CG Focus :: The Translight Lighting Method: HDRI-Dome Quality At Blazingly Fast Speeds.

Lighting with HDR

Translight_02

This is the render we get from the previous section. It's lighting information comes only from the illumination "cast" from the HDR Image-Mapped dome.

Translight_03

To set-up a "HDRI/Radiosity" render, you set LightWave's obligatory light to Intensity: 0%.

You've also got to change LightWave's Ambient Intensity to 0%, so there is absolutely no light in the scene.

Translight_04

Then, you've got to tell LW to calculate for light as it is cast from and bounces off Objects in the Scene. You do this under the Render Globals Panel, Global Illum. Tab, by Checking Enable Radiosity, accepting the default settings of "Monte Carlo" as the Radiosity Type, and 4x12 as the Rays Per Evaluation, and 1 for Indirect Bounces. However, for this render, let's change the Intensity of our Radiosity lighting to 200%.

(Click Image For A Larger View)

Looking at the Surface Editor for our HDR hemisphere, we see, it's just a simple, Planer texture-map applied to a Surface that is 100% luminous, with 0% Diffuse. This makes our surface emanate "rays" in a 1:1 ratio with the intensity of the colors of its texture-map.

Based on our Global Illumination settings, LightWave will calculate for "photons" cast based on the "density" specified in the Rays Per Evaluation setting, allowing those "photos" one bounce before they "die." This is how the colors of the image-mapped dome are "case" onto the Objects in the Scene, and "bounce lighting" works its way into all the cracks and crevices so nicely.

Obviously, there's a lot of "photons" being thrown about and calculated for. This is why full-on Radiosity takes so long to render. Also, there's a lot of "graininess" to HDRI renders that requires either a higher level of AntiAliasing, or Rays Per Evaluation to smooth-out, both of which significantly increases render time.

And... (at least in LW,) Radiosity renders lit without "true" lights won't calculate any Specularity... this is a big deal when you've got metallic surfaces that are designed to look correct with a nice Specular sheen from the lights in the Scene, without which, something that once looked chrome may turn-out looking like asphalt.