Hi my name is Laurent Renaud, you may visit me also at my web site at: http://loran-cg.blogspot.com/

In this 3D Studio Max FX tutorial we will use Reactor to animate the explosion of an object. You will understand the way Physic simulation works in 3ds Max.

Step 01 – Models and cuts

First  let’s build a basic scene. We have to start by adjusting the scene unit because we will use physical value for Reactor.

Go to Menu/Customize/Unit Setup… Choose Metric then Centimeters.

Now, create a Box with Length :50 Width: 50 Height: 100 and a Plane with Length: 100, width:100, Length sgs: 20 and width lgs: 20.

Add a Noise modifier to the Plane. Adjust the parameters to obtain moderate chaotic surface. I use Scale:14 and Z Strength : 11,2.

This Plane will be used to cut the Box.

Move the Plane to the Center of the Box. Rotate, move and scale the plane while pushing Shift Key to duplicate.

Duplicate it 5 times. Be careful : The plane must always be larger than the Box.

With one Plane selected, go to Create tab/Geometry/Compound Object/Pro Cutter . Check Auto Extract Mesh and Explode By Elements, Stock Outside Cutter and Stock Inside Cutter.

Use the Pick Cutter Objects to add the other planes. Then Use the Pick Stock Objects to add the Box.

Delete the planes.Your Box is now cut into blocks. Select the blocks, Right-Click on it and convert it to Editable Poly.

Here is what Procutter really do (Don’t move blocks like this! it s just to show you the cut result)

Select all the blocks and add a Smooth modifier. Check Auto Smooth and adjust Threshold to 30. It looks better now.

Now the tedious part. We have to change the inner faces ID so we can apply a specific material to it later.

To do that, select one block then right-click on it, then choose Isolate selection. Everything but the block is hidden now.

Right-click on the smooth modifier and choose Collapse to. In the Editable Poly modifier settings, check By angle and set it to 20.

Select
all the faces, then Ctrl-click on the external faces (the flat ones)
until everything but the inner faces are selected.

Go to Polygon material IDs in the EditablePoly modifier and adjust Set ID to 2. Repeat this operation for each blocks.

Now we will apply mapping coordinates for the booth ID. Select all the blocks then add a UVW mapping operator. Set the Mapping to Box and Length, Width, Height to 100 cm. Add a second UVW mapping operator with the same settings and change the Map Channel to 2. Right-click on the blocks selection and  choose convert to Editable Poly so the UVW dummy disappear.

Lets create the material now. Hit M to open the Material editor. Click on the Get Material button and choose Multi/Sub-Object in the list.

Set number to 2. Enter the first one (ID 1), rename it and add a bitmap of your in the Diffuse Channel.

Do the same for the second one with another bitmap. the Isolated block
in the picture bellow show you the result you should have. Select all,
go to Menu/Tools/Rename objects… Enter Block as base name and check Numbered.

Some very nice free maxscript tools exists to do in one click most of what we’ve done here. Search for “fracture” on scriptspot.com if you are interested in.

Ok. We have the scene ready to animate!

Step 02 – Physical simulation with Reactor

Right-click in the menu bar, in a free area at icons levels, choose “reactor“. A new toolbar appear with the Reactor tools.

Pick the Create Plane icon and create a reactor plane in the scene. Drag it down in Z
direction to leave some space between Reactor Plane and the Blocks.

The
Reactor plane do a floor collision. Select all (blocks + reactorplane)
and click on the Create Rigid Bodies Collection button (the first one from the left).

Now go to the 3ds Max Utilities tab (the hammer) then click on Reactor Button. In properties set Mass to 10 and Friction to 0,8. Mass is the weight of the block and Friction is about the sliding  level of the blocks surface.

In the Reactor toolbar, click on the Preview animation button. When the
Reactor Real-Time Preview window opens, hit P to play the simulation.
The Blocks fall on the floor.

If everything explode around, you might have a problem of collision tolerance. If the collision tolerance is too high, the different blocks and even the floor push each other away.
Reactor is a physical simulator so it is hard to work with real physic constraints.
Go to Utilities/Reactor/havok 1 World then set the Col.tolerance to 1cm

All right, lets create a bomb now! For this we will animate a growing object inside the blocks.

Create a Geosphere. put it in the center of the blocks.  Animate  its Radius like this : frame 1 = radius 1cm, frame 2 radius  14 cm, frame 3 = radius 1.

Animate its position like this: frame 2 = in the center of the blocks, frame 3 = under the floor level.

Ok, with the Geosphere selected, create a Deforming Mesh Collection from the Reactor bar (the 5th icons from the left).

In the Reactor toolbar, click on the Preview Animation button. When the Reactor Real-Time Preview window opens, hit P to play the simulation. Boom! adjust the Geosphere position and the radius animation until your simulation looks great.

When its ok, hit the Create Animation button in the reactor toolbar. This will key frame the entire simulation for each blocks.

If needed you can reset this animation by selecting all the blocks, then select all the key frame in the timeline and hit Del.

So you’re done with reactor now! You can delete the Geosphere and select all the blocks then move the key frames so the explosion happen later in the timeline.

In a next part, we will enhance the animation with particles.

Hi my name is Laurent Renaud, you may visit me also at my web site at: http://loran-cg.blogspot.com/

CONTINUE TO PART 2