Making simple collision objects

Let's run through the process of adding simple collision objects within Autodesk Maya.

Most dynamics within 3DS Max will be done through the MassFX toolkit. You can access most of the functions of MassFX through the main menu but I would recommend going to "Animations > MassFX > Utilities > Show MassFX tools" to open a pane of all of the tools at once.

Let's go over the most basic way to create physics objects in 3DS Max.

  1. Select an object.
  2. Then choose what type of physics to apply.

    For objects that will be moving.
    "Animations > MassFX > Rigid Bodies > Set Selected As Dynamic Rigid Body"
    For objects you don't want to move (walls, floors, furniture).
    "Animations > MassFX > Rigid Bodies > Set Selected As Static Rigid Body"
    You can convert either of these from one to another easily since they both just add the MassFX Rigid Body modifier to the selected object stack - just with different presets.

While messing with the settings you'll see the option to switch an object between three different types besides just "rigid" or "soft". "Dynamic", "Kinematic", and "Static" are seperate types as well.

  • Dynamic are free moving objects. Things you want to throw around and laugh at.
  • Kinematic is for objects you want to have complete control over but still allow to affect other objects within the scene. They themselves will not be affected by other physics object.
  • Static is for objects that you want to be considered by the physics solver, but that you don't want to move. For instance the architecture of a scene, a floor, or a wall.

Collision Meshes

In 3DS Max the the MassFX modifier has a section built into it to accomidate the use of collision meshes. Under the "Physical Shapes"

To select a custom collision mesh of your own making.

  1. Shape type to "custom"
  2. Click the "pick mesh from scene" button.
  3. You'll now get a duplicate of your mesh.

The approach 3DS Max has of having a collision mesh list is useful as one model can use multiple collision meshes AND multiple copies or instances of an object can all reference the same collision mesh.

Max has the ability to use primitives for these collision meshes as well and it may sometimes best to take advantage of them. Especially since they may both fit individual parts better and calculate faster. For instance the spheres that you can add as collision meshes should rotate smoother when rolling on the ground than a custom polygonal sphere object and, again, calculate faster as well.

For further information see the Autodesk site..
LINK

Note: If you change the shape of the mesh, with the edit poly modifier or a deformer for instance, you'll need to press "Regenerate Selected" to recreate the collision mesh for the object.

Cloth

Creating a cloth object in 3DS Max is fairly simple and tightly integrated into the same MassFX system used to create rigid and soft bodies.

  1. Select an object to become cloth.
  2. Choose the appropraite modifier from the menu.
    "Animations > MassFX > Rigid Bodies > Set Selected As Dynamic Rigid Body"
  3. Collision objects can be set up the same way as in the rigid / soft body process. But if you want the colliding object to move and have that movement to affect the cloth then remember it will have to be a Kinematic object and NOT a static object.

Cloth objects work the same way as rigid / soft bodies and require you to preview their animation through the MassFX tools utility instead of the main timeline "play" button.

By default the cloth may appear a little stiff, like paper, but this of course can be alleviated with the modifier settings. The fisrt one you may want to increase is the "bendiness" setting of the modifier.

Because of the default settings you might also sometimes find that your cloth is "floating" above rigid body colliders.

Go to the mCloth I just keep reading "Mmmmmmmmmm cloth." modifier on the cloth object and look for the "Interaction" section. Under "collide to rigid bodies there should be a settings simply called "thickness" which you can lower to make the cloth get closer to a surface. Just be aware that since collision is calculated via points you'll need to have a high density mesh to keep the rigid body collider from poking through the cloth object.