Lighting With Textures
Monday, 21st May 2007
Lighting with textures is a way to give your light more spectrum
range and can add realism to your scene. This tutorial is more for
those who have come from a level-design background (specifically,
Half-Life and Quake engine in origin). Both built upon the Quake 1
engine, they would bake a primitive version of Global Illumination
in a way that would allow you to use a textures as a method of
producing light.
The obvious benefits of this were the realism of the
lighting versus the competition (at the time, Unreal). It came at
the expense of dynamic lighting - lighting changes basically became
a switch between one light-map and another.
A 3D package isn't constrained by the requirement of
being real-time, so dynamic changes aren't a big concern.
Step 1
Build a floor and some surrounding walls. For my stairs I've dropped
in a Chamfer-Cylinder and bevelled a few of the polys inward a bit.
What is important here is scale. In order to make a texture emit
light, it requires use of a standardised luminance scale which is
purely based upon scale, so go to Customise --> Units Setup
and make sure you're working in Metric or Imperial (whatever you're
used to).
In your render panel, set the default renderer to
Mental Ray.
My basic scene - Note the lights
Step 2 (Optional)
Lets make some textures! We're going to be using Final Gather which
takes the colour of the surface the light hits into account
(specifically for colour bleed through indirect light bounces). The
reason for texturing things is purely so you get immediately
disheartened, since lighting can be a hit-and miss affair.
Some textures put on to aid the 'Realism' of the
indirect light.
Step 3
You'll note anything that's orange or white is an emitting light. So
now its time to specify which textures you want to emit lights.
Set your material type to Architectural, set your
colour and drag up the Luminance to 7500 cd/m3 (Due to the author
being forgetful, the numbers in this tutorial are likely to be too
high. This is because I built the scene out of scale).
Put a light in the scene with a multiplier of 0.0.
This will allow you to see ONLY light generated by the textures.
The architectural texture in action!
Step 4
Now you need to turn on Final Gather at very low (and hence fast to
preview) quality. I have provided a Max 9 and a Max 8 screenshot
(since there has been a modification to the Final Gather system
between versions).
These are ultra-low quality settings to speed up
your previews. Final quality versions will have Rays (Samples, in
Max 8) set to 256 or higher.
|
Max 9 Final Gather Settings |
Max 8 Final Gather Settings |
Step 5
Playing with numbers time! If there's not enough light being pumped
out, turn up the Luminance on your texture. Its pretty simple stuff
and it may end up taking a lot longer than you thought (if you're
picky) or you might think its fine.
Low quality Texture-Only light.
Step 6
Texture lighting is a great way to aid direct-lighting. Just for the
sake of some highlights, I've put in two spotlights (shadow-mapped
for speed), one of the teapot and one on the far side of the stairs.
Direct, Indirect and Texture Lighting. This shot has
no post effects.
Things to Remember
In a closed scene (with walls), turning up your Max Bounces will
give more ambient light. You can also mix the final gather lighting
with ambient occlusion, and failing all of this, you can render out
a separate lighting pass (Lighting multiplying your diffuse layer)
and fiddle with it that way.
Download the Scene
File
