Rain on windshield

This project demonstrates an effect of rain drops falling on a glass surface and dripping down. It is based on Alix Michel's original rain on window effect, slightly tweaked, so all credit goes to her. It works with HDRP and relies on a Custom Render Texture and shader graphs.

Press 'Play' to see the effect in action.

Description

The scene has an instance of the Quad_rainEffect prefab which you can find, along every other asset necessary for the effect, in the Assets/RainOnWindow folder. This is basically a quad with the RainOnGlass_Material, a Lit shader using the RainOnGlass shader graph.

The CRT_WindowRain Custom Render Texture is updated through the CRT_WindowRain_Material based on the CRT_WindowRain_Shader shader graph.

RainOnGlass shader

This shader uses the heightmap rendertexture to create a normal map effect and much of the shader graph could be simplified.

The main controls are:

• Rain:
  • Normal Strength: the intensity of the normal mapping
  • RainFogTiling: the tiling factor of the fog texture mask. The fog texture defines zones where the glass is blured to simulate a foggy effect on the glass. (see Smoothness)
• Smoothness:
  • Smoothness Rain: the material smoothness for the drops
  • Global Smoothness 1 & 2: controls the range of material smoothness as it is mapped to the Fog texture. For perctly clear glass, set this to 1 on both.

CRT_WindowRain_Shader

This is where the dynamic rain effect happens.

The main controls are:

• Droplets Intensity: controls the height of each drop
• Droplets Size: the size of each drop
• Droplets perFrame: the number of drops created over the entire texture at each update
• Droplets Fade Ratio: how much previous drops are faded at each update. High values make the drops disappear very quickly. For water streaking effects, lower this to 0.0001
• Gravity Force: the amount of 'gravity', but reality velocity of the rains dropping down, for drops that fall down the window. Actually multiplied by the following value.
• Gravity Standing Droplets: same as above but for drops that tend to stick in place.
• Laterial Force: amount of speed pushing the drops to the edges. Used to simulate the window moving at speed in the Z direction
• Wiper Min Max Radius: the wiper rotation point is at the top (can be changed in the shader) and this defines in normalized coordinates the start and end distance of the wiper effect
• Wiper Angle Range: in radians the angle range of the wiper effect
• Flow Map Weight: the intensity of the flow map effect
• Flow Map: the flow map texture
• Flow Map tiling: how many times show the flow map be tiled
• Clear: clears the entire texture when enabled