--- title: "Render Smoke Color" canonical: "https://documentation.chaos.com/space/PHX4MAX/125312994/Render%20Smoke%20Color" format: markdown --- This page provides information on the Smoke color rollout the Rendering Volumetric Options dialog. ## **Overview** --- 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. In the volume shader, there are two types of content — **diffuse** and **emissive**. For simplicity's sake, we call the diffuse content **Smoke **and the emissive content **Fire**. Diffuse (Smoke) needs external light in order to become visible, and also casts shadows. On the other hand, emissive (Fire) is visible even without being lit by lights. It also ignores their illumination, and does not cast shadows on itself. > Macro (ui-text-box) > > Phoenix has different tools that help you to control how the emissive fire illuminates the smoke and the scene - see the [Create Fire Lights](https://docs-chaos.atlassian.net/wiki/spaces/PHX4MAX/pages/124629510/Render+Fire#Light) section in the Render Fire rollout for more details. Fire and smoke also have their own Color and Alpha. Alpha is a synonym for opacity, and transparency is the opposite of opacity. The **Smoke Color**, **Smoke Opacity**, as well as the **Fire's Color** and **Opacity**, can be mapped to a physical **Grid Channel **from the simulation, using the [Based on](https://docs-chaos.atlassian.net/wiki/spaces/PHX3MAX4EDIT/pages/115049318) parameter. The **Based on** parameter specifies the source channel that will be rendered, and is set independently for the Fire, Smoke Color, and Smoke Opacity respectively. This makes shading very flexible, so that you can even render a simulation's fire as smoke, and smoke as fire, depending on the channel you set the Based on parameter to for each. > Macro (ui-text-box) > > Fire, Smoke Color, and Smoke Opacity, can also be **mapped to a texture**, or to a Grid Channel multiplied by a texture, to achieve a wide variety of different results. > > Textures have infinite resolution, and so they can increase the detail above the resolution of the grid, meaning that even with a low resolution simulation, you can get a detailed result when using a texture. > > By default, textures are static in space. However, if you export the **Grid Texture UVW Channel **and use the [TexUVW](https://docs-chaos.atlassian.net/wiki/spaces/PHX4MAX/pages/124362975) feature, textures can move together with the fluid to create even more possibilities, such as melting textured icing on a cake. > Macro (ui-text-box) > > > Macro (legacy-content) > Macro (rw-ui-expands-macro) > > > Macro (rw-expand) > > ![image](media://a9fada34-dbc2-42ee-aaf9-077059d766de) ## **Parameters** --- > Macro (ui-text-box) > > When there is both **Smoke **and **Fire** (diffuse and emissive) in the same voxel, you can use the **[Fire Opacity Mode](https://docs-chaos.atlassian.net/wiki/spaces/PHX4MAX/pages/124629510/Render+Fire#IgnoreAlpha)** option in the **Render Fire** rollout, to determine the resulting color and alpha. > > The Fire can simply use the opacity that is set for the smoke in the [Smoke Opacity rollout](https://docs-chaos.atlassian.net/wiki/spaces/PHX4MAX/pages/125056277/Render+Smoke+Opacity#SmokeOpacity), or you can separate their opacities for additional control, using either the **Fully Visible** or **Use Own Opacity **modes. > Macro (ui-text-box) > > Using the **Based on** parameter below, you can achieve a wide variety of results when shading **Fire** & **Smoke**. > > For example, the [Fire](https://docs-chaos.atlassian.net/wiki/spaces/PHX4MAX/pages/124629510/Render+Fire#BasedOn) (emissive content) is by default based on the **Temperature Grid Channel**. If instead it were based on **Smoke Grid Channel **data, then voxels containing Smoke values would be shaded as emissive (Fire). In other words, the Smoke would be rendered as Fire. > > On the other hand, if the **Smoke Color** (diffuse) & [Smoke Opacity](https://docs-chaos.atlassian.net/wiki/spaces/PHX4MAX/pages/125056277/Render+Smoke+Opacity#BasedOn) were based on Temperature, then voxels with Temperature values would be shaded as diffuse volumetrics (Smoke Color & Opacity). In other words, the Fire would be rendered as Smoke. > Macro (anchor) **Example: Phase Function with front lighting** --- The orange arrow represents a ray of light going through the volume and the possible scattering directions for the ray. ### **Example: Phase Function with back lighting** --- The orange arrow represents a ray of light going through the volume and the possible scattering directions for the ray. ### > Macro (anchor) > Macro (anchor) Example: Smoke Color Based on Speed --- > Macro (viewtracker)