Final Render 101:
Simple environmental and object based global illumination
by
Stephen Reb
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.
3DTotal
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