Colliding Objects Using Reactor in 3D Studio Max

By Aziz Khan | 3D Studio Max | Intermediate | Edited by Oman3D

This 3D Studio Max tutorial for Reactor shall teach you how to animate a realistic looking collision of objects. This is an intermediate level tutorial that expects you to know your way around 3DS and the basics of Reactor. Here is the end result video that we are going to create in this lesson.

We will use Reactor to convert the boxes to rigid bodies that will not go through each other, we will add a reactor spring to the lamp, and rigid bodies will be created to make the boxes bounce off the walls instead of going through them.

We will supply you with the starting scene to be able to start straight away with the topic of the tutorial, download the file here. This file contains the boxes, the lamp, and the walls all positioned on the stage. The hit box, the one that is going to hit the target boxes, has already been animated using Auto Key animation to move in straight direction through the other boxes. Follow this tutorial to learn how to make the scene react to the hit box.

The Initial Scene - Starting Off

You should see the following scene upon opening the file provided, here are images from all the different viewports in case you wanted to create the scene yourself instead of using our files. If you do so, remember to animate the hit box using Auto Key to move towards the other boxes before carrying on with this tutorial.

Configuring the Hit Box

Select the box named Hit Box on the scene and go through Reactor>Open Property Editor. A window should appear, set the Mass Value to 5, look for the Simulation Geometry rollout and select Proxy Convex Hull, then click on the None button next to Proxy and select the Hit Box you previously selected. Look for the Display rollout below and check the box next to Use Display Proxy.

Configuring the Receiving Boxes

Upon assigning the Mass Values and Proxy Settings to the first box, we have to repeat the same procedure for the rest of the boxes, i.e. the receiving boxes. Select one of the boxes located under the lamp and then go through Reactor>Open Property Editor. In the window that pops up, repeat the same steps we did for the Hit Box, but with one exception, under Physical Properties, look for the Inactive check box and activate it.

Receiving Boxes

Select the second box and go through Reactor>Open Property Editor. Apply the settings illustrated in the image below in the window that pops up. You should repeat this process to all the boxes found under the lamp.

Property Editor

Creating the Walls, Floor, and the Roof

We are going to create Reactor Planes to stop the boxes from going through the walls in our scene upon colliding with each other. The Reactor Planes will be placed at the same places as the walls already existing on the scene to act like real walls. To create a Reactor Plane go through the Reactor Panel and click on the icon highlighted in the image below.

Reactor Panel - Reactor Plane

You will now have to click once on each of the viewports (left, right, front, and top) to add reactor to each of the walls visible on these viewports. You might need to alter the initial position the planes so that they are placed at the same position as the walls that we already have as illustrated in the image below.

Adding the Reactor Plane to act like the roof is a little trickier as you will have to precisely position it above the lamp. Create a Reactor Plane in the Top Viewport and then use the other viewports to place it at the right position.

Reactor Plane - Roof

Adding a Reactor Spring to the Hanging Lamp

Access the Reactor Panel and Select the Spring Reactor as illustrated in the image below.

Reactor Panel - Spring Reactor

Look for the Spring Properties rollout and mark the check box next to Parent, you will then have to click on the first box labeled None and select the Lamp Cone, click on the Child button and select the Reactor Plane. You will then have to alter the values of the Dynamic Properties as illustrated in the image below. The Lamp, Spring and the Reactor Plane should now look like the second image below.

Spring Reactor - Spring PropertiesSpring Reactor Done

Setting up the Reactor Animation

Go through Utilities>Reactor>Preview Animation and apply all the settings illustrated below in both the Preview & Animation rollout and the World rollout below it.

Reactor - Preview & AnimationWorld Rollout

Creating the Rigid Body Collection

Access the Reactor Panel and click on the Rigid Body Collection icon as illustrated in the image below.

Reactor Panel - Rigid Body Collection

Click anywhere on the scene and then access the Modify Panel and click on the Add button as illustrated in the image below. The Select Rigid Bodies window shall appear, add All of the objects in the scene to the Rigid Body Collection. You should then be able to see all the objects you added to the Rigid Body Collection in the RB Collection Properties rollout.

Select Rigid Body Collection

Finalizing the Animation

Access the Reactor Panel and click on the Preview Animation button as illustrated in the image below. Do not worry if you get a World Analysis error saying that Reactor results in some interpenetration and that the density of some objects is very low, this will not affect the animation.

Reactor Panel - Preview Animation

World Analysis

We are done, click on the Create Animation button on the Reactor Panel to get a render similar to the one below.

Reactor Panel - Create Animation

This concludes our tutorial, you can download the end scene from here. I hope that you learnt how to create a collision of objects using Reactor. If you have any comments or questions please feel free to email me, you can alternatively post at the Oman3D Forum.

Links to other Reactor tutorials:

- End of Tutorial