unity-shaders

unity-shaders

Core Philosophy

Real-time shaders are programs executed concurrently across thousands of GPU cores for every single vertex and pixel on screen. In modern Unity (URP and HDRP), authoring game visual effects requires mastering both node-based Shader Graph and text-based HLSL. Writing efficient shaders is an exercise in computational frugality: every trigonometric function, dependent texture read, or unnecessary full-precision float in the fragment shader directly burns GPU fill-rate and tanks mobile/console frame rates.

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4-Step Unity Shader & VFX Pipeline

Step 1: Pipeline Architecture: URP vs HDRP Custom Passes

1. Universal Render Pipeline (URP):
   • Optimized for mobile, Nintendo Switch, VR, and PC.
   • Single-pass forward and deferred rendering paths.
   • Extensible via ScriptableRendererFeature and custom Render Passes.
2. High Definition Render Pipeline (HDRP):
   • High-end PC and current-gen consoles (PS5, Xbox Series X).
   • Compute-shader-driven deferred clustered lighting, volumetric fog, and ray-tracing.
   • Extensible via CustomPassVolume.

Step 2: HLSL Structure & Precision Optimization

1. Precision Standard:
   • float (32-bit): World-space coordinates, UV coordinates, depth calculations.
   • half (16-bit): Colors, normals, vector directions, ambient lighting calculations (saves 50% ALU register pressure on mobile GPUs).
2. Core Shader Pass Layout:
   • Vertex Shader: Transforms object-space vertices to clip space: $$P_{\text{clip}} = M_{\text{projection}} \times M_{\text{view}} \times M_{\text{model}} \times P_{\text{local}}$$
   • Fragment / Pixel Shader: Calculates final RGBA color per rasterized pixel.

Step 3: Math & Procedural Effects (Dissolve, Rim Light, Fresnel)

1. Schlick's Fresnel Approximation (Rim Lighting): $$F \approx F_0 + (1 - F_0)(1 - \vec{N} \cdot \vec{V})^5$$
   • Where $\vec{N}$ is surface normal and $\vec{V}$ is normalized view direction vector.
2. Procedural Dissolve with Alpha Clipping:
   • Sample a Simplex/Voronoi noise texture, subtract a _Cutoff property, and execute clip(noise - cutoff).