Paint on Object at runtime(UV Painting)

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@Leonidas Hi, Leonidas
As you mentioned here:

@Leonidas

Usually to do something like this in the most performant way you will use pixel shaders. To offset in real-time the coordinates of a texture with almost zero performance cost.

I want to implement a shader like this but I am new to shader programming ,after a period of learning,I’v known how to change the color of specific pixel,but have no idea how to fill the whole object with this color.I guess it has something to do with the uv coordinates?but how?is this difficult to implement?

my test project is here:
https://playcanvas.com/project/704805/overview/leran-shader

Can you give me some advice？thanks so much