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This page provides information on V-Ray Attributes that can be added to fluids.

 

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Overview


Additional V-Ray attributes can be added to fluid shape nodes in Maya. If these attributes are not present, the default volume shader will be used, and the shading quality will be determined automatically, taking into an account the "Quality" fluid attribute and the cell size. Note that there isn't an exact correlation with the shading quality of the Maya Software renderer.

UI Path


 

||Select fluid|| > Attribute Editor >  Attributes menu > VRay > V-Ray fluid shading quality

 

 

 

Fluid Shading Quality





Volume Shader – Determines which volume shader to use.

Auto – Picks the best available shader. In V-Ray 3.0 this will always resolve to Phoenix FD. In V-Ray 2.x, Phoenix FD will be used only if available.
VRayEnvironmentFog – Uses a generic purpose volumetric shader that V-Ray is using in VRayEnvironmentFog node.
Phoenix FD – Uses the Phoenix FD shader which is optimized for grid based volumetric data.

Scatter GI – Enables the tracing of GI through the fluid. The standard GI engine in the V-Ray settings is used.

Scatter bounces – When Scatter GI is enabled, this attribute limits the number of GI bounces that will be calculated inside the fog. It can be used to increase the rendering performance.

Simplify textures for GI – When enabled, V-Ray uses a simplified method for calculating the GI when rendering parts of the liquid that are textured or that are being faded out.

Step size – Determines the size of one step through the volume of the liquid. Smaller steps produce more accurate results but are slower to render. In general, dense volumes require smaller step sizes than more transparent volumes.

Max steps – (VRayEnvironmentFog only) Specifies the maximum number of steps through the liquid. Its purpose is to prevent too many steps inside the volume. However, it can cause parts of the fluid to not render!

Texture samples – (VRayEnvironmentFog only) Determines the number of texture samples for each step through the liquid. Thus, textures are sampled more accurately than the volumetric lighting. It is useful in cases where the textures vary much faster than the lighting itself (e.g. for detailed fractal textures). Note that this parameter is used only with the shader.

Cut-off threshold – Controls when the raymarcher will stop traversing the volume. If the accumulated volume transparency falls below this threshold, the volume will be considered opaque and tracing will be aborted. Higher values make the rendering faster but may introduce artifacts.

Subdivs – (VRayEnvironmentFog only) Determines the number of points inside the fog at which volumetric lighting is evaluated. If this value is 1, a single sample along the ray will be calculated, otherwise, the  Step size will be used instead.

Diffuse color multiplier – Specifies an extra multiplier for the diffuse lighting. This can be used to produce a non-physically correct result. The VRayEnvironmentFog shader requires this parameter to be set to 4.0 in order to produce a result similar to the Maya Software renderer. The Phoenix FD shader does this automatically.

Jitter – Used to offset the starting point of shading in order to hide regular patterns.

Solid mode – When enabled, the fluid will be rendered as a solid object with a sharp surface, determined by the Solid threshold attribute.

Solid threshold – Specifies the value below which the fluid is assumed to be "solid."

Use light cache – (Phoenix FD only) Enables the use of Light Cache data. This can increase the performance but can present lighting splotches, especially when used with a low resolution grid and noise textures.

Full Motion Blur – Turns on the motion blur caused by the fluid movement inside the container. This is slower than calculating only the motion blur of the fluid container.

Disabled – Disable to increase the rendering performance.
Blend – Uses simple fade out between two states of the fluid. Note that this will not actually produce a fluid moving effect.
Velocity – Uses the velocity field to actually move the fluid in the time. Since this method is using a snapshot of the velocity at the start of the motion blur interval, the end position will often not correspond to the start of the next motion blur interval.
Velocity + Blend – Uses the velocity to try blending more accurately between the current and the next frame. This is the most advanced, but slowest method.

Render as Geometry – Enables the fluid to generate deep image data when saving to Deep EXR or VRST.
 

 Scripting

 Add to node:

vray addAttributesFromGroup "fluidShape1" "vray_fluid_shading_quality" 1;

Attributes:

vrayFluidShader
vrayFluidScatterGI
vrayFluidScatterBounces
vrayFluidSimplifyTexturesForGI
vrayFluidStepSize
vrayFluidMaxSteps
vrayFluidTextureSamples
vrayFluidCutoffThreshold
vrayFluidSubdivs
vrayFluidColorMult
vrayFluidJitter
vrayFluidSolid
vrayFluidSolidThreshold
vrayFluidLightCache
vrayFluidFullMB
vrayFluidDeep

 

Notes


  • The ambient and fake lighting in the "Lighting" rollout are not currently supported.
  • The "Self Shadowing" option is ignored, and the shadow option of the lights is taken into an account.
  • The VRayEnvironmentFog shader do not support accurate blending of intersecting fluids.
  • The VRayEnvironmentFog shader do not support light cache.
  • The VRayEnvironmentFog shader can discard part of the fluid if the Max Steps attribute is set to too low value.