Godot 4: Rainy window shader (tutorial) (www.youtube.com)

submitted 1 day ago by FencerDevLog@programming.dev to c/godot@programming.dev

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Hi everyone! I think that a simulation of a raindrop trickling down a window is a very nice effect, and if there are more of them, they can be both highly useful and visually striking in games. So, let’s explore how this shader works from a programming perspective.

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[-] flovoit@programming.dev 3 points 13 hours ago

I watched it, very interesting effect, but one of the problems I have when trying to implement an effect is understanding how to manipulate the color, in your case the magic was happening in the drop_layer function. How did you know that doing that calculation (I.e. the uv offset into the base texture) would look like a drip?

[-] FencerDevLog@programming.dev 1 points 3 hours ago

Thanks! The offset of UV coordinates works like refraction, localized to the corresponding cell of the defined grid. Without using a noise texture, such light refraction would be circular, similar to the magnifying glass effect. However, this approach creates slightly irregular shapes, which better simulate droplets on a window pane. If you reduce the drop_layer function to its absolute minimum, you should see the mentioned grid before the shaping and movement of the droplets.

Like this:

vec2 drop_layer(vec2 uv, float time) {
	vec2 grid = vec2(grid_x, grid_y);
	vec2 drop_uv = fract(uv * grid);
	drop_uv = 2.0 * drop_uv - 1.0;
	vec2 drop_size = drop_uv / grid;
	return drop_size;
}

this post was submitted on 13 Jan 2025

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