Manual/Specular Shaders
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Specular Shaders
Mode: All Modes
Panel: Shading/Material Context → Shaders
Hotkey: F5
Description
Specular shaders create the bright highlights that one would see on a glossy surface, reflected by light sources. Unlike diffuse shading, specular reflection is viewpoint dependent. According to Snell's Law, light striking a specular surface will be reflected at an angle which mirrors the incident light angle, which makes the viewing angle very important.
| Note:
It is important to stress that the specular reflection phenomenon discussed here is not the reflection we would see in a mirror, but rather the light highlights we would see on a glossy surface. To obtain true mirror-like reflections you would need to use the internal raytracer. Please refer to section XI - RENDERING of this manual. |
Options
Each specular shader shares two common options:
- Specular colour
- The colour of the specular highlight
- Spec
- The intensity, or brightness of the specular highlight. This has a range of [0-2], which effectively allows more energy to be shed as specular reflection as there is incident energy.
As a result, a material has at least two different colours, a diffuse, and a specular one. The specular color is normally set to pure white, but it can be set to different values for various effects.
Technical Details
In reality, Diffusion and Specular reflection are generated by exactly the same process of light scattering. Diffusion is dominant from a surface which has so much small-scale roughness in the surface, with respect to wavelength, that light is reflected in many different directions from each tiny bit of the surface, with tiny changes in surface angle.
Specular reflection, on the other hand, dominates on a surface which is smooth, with respect to wavelength. This implies that the scattered rays from each point of the surface are directed almost in the same direction, rather than being diffusely scattered. It's just a matter of the scale of the detail. If the surface roughness is much smaller than the wavelength of the incident light it appears flat and acts as a mirror.
CookTorr
Mode: All Modes
Panel: Shading/Material Context → Shaders
Hotkey: F5
Description
CookTorr (Cook-Torrance) is a basic specular shader that is most useful for creating shiny plastic surfaces. It is a slightly optimised version of Phong.
Options
- Hard
- The hardness, or size of the specular highlight
Phong
Mode: All Modes
Panel: Shading/Material Context → Shaders
Hotkey: F5
Description
Phong is a basic shader that's very similar to CookTorr, but is better for skin and organic surfaces
Options
- Hard
- The hardness, or size of the specular highlight
Blinn
Mode: All Modes
Panel: Shading/Material Context → Shaders
Hotkey: F5
Description
Blinn is a more 'physical' specular shader, often used with the Oren-Nayar diffuse shader. It can be more controllable because it adds a fourth option, an index of refraction, to the aforementioned three.
Options
- Hard
- The hardness, or size of the specular highlight. The Blinn shader is capable of much tighter specular highlights than Phong or CookTorr.
- Refr
- The 'Index of Refraction'. This parameter is not actually used to compute refraction of light rays through the material (a ray-tracer is needed for that), but to correctly compute specular reflection intensity and extension via Snell's Law.
Toon
Mode: All Modes
Panel: Shading/Material Context → Shaders
Hotkey: F5
Description
The Toon specular shader matches the Toon diffuse shader. It is designed to produce the sharp, uniform highlights of cartoon cels.
Options
- Size
- The size of the specular highlight
- Smooth
- The softness of the highlight's edge
Hints
Toon shader can be also be accomplished in a more controllable way using ColorRamps.
WardIso
Mode: All Modes
Panel: Shading/Material Context → Shaders
Hotkey: F5
Description
WardIso is a flexible specular shader that can be useful for metal or plastic.
Options
- rms
- rms controls, in effect, the size of the specular highlight, though using a different method to that of the other specular shaders. It is capable of extremely sharp highlights.
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