Final Render 101: Simple environmental and object based global illumination
This is the first in a series of Final Render tutorials that will cover the basics of global illumination, HDRI, ray tracing, lights, caustics and sub-surface scattering. In this first, two-part lesson we'll go over the essentials of global illumination using two methods of light generation. Part 1 will address environmentally produced GI. Part 2 will examine HDRI basics and self-illuminated objects. If you have any suggestions or comments, please send me an email.
1. Start by creating a box and flipping the normals. To prevent color bleeding in the corners you might instead assemble your room with six overlapping planes or boxes. Place two spheres in one corner and aim a target camera at them. To allow light into the room we need to boolean out a window in the wall behind the camera, or simply remove the wall or ceiling. In the example scene I used a box and removed the top poly. Place an omni anywhere in the scene and turn it off. This is to inactivate Max's default lighting.
2. Right click every scene object and select "Properties." Under the Mental Ray Rendering Control check the relevant options. In this case we want each object to receieve and generate global illumination. It's a good idea to do this immediately after placing an object in the scene.
3. Go to the Material Editor and create three FinalRender materials, two for the spheres and one for the walls. Under the Caustics and Global Illumination rollout, turn off caustics and make sure both send and recieve are checked under Global illumination. Leave the settings at their default of 1. Apply them to your objects. By now you've noticed that your shaded viewports are blacked out. In order to see your shaded viewport you need to temporarily turn on your omni or create another. Don't forget to turn it back off before rendering. For at least one of the spheres set a specular and glossiness level similar to mine.
4. Open the Environment Dialogue and set the background color to pure white.
5. Right click any viewport and select Final Render Globals from the quad menu. Open the Global Illumination Parameters dialogue and enable GI. For test renders keep the prepass size at the default level of 1/4. And for test renders the RH-Rays should usually be considerably lower lower than the 300 rays I'm using here, but this is a simple, low-poly scene and render times should be fairly painless. Go ahead and render the scene.
6. Somewhat smooth. Not too much artifacting evident, but it's hard to tell. I want the image lighter than this. Remember, too, that the amount of light reaching the scene is partially dependant upon the size and placement of windows, etc.
Go back to the Material Editor and increase the Recieve parameters for each Material to 2.0. Render again.
7. Better. A little artifacting, but that can be fixed later by pumping up the RH Rays and prepass size. If you used high specular and glossiness levels in either of your materials, you'll notice that the GI doesn't bring out highlights on the spheres.
To do that, add another omni and this time turn it on. Under Affect Surfaces uncheck diffuse but leave specular on. Go back to the Final Render Globals dialogue and increase the RH-Rays to 600. Increase the prepass size to 1/2 and render again.
Part two of this tutorial will cover HDRI basics and self-illuminated object based GI.