This page provides general information about the Smoke Color sub-section of the Rendering rollout of Phoenix FD.

Overview

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This rollout This roll-out controls the diffuse Diffuse color of the volumetric shader. The smoke color is affected by lights and shadows, unlike the color and transparency that can be achieved from the Fire rollout. The diffuse color can be a uniform Constant ColorVolumetric Shader. The Smoke Color can be a uniform color, a mixture of RGB colors advected dragged by the simulation (RGB), a function of any loaded cache physical channel, or it can be sampled from a texture. It is also affected by lights and shadows cast by objects in the scene.

Parameters

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Based on | difSource – Allows you to select where Specifies the source channel that will be used to determine the smoke color will be taken from. By  By default, it is a uniform simple color set by the Constant Color option is used. It This could also be taken from a texture map, or read from the cache files - in that case the corresponding grid channel must be enabled from the Output rollout roll-out before the simulation is run.

• Disabled - the smoke color will not be rendered.
• Temperature - the smoke color will be based on the values of the Temperature cache channel and can be remapped using the color gradient.
• Smoke - the smoke color will be based on the values of the Smoke cache channel and can be remapped using the color gradient.
• Speed - the smoke color will be based on the values of the Speed cache channel and can be remapped using the color gradient. See the Smoke Color by Speed example below.
• Texture - the smoke color will be based on the values of a texture map plugged into the Texture slot.
• Constant Color - the smoke color will be the same for the entire volume and will be taken from the Constant Color box.
• RGB - the smoke will be based on the values of the RGB channel.
• Fuel - the smoke will be based on the values of the

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• Fuel channel and can be remapped using the color gradient.

Texture | difTexture – If Based on is set to Texture, this slot specifies which texture to use.

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

Color gradient – 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.

This sim 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 Simulation rollout of Phoenix.

Constant color | difSimpleColor – If Based on is set to Constant Color, this color is used.

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Ray-traced (GI only) – Enables physically accurate scattering of light rays. This mode produces the most realistic results but it's the slowest to render. It requires V-Ray with enabled Global Illumination, otherwise , the rendered result would be the same as if the option is Disabled. The Diffuse Master Multiplier does not affect the rendering in this mode.
Disabled – Disables scattering. The Diffuse Master Multiplier value can be used to correct the brightness because without light scattering the volume would generally render darker.
Approximate – Uses an approximate formula which is faster than Ray-Traced scattering and produces good-looking results. Brighter areas of the volume would transfer light farther than dark areas. This option is not supported by the Volumetric Geometry render mode in the Rendering rollout.
Approximate+Shadows – Same as Approximate, but also affects the strength of shadows over the scene geometry. Approximate+Shadows is  This option is not supported by the Volumetric Geometry render mode in the Rendering rollout.

Scatter Depth | difScatterDepth – Specifies the maximum depth of the GI rays.

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Light Cache Speedup | difLightCacheSR – [Valid only when Use Light cache is enabled] The higher this option is set, the faster the rendering will be, but the lower the quality of the Phoenix 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.

Own Light Scatter Mult | difOwnLightsBoost –  – [Valid only when Scattering is set to Approximate or  or  Approximate+Shadows. This ] This multiplier determines how far the light travels through the volumetric, based on the distance from the emissive light itself.

External Scatter Mult | difExtLightsBoost –  – [Valid only when Scattering is set to Approximate or  or  Approximate+Shadows. This ] 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 the camera, and only apply to the illumination.

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Shadow Strength | difShadowStrength – A multiplier for the opacity of the shadow that the volumetric casts on other objects.

Color gradient – 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.

This sim 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 Simulation rollout of Phoenix.

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