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Dynamically update mask to reveal different effect?

In my game, i want to paint an effect onto the ground as an object moves around. Instead of putting down geometry, i’d prefer to update a texture so that nothing ‘expires’ and fades out. My rough plan was to have the object act as a ‘brush’ that updates a mask, which exposes the special effect material.

Has anyone done this in UE4? Is it a good path? Any tutorials on the technique, or is it just unworkable? The world is small (2ish screens worth) so I don’t think memory will be a concern if i just paint into a big 2k-ish texture.

just a bump. no one has an idea here?

Can’t you use a decal for that?

can i apply (near) infinite decals? That would work if so. I thought they had geometry under them.

I don’t understand why you need infinite decals. I thought you need something like a fake shadow following the object wherever it moves, in which case a decal would do the job and you can even control its material properties depending on the height and position of the object. Can you post a screenshot of what you are trying to achieve?

No, it’s not a fake shadow or something like that. I want to paint a texture with a brush, and have that change persist, so that I can have an effect that only occurs where the object has been. It’s an overhead game, and the object is (say) clearing snow from the world, so that everywhere the character has been is exposed, and places where it has not yet been are still snow-covered. I don’t want to fade this stuff out though, so leaving a trail of geometry probably won’t work out.

generate a trail just like you would generate footsteps or like a tank would leave marks of his treads.

Yea, that’s what I’m thinking, but what’s the mechanism in UE4 editor to do that?

I’m not aware of any mechanism for that. You would have to build the shader and create the mechanics for footstep either in script or code.

I suspected as much. I was going to custom-code this engine, but then when UE4 came out for such a great price i figured I’d jump on board. Sounds like I still have to code :slight_smile: Thanks.