--- title: "VRayVolumeMtl" canonical: "https://documentation.chaos.com/space/VMAX/1442447899/VRayVolumeMtl" format: markdown --- This page covers the parameters of VRayVolumeMtl.   ## **Overview** --- The VRayVolumeMtl is the core node of V-Ray’s new implementation of volumetric rendering. The VRayVolumeMtl enables work with volumetric shading graphs by exposing inputs for density, color, absorption, and anisotropy. Map the inputs with textures to create procedural shading graphs by sampling the voxel information for each VDB primitive in the VDB file. Use the VRayVolumeMtl for clouds, smoke, and magical effects. Currently, it does not support rendering fire on its own (i.e., without smoke).
UI Path ||Material Editor|| > **Material **> **Map Browser** > **Materials** > **V-Ray** > **VRayVolumeMtl** ![Max2027_VRay7.5_VRayVolumeMtl_UIPath.png](media://e77f8c34-21d3-4806-9d7b-e111d887b40a)
## **Smoke** --- **Density **– Multiplier for the volume thickness. **Density channel** – Specifies the cache channel (such as *Smoke*, *Temperature*, or *Fuel*) used to drive the volume's density. If left empty, it applies a uniform density across the volume using the **Density** multiplier. --- **Smoke Color** – Specifies the volume's base scatter color when illuminated by a light source. **Smoke channel** – Specifies the cache channel used to map and distribute the base scattering color throughout the volume. This lets the smoke's color gradients shift dynamically based on simulated data (such as *Smoke* concentration or *Temperature*). When the channel field is filled, it overrides the Smoke color swatch and map. --- **Absorption color** – Specifies how much light is attenuated as it passes through the volume. **Absorption channel **– Specifies the cache channel used to determine where and how intensely light is absorbed (attenuated) as it passes through the volume. This can be mapped to simulated channels to create varying material thickness and realistic light-blocking behavior inside the volume. When the channel field is filled, it overrides the Absorption color swatch and map. --- **Extinction Falloff** – Specifies how quickly volume density decreases with higher scatter bounces. Values greater than 0 exponentially reduce volume density for successive scatter bounces. This lets you simulate light propagation through highly scattering volumes, such as clouds, with fewer scatter bounces. Values around 0.25 can be used as a starting point for creating a cloud shader. **Extinction Start** – Specifies the scatter bounce where density reduction begins. The parameter value indicates the last scatter bounce unaffected by the falloff. ![Max2027_VRay7.5_VRayVolumeMtl_Parameters_Smoke.png](media://f495814a-dc42-4002-9ebf-e5ae6d4853c8) ## **Fire** --- **Mode **– Specifies how fire is calculated based on the emission and temperature. **Disabled **– No fire is rendered. **Artistic **– Uses the emission parameters to render fire. This mode can use GradientRamp map with mapping source based on VRayVolumeFloatSampler where channel data from the vdb is used to control the map transition. **Blackbody **– Uses the temperature parameters together with the emission. A GradientRamp map with mapping source based on VRayVolumeFloatSampler can be set respectively in the Temperature map slot. **Emission color **– In Artistic mode, specifies the volume emission (self-illumination) color. In Blackbody mode, it acts as a multiplier. **Emission channel **– Specifies the cache channel (such as *Fuel*, *Heat*, or *Smoke*) used to drive the fire's emission intensity and distribution when using **Artistic** mode. If left empty, it calculates uniform emission based on the **Emission color**. When the channel field is filled, it overrides the Emission color swatch and map. **Temperature channel** – Specifies the cache channel (typically *Temperature*) that drives the fire's color and intensity in **Blackbody** mode. This channel maps physical heat values to corresponding blackbody radiation colors and intensities. When the channel field is filled, it overrides the linked Temperature map. **Temperature scale** – Multiplier for the temperature. It provides a handy scale factor to bring the default simulation values into a real-world, physical Kelvin range **Scaling **– Specifies how the final illumination is calculated. **None** – Used when the goal is to render fire without smoke. **Density** – Multiplies emission by the Smoke. Thus, setting the Density Scale to 0 also produces no illumination. **Absorption** – The final illumination is affected by both the Smoke Scale and Smoke Color. ![Max2027_VRay7.5_VRayVolumeMtl_Parameters_Fire.png](media://ca07f47f-c6f7-42a3-af6d-d3fc8e461dcc) ## **Anisotropy** --- **Anisotropy **– Controls forward or backward scattering (Hen–Greenstein phase function). Accepts values in the interval [-1 1]. Negative values correspond to backward scattering, positive values to forward scattering, and 0 to isotropic (diffuse) scattering. **Roughness **– Specifies the rate at which the Anisotropy is reduced for higher scatter bounces. Setting Roughness to a value greater than 0 leads to an exponential reduction in phase-function asymmetry for successive higher-scatter bounces. This simplifies the multiple scattering computation, which can significantly reduce render times. Additionally, roughness can potentially restore volume shape details that would otherwise be lost with a highly anisotropic phase function, while retaining the silver lining effect. A roughness amount of around 1 can be used as a starting point for creating a cloud shader. By default, anisotropy reduction engages after the first scatter bounce. **Roughness Start** – Specifies the bounce after which roughness effects begin. ![Max2027_VRay7.5_VRayVolumeMtl_Parameters_Anisotropy.png](media://0c886226-8569-481f-9a13-8b4a278e631c) ## **Options** --- **Color multiplier** – Acts as a global scaling factor for both the scattering (Smoke) and absorption colors. Increasing this value intensifies the overall visual density and opacity of the volume. **Emission multiplier** – Specifies a global multiplier for the self-illumination (Fire) intensity. This scales the volume's final emission output without changing individual emission ramp or blackbody settings. The parameter is available for Fire modes Artistic and Blackbody. **Use render GI bounce limit** – When enabled, the volume shader ignores the local **Scatter Limit** parameter and instead uses the global Global Illumination (GI) depth or diffuse bounce limit configured in the renderer settings. **Scatter Limit** – Specifies the number of scatter bounces. The actual number of scatter bounces computed is still limited by the number of diffuse bounces set in the scene/renderer settings. Setting the number of scatter bounces to a negative value is equivalent to using the scene/renderer diffuse bounces limit. ![Max2027_VRay7.5_VRayVolumeMtl_Parameters_Options.png](media://496fbfca-2431-42e4-b046-88609aadcde7) ## **Maps** --- Use the checkboxes in the Maps rollout to enable or disable the maps linked to this material. ![Max2027_VRay7.5_VRayVolumeMtl_Parameters_Maps.png](media://f7cece28-10c2-4f52-921d-3671fe17c99c)