Materials

• Back lighting (rendering/pathtracing/back_lighting): light through leaves, paper and curtains, with coloured shadows; back light texture.
• Transmission (BaseMaterial3D section, rendering/pathtracing/transmission): thin glass, tinted and blurred by roughness, with tinted shadows; transmission texture; TRANSMISSION in shaders; glTF KHR_materials_transmission.
• Clearcoat (rendering/pathtracing/clearcoat): matches raster, with traced coat reflections; coat texture.
• Subsurface scattering (rendering/pathtracing/subsurface_scattering, radius subsurface_scattering_scale): random walk inside closed meshes; skin, wax and marble soften and thin parts glow when backlit.
• Wet surfaces (BaseMaterial3D Wetness: wetness_enabled, wetness_porosity): porous surfaces darken and turn glossier as the weather map gets wet, raster and path traced; get_wetness_shader_code() for ShaderMaterials.
• Shaders writing BACKLIGHT or TRANSMISSION tint their shadows.
• Textures filter like raster (ray cones, anisotropic).
• Even, tinted glass shadows.
• Back-face normals in vertex(); IN_SHADOW_PASS in custom shaders; SPECULAR_NORMAL output, a separate normal for the specular lobe under path tracing.

Images#

Transmission: the spheres show through and the floor gets green-tinted light.

Back lighting: green and red light on the floor.

Clearcoat: sharp coat highlights, as in raster.

Layer textures: checkered coloured shadows.

Subsurface scattering: thin slabs glow, thick ones stay dark.

Wet surfaces: the more porous, the darker and glossier when wet; raster and path traced match.