By sending a ray from the camera out towards the direction you're looking and sampling density at multiple points, a cloud can be formed!

More in depth, for every pixel on the screen a ray is sent out in a shader. It takes small steps and samples noise textures to know how dense it is in that point. By sending out a second ray march towards the light source we can get shadows as well.

These noise textures are generated by me following a structure described in Andrew Schneiders talk at SIGGRAPH 2015 (The Real-Time Volumetric Cloudscapes of Horizon: Zero Dawn (SIGGRAPH 2015 Course - Advances in Real-time Rendering in Games))

It also has support for cloud types which takes in a start altitude, height, density curve, and coverage curve. The values for the noise and cloud types are Classes which makes it easy to add new ones.

The biggest difficulty in this project was getting the clouds to have the right shape. It took many hours of experimenting with noise following different tutorials until I finally got decent shapes. Even after all this time I am not completely happy with it and will continue experimenting to make sure it looks exactly how I want it to look.

I was able to get ~120 fps while looking at the clouds with 60 steps, which is what the demo uses using my RX 6600.

When using temporal upscaling (although it is broken I believe the performance is about what you'd expect with it working) I get around 300 fps with 60 steps.

• Simple customizability
• Support for multiple cloud types
• Light effects from the sun
• Cloud shadows from an extra shadow raymarch
• Ground shadows ( Plans to add cascades as the shadows only cover a small area around the player in high quality or large are with low quality)
• Weather map: Currently only decides the coverage of the clouds but in the future will also decide the precipitation and cloud type.
• Temporal Upscaling / reprojection. Already exists but is currently broken >:( and since I don't know what's wrong with it I don't want to spend time maybe figuring it out.ut.
• Automatic addition of cloud types. I want to make it possible to add cloud types just by adding another CloudType class. Even during runtime.
• TOD effect. Different sun / ambient colors depending on the time of day. Right now the sun decides how the shadows are pointed and the color values are decided in the inspector.

I want to give credits to Andrew Schneider who made the volumetric clouds for the Horizon game series. His published work helped a lot in the making of this project. I also want to give credit to Blackrack who made the volumetric clouds mode for Kerbal space program and made the volumetric clouds in Kitten Space Agency. I took inspiration from his debug view when adding cloud types by adding curves, which made modeling cloud types a lot easier. Lastly I want to give credit to Technically Harry on YouTube for making me interested in volumetric rendering with his video ( (Your first volumetric fog Shader | Unity URP).