Reactor Physics Hinge Tutorial

Reactor is the Physics system used in 3ds Max 2011 and earlier. I created this tutorial for a post on Polycount.com, but many people still use older versions of 3ds Max. So I thought I should post it here as well. Please comment and let me know if it works for you. The tutorial is written in a general way so that you can reproduce the steps on your own objects.

Click here to download the completed Max File

Reactor Hinge Tutorial Max File

Creating the Hinge:

1. Parent object b (the Small Box) to object a (the Larger Box).
2. Change the pivot on object b so that rotating the Z axis gives the effect you want.
3. Hold ALT + Shift and Right click for the reactor menu.
4. Select Hinge Constraint and click on the ground near your objects.
5. Select the Hinge object and in the modify panel set object B as the Child.
6. Check the Parent option and set object A as the parent.
7. Click on Child Space and Child Body.
8. Don't worry about the Min and Max Angles, the collisions will take care of that.

Creating the Hinge Solver:

1. Hold ALT + Shift and Right click for the reactor menu.
2. Click on Constraint Solver and click on the ground near the objects to create one.
3. Select the Solver and in the modify panel click on Pick and select the Hinge.
4. Select object a and b
5. Hold ALT + Shift and Right click for the reactor menu.
6. Click on Rigid Body Collection, the selected objects will be added automatically.
7. Select the Solver and in the modify panel set the RB Collection as the Rigid Body Collection object.

Create the Rigid Body Collection:

1. Open the Reactor right click menu and click on Open Property Editor
2. Select object A, and in the Property Editor check Unyielding and set Shell to 0.
3. (This means it's a hand keyed object that influences physics)
4. Select object B and give it mass.
5. (Doesn't matter how much, unless it hits other objects.)
6. Also and set Shell to 0.

Preview and Bake:

1. Go to the utility panel and open the Reactor utility.
2. Click on Preview animation.
3. You can edit the Timing setting and preview again.
4. If everything is cool you can click on Create Animation to bake.