#lighting

The practical patterns for Sandbox.Decal: orienting the projection box to a hit normal, keeping a decal byte-identical across multiplayer peers, making paint follow an animated character, and scaling to thousands of decals without a performance cliff, plus the pitfalls that catch each one.

At single-digit sun elevation a street canyon gets no direct ground light, so nothing on the ground casts a visible shadow while the cascade is billed in full; fix it with sun azimuth, not renderer flags.

On current builds a PointLight created with Shadows = true contributes nothing to the frame: no light, no shadow, silently. The six-face cubemap shadow path is broken while SpotLight's single-view path works. For a directional lamp, cast with a downward SpotLight instead.

A projected Sandbox.Decal renders its colour as lit surface albedo, not an unlit overlay: a pale/pastel tint washes out to a barely-there stain on a bright surface.

Scaling DirectionalLight.LightColor does not dim the sun: from 0.001 to 5.0 it renders identically; only Color.Black turns it off. LightColor sets hue, not brightness. A day/night brightness ramp built on it is a silent no-op.

Geometry parented under an IsStatic root samples its lit appearance at creation time and never resamples. A runtime write to a light component is invisible on that geometry until the world is rebuilt. So a lighting A/B that mutates a light live and re-observes static geometry shows no change, no matter how large the delta. The comparison reads as no effect when the real answer is never re-sampled. Run static-geometry lighting tests through the world build command, not a live component write.

A near-white chalky sky stays mid-grey or blue: fixing the sky texture alone isn't enough because the default tonemapping curve crushes highlights.

The engine ships its own render quality profiles, backed by real convars, that CAP what your scene asked for. A scene authoring 4 shadow cascades renders 2 for a Low-shadow player. And post-processing (AO, DOF, bloom, tonemapping, SSR) is opt-in per camera: none of it runs until the game adds the component, so a code-created camera renders flat, ungraded, and un-occluded no matter how well the lights are authored.