Lighting & Materials

The Light Studio

Those glowing orbs in the center of the top bar are your lights. Click an orb to toggle that light on or off. Hover to open a popup with its most common settings. Click the chevron (↓) to expand the studio and see all eight slots.

GMT supports up to 8 independent lights. The default scene uses a classic three-point setup: Key (primary), Fill (opposite the key, cooler), Rim (behind the subject for an outline).

Two light types

Point light

Emits from a specific (x, y, z) coordinate and falls off with distance. Best for lamps, glowing objects, interior illumination.

Directional / Sun

Parallel rays from infinity. Only rotation matters, not position — it's like sunlight. Set the angle using the Heliotrope control: the 2D circle represents the sky dome. Centre = overhead; edge = horizon.

World vs Headlamp

In each light's popup, the anchor icon toggles between two modes. Cyan anchor = World (fixed in the fractal universe); orange crossed-anchor = Headlamp (attached to the camera, moves with you).

• Headlamp: always illuminates what you're looking at. Great for exploration.
• World: stays put as you fly — creates a sense of place, like suns or glowing artifacts.

Intensity and color

Intensity is a multiplier. 1.0 is baseline, higher values overexpose (and can trigger bloom). Two ways to set it:

• Raw — simple 0–N multiplier
• Exposure (EV) — photographic scale, −4 to +10. Each step doubles/halves brightness. Much easier to balance multiple lights.

For color, use the picker for artistic control, or switch to Kelvin temperature mode for natural warm/cool tones. 2000K is candlelight; 6500K is noon daylight; 10000K is overcast shade.

Shadows

Each light has a "Cast Shadow" toggle. GMT uses raymarched soft shadows — rays march from the surface toward the light. Key controls:

• Softness — simulates the size of the light source. Low = sharp; high = diffuse.
• Intensity — shadow opacity. Lower values let some ambient light into dark areas.
• Bias — critical. Too low causes "shadow acne" (black speckles); too high causes "Peter Panning" (shadow detaches from objects). Start with the default.

Stochastic shadows (area lights)

Enable this (compile-time feature) for photorealistic soft shadows that simulate real area lights. They look noisy while you're moving but clean up beautifully when the camera is still (via temporal accumulation). Three quality levels: Hard Only (fastest), Lite Soft (balanced), Robust Soft (highest quality).

Surface materials (PBR)

Open the Shader tab in the right dock. GMT uses physically-based rendering with five main controls:

• Metallic — 0 for non-metals (plastic, stone), 1 for metals (gold, chrome). Metals have no diffuse color; they reflect tinted by the gradient.
• Roughness — 0 is mirror-smooth, 1 is chalk-rough. Controls how sharp highlights are.
• Specular — even matte surfaces reflect a little. Dial up for "wet" looks.
• Diffuse Strength — base brightness of the surface color.
• Emission — make the surface glow on its own. Choose source: full surface, a specific gradient layer, or solid color.

Advanced: reflections and volumetric glow

Reflections can be Environment Map (cheap, fake sky reflection) or Raymarched (physically accurate, fractal reflects itself — expensive, adds ~7s compile time). Use Environment Map while editing, switch to Raymarched for final renders.

Volumetric Glow lights the air near fractal surfaces. Tightness < 1 creates an outer aura; higher values give you neon Tron-style outlines. Combine with fog for atmospheric scenes.

Ambient occlusion

Darkens crevices to add depth perception. In the Shader panel, find AO Intensity and Spread. Enable Stochastic Mode with temporal AA on for photorealistic soft shading (look for the accumulation indicator to confirm it's converging).