Animating Boolean Cuts with Assistance from Xform

Boolean and XForm

Animating Boolean cuts with assistance from XForm

In this tutorial we will look at animating Boolean Primitives. We all know that Boolean can help us subtract shapes from one another, but did you know you could animate the effects as well?!

Let's start by opening a new 3DS Max file.

Then create a cylinder in your Front viewport, with the following settings.

Now, we are going to cut a slice off of our cylinder here in this tutorial. Is anyone else thinking about a pepperoni pizza right now? >.>

In order to do this we need to create an edged shape to stand in for our cutting knife.

Go to your create tab, and in the shapes select the line tool.

Then in your left viewport, draw a wedge shaped triangle, think ... a cleaver from

the top. Like below:

Make sure you close the line by clicking last on the very first vertex in your line, and answering yes to the "Close Spline?" dialogue box that shows up.

Now with your wedge shape still selected, go to your Modify Tab, and in the Modifier list add the one that says "Extrude"

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Then Set the Extrude settings like this:

Give it an amount of 75.0

The rest can remain at default.

Now we have our two objects for the Boolean, Our knife, and our pepperoni!

Next, select your cylinder and go back to the create tab, click the geometry button, and then in the drop down menu find "Compound Objects"

------> Click on the Pick Operand B button

and then click on the blade wedge.

The blade will vanish, but don't worry you haven't messed anything up. Now with Cylinder selected still go to your Modify tab to adjust some settings further.

Your Cylinder should show up as A:

and your Line should show up as B:

Make sure the Operation is marked as Subtraction (A-B) so that the knife shape is being subtracted from the cylinder.

In Display, check the box that is marked "Result + Hidden Ops"

Your blade should return as a wireframe, but you can see it once again.

Once your settings match mine, scroll up to the top where the Boolean shows up in the Modifier stack, then click on the little black + sign to open up the sub object selections.

Click on the Operands sub object from the resulting list.

This will let you adjust the position of the blade and the cylinder to your liking, you can also animate them using the operands.

Click on the AutoKey button to turn on Autokey.

Then click on the Blade wireframe in your scene, you should be able to select it as long as you have the Operands sub object selected under your Boolean modifier.

Move your timeline scrubber to frame #20. and then Move your blade until it completely cuts all the way through the cylinder.

Then turn auto key off, and scrub back and forth along the timeline to see the result. The blade will start completely away from the sphere, and then cut through it with the same wedge shaped blade we chose as operand B.

Completely slicing through our cylinder.

Now click on the keyframe that was created at frame #0 and move it forward to Frame #5.

This gives us a short space before the slice animation begins.

Step one is complete! You just animated a Boolean cut.

Now let's talk about what comes next, the XForm modifier.

An XForm modifier allows us to manipulate sub objects as though they were individual objects. In order to do this, we must first have some sub objects.

Leave your timeline at frame 20 or above, and in the Modifier drop down menu, add a Poly Select Modifier to your Boolean.

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The Poly Select modifier allows us to select our sub-objects like vertices, edges, borders, polygons, and elements. It allows us to do this without having to add an actual editable poly to the scene as we don't need to modify the model itself, we just want to select the now 2 parts of our cylinder.

Click on the Element sub-object selection.

Then select the small slice we cut off of the cylinder in our scene.

Then with the element still selected go back up to your modifier drop down menu, open it up and find all the way at the bottom the Modifier called "XForm"

It will add it to the modifier stack above the Poly select, and you should noticed that it has drawn an orange wireframe box around the smaller slice of our cylinder.

Next click on the small black + sign next to the word XForm in your modifier stack.

Then select Center from the resulting list.

The Center sub-object in the XForm modifier allows you to move the pivot point of our sliced off piece of cylinder.

In your Left Viewport, use the move tool to move the center pivot point to the lower front edge of the cylinder, like this:

Then, grab your rotate tool, and go back to your Modifier stack and click on the sub-object called "Gizmo" under your XForm modifier.

Now you can animate the slice of our cylinder by manipulating the placement of the XForm gizmo.

Turn on your Auto Key button again, move your timeline scrubber to frame 21 and hit the Keyframe button.

Then in your left viewport, rotate the slice of our cylinder as though it has fallen off and over away from the rest of the cylinder.

Then turn off your AutoKey.

You will notice two new keyframes have appeared. One at frame #0 and the other at frame #30.

Click and drag the one at frame #0 over to frame #21.

This will make it so that the sliced off part of the cylinder doesn't start rotating away until after the cut is fully made.

Now click on the word XForm in your modifier stack to unselect the gizmo and test your animation. It should start by cutting off the slice of cylinder and end with the slice falling away from the rest of the body of our original cylinder.

Just like slicing up a stick of pepperoni for a pizza! ... Ok time for lunch! Have fun and don't forget to check out the action moving animation here:

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