PathMax

A voxel path traced shaderpack for Iris.

PathMax lights the world by tracing rays through a voxel copy of it that is rebuilt every frame. A torch lights the room from the direction it actually sits in and casts a real shadow. Colour bleeds off the block it bounced from. A lava lake lights the ceiling above it, and nothing in the Nether is lit by a sun, because there isn't one.

Reflections are screen-space, so what you see in water is the finished frame — global illumination, emission, fog and all — rather than a simplified copy of the world re-lit by an approximation.

What's in it

Lighting

• Path traced global illumination, denoised in screen space
• Block lights sampled straight out of the voxel grid with a shadow ray each, so two lamps in one room are two lamps and not one average
• Sun visibility read from the shadow map at every bounce — finer than the grid and eight times cheaper than a second march
• Coloured light through stained glass: on the floor, in the air, and carried by the bounce, so a rose window paints the whole room
• Emissive surfaces driven by the texture rather than a flat per-block value

Atmosphere

• Volumetric light, with an optional second pass lit by lamps instead of the sun
• Volumetric clouds that also show up in reflections
• Light pollution — a town over the hill, its glow standing on the horizon and drowning the faintest stars first
• Height-based aerial perspective tuned against real visual-range figures
• Procedural stars, fixed size on screen

Water

• Screen-space reflections with roughness, refraction, foam and caustics
• Optional volumetrics above and below the surface, with real absorption over the real path length
• Optional waves and surface detail

Materials

• labPBR, with an integrated fallback for packs that ship no specular map
• Subsurface scattering for foliage, driven by shadow-map thickness
• Optional parallax occlusion mapping