A diffuse shader determines, simply speaking, the general color of a material when light shines on it. Most shaders that are designed to mimic reality give a smooth falloff from bright to dark from the point of the strongest illumination to the shadowed areas, but Blender also has other shaders for various special effects.
All diffuse shaders have the following options:
- Select the base diffuse color of the material.
- The shader’s brightness, or more accurately, the amount of incident light energy that is actually diffusely reflected towards the camera.
- Allows you to set a range of colors for the Material, and define how the range will vary over a surface. See Color Ramps for details.
Light striking a surface and then re-irradiated via a Diffusion phenomenon will be scattered, i.e. re-irradiated in all directions isotropically. This means that the camera will see the same amount of light from that surface point no matter what the incident viewing angle is. It is this quality that makes diffuse light viewpoint independent. Of course, the amount of light that strikes the surface depends on the incident light angle. If most of the light striking a surface is reflected diffusely, the surface will have a matte appearance (Light re-irradiated in the diffusion phenomenon).
Some shaders are – traditionally – named after the people, who first introduced the models on which they are based.
This is Blender’s default diffuse shader, and is a good general all-around workhorse for materials showing low levels of specular reflection.
- Johann Heinrich Lambert (1728-1777)
- was a Swiss mathematician, physicist and astronomer who published works on the reflection of light, most notably the Beer-Lambert Law which formulates the law of light absorption.
This shader has only the default option, determining how much of available light is reflected. Default is 0.8, to allow other objects to be brighter.
Oren-Nayar takes a somewhat more ’physical’ approach to the diffusion phenomena as it takes into account the amount of microscopic roughness of the surface. Michael Oren and Shree K. Nayar Their reflectance model, developed in the early 1990s, is a generalization of Lambert’s law now widely used in computer graphics.
- The roughness of the surface, and hence, the amount of diffuse scattering.
The Toon shader is a very ’un-physical’ shader in that it is not meant to fake reality, but to produce cartoon cel styled rendering, with clear boundaries between light and shadow and uniformly lit/shadowed regions.
- The size of the lit area.
- The softness of the boundary between lit and shadowed areas.
Minnaert works by darkening parts of the standard Lambertian shader, so if Dark is 1 you get exactly the Lambertian result. Higher darkness values will darken the center of an object (where it points towards the viewer). Lower darkness values will lighten the edges of the object, making it look somewhat velvet. Marcel Minnaert (1893-1970) was a Belgian astronomer interested in the effects of the atmosphere on light and images who in 1954 published a book entitled «The Nature of Light and Color in the Open Air».
- The darkness of the ’lit’ areas (higher) or the darkness of the edges pointing away from the light source (lower).
With a Fresnel shader the amount of diffuse reflected light depends on the incidence angle, i.e. from the direction of the light source. Areas pointing directly towards the light source appear darker; areas perpendicular to the incoming light become brighter. Augustin-Jean Fresnel (1788-1827) was a French physicist who contributed significantly to the establishment of the theory of wave optics.
- Power of the Fresnel effect, 5.0 is max.
- Blending factor of the Fresnel factor to blend in, 5.0 is max.
- Amount of light to emit.
- Amount of global ambient color the material receives.
- Amount of diffuse shading on the back side.
- Make this material insensitive to light or shadow.
- Tangent Shading
Use the material’s tangent vector instead of the normal for shading – for anisotropic shading effects (e.g. soft hair and brushed metal).
Settings for strand rendering in the menu further down and in the Particle System menu.
- Cubic Interpolation
- Use cubic interpolation for diffuse values, for smoother transitions between light areas and dark areas.