deps: the renderer renders from back-to-front. So if you have a bunch of particles sharing the same texture, so long as they're on the same layer or are at least contiguous in the Z-order, there won't be any texture changing. If you intermingle other textures (say, other particles) in the Z order with a high degree of randomness, you will give the GPU more work since it will keep changing texture. At the moment, Construct makes no such optimisations on its own. It's up to you to organise your Z ordering.