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Renderer Overview

ForgedThoughts is built around a CPU-first SDF renderer. The main production path today is trace, a classical Whitted-style recursive renderer tuned for fast iteration on signed distance field scenes.

Why Whitted​

The project deliberately prioritizes:

  • fast feedback while modeling
  • predictable render cost on the CPU
  • clear reflections and refractions for SDF scenes
  • practical lookdev over slow global-illumination convergence

That is why the current renderer is not centered on a path tracer. For this project, a CPU path tracer quickly becomes too slow and too noisy to be the default tool.

Current Render Paths​

  • trace The main renderer. It handles direct lighting, recursive reflection, recursive transmission, medium attenuation, soft-shadow-capable sphere lights, environment backgrounds, and debug AOVs.

  • depth A fast grayscale depth preview for quick shape iteration and scene inspection.

Current Trace Features​

  • Whitted-style recursive reflections
  • dielectric transmission and refraction
  • rough dielectric approximation with deterministic multi-sample branching
  • Beer-Lambert medium attenuation
  • smooth-boolean shading/material blending
  • point lights
  • sphere lights for softer shadows
  • environment lights and procedural environment backgrounds
  • debug AOVs such as depth, normal, material id, IOR, transmission, Fresnel, and hit distance

Acceleration​

The renderer currently supports three scene acceleration modes:

  • Naive Direct scene evaluation with no extra acceleration structure. This is simple and still useful for very small scenes or debugging.

  • Bvh A hierarchy over lowered scene leaves. This is currently the default fallback when no CLI or RenderSettings.accel override is provided.

  • Bricks A uniform 3D grid accelerator over lowered scene leaves.

In practice, the best mode depends on scene structure. CLI --accel still overrides RenderSettings.accel when both are provided.

Forge Runtime​

Forge is JIT-accelerated where it matters most for rendering, especially for hot custom SDF code and supported material hooks.

That lets performance-sensitive assets stay in Forge instead of forcing every useful object or material into native Rust just to get acceptable render speed.

Important Tradeoffs​

  • trace is not a full global-illumination renderer
  • rough glass is approximate and budgeted to stay practical on the CPU
  • some material behavior is still renderer-specific rather than fully generic
  • renderer correctness is improving incrementally, but speed remains a core design constraint

Direction​

The renderer direction is incremental improvement of trace, not replacing it with a slow unbiased architecture.

Near-term goals:

  • better dielectric quality
  • better light types and softer shadow control
  • stronger environment lighting and reflections
  • more GI-like features where they fit the CPU/Whitted model
  • continued regression coverage for stable scenes