How to render multiple dynamic instances efficiently?

[m10s]

First of all, I'd like to thank you @asny for the great work you're doing. The crate is exactly what I was looking for for a new project I'm working on.

There's currently just one thing I'm struggling to understand: I'm not sure how to render multiple instances of an object efficiently, considering the transform of each instance potentially changes every frame.

Let's say I want to make a chess game. My first naive approach would be to create a Mesh for the board and one for every of the 32 pieces. However, this seems to be a lot of overhead, because every Mesh stores its own vertex data, even though many pieces share the same geometry.

Using InstancedMesh seems to be the better alternative in this case. For every type of piece, I'd create a single InstancedMesh, using Instances to set the transform of each instance. As far as I understand, the only way to change the transform of an instance is through InstancedMesh::set_instances(). Looking at the implementation, this method seems to be quite expensive and I'm not sure if it's supposed to be called multiple times per frame.

I'm not sure if I miss something here or if my approach is somehow flawed. I'd be happy to hear your thoughts on this.

[asny]

Thank you for your kind words 🙏

First of all, I don't think you need to worry too much about it for a chess game. The main use-case of instanced meshes is if you have thousands or millions of instances (you can try its effect in the instanced_shapes example). However, I think it's an interesting question so I'll be happy to provide my thoughts 👍

• First solution, as you said, would be to create a Mesh for each chess piece. If you choose some really high poly models, that might be a problem since you are then wasting a lot of memory, but in most cases it's a good and simple solution.
• The other option is to reuse the model data, but render them one by one. So for each chess piece type you create one Mesh. Then you render that Mesh as many times as there are chess pieces of that type on the board, and, before each render, you update the transformation.
• The last option is to use InstancedMesh and then update the Instances each time at least one of them changes, this should still be pretty damn fast. If you have millions of instances and only few of them that needs to be updated, you would probably split them into multiple InstancedMesh to avoid updating everything, but for your use-case I'm not worried 🙂