This value stands for – change the shader for nodes to the shader with the name Override_mtl for all nodes that we defined in the previous parameter. In the Assignment Expressions parameter, set the value: shader = '/Override_mtl' and click the + button to the right of the parameter to add this value to the shader settings.Which would lead to the fact that the the scene would have lost illumination if the in Environment was used an HDRi map. If we wrote / *, the shader would be replaced in Environment. (This value stands for – take into account all the nodes in which the polymesh class (these are geometric objects) and the nodes whose class is ginstance (these are geometric objects in the form of an instance). In the Selection parameter, set the value to: = 'polymesh' or = 'ginstance').Add the “Set Parameter” operator in Arnold’s Operator Graph editor, and change the name to “Override operator”.This needs to be done in order to initialize the shader during rendering. In the render settings, in the AOVs tab, assign our Override_mtl to the slot AOVs -> Shaders -> Materials.

Add the material Standard Surface to the material editor, setup it at your discretion and change the name to “Override_mtl”.So, below instruction how assign Override material in 3ds max 2018 and for 2019 separately. Update: I updated this post because in 3ds max 2019 was changed operators functional. Standard Surface, which will act as an override of the material (can be any other shader) and Set Parameter (operator) which will determine which objects need our override material during render. In order to setup override material, we need two shaders from the standard package of Arnold MAXtoA 2.x. Usually this is usefull to check the lighting settings, uv maps, etc. The essence of the override material feature is to replace the existing materials on the objects with single material during the render, and after the end of the rendering, return them on objects. In the settings of the Arnold rendrerer in 3ds max there is no Override material parameter as we have in the Vray parameters, but there is a functional allowing it to be recreated.

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