3Delight Principled Material
The 3Delight Principled material is our interpretation of Disney's "principled" BRDF1. Quoting from this reference, our principled material adhere to these principles:
- Intuitive rather than physical parameters should be used.
- There should be as few parameters as possible.
- Parameters should be zero to one over their plausible range.
- Parameters should be allowed to be pushed beyond their plausible range where it makes sense.
- All combinations of parameters should be as robust and plausible as possible.
3Delight Principled shader has more than the 11 parameters listed in Disney's reference in order to offer more control on the coat and also has subsurface parameters.
1 The reference document entitled "Physically-Based Shading at Disney" by Brent Burley is available for download here (as a PDF).
Coating affects the overall look in three main aspects:
- It provides a richer specular response to light as it adds a specular highlight on top of the base surface's highlight.
- It can colour light as it passes through the coating.
- It contains metallic particles (a.k.a flakes) suspended inside the coat.
The thickness of the coating layer. The thicker the layer the more it absorbs light and the less of the base layer is visible. A thickness of 0 disables the coating
How "shiny" is the coating. A value of 1 means a very shiny coating.
The colouring producing by this coating layer. Colouring will be more prominent in thicker layers.
Roughness of the coating layer.
The colour of the base layer.
Mainly controls the colour of the reflections: a reflection is metallic if the highlights and reflections retain the color of the reflective object.
Controls the strength of specular reflections on the base layer.
The roughness of the base layer.
Colour of the emitted light.
Intensity of emitted light. Final colour is Colour * Intensity.
Bump / Normal / Displacement Map
Specifies the type of mapping desired – Bump Map, Normal Map or Displacement Map. In the case of a Normal Map, a color is expected in as a value, it can be encoded in the style or DirectX or OpenGL. In case of Bump Map or Displacement Map the shader will only consider the R value. Displacement maps can be interpreted as having their center value (the one that produces no effect) at 0.0 or 0.5. Displacement is performed in Object Space, so the scale of the geometry affects its intensity. For more intuitive results, a value of 1 for the object scale is recommended. The Displacement bound used is 1, so the ideal range of values is from 0 to 1. Above 1, displacement cracks might occur. Below 1 it might be inefficient. To achieve displacements bigger that 1, using the Intensity control is recommended.
A colour input specifying bump direction (Normal Map) or intensity (Bump Map / Displacement Map).
Specifies how intense is the the bump/normal/displacement mapping effect. A value of 0 means that geometry or normals will stay unchanged whereas a value of one will affect them fully.
Select to apply bump/normal mapping to the Coating, Base Layer or Both Layers (default). Has no effect when Type is set to Displacement Map.