Lightscape 3.2    

 
Lightscape Version 3.2 Has New Radiosity Tools for Creating Incredibly Realistic Imagery

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 easier.

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.



Louis I. Kahn: Unbuilt Palazzo dei Congressi, Venice, Italy
Lightscape image by Kent Larson
From the book "Louis I. Kahn: Unbuilt Masterworks," by Kent Larson, Monacelli Press
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.

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

source: www.digitalanimators.com