Hi, to answer your question: you need to export the model to a folder on your computer (it is better if there is nothing in it) and while you are choosing a place to put it click the options button and uncheck everything in materials. Open up Anim8or and click object>import and select your model. Click the four ball button and boxes will appear with spheres in them. Double click a box and settings for the texture will appear. Click the = sign and close the box. Do this for all of them. Once you are done go to object>export and export your model and overwrite the older one. Go into Nolimits objects folder and make a new folder inside it and name it what you want. drag your model and it's textures (image files) into that folder. Place the model in Nolimits and run the sim. The black faces should be gone but if not go back into Anim8or and make sure all the = signs are clicked. and if the model is red go back the the sketchup export options and experiment with them.
Hope this helps:-)
