Monday, November 5, 2012

Andrew F. Scott: Keyshot Rendering in Passes

Rendering in Passes provides a more efficient workflow for creating images that will be used for project proposals. Keyshot provides a good rendering platform for creating images that can later be composited using photoshop. In this workflow an image will be created using Diffuse, Specular, Reflection, Mask and Beauty Passes using Keyshot.

Beauty Pass01: wood

 Beauty Pass01: gemstone material

Two Beauty Passes were created in keyshot. In one image a wooden texture was applied top the model in the second a gemstone material was used. The model was placed against the backplate and a 3point light studio was chosen for the environmental lighting. It is very important to lock the camera once the beauty shot has been established. It is also important to give that camera view its own unique name.

 Mask Pass

A flat material was created in the Edit-Materials panel and assigned a  green color. This color was then applied to the object so that it cans be masked from the background in Photoshop. Rendering with alpha channels can also be used to achieve the same goal. Masking elements with flat materials extends this capability because you can mask different elements of your composition using different colors.

Ambient Occlusion Pass

Ambient occlusion are used to show objects that are occluded or blocked from the light. In many Mental Ray rendering setups it provides one of the simplest forms of global illumination. It is used to provide a shadow kicker that gives objects a greater sense of realism. In the version of Keyshot that I am currently using there is not a true ambient occlusion solution. To get around this I created a diffuse material that is painted white with the startup lighting environment.

Reflection Pass

The reflection pass was created by creating a chrome material and painting it black. Ideally you want the roughness to be set at 0. For this pass it is also important to have an environment that matches your beauty shot since this is what should be reflected in your object. With this setup you will get a 100 percent reflection of your environment on your object.

Specular Pass

The specular pass is your highlight pass. For this pass any black metal material can be used. You will use the roughness slider to control the sharpness of the reflections. For even greater control, anistropic materials painted black provides a material for creating a wider variety of reflection passes.

Final Composition in Photoshop

The image above is the final composition combining all off the passes in Photoshop. In the second part of this tutorial I will go over the workflow in photoshop used to produce this image. A good overview of  Rendering in Passes and Layers can be found on the Gnomon Website written by Alex Alvarez.

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