Basically, fast raytraced shadows on large databases was the goal here. Rendering large outdoor scenes, say a city viewed from altitude during the day, has consistently been a problem in Max. Shadow maps are problematic, since the resolution would have to be ridiculously large, and even then, zooming in close would still reveal errors in the map. The only alternative has been to use the default Raytraced shadows. The raytraced shadows in Max use a quadtree to accelerate things. It is very efficient on lighter scenes, but once face counts get into the six figure range, Max's raytraced shadows start to choke. Also, directional raytraced lights are pretty much always slow. Achieving this is requiring some ongoing improvements to the core RayFX raycaster as well. Another goal was softer raytraced shadows.
Antialiasing Options
Detect
Supersampling
Detect
Recursion
Pass
1 Quality
Pass
2 Quality
Contrast
Blur
Ray Bias
Jitter Amount
Coplanar Face Culling
Skip
Coplanar Faces
Threshold
Transparent Objects: Enables the detection of transparent, or semitransparent objects. This includes opacity mapped, or transparency mapped objects.
Mode: There are currently 3 modes available, at least 1 more is in the works (progressive antialiasing-primarily for transparent shadows)
Simple - Cast a single ray from the light toward the surface. No antialiasing is performed.RayFX Global Params: Pops up the RayFX Global Parameters dialog box. This dialog is currently the same as the one that shipped with Max 3.x.
Antialias 1-Pass - Cast a bundle of rays. The same number of rays are cast from each illuminated surface. The number of rays is set using the Pass 1 Quality spinner.
Antialias 2-Pass - Casts two bundles of rays. The first batch of rays determines if the point in question is fully illuminated, shadowed, or in the penumbra (soft area) of the shadow. If the point is in the penumbra, a secondary batch of rays is cast to further refine the edge. The number of initial rays fired is specified using the Pass 1 Quality spinner. The number of secondary rays is specified using the Pass 2 Quality spinner. Currently this doesn't always work right with transparent objects.
RayFX Global Exclude: Pops up the RayFX global exclude/include dialog box. This dialog is currently the same as the one that shipped with Max 3.x. Excluding an object using this dialog will exclude it from all raytracing, including reflection and refraction using the Raytrace Texture and Raytrace Material. If you want to exclude the object from shadow casting, you must use the parent light's exclusion list.
Note: The shadow casting / illumination option in the RayFX global exclude dialog currently has no effect. We may use this to generate two separate global exclusion lists, one for standard raytracing (reflections / transmission) and one for shadows, at some point in the future.
Detect Supersampling: Suppresses antialiasing on supersampled surfaces, 1 ray is cast per material sample. Antialiasing the shadows requires casting multiple rays from each pixel. If the surface receiving the shadows is supersampled, the number of rays cast will be multiplied by the number of samples the supersampler is evaluating. So if you are using the default max 2.5 star, the supersampler is shading the surface 5 times. If the raytraced light is casting 5 rays initially, that becomes 25 rays for the supersampled surface. By preventing the raytracer from antialiasing, the supersampler alone will antialias the shadow. In this case, the blur setting for the shadow will no longer have any effect.
Detect Recursion: Suppresses antialiasing for surfaces visible in raytraced reflections and refraction. Like Detect Supersampling, this is to prevent ray count explosions due to conflicting antialiasers. If the current ray level is greater than 1, no antialiasing is performed. This occurs when objects are being reflected or refracted through other objects via a raytracer.
Pass 1 Quality: Sets the number of rays in the initial bundle of rays cast. These rays are fired from every surface that receives light from the parent lightsource. The number of rays are as follows: Q1=4 rays, Q2=5 rays, Q3 to N = NxN rays. Quality 5 would mean 25 rays.
Pass 2 Quality: Sets the total number of rays cast in the penumbra region, including the rays fired in pass. These rays are fired from every point that is in the penumbra, or antialiased edge of the shadow, to smooth it out. The number of rays is as follows: 2=5 rays, 3 to N = NxN. Quality 5 would mean 25 rays. Pass 2 Quality should always be greater than Pass 1 Quality. This is because the secondary rays are overlaid on top of pass 1's rays using the same algorithm. If Pass 1 Quality is set to 3, it will trace 3x3=9 rays. If Pass 2 Quality is set to 5, the number of secondary rays will be 5x5 = 25 total-9 initial = 16 secondary rays.
Contrast: The maximum color difference allowed between transparent object samples before antialiasing (Pass 2) is triggered. Increasing the value of this color will make the shadow less sensitive to aliasing artifacts and improve speed, decreasing the value will increase the sensitivity, improving quality.
Blur: The radius, in pixels, to blur the antialiased edge. The larger this value, the higher the quality required. Increasing the blur also increases the likelyhood of missing small objects. In this case, Pass 1 Quality will have to be increased.
Ray Bias: The minimum distance from the point being shaded that an object must be to cast a shadow. This prevents blurred shadows from affecting surfaces they shouldn't. The higher the blur, the higher the required bias.
Jitter Amount: How much randomness to add to the ray positions. The rays are initially in a very regular pattern, which can show up in the blurry part of the shadow as regular artifacts. Jittering will convert these artifacts to noise, which is generally less noticeable to human perception. Recommended values are 0.25 to 1.0. Very blurry shadows require more jitter.
Skip Coplanar Faces: Prevents adjacent faces from shadowing each other. This is of particular concern at the terminator on curved surfaces such as spheres. The threshold is the basically the angle (range 0 to 1.0)
Threshold: Essentially the angle (range 0.0=perpendicular to 1.0=parallel)