Color a texture at contact positions

Hi,
my problem is the following: I have to distribute splashes of paint over a table, a lot of splashes. So my idea was to create a splash, and at the contact points of the splash with the table, I modify the color of a texture (visualized in the image with the splash on the right side). What I was able to do until now is: Load a splash (created in Houdini and exported via VAT) and I was able to create a shader graph which can paint mouse strokes on a texture via shader graph (the attachted image with the brickwall).

Now I have no idea how to combine these two elements since the splash is a shadergraph as well. Is there a way to use the output of a shader graph as input for another? Or are there any other possibilities to do that, with particles or someting like that?

 

Generally you use a RenderTexture for this and repeatedly accumulate painting to it.

Here is a lotto scratcher I made that works like this, with repeated painting:

Full source code linked in comments:

https://forum.unity.com/threads/how-to-make-scracthcard-2d.1128605/#post-7253498

 

Thank you very much, very appreciated, I'll have a look at it.

 

Okay, I had a closer look and your code and scene setup was quite helpful for a beginner like me.

Unfortunately it does not help very much in my case. To visualize it I made a small video from Houdini.

I was able to import the splashes via VAT into Unity. But now I'm stuck because I have no idea how to transfer the contact areas between the splashes and the grid to the texture of the grid. Is that possible?

 

You would need some kind of visible object (eg, Renderer), either some generated geometry (the way I do it in the example project), or else a sprite with your textures on them. The presence of those visible objects is what the Camera then "paints" onto the target texture.

 

Ah, now I think I have a clue how to proceed, thanks.