Cook Torrance Material Node

Cook Torrance is a major step up from Blinn/Phong. It uses a microfacet model: the surface is modeled as countless micro-facets of varying size, and the shader computes how light reflects off those facets based on:

• D - distribution of the micro-facets (Beckmann).
• G - geometric attenuation (mutual shadowing).
• F - Fresnel equation (angular reflectivity).

Result: a physically correct render of metals, rough surfaces, and anything with strong Fresnel behavior (more reflection at grazing angles).

• Effects Library: Tools > 3D > Material > Cook Torrance
• Quick add: right-click in the Node Editor → Add Tool > 3D > Material > Cook Torrance

• Diffuse Color (orange) - base color and texture. For a pure metal: set it very dark (black or nearly) because metals barely diffuse light.
• Specular Color (green) - highlight color. This is where the metal's tint is set: gold (RGB 1.0, 0.86, 0.57), copper, aluminum, etc.
• Specular Intensity (magenta) - highlight intensity map.
• Specular Roughness (white) - roughness map. Textures that vary per area to simulate local wear.
• Specular Refractive Index (white) - map controlling Fresnel.
• Bump Map (white) - 3D material for apparent relief.

Cook Torrance → Shape 3D (MaterialInput) → Merge 3D ← Camera, Lights → Renderer 3D

For a convincing metal, you also need an environment map reflecting on it - add it with a Reflect node in combination.

For a pure metal: a very dark (black) Diffuse Color - metals diffuse almost no light, everything goes through the specular.

For a rough non-metallic surface (dirt, rock): a normal Diffuse Color + high Roughness + moderate Specular Intensity.

Specular Color

Color of the highlight. PBR rule:

• Metal → tinted Specular Color (gold, copper, silver, iron…).
• Non-metal → gray/white Specular Color (neutral reflectance, always ≈ 0.04 in PBR).

Specular Intensity

Strength of the highlight. Combine it with Roughness for the final look.

Roughness (0.0 - 1.0+)

Roughness of the surface. According to the docs: "the higher the value, the wider the falloff, and the more brushed / metallic the surface looks".

• 0.05 - mirror surface (polished chrome).
• 0.2 - standard polished metal.
• 0.5 - brushed metal, wide highlight.
• 0.8+ - very rough, barely visible highlight.

Do Fresnel is the essential checkbox that enables the physically correct behavior of a reflection: the more the surface is seen at an angle, the more it reflects.

• Without Fresnel - the reflection has a constant intensity across the whole surface. "Metallic" but not very realistic.
• With Fresnel - strong reflection at grazing angles, weak head-on. The real behavior of metal or glass.

Refractive Index sets the strength of the Fresnel:

• 1.0 - no Fresnel (vacuum / air).
• 1.5 - standard glass.
• 1.33 - water.
• 2.4 - diamond.
• 10+ - metal (high values to simulate the strong reflectivity of metal).

Rule: enable Do Fresnel as soon as you want realism. Without it, your metals will look like "plastic painted to look like metal".

Blinn

Fast, non-physical model. Perfect for plastic, paint, simple materials. Less control but lightweight to compute.

Cook Torrance (this node)

Physically based PBR model. Required for believable metals, brushed metal, and any material with a strong Fresnel. Slower but much more realistic.

Rule: Blinn for matte and plastic surfaces, Cook Torrance for metals, glossy ceramics, and anything that needs Fresnel.

• Polished gold - nearly black Diffuse, Specular Color (R 1.0, G 0.86, B 0.57), Roughness 0.15, Do Fresnel on, Refractive Index 10+.
• Mirror chrome - black Diffuse, white Specular Color, Roughness 0.05, Fresnel on. Reflections through a Reflect node or an environment map are a must.
• Brushed aluminum - dark Diffuse, Specular Color (0.91, 0.92, 0.92), Roughness 0.5-0.6, Fresnel on.
• Colored glossy ceramic - bright Diffuse color, white Specular Color, Roughness 0.1, moderate Specular Intensity, Fresnel on (IOR 1.5).
• Local wear - a variable roughness texture connected to Specular Roughness (smooth parts in frequent-contact areas, rough elsewhere).
• PBR pipeline from Substance / Blender - import the Base Color, Roughness and Metallic maps and connect them to the matching inputs.

• Black Diffuse for pure metal - a classic mistake: leaving Diffuse gray. A metal has almost no diffuse; all the color is in the Specular Color.
• Do Fresnel always on for photorealism. Never compromise on that.
• Textured Roughness to break uniformity - even a subtle variation in roughness instantly makes the material more believable.
• Environment map required - without environment reflections, a metal looks dull (just point highlights from the lights). Combine with Reflect + CubeMap.
• Slower than Blinn - for background or barely visible objects, Blinn is enough. Cook Torrance for hero objects.
• PBR metallic workflow - to match a Substance/Blender render exactly, the maps must be in linear color space (not sRGB). Use a Gamut node before if needed.