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You can open this dialog from the 3D Visualization palette or from the menu Options > Element Attributes > Material.
There are 2 separate mechanisms for handling materials:
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Removes MXM material attribute from ARCHICAD material.
Creating materials within ARCHICAD
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After you download the desired material file program returns back to the browser window (your new mxm file selected).
Maxwell Grass
Maxwell Grass is handled as material property in the ARCHICAD plugin. It means you can enable the Grass property on the material level, and the plugin translates it automatically to Maxwell Geometry modifier.
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