VRayMetaball

VRayMetaball is a geometric primitive that can be used to create a raytraced iso-surface out of an existing particle system. The iso-surface is created at render time and is not generated as actual geometry.

Enable – Turns the metaball object on and off.

Use particle size – When enabled, the particle size from the source particle system is used.

Particle radius – When Use particle size is disabled, this parameter determines the size of the particles.

Threshold – Controls how close the iso-surface is to the particles. Lower values move the surface away from the particles, while higher values make the surface cling close to the particles. For more information, see the Threshold example below.

Step length – The main control for quality vs. render time of the metaballs surface. Lower values produce a more precise surface, but may take more render time. Higher values reduce the render times, but can produce artifacts. The metaballs object uses a larger step length for GI rays in order to reduce the render times. For more information, see the Step Length example below.

Distance function – Determines the type of function that is used to produce the metaballs field around the particles. For more information, see the Distance Function example below.

Smoothing field bumps – When enabled, smooths out the surface by culling away small stray particles. For more information, see the Smoothing example below.

Smooth radius – Specifies the radius value when Smoothing field bumps is enabled. 

Smooth expansion – Further controls the smoothing. 

Color source – Determines the color source when a material that uses a VRayParticleTex texture is assigned to the VRayMetaball object. VRayParticleTex is commonly used to vary shading of particles within a single particle system based on Particle Flow operators such as the standard Display operator, the VRayParticleColor operator, or an operator that uses a script to supply color data. For more information, see the Color Source example below.

Display color – The VRayParticleTex texture returns the display color of the particles as specified in the Particle Flow Display operator.
VRayParticleColor – The VRayParticleTex texture returns the color specified by the VRayParticleColor operator in the Particle Flow system. 
Script vector – VRayParticleTex returns the point3 value set in the .particleVector channel of each particle to determine the color. These values present vectors from per particle script channel data as a color source. Script channel data is settable using script-based operators (Script Operator, Script Test and Birth Script) and Data operators.

Object xyz – Specifies a node relative to which textures with Object XYZ mapping are computed when they are used for field texture.

Example: Threshold

Example: Step Length

Example: Distance Function

Specifies the particle systems that are used as a base for the metaballs surface.

Positive particles – Specifies particles that add to the metaball field.

Negative particles – Specifies particles that subtract from the metaball field. Negative particles may be used to produce holes in the metaballs surface.

Specifies events from the particle flow systems to affect the metaball instead of the complete particle system.

Positive Particle Flow Events – Specifies particle flow events that add to the metaballs surface.

Negative Particle Flow Events – Specifies particle flow events that subtract from the metaballs surface.

All Particle Flow Events – When enabled, all particle flow events affect the metaballs surface.

Specifies a 3D procedural texture that modifies the metaballs field.

Use texture – Enables the use of a texture to modify the metaballs field. 

Field texture – Specifies the texture itself. 

Texture multiplier – Specifies a multiplier for the texture result. 

Operation – Determines the way the texture is combined with the metaballs field.

multiplication – The texture is multiplied to the field.
addition – The texture is added to the field.

Clamp field – Clamps the resulting field value so that it doesn't become too large.

Clamp level – Determines the maximum field value when Clamp field is enabled.

The VRayMetaball object can optionally use a 3D grid cache to speed up the intersection of rays with the metaball surface. The cache is currently experimental and may lead to artifacts in the metaball surface.

Use cache – Enables the cache. 

Fast build – When enabled, uses a faster but less accurate algorithm to compute the cache. 

Size – Specifies the size of the cache in voxels (internally the values 1-5 are mapped to 32-1024).

Block size – Higher values may optimize the cache size to take up less RAM, but may reduce the precision of the calculations.

This group controls the viewport preview of the metaball surface. Note that the preview uses the particles that are displayed in the viewport by the Particle Flow systems, and this may be different from the number of particles in the rendering, which may lead to the preview looking different. To avoid this, set the Particle Flow system to display 100% of all particles in the viewport.

Use preview – Enables the viewport preview.

Shaded – Enables shaded drawing of the viewport preview. When disabled, the preview is drawn in wireframe mode. 

Resolution – Specifies the maximum grid resolution used to compute the viewport preview. Lower values produce a rougher approximation of the metaballs surface that takes less memory and is faster to compute. Higher values produce more accurate previews at the expense of more RAM and slower calculation speed. 

Max particles – Controls the maximum number of particles that are used to compute the viewport preview. 

Max faces – Specifies the maximum number of triangle faces in the viewport preview.