What are my options if I want a million impact decals on screen at once?

poopipe

So yeah.  I want unlimited instances of material dependent surface damage plastered over my level at runtime and I want it to be free(ish) 

This probably rules out traditional polygon decals (unless there's a magic buffer someone knows about? ) so my thoughts turn to ways of passing damage  location information to shaders and doing something clever there. 
I guess what I'm going for is some sort of damage volume voxel/3d texture - similar to mesh distance fields or a wind map. . Does anyone know of an example of this sort of thing that's been built or even a built in system I could piggyback?  

Ta

Obscura

You could just spawn decal actors. Thats the common way of doing it.

poopipe

Cheers,  from reading up a bit it looks like they probably won't cut it if I want millions of the things on screen.  I'll give em a shot but I'm not entirely hopeful.

What I really want is to be able to generate a mask at runtime and then query it. 

Obscura

That is also possible with a render target, but unnecessary in the most of cases. Decal actors works well when you want to leave an impact decal from weapons. Thats how people normally do it in a shooter game. 

poopipe

That might work, thanks  

Part of the reason I don't want to use individual decals is that I want the marks created to be permanent and additive - Eg. You scratch a surface and then scratch it again and again to reveal more of the underlying structure.  I can't imagine it'd take long to start seeing issues with decal  actors or any other method that relies on blending - also iirc decal actors disappear after a while.. 

Obscura

There is a performance reason behind that, but you can make them staying forever if you want to...Same reasons as why people don't really do this kind of stuff in games. Its kind of hard to do, and gets heavy on the hardware when it comes to a more advanced approach.

poopipe

having done some tests it looks like the render target approach is best for me - I need a way of smashing a load of objects into a single atlas automatically which I suspect will require delving into c++ 

One of the perks of having a tame proper programmer is that these things are doable