Lightscape Version 3.2 Has New Radiosity Tools for Creating Incredibly
By Todd Perry
One of the goals in the computer graphics world, for the longest time, has
been to create photorealism in the digital world. Everyone who had initally
been developing algorithms for graphics was trying to create a representation
of the real world.
The basis for all of this -- the real world and the digital representation
of it -- is light and how that light behaves when it hits the surface of
a physical object in space. Without light, our discussion of computer graphics
would be at an end because it's based soley on what we see. In most rendering
systems like Renderman, 3D Studio MAX's scanline renderer, Mantra, Maya's
renderer, etc., the calculation for light is backwards. A ray of light is
traced through a pixel on the screen until it hits a surface. The ray bounces
from the surface until it hits another surface or finds a light. If the ray
hits another surface, then the intial surface is in shadow and is black.
If the ray finds a light, then a calculation is made taking the color of
the light, color of the surface, specularity of the surface, etc. into account,
and the result is the color of the pixel on your monitor. This method is
fast and occasionally adequate, but not accurate.
Lightscape's forte is to simulate the physics of light.
The way that light actually works is that it begins from a light source (and
not from your eyeball, as most would lead you to believe). The light, carrying
a certain amount of energy, travels until it hits a surface of an object.
At that point, the surface absorbs some of the energy of the light and reflects
the rest. The reflected light will then travel away from the surface ---
some energy will reflect directly to us, while others will travel to other
surfaces. The new surfaces will receive the bounced light which will: a)
be less intense, because it has left some of its energy back at the other
surface; and b) slightly tinted, because the previous surface absorbed color
and reflected the remaining color. The new surface will now have a slight
tint toward the color of the previous surface. This process continues as
light bounces from surface to surface and ends when all the energy of the
initial light source is absorbed. This process is called radiosity. Note:
this is a definition that merely glazes over the intricacies of the physics
behind light, but it gives you the right idea.
Lightscape is a product that has been around for some years and has provided
for us the ability to use radiosity to create incredibly realistic imagery.
And, the newest version 3.2 has brought us some new tools to make the process
Before we delve into Lightscape itself, we should come to grips with what
it is and is not. Lightscape is not a modeler. Nor is it a texture-mapping
or animation program. Granted, Lightscape can handle some of these processes,
but its forte is to simulate the physics of light.
Therefore, you can take the modeling program of your choice, import the geometry
into the Lightscape and create the perfect lighting for your scene. The tools
within Lightscape are intuitive and mirror similar features in other 3D programs.
You can orbit, pan, tilt, and dolly the camera through your scene (as well
as animate it). There are perspective and orthographic views. You can see
the scene through wireframe and shaded modes. The object that you bring in,
and the lights you create can be translated, rotated, and scaled. Essentially,
everything you need to set up the scene to your liking. Once your scene is
in order, the lighting process begins, and Lightscape shows its power.
First, Lightscape is based on photometry, which is the measure of light and
its psychophysical effects on the human optical system. So, when you are
adjusting parameters in Lightscape, the results are going to translate to
the real world. You are working with parameters such as luminous flux, illuminance,
luminance, and luminous intensity. This is refreshing when you are trying
to emulate real lighting and all you have is Value and Multipler. The accuracy
and approach to this lighting scheme, not only allows you to provide real
numbers to the lights in the scene, but you may also import lighting specifications
from lighting manufacturers. With this information, you can place the actual
lights that would be present either on set or in the building that you are
representing for previsualization.
And the accuracy does not stop there. The lights can be edited based on what
is known as a photometric web. This web represents how the light source,
or luminaire, emits light which is called luminous intensity distribution
(LID). This information relates also to the physics behind luminaires and
can be associated with actual lighting information for manufacturers. The
fact that Lightscape's lighting approach is so accurate is only one of the
reasons it provides such lifelike imagery.
Louis I. Kahn: Unbuilt Palazzo dei Congressi,
Lightscape image by Kent Larson
From the book "Louis I. Kahn: Unbuilt Masterworks," by Kent Larson,
The second stems from the subject that we spoke about above --- radiosity.
The light emitted from the luminaires is calculated as it would be in reality,
but this comes at an extreme cost. The calculations for this type of process
is extremely time-consuming. In the beginning days of radiosity, one would
have to start the process and leave for a few days and pray that everything
would look okay.
Lightscape has alleviated some of that by allowing you to pause the calculation
of the propogation, make changes to the lights, and continue the calculation
from where you left off. Despite the intensity of the radiosity calculation,
once you have it, it is there for good. The lighting is literally burned
into the textures and materials on the object surfaces. You can bring the
scene back into a program like 3D Studio MAX, and the lighting comes along
with it --- without lights. And since there are no more light preparations,
the scene will render in no time.
Todd Perry is CG Supervisor/Partner at MAX Ink Cafe, LLC in Venice,
CA. He can be reached at TSP@MaxInkCafe.com