Doesn't look good, does it?. No matter how many particles you add in the mid section of the capsule, the result will look terrible since the mesh doesn't have enough vertices in that region. This mesh isn't supposed to be deformed as-is. If you want decent deformation by any means, you need to add vertices in there:


  Captura de pantalla 2021-06-02 a las 9.17.48.png (Size: 93.61 KB / Downloads: 22)

For a model to be deformable, it has to have proper topology and enough vertex density. This not exclusive to Obi but just how geometry works: having more deformation targets -particles in Obi, but also lattice points, skeleton bones, clusters, spline control points, etc... in other deformation systems- than vertices in a mesh doesn't make sense in any case than I can think of. You usually want the opposite: less bones than vertices, less lattice points than vertices, less particles than vertices, etc.

It's like trying to get a good flag simulation from a single quad: you simply can't, unless you add more vertices.