How to make particles render a smaller sub-image from a subUV sprite sheet?


apologies if this is a naive question, but I’m trying to create a particle system whose material indexes a subUV texture. The difference is that each element of my subUV is large, and I want each particle to render a smaller sub-image, by using the particle’s position to select a subpart of each subUV. So each particle is basically a small sample of the subUV. Basically I’m trying to recreate the volumetric textures shown in the Infiltrator demo: Infiltrator Breakdown: Visual Effects | 03 | Feature Highlight | Unreal Engine - YouTube . My question is: how to select a subimage? I’d like to be able to set the dimensions of this completely separately from the dimensions of the subUV.


Are you talking about SUB-UV’s within SubUV’s?

Yes if we could have that explosion files would be nice for an example.

I think I probably am. What I want to happen is: the lifetime of the particle is used to index a subUV, assigning ‘frames’ to time values. But then, instead of rendering that entire frame from the subUV for each particle, I want to render a small window on it, where the centre of the window is given by the position of the particle. The idea is that I can have loads of particles, and instead of them each rendering overlapping copies the subUV, they render little windows on it based on their position. If my subUV was an animated explosion, I could have 10 or 10,000 particles and you would only see one explosion. This is the basis for the ‘volumetric textures’ in that demo.

I’m currently experimenting with TextureCropping, not sure if this is the right approach though…



Hey -

I believe you may be talking about using the MacroUV functionality in Cascade. Take a look at some of the UDK documentation which is still applicable to Cascade now.

Also, I have word from an inside source that Infiltrator will eventually be coming to Marketplace, so could always hang around for that :slight_smile:

We all knew that, I didn’t wanna say it in public :stuck_out_tongue: why did u do that? :slight_smile:

Thank you!!

It would be great to see this on the marketplace, but it’s always nice to build stuff yourself, helps me understand a bit better how things work - and maybe extend them a little.

thanks again :slight_smile: