Curved Silhouette Parallax Occlusion Mapping (CSPOM)

Curved Silhouette Parallax Occlusion Mapping (CSPOM)

CSPOM is an advanced shader that creates the illusion of complex geometric detail on flat surfaces using heightmaps and ray marching, avoiding the heavy cost of actual mesh tessellation.

Building on traditional POM, CSPOM adds silhouette clipping for convincing cut-out edges and extends the technique to curved or spherical surfaces.

Supports:

• URP

• HDRP

Created and tested in Unity 6.

🚀 Additional Features

📏 Pixel Depth Offset (HDRP)

HDRP supports Pixel Depth Offset (PDO), allowing displaced pixels to write to the depth buffer for:

• Improved depth perception

• Better interaction with scene geometry

• Shadow casting

• Ambient Occlusion support

• Improved decal projection alignment

Note: URP does not support PDO.

⚡ Built From Scratch

A POM implementation written in HLSL and integrated into Shader Graph through reusable subgraphs to make it modular.

Useful both as a production-ready solution and as a reference for developers that are simply interested in advanced shader techniques.

🧩 Shader Graph Ready

Modular Shader Graph workflow with included:

• Core POM Subgraph

• Flat Silhouette Subgraph

• Curved Silhouette Subgraph

• Combined CSPOM Subgraph

• Example Lit Shader Graph

Use the included Lit shader immediately or add the CSPOM node to your own graphs.

🎯 View-Angle Step Optimization

Ray march steps are reduced when viewing surfaces head-on and increased only at grazing angles, minimizing unnecessary texture sampling.

📉 Distance-Based LOD

Automatically reduces cost at distance by lowering ray march steps and sampling lower mip levels.

📦 Included

• Full HLSL source code for a POM implementation

• Shader Graph subgraphs

• Example Lit shader

• Example materials and textures

• Documentation

• Demo scene

⚠️ Limitations

• CSPOM simulates geometric detail entirely in the shader; it does not modify the underlying mesh. Because of this, the original mesh silhouette can become visible from certain viewing angles where the actual geometry is exposed, such as when looking toward a sharp corner. This is an inherent limitation of Parallax Occlusion Mapping as a technique, rather than a limitation specific to CSPOM. The effect works best on relatively simple geometry and should not be expected to perfectly reproduce arbitrary 3D geometry.

• Curved silhouettes require carefully tuned clipping thresholds. At extreme grazing angles, some visual artifacts may occur as the shader determines where the virtual silhouette should be clipped.

• Pixel Depth Offset (HDRP) disables early-Z culling, which can increase the rendering cost of affected pixels.

• CSPOM is significantly cheaper than approaches such as dense geometry or tessellation, but it is still a ray-marching technique and therefore has a non-zero performance cost. The cost depends on factors such as screen coverage, viewing angle, ray-march step count, and distance.