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The VRscan material allows the rendering of scanned BRDF material data stored in .vrscan files. These files are produced by Chaos Group's own internal material scanner and accompanying material creator software.

The scanned material renders the captured appearance of an actual physical material sample, that has been scanned with special scanner hardware. The material goes beyond single-point BRDF capture and can faithfully represent the textured appearance of a large number of real-world surfaces using bidirectional texture function (BTF) approximation.

Because the scanned material simply reproduces the way a physical material responds to light, is has no notion of "diffuse" or "reflection" components, "normal" or "bump" maps.

Currently, the material can render only opaque surfaces. Also, for the moment except for some general tint control, the material is unmodifiable - i.e. you can't change glossiness, increase reflectivity etc. You can only change the overall tint of the material. In its present form, the material is targeted at users that need to match exactly a given real-world sample.

The .vrscan files tend to be quite large as they need to pack a lot of data (they need to describe the BRDF of the material over its entire surface).

For more details on VRscans, please see the VRscans Chaos Scans documentation space for information on downloadable sample scenes projects and Frequently Asked Questions or visit the VRscans.com Chaos Scans website.

File – The file name with the data for the scanned material; usually has a .vrscan extension.

Tiling Factor – Global multiplier for U and V coordinates. See the Tiling Factor example below.

Plain Material – A strategy used for material display. It controls the visibility of textures (if present). Possible values are:

Average BRDF – Averages the BRDF and removes any anistropy. This mode can be used on objects without proper UV coordinates. 
Average isotropic BRDF – Averages the BRDF and can be used to speed up the rendering for previews. Because texture details are removed, this also removes any tiling artifacts that might arise if the scanned sample does not tile very well. UV coordinates are still needed because most BRDFs are slightly anisotrpic. 

Two Sided Sided – Forces the back-facing polygons to be shaded in the same way as the front-facing ones. When this option is disabled, the back-facing polygons appear black.

Transparency – Disables transparency for materials that store such information. this can be useful for speeding up the rendering, especially when the transparency produces little or no effect.

Trace Depth – Controls the number of reflection bounces. A value of -1 means that the reflection bounces are controlled by the global V-Ray trace depth in the Global switches rollout of the Renderer Settings Settings > Renderer Tab > Optimization.

Cutoff – A threshold used to speed up reflections. If the contribution of reflections falls below this threshold, the reflections are not traced. This is similar to the Cutoff threshold of the Vthe V-Ray Generic material.

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The section displays some useful information contained in the .vrscan file, like the actual material sample size.

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The Appearance parameters allow for further customization of the scanned material. 

Filter – Enables the use of the color filter.

Filter Color – A color multiplier for the material sample and can be used to tint the material (it affects the color of the reflections as well as a post effect). See the Color example below.

Filter Strength – Multiplies the effect of the filter.

Paint – Enables the use of Paint Color.

Paint Color – Changes the color of the material without loosing the texture or change the reflection color. For example, changing the color of wood or leather without losing their textures. See the Color example below.

Paint Strength – Multiplies the effect of the paint.

Gamma – Adjusts the gamma of the material (including paint color and filter color if used) as a post effect.

Saturation – Controls the saturation of the material (including paint color and filter color if used) as a post effect.

The clear coat parameters are similar to those found in the VRay Car Paint Material. These parameters are only available if while scanning an object, it is determined that the object possesses the properties of a material with a clear coat.

Reflection – Enables the tracing of a clear coat layer for the material's reflection.

Specular – Enables highlights from point light sources for the coat layer.

IOR – Determines the Index of Refraction of the coat layer and controls the strength of the reflections. A value of 1.0 does not produce any reflections and disables the coat layer. Higher values produce stronger clear coat reflections. The .vrscan file contains the correct value (typically 1.6) for this parameter, which is set automatically when the file is loaded but can be adjusted higher or lower if needed.

Bump Strength – The coat layer has a built-in bump map stored into the material sample file. This parameter allows control over the strength of that bump.

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