*************** Diffuse Shaders *************** .. admonition:: Reference :class: refbox | Mode: All Modes | Panel: :menuselection:`Shading/Material --> Diffuse` 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. Common Options ============== All diffuse shaders have the following options: Color Select the base *diffuse color* of the material. Intensity The shader's brightness, or more accurately, the amount of incident light energy that is actually diffusely reflected towards the camera. Ramp Allows you to set a range of colors for the *Material*, and define how the range will vary over a surface. See :doc:`Color Ramps ` for details. Technical 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). .. figure:: /images/matgen02.jpg Light re-irradiated in the diffusion phenomenon. .. tip:: Shader Names Some shaders are -- traditionally -- named after the people, who first introduced the models on which they are based. Lambert ======= .. admonition:: Reference :class: refbox | Mode: All Modes | Panel: :menuselection:`Shading/Material --> Shaders` .. figure:: /images/material-shader-lambert.jpg :width: 320px Lambert Shader. 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. .. figure:: /images/material-shader-lambert-settings.png :width: 220px The Lambert diffuse shader settings. Oren-Nayar ========== .. admonition:: Reference :class: refbox | Mode: All Modes | Panel: :menuselection:`Shading/Material --> Shaders` .. figure:: /images/material-shader-oren-nayar.jpg :width: 320px Oren-Nayar Shader. 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. Options ------- Roughness The roughness of the surface, and hence, the amount of diffuse scattering. .. figure:: /images/material-shader-oren-nayar-settings.jpg :width: 200px The Oren-Nayar diffuse shader settings. Toon ==== .. admonition:: Reference :class: refbox | Mode: All Modes | Panel: :menuselection:`Shading/Material --> Shaders` .. list-table:: * - .. figure:: /images/material-shader-toon.jpg Toon Shader, Different Spec. - .. figure:: /images/material-shader-toon-vary.jpg Toon Shader Variations. 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. Options ------- Size The size of the lit area. Smooth The softness of the boundary between lit and shadowed areas. .. figure:: /images/material-shader-toon-settings.jpg :width: 200px The Toon diffuse shader settings. Minnaert ======== .. admonition:: Reference :class: refbox | Mode: All Modes | Panel: :menuselection:`Shading/Material --> Shaders` .. figure:: /images/material-shader-lambert.jpg :width: 320px Minnaert Shader. 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". Options ------- Dark The darkness of the 'lit' areas (higher) or the darkness of the edges pointing away from the light source (lower). .. figure:: /images/material-shader-minnaert-settings.jpg :width: 200px The Minnaert diffuse shader settings. Fresnel ======= .. admonition:: Reference :class: refbox | Mode: All Modes | Panel: :menuselection:`Shading/Material --> Shaders` .. list-table:: * - .. figure:: /images/material-shader-fresnel-vary.jpg Various settings for the Fresnel shader, Cook-Torr Specular shader kept at Intensity 0.5, Hardness: 50. - .. figure:: /images/material-shader-fresnel.jpg Fresnel Shader, Different Spec. 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. Options ------- Fresnel Power of the Fresnel effect, 5.0 is max. Factor Blending factor of the Fresnel factor to blend in, 5.0 is max. .. figure:: /images/material-shader-fresnel-settings.jpg :width: 200px The Fresnel diffuse shader settings. Emit Amount of light to emit Ambient Amount of global ambient color the material receives Translucency Amount of diffuse shading on the back side Shadeless 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). .. seealso:: 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.