UnityVolumetric

This project is an exploration of volumetric rendering within unity, it comes with two modules, the slicer, and the renderer.

The roots of this tool are in a VR project developed at Dpt., where i first experimented with volumetric rendering.

Slicer

This component lets you generate a Texture3D storing volumetric data from a mesh. To do so, it renders the mesh slice by slice, using a custom shader to isolate pixels which are inside the mesh.

Specifically, for each slice:

• on the left, we render the mesh normals in a renderTexture
• on the right, we then sample this texture, a pixel is inside if the dot product of its normal and the backward vector is above zero. We use the gradient of the normal field to remove pixels at the edges of the model that might cause aliasing

Component Inpector:

• Resolution size of the volumetric data, which will contain Resolution^3 voxels (we only handle cubic volumes at the moment)
• Margin how much empty space should be left around the mesh
• Slice Position normalized position of the "cut" within the volume, useful for preview, is animated form 0 to 1 when rendering the volume
• Step a threshold applied to the dot product of a normal and the back direction vector to decide wether a pixel is in the volume, you typically want it to be slightly above 0 as a false positive is worse than a false negative

Renderer

The renderer gets passed a Texture3D representing a volume, and renders it using raymarching. It is possible to set:

• the number of steps for raymarching,

• wether or not depth is taken in account (in this case at each step on the ray depth is tested against the scene depth read from the camera depthbuffer).

Rendering without depth, the object is overlayed on the scene

Rendering with depth turned on, the volume blends with scene elements