---
title: "FireSmoke Interaction"
canonical: "https://documentation.chaos.com/space/PHX4MAX/124530392/FireSmoke%20Interaction"
format: markdown
---
This page provides information on the Interaction rollout for a Fire/Smoke Simulator.

## **Overview**

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> It is strongly recommended that each geometry interacting with the fluid simulation:
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> - has no open edges or holes;
> - does not self-intersect;
> - has normals pointing outwards.
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> Phoenix will try to handle any geometry that does not comply with these conditions, but the simulation might not behave properly. For example, in the case of fire/smoke simulations, some areas of the simulation may lose velocity and freeze for no apparent reason, whereas in liquid simulations, particle explosions can appear.

This dialog is used to enable/disable the interaction with objects in the scene. There are several different types of objects that may affect the simulation: Sources, Solid objects, Forces, etc.

By default, all these scene elements will interact with the simulator unless otherwise specified by the **Include/Exclude list**. If you want to disable the interaction, you have to put the objects in the **Exclude list**. If there are more objects that don't need to interact with the simulator, you may alternatively switch to the **Include list** mode. In this mode, you will need to add to the list all the objects that you want to interact with the simulator.

Since all forces affect the simulation by default, adding a force in your scene to be used by PFlow, for example, will also automatically affect your simulation and this might not be desirable. In the Active Forces list, you can check which 3ds Max forces interact with the simulator, and you may exclude forces if you wish to.

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> UI Path: ||Select [Fire Smoke Simulator](https://docs-chaos.atlassian.net/wiki/spaces/PHX4MAX/pages/124760253) object|| **> Modify panel > Interaction rollout**

## **Parameters**

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### **Example: Geom Border Voxels**

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> The example below shows the difference in emission when the object uses Inscribed (voxels intersecting the surface are non-solid therefore do *not* emit) vs Circumscribed (voxels intersecting the surface are solid) voxelization.

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> | ![image](media://ae2d0f2e-a7c7-4cc0-b0ed-8d82d9354d5d) |
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> | ![image](media://322e6cec-dd57-4664-8e4a-deab3604946d) |