ECS component dependencies / sharing and cache locality

by Driv   Last Updated November 14, 2017 16:13 PM

I have been trying to wrap my head around how ECS works when there are components which are shared or dependent. I've read numerous articles on ECS and can't seem to find a definitive answer to this.

Assume the following scenario:

I have an entity which has a ModelComponent (or MeshComponent), a PositionComponent and a ParticlesComponent (or EmitterComponent).

The ModelRenderSystem needs both the ModelComponent and the PositionComponent.

The ParticleRenderSystem needs ParticlesComponent and the PositionComponent.

In the ModelRenderSystem, for cache efficiency / locality, I would like run through all the ModelComponents which are in a compact array and render them, however for each model I need to pull the PositionComponent. I haven't even started thinking about how to deal with the textures, shaders etc for each model (which will definitely blow the cache).

A similar issue with the ParticleRenderSystem.. I need both the ParticlesComponent as well as the PositionComponent, and I want to be able to run through all ParticlesComponents in a cache efficient / friendly manner.

I considered having ModelComponent and ParticlesComponent each having their own position, but they will need to be synched every time the models position changes (imagine a particle effect on a character). This adds another entity or component which needs to track and synch components or values (and potentially negates any cache efficiency).

How does everyone else handle these kinds of dependency issues?

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