VRayShadow for Standard Lights

This page describes the use of ray traced shadows on standard Max lights within V-Ray.

Overview

When standard lights are used instead of V-ray lights, the Ray Traced Shadows is the option to control shadows correctly for these. The VRayShadow plugin can be used to achieve raytraced shadows with standard 3ds Max lights and V-Ray. Note that in most cases, the standard 3ds Max Ray Traced Shadows does not work with V-Ray. You must use the VRayShadow shadow generator instead. In addition to supporting blurry (or area) shadows, they also cast correct shadows from objects with V-Ray displacement, as well as from transparent objects.

UI Path: ||Create a standard 3ds Max light|| > Modify panel > General Parameters rollout > choose VRayShadow from dropdown

Parameters

Transparent shadows – Determines the behavior of the shadows when there are transparent objects in the scene. When enabled, V-Ray calculates shadows regardless of the light's Object Shadows settings (Color, Density, Map, etc.), however the color of shadows from transparent objects is correct. When disabled, the shadows take into account the Object Shadows parameters of the light, but shadows from transparent objects are monochromatic (shades of gray only). For more information, see The Changing Shadow Colors example.

Bias – V-Ray can compute the shadows at a point that is slightly displaced towards the light from the actual surface being shaded. This may be useful to prevent "surface acne" (black spots on the surface because of incorrect self-shadowing).

Area shadow – Turns area shadows on and off.

Type – Determines the way in which the area shadows are calculated. See the Area Shadow Types example.

Box – V-Ray computes the shadows as if they were cast by a light source with the form of a box.
Sphere – V-Ray computes the shadows as if they were cast by a light source with the form of a sphere.

U size – Specifies the U size of the light source V-Ray takes into account when computing area shadows (if Sphere light source is selected, U size corresponds to the sphere's radius).

V size – Specifies the V size of the light source V-Ray takes into account when computing area shadows (this parameter has no effect when Sphere light source is selected).

W size – Specifies the W size of the light source V-Ray takes into account when computing area shadows (this parameter has no effect when Sphere light source is selected).

Example: Area Shadow Types: Box vs Sphere / U, V, W Sizes

When the Sphere type is chosen, the VRayShadow takes under consideration only the U size value. The V and W sizes don't affect the final result. In other words, this means that our light source has a Sphere form and emits rays equally in all directions.

Type: Sphere, U: 1, V: 1, W:1

Now the light source has a Box form. In this case, VRayShadow considers all the U, V, W size values. See how the shadow is strong according to the U axis and is much softer to the V axis.

Type: Box, U: 1, V: 10, W: 5

Now the shadow is looking very different compared to the previous one. You can notice how the size values has influenced the final result of it.

Type: Box, U: 10, V: 1, W:5

Example: Changing the Shadow Color

In this case the Color value (R,G,B) in the Shadow Parameters rollout has no effect. In order to change the shadow color, the Transparent parameter has to be off.

Transparent shadows: On

Transparent Shadows: Off, Shadow Color: Green

Transparent Shadows: off, Shadow Color: Red