Every surface and polygon object can be equipped with a "RFVolume" world space to modifier to refine the collision geometry and control how the particles "see" the object.

Collision Geometry Detail

Here you find five levels of quality. The higher the level, the longer the simulation will take, but the fluid-object collision will also be more accurate. Changing the level influences and updates the "Cell Size" value found in the "Volume" section. In most cases, the calculated value provides the best balance between simulation speed and accuracy. If you want to control "Cell Size" manually deactivate the associated "Auto Cell Size" checkbox.

Cell Size

RealFlow | 3ds Max's fluid and material engines are cell-based and therefore, colliding objects have to be rasterized internally. The smaller the cells, the better and more accurate the collision, but at the cost of longer simulation times. By default, "Cell Size" is calculated automatically based on the "Collision Geometry Detail" level. For manual control uncheck "Auto". With "Auto Cell Size" turned off, "Cell size" can be animated. This allows you to refine collision detection over time and speed up the simulation, e.g. from coarse to accurate.

Surface Offset

This parameter creates a solid extension around the object and prevents the fluid from penetrating its surface:

The offset can be visualized with "RFVolume (WSM) > Display Volume"
Positive and negative values are accepted.
To control this parameter manually, disable "Auto Surface Offset".

Domain Offset

In order to improve fluid-object interaction you can increase this parameter. The effect is that the fluid will “see” the object earlier. This can be interesting for fast-moving fluids. By default, "Domain Offset" is calculated automatically based on the "Collision Geometry Detail" level. For manual control uncheck "Auto Domain Offset".

Volume Mode

Here are the three possible modes:

"Solid inside" makes the fluid collide with object's outer surface.
"Solid outside" creates a hollow object and the fluid interacts with the inner surface.
"Shell" is normally used with open objects like glasses, vases, but also planes. When active, an invisible layer is added around the object's surface. The thickness of this layer is Cell size * 3 on each side of the surface. As a consequence, there will always be a gap between the fluid and the object.

By default, "Volume Mode" is determined automatically by analyzing the object's geometry, but this test is not always reliable. For manual control uncheck "Auto Volume Mode". If you can see leaking particles in conjunction with thin or single-walled objects please consider activating → "Continuous Collision Detection" in the "Collider" element.

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