Overview

This rollout controls the diffuse color of the volumetric shader. In general, the diffuse color may be uniform (simple color), a mixture of colors dragged by the simulation (RGB), a function of any physical channel, or sampled from a texture.

UI Paths

||Select V-Ray Volume Grid|| > Modify panel > Rendering rollout > Volumetric Options... button > Volumetric Render Settings window

Parameters

Based on | darg – Specifies the source channel used to determine the smoke color. By default, it is a uniform simple color.

Disabled – Disables the diffuse color.
Temperature – Uses the temperature channel.
Smoke – Uses the smoke channel.
Speed – Uses the magnitude of the velocity channel.
Texture – Uses an external texture map.
Constant color – Uses the color in the Constant color swatch.
RGB – Uses a plain color.
Fuel – Uses the fuel channel.

? – Opens the help documents.

Texture | dtxt – If the Based on parameter is set to Texture, or if Modulate is enabled, this slot specifies the texture to be used.

Modulate | mod_d – When Based on is not set to Texture and this option is enabled, the Texture slot is enabled and the color is multiplied by the texture in the Texture slot.

Reset to Defaults – Resets the settings to their default values.

Constant Color | simple_color – Specifies the color to use if Based on is set to Constant color.

Use Light Cache | lightcache – Enables light caching for each voxel of the grid. This speeds up rendering considerably when the voxel size of the grid is significantly larger than the rendering pixel. If the grid resolution is large enough compared to the rendering resolution, disabling the light cache will speed up rendering.

1. This option refers to the internal Volume Grid Light Cache, which is not related to the V-Ray Light Cache.

2. When using V-Ray Progressive Rendering, this option might slow down rendering startup or the overall render speed.

3. This feature might produce artifacts when the smoke is very dense.

4. This feature might produce artifacts when objects cast shadows through the smoke.

5. Rendering multiple copies or instances of the Volume Grid node with this option turned on might lead to slow-downs.

6. When rendering in Volumetric Geometry mode, for any of these Render Elements: [ Shadows ], [ Raw Shadows ], [ Global Illumination ], [ Raw Global Illumination ] , the Volume Grid Light Cache will require additional memory to produce the correct result. Please be aware that these Render Elements (and most other V-Ray Render Elements except for [ Atmosphere ] and [ Self-Illumination ] ) do not work in Volumetric mode.

7. This option is ignored when using V-Ray GPU. It is a CPU-only feature that helps speed up Bucket rendering.

Light Cache Speedup | subred – This value affects the amount of light sampling. Lower values cause less sampling, which speeds up the rendering but decreases the smoke's quality and increases noise. This option is available only when Use Light Cache is enabled.

Scattering | noscatter – Controls how the light rays are scattered inside the volume.

Ray-Traced (GI only) – If Global Illumination is enabled, this mode enables the scattering of light rays. Otherwise it is the same as Disabled.
Disabled – In this mode the scattering of light through the smoke is disabled. The Master Multiplier can be used to correct the brightness of the diffuse color in this mode.
Analytic – Without actually altering the rays, an analytic formula is used to calculate the contribution of the scattering to the illumination. Brighter smoke transfers light further than dark smoke. This effect can be controlled from the Constant color box. This option is not supported when Mode is set to Volumetric Geometry.
Analytic+shadows – Same as Analytic, but geometry is also affected via the shadows. This option is not supported when Mode is set to Volumetric Geometry.

Own Light Scatter Mult | transfown – Multiplies the distance that light from emissive lights travels through the volumetric. This value doesn't alter the visual density of the smoke to the camera, and only applies to the illumination. This value affects the lighting only when Scattering is set to Analytic or Analytic+shadows.

External Scatter Mult | transfext – Multiplies the distance that light from all external light sources travels through the volumetric. This value doesn't alter the visual density of the smoke to the camera, and only applies to the illumination. This value affects the lighting only when Scattering is set to Analytic or Analytic+shadows.

Shadow Strength | shad_strength – Multiplies the opacity of the shadow that the volumetric casts on other objects.

Master Multiplier | difmul – A general multiplier for the diffuse color. This value is ignored when Scattering is set to Ray-Traced (GI only).

Color gradient | dcolorx_t, dcolory_t, dcolorx_s, dcolory_s, dcolorx_v, dcolory_v, dcolorx_f, dcolory_f – If Based on is set to a channel of the VRayVolumeGrid, this parameter controls how the smoke color appears based on the channel's value. The selected channel's data range is denoted by a blue-green line.

You can use the following controls in the color gradient:

Double click – Creates a new point or changes an existing one.
Left button drag over a point – Moves the point. If several points were selected beforehand, they will move the same amount.
Left button drag over several points – Selects several points.
Middle button drag over the background – Drags the visible area.
Mouse wheel – Zooms in/out.
Right click – Displays a drop-down menu where you can add a point, edit or delete a selected point, and fit the entire gradient into the view. If multiple points are selected, they can be edited simultaneously

Notes

• The diffuse color needs external light to become visible. If you are using a 3ds Max omni light, it should have Shadows and Atmosphere Shadows enabled, as well as Ray Traced Shadows for defscanline or VRayShadow for V-Ray. V-Ray lights will work right off the bat with their default settings.