Transmission Tips in Arnold
The point of this page is to help our contributors in the creation of transparent textures and materials. This is not to say our way is superior, but in fact a way to achieve the most consistent conversion results to date. The following notes are based on real time friendly modern day practices, so most content should flow seamlessly into current DCC and RT applications.
Note that this workflow within 3ds Max uses Arnold’s Standard Surface shader. Weights for Base Color and Specular should always be set to 1.0. If a transmission or emissive map are used, then their weights should also be set to 1.0.
In the world of 3D, there is opacity, and there is transparency.
When we say opacity, we typically mean an opacity cutout. Which means an object or part of an object is either visible or not visible. The opacity map should contain only pure black or pure white values to determine which areas of the object will be visible and not. This should be the only method in which opacity maps are used. Besides this use case, Opacity is not used in any other way for the purposes of StemCell models.
When the term transparency is used, we refer to objects that are translucent, such as glass or water. With Arnold as the renderer, the map used for transparency is called the transmission map. The transmission map can be set as any RGB value you would like.
Transmission
The brighter the Transmission Color value, the more transparent the object becomes.
Transmission Value Shift from RGB(0,0,0) – RGB(255,255,255)
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Since the Transmission Weight will be set to 1.0 when a transmission map is used, The Base Color map does not actually contribute to the overall scene.
I have removed the Base Color map for this example and used a simple red color value within the Base Color parameter. Notice that it does not contribute to the shader until the Transmission Weight is reduced to a value below 1.0.
Because of this, the best solution is to keep the base color map or parts of the base color map that pertain to transmissive objects pure black.
This step will help our automation pipeline produce accurate conversion results in other DCC applications.
Roughness
The Roughness map is a great way to reduce the amount of transparency. By brightening the roughness, the objects becomes less transparent. Potential applications of this method would be for areas that are worn down, scratched, dirty, or frosted glass.
We currently do not support the use of Specular Level maps, but we do understand that this value is important to the way a model renders. This is why we strongly recommend setting the Specular Weight to 1.0, Specular Color to pure white, and then making any adjustments needed to the Base Color, Roughness and Transmission maps for your desired result.
Now let’s bring it all together.
First, make sure that the Specular Weight is set to 1.0, and the Specular Color value is set to pure white.
Base Color – Since the Transmission Weight is set to 1.0, the Base Color map will not contribute to the render. Therefore set the Base Color to pure black for any transparent objects.
Refraction – Select desired value for the Refraction Color. The brighter the value, the more transparent the object becomes. Test render and adjust if color or visibility through the transparent object is not to your liking.
Roughness – Adjust the grayscale value until desired look is achieved. Brighter the map is, the more diffuse highlights become, and less transparent the object becomes as well.
We hope this information helps. Please keep an eye out for future SCv2 updates!