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This page provides information on the Smoke color rollout of the Volumetric Options dialog.
This rollout controls the Diffuse color of the Volumetric Shader. The Smoke Color can be a uniform color, a mixture of colors dragged by the simulation (RGB), a function of any physical channel, or sampled from a texture. It is also affected by lights and shadows cast by objects in the scene.
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Based on | darg – Specifies the source channel that will be used to determine the smoke color. By default, a uniform simple color set by the Constant Color option is used. This could also be a texture map, or read from the cache files - in that case the corresponding grid channel must be present in the cache files and remapped to the internal Volume Grid channels using the 3rd Party Channels Mapping dialog in the Input rollout.
? – Opens the help documents.
Texture | dtxt – If Based on is set to Texture, this slot specifies which texture to use.
Modulate | mod_d – When Based on is not set to Texture, 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 – If Based on is set to Constant color, this color is used.
Scattering | noscatter – Controls how the light rays are scattered inside the volume.
Phase Function | phase_function – Controls the direction in which the light will scatter inside the volume. Negative values correspond to backward scattering, which mimics a volume made up of solid particles and will produce denser and more detailed looks. Negative values are more suitable for smoke or dust effects. Positive values correspond to forward scattering, which mimics a volume made up of water droplets where light will scatter more. Positive values are suitable for highly scattering volumes such as clouds. The default value of 0 will scatter the light in all directions and create an even and diffuse look. See the Phase Function example below.
Note that values very close to 1.0 or -1.0 will produce very directional scattering that will be invisible from most angles, so such values are not recommended. When rendering with a Phase Function different than 0 and Volume Light Cache is enabled the rendered result will be brighter. The Phase function is ignored when the scattering is set to Approximate or Approximate+Shadows.
Optimize Anisotropic Scattering | anisotropic_scattering_optimization – When enabled it can greatly reduce the render times for highly scattering volumes such as clouds. Due to certain assumptions made for the optimizations, the optimized render result might produce different results compared to the exact brute-force anisotropic scattering. The option is ignored when the scattering is set to Approximate or Approximate+Shadows.
Volume Light Cache | lightcache – Enables light caching for each voxel of the grid, which speeds up bucket 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 this option speeds up rendering.
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Light Cache Speedup | subred – [V-Ray specific] [Valid only when Volume Light Cache is enabled] The higher this option is set, the faster the rendering is, but the lower the quality of the Volume Grid Light Cache. You can increase this parameter and gain render speed as long as you don't start getting dark cubic grid artifacts on the smoke.
Master Multiplier | difmul – A general multiplier for the diffuse color. It is ignored when the Scattering mode is set to Ray-traced (GI only).
Own Light Scatter Mult | transfown – [Valid only when Scattering is set to Approximate or Approximate+Shadows] This multiplier determines how far the light travels through the volumetric, based on the distance from the emissive light itself.
External Light Scatter Mult | transfext – [Valid only when Scattering is set to Approximate or Approximate+Shadows ] This multiplier determines how far the light from all external light sources travels through the volumetric. Both Scatter Boost parameters don't alter the visual density of the smoke to the camera, and only apply to the illumination.
Shadow Strength | shad_strength – A multiplier for the opacity of the shadow that the volumetric casts on other objects.
Color gradient | dcolorx_t, dcolory_t, dcolorx_s, dcolory_s, dcolorx_v, dcolory_v, dcolorx_f, dcolory_f – When the Based on option is set to a grid channel, this color gradient remaps grid simulation data to render smoke color. The sim data channel is laid out horizontally along the X axis in the color gradient.
Simulation data has different ranges, depending on the solver it came from - Phoenix Smoke usually goes from 0-1; Fuel goes from 0-1; Temperature is in Kelvins, so it goes from 300-2000, or a few thousand; Speed is in Voxels/sec, so it depends on the grid size and resolution, but usually goes from 0 to several hundred. Data from other solvers often differs a lot from Phoenix ranges. The channel data range is highlighted in the gradient with a light-blue range which can change as you scroll the timeline as the temperature in a cache file rises, smoke dissipates, speed changes, etc., so keep in mind that the data range for one frame might not be representative for the entire cache sequence. You can also check the data ranges for the currently loaded cache file under the Frame Info rollout of the Volume Grid.
You can use the following controls in the color gradient: Double click – Creates a new point or changes an existing one. |
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The orange arrow represents a ray of light going through the volume and the possible scattering directions for the ray.
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The orange arrow represents a ray of light going through the volume and the possible scattering directions for the ray.
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