Material SettingsWhen setting up materials for StemCell there are some general setting that must always be used. These settings are necessary to maximize consistency and portability to other renderers. Setting up for V-Ray is pretty straight forward with a few minor adjustments. With V-Ray you will be using the VRayMtl material. Download the Calibration scene with example materials here, or below the example image. Download Material Example Calibration Scene for these five material examples.
IOR values can also be set on the Refraction IOR settings as long as the Fresnel IOR is linked. Refractive materials must use only the Refract IOR.
BRDF type must always be set to GGX. This shading model provides the most physically accurate reflections for metallic materials.
Texture Map SettingsTexture maps must be applied to the right slots with the correct gamma. This section is a guide to correct material setup. You can also find the correct gamma types listed in the tables located in the Textures & Materials section of the StemCell 3D Modeling Specification.
Plug the Diffuse map into the Diffuse slot. This is a sRGB map so it needs to be left on Automatic(Recommended) for bitmap gamma.
The Specular map needs to be plugged into the Reflect slot. This is a sRBG map so it needs to be left on Automatic(Recommended) for bitmap gamma.
If the model uses an Emissive map, this will be plugged into the Self-Illumination slot. This is a sRBG map so it needs to be left on Automatic(Recommended) for bitmap gamma.
The Glossiness texture map is going to be plugged into Reflection Glossiness/RGlossiness. This is a Linear map so it needs to use Gamma Override set to 1.0.
When plugging in a Linear map make sure that Gamma is changed to “Override 1.0”. This applies to the Glossiness, Normal, and Refraction Map.
Transparent MaterialsIf transparent materials are present, they must follow the guidelines in How to setup Transparency & Opacity for StemCell.
If the model uses an Opacity map, this will be plugged into the Opacity slot. This is a sRBG map so it needs to be left on Automatic(Recommended) for bitmap gamma.
If the material uses Refraction, you may choose a value from the color picker that is Achromatic, meaning it possesses no hue information. The value used for Refraction Color should be Black, White, or a varying shade of Grey.
If the material uses a Refraction map, this will be plugged into the Refract slot. This map should also be Achromatic. This is a Linear map so it needs to use Gamma Override set to 1.0, shown above. Then set the other required settings for Refraction below.
Turn on “Affect shadows” check box in the Refract section’s settings.
Change the “Affect channels” option to “Color+alpha”.
What if my texture map set has multiple material types?There are some situations where a material may require a dielectric and metallic materials on the same surface. See When to use Blend Materials for more information on these situations.
When an individual dielectric or metallic material can not be separated by object, that is the only time a blend material needs to be used. The Blend material is used to combine the 2 different IORs for dielectrics and metals. This way one material applied to the single object represents both surface types. A dielectric version of the material is created as Material 1 using correct low IOR value. A copy of that material is made for the metallic version as Material 2 with correct high IOR. The Metallic map is used as the Mask.When plugging in your materials to the Blend material, typically the lower IOR material will be plugged into Material 1 while the higher IOR material will be plugged into Material 2. The two materials will then be blended together by adding the Metallic map to the Mask slot.