The metaball level object creates a boundary surface for a density distribution defined by sub objects. The sub objects can be symmetric or elliptic spheres or 1D particles and a VSL material can be applied to modify the density in space. By default, the density decreases from 1.0 at half radius distance from the sphere center to zero at the sphere edge. The boundary surface of the metaball system follows the area where density is exactly a given Iso Value. Because the density distributions of metaballs melt together, the result surface behaves like liquid.
The following controls are available:
Iso Value: The density value which defines the surface. Decreasing the value makes the result object thinner.
Channel: An optional channel that modifies the density distribution. If set, the materials (more exactly, the Surface Geometry shaders) that affect the metaball system are evaluated. The total density field is the product of the spherical density fields and the material defined channel values. |
Create a material that assigns a value to the density channel and map it to the metaball system.
Resolution X, Y, Z: The accuracy of the 3D grid which is used for searching the iso surface. The resolution defines the density (and quality) of the generated surface. For example, if the diameter of a metaball system is 20 cm and the resolution values are 40, the surface will show details of the magnitude 20 cm/40 = 0.5 cm.
Expansion: Expands (or shrinks) the size of metaballs from their true geometric size. For instance, an expanded size allows simulated meta objects to melt together, while collision detection prevents excessive penetration.
Test Interval: A speed optimization setting. Boundary surface is searched using the given test interval stepping along the Resolution X, Y & Z grid, and the exact surface is computed only if the density changes across the iso value limit. If the density distribution does not contain small details, the test interval can be several resolution units.
Accuracy: Defines how accurately the surface points are computed to match the exact iso value surface.
Field: Defines how the density field increases from zero at the metaball outer edges towards the full value 1. The higher the degree, the smoother metaballs melt together.
Linear - Density increases at a constant rate along the sphere radius.
Quadric - Density grows proportionally to the square of the radius.
Cubic - Density increases proportionally to the third power of the radius (d = c * r*r*r).
Volume - Density jumps to the full level at the metaball edge.
4th Degree: - The density decreases proportionally to the 4th power of the radius. The smoothest way to blend metaballs.
Rendering:
Hierarchical: If set, the full sub hierarchy of the metaball level is examined to find metaballs. Otherwise only direct children of the metaball level are considered. Full hierarchy scan is not always desirable, because the hierarchy can contain animation parameters (morphing keys, creator object's samples etc.).