This example project demonstrates the water transition shader from my "Drone Simulator" prototype project made in Godot Engine 3.5+.
All required code is rewritten in GDScript for this project (instead of C++). A simple first person character is provided to walk around and dive into the water.
| Input | Description |
|---|---|
| W/A/S/D | Move player character. |
| Mouse | Look around. |
| Escape Key | Exit game. |
| Alt + Enter | Toggle fullscreen mode. |
For this implementation I use a Viewport inside the Player.tscn scene to draw the water transition texture - or "clip plane" - onto the mesh in front of the viewport's camera. This texture is later used by the post processing overlay panel node PostProcessingOverlay inside the main scene WaterLevel.tscn to render the split between the water surface and the underwater color - the actual water transition effect shader.
This extra step is required to have access to the camera's transform data and matrices on a per-pixel basis inside the fragment shader code. Also, unfortunately the texture behind the SCREEN_TEXTURE built-in variable does not yet include the "shaded" transparency pass of the water surface from the water plane mesh at this stage. Both materials use the same "raw" screen texture.
I also make use of cull masks here for the cameras and the render target mesh to only draw what's necessary. Layer 16 is being used for the water transition pass.
For performance optimization, all affected nodes for the water transition effect get hidden when above the water level.
If you're familiar with RenderDoc https://renderdoc.org, feel free to inspect Godot's rendering architecture in more detail by analyzing this project. It's fun!
I'm quite sure there's a somewhat smarter and/or a more performant solution. Just feel free to contact me on Twitter https://twitter.com/bifractal, if you have any questions or ideas. Also checkout the YouTube playlist for my "Drone Simulator" update videos: https://youtube.com/playlist?list=PLB0a9ZaCofXPzLFlA6gbKrDyfETi8pO1b.