# Raymarching SDF Scenes

**Track:** Advanced Shaders & GPU — Advanced Creative Coding — proposed (50)
**Framework / surface:** GLSL
**Level:** Hard
**Prerequisites:** Distance Fields for Shapes, The Fragment Toolkit Beyond UV

**In one line:** Sphere tracing, analytic normals, lambert + soft shadows + AO.

## Theory, aesthetics & inspiration

Raymarching renders without polygons: a signed-distance function reports how far any point lies from the nearest surface, and sphere tracing advances a ray by exactly that safe radius until it grazes geometry. John Hart named the method in 1996, but Inigo Quilez turned it into an art form on Shadertoy, where shaders like Rainforest and Snail reconstruct entire ecosystems in a single fragment program. Surface normals follow from the field's gradient, sampled by small offsets; Lambert diffuse, soft shadows estimated from the closest approach along the light ray, and distance-based ambient occlusion complete a lighting model that is compact, analytic, and unmistakably luminous.