Check these Tutorials

[CADTutor]

You may not realise it but the CADTutor web site has a number of tutorials that cover render, lighting and materials topics. Have a look at "Adding Sunlight to your Drawings" http://www.cadtutor.net/acad/acad2ki/sun/sun.html and "Creating Custom Bitmap Materials" http://www.cadtutor.net/acad/acad2ki/bitmat/bitmat.html. These tutorials and others might contain the answer you're looking for and save you some sweat.

[asos2000]

The links not working

[Cad64]

That's because it was posted 6 years ago.

Just go to the Tutorials area and have a look around: http://www.cadtutor.net/tutorials/autocad/index.php

[papagyi]

Hi,...I think these render tutorials should be add about acad 2008/9!