Coloring & Gradients

Fractals don't have texture maps

Real-world 3D models get color from painted textures. Fractals can't, because they're infinite — there's no "UV map" to paint on. Instead GMT colors each point mathematically, using one of several mapping modes:

1. At each surface point, the engine measures a number (distance from origin, iteration count, etc.)
2. That number is transformed by Scale, Offset, Phase, and Repeat
3. The final value (0.0 to 1.0) looks up a color from the gradient

Two tabs work together: Shader (controls mapping) and Gradient (the color ramp).

Mapping modes — the big picture

Pick the "Mapping" dropdown. Modes divide into two families:

Geometric mappings

• Orbit Trap — minimum distance the orbit point reaches to origin. Cellular, techno-organic interiors.
• Orbit X / Y / Z — like orbit trap but projected onto one axis. Reveals internal strata.
• Orbit W — full 3D orbit distance. Smooth, rounded color regions.
• Radial — distance from origin to the surface point. Spherical gradients.
• Z-Depth — based on the Z coordinate. Height-map / landscape look.
• Angle — polar angle around the Z axis. Spirals and pinwheels.
• Normal — surface slope. Pseudo-lighting; "snow on peaks" effects.

Fractal mappings

• Iterations (Glow) — how many steps before divergence. Classic "Electric Sheep" glowing bands.
• Raw Iterations — same but un-smoothed. Banded, step-like look.
• Decomposition — analytic angle decomposition. Checkered, grid-like patterns. Very sensitive to Escape Radius.
• Flow — combines decomposition with iterations. Spirals that follow internal flow lines.
• Potential (Log-Log) — electrical potential of the set. Ultra-smooth gradient bands.

Transform controls

Once a mapping is selected, these sliders shape how its values spread across the gradient:

• Scale — stretches or compresses the pattern. Higher = more repetitions.
• Offset — scrolls through colors without changing pattern shape.
• Phase — rotates the gradient starting point. Same colors, different alignment.
• Repeats — how many times the gradient tiles across the value range. Works beautifully with smooth mappings like Radial or Potential.
• Gamma (Bias) — reshape the distribution without changing the gradient. < 1 pushes toward bright; > 1 toward dark.
• Twist — warps the mapping. Subtle values add organic flow; extreme values go psychedelic.

The histogram

The coloring panel shows a live histogram of how color values are distributed across the fractal surface. If all your values are bunched on one side, colors will look flat. Adjust Scale, Offset, and Gamma while watching the histogram spread out — that's the key to vibrant, well-balanced color.

Dual-layer blending

You can run two different mapping setups simultaneously and blend them. Think "base rock + glowing veins." Each layer has its own mapping mode, its own gradient, its own transform sliders.

Blend modes:

• Mix — straight linear blend
• Add — layer 2 brightens layer 1
• Multiply — layer 2 tints/darkens layer 1
• Bump — layer 2 acts as a mask

A classic combination: Layer 1 = Orbit Trap for interior cells, Layer 2 = Iterations for glowing edges, blend = Add. You get detailed mass with a luminous outline.

The gradient editor

Open the Gradient tab. Click anywhere on the ramp to add a color stop. Drag stops to reposition; double-click to set the color; right-click a stop to delete. Many built-in palettes are available from the dropdown at the top.

Color Iterations — the power slider most users miss

In the Shader panel's advanced controls, Color Iterations (0–24) sets the iteration count at which orbit-trap colors are sampled. Low values color based on early, large-scale structure of the fractal. High values reveal deep internal detail. Sweep this slider — the same fractal with the same gradient looks like ten different objects at different values.