3D Rad is sensitive to geometry and texture mapping. Follow these rules to avoid "invisible" or distorted models:
Download the .rbz file and use the Extension Manager in SketchUp to install it. 3d rad exporter plugin
I managed to get the plugin working. Here is the dark magic required. 3D Rad is sensitive to geometry and texture mapping
The proprietary .rad output is an ASCII or binary file structure organized hierarchically. 3d rad exporter plugin
Error handling is critical. If the exporter encounters a mesh with more than 65,535 vertices (the limit for 16-bit indices in 3D Rad), it must either split the mesh into sub-meshes or warn the user to reduce geometry. Without this, the exported file will trigger a silent memory overflow in the 3D Rad runtime.