This tutorial shows you how to add a material to an object and to a single face of an object.
I hope it helps ;-)
Open Autodesk Showcase.
Click on 'Open File' and then 'Your File'.
Next select the model you want to render.
In this tutorial I've used a simple cube, made in AutoCAD.
Once the model is loaded, you will see that it is all black or that it has the colors you gave it in the CAD software.
To give apply a material to it, you click 'Look' and then you clik on 'Materials'. The material library will now show up.
To apply a material to the model, we select the model and then click on the preferred material. In this case: green car paint.
As you will see, the whole model will color green. This is because in the CAD software there was made no difference in material between the different faces.
When you DO want different materials for certain faces, you must first fold down the menu by clicking on the little black triangle on top of your screen.
Next you have to go to 'Edit' -> 'Fix Object Patches' -> 'Extract Patches as New Object...'. This will make you able to seperate faces from the rest of the model and giving them another material.
As soon as you clicked 'Extract Patches as New Object...', you will be asked to select the face you want to extract. In this tutorial I've extracted the face on the right. Once ready click 'Extract as New Object(s)'.
You will now see that the extracted faces have a blue grid on them. Click 'Done'.
Now the last thing you have to do, is selecting the face again and click on the desired material. You now have an object with different materials on selected faces.