CAP 201a - Computer Animation I
Lesson 5 - Applying Modifiers
This lesson introduces the modifier stack and some of its uses. Objectives
important to this lesson:
- Modifier stack basics
- Modifier controls
- Basic modifiers
- Collapsing the modifier stack
The lesson begins with a discussion of the benefits to having a modifier
stack, a series of modification commands for one or more objects.
- 3DS Max has a large collection of built in modifiers.
- Modifiers are applied in a stack, a sequence in which each
new (higher) one is applied after the previous (lower) one.
- You can turn the visibility of a modifier on or off, and you
can rearrange the order of the stack
- You can change the parameters of any modifier in the stack
This set of features allows you to apply a modifier, remove it, change
it, and change the order in which modifiers are applied. When you choose
to work on a modifier, 3DS Max may warn you that doing so could
affect modifiers above it. When this happens, the text advises you to
use the Hold choice in the dialog box that comes up. Good advice:
when the program warns you that something to could go wrong, it is a good
time to save. (Hold saves a temporary copy of the file, remember?)
- To change a modifier in the stack, select that modifier
- Click the Show End Result button to enable turning modifiers
on and off.
This is not named well. At any given time, you see the end results
of all the modifiers. What this button does is enable selectively turning
off the effect of any modifier. However, you must first select
one of the modifiers in the stack, then enable the Show
End Result button. Then, you can toggle that modifier (and any
modifier above it) on or off.
- In addition to adding a modifier to an object (as you have
done) you can copy a modifier from one object and paste
it on the modifier stack of another object. This allows you to customize
the settings first, then apply the custom modifier to a second object.
- When you copy a modifier from one object and paste it
on another, you have the option of pasting an instance of the
modifier. Recall from the last lesson that an instance is linked
to the original it was made from, so changes made to one will
be made at the same time to the other. Another way to make an instance
of a modifier is to ctrl-drag it from the original stack and
drop it on a new object.
Autodesk realizes that the list of modifiers is long, and it is easy
to make a mistake when adding several modifiers to objects. So they built
in several sets of modifiers that are commonly used together. Click
the Configure Modifier Sets button to see ready made sets,
or to construct sets of your own.
The text shows in a simple illustration that the order of modifiers
in the stack makes a difference. In their example, it starts with two
similar objects, then applies two modifiers to each. One is tapered,
then bent. The other is bent, then tapered. The result
is two very different looking objects. If this is an error, you
can correct it by dragging a modifier to a new position in its
Exercise Notes and Questions
Note: You get it by now, right? Do the exercises.
Work through the exercises and turn in your answers to
all questions below as part of the homework for this assignment.
Exercise 1: This exercise reviews the points
above. An additional point is raised: some modifiers require more that
the default number of polygons to work well with an object.
The lesson continues to discuss specific modifiers:
- bend - used to bend all or part of an object
- taper - used to make all or part of an object progressively
- noise - used to add random deformation to the vertices of an
- twist - progressively rotates the vertices of an object along
its length (Think of a licorice
- shell - changes a two dimensional object, like a circle, by
giving it thickness, a front, and a back. The text is not clear on this.
Watch the video
on this page.
- lattice - removes the faces of an object's polygons, leaving
the edges and vertices visible
- FFD - Free Form Deformation, allows you to deform any vertex
on an object, like sculpting clay
The lesson describes collapsing the stack of an object. This is
like merging all the commands that were used to create an object
into a compressed form. The text warns us that this will lock the properties of the base type and the properties of the modifiers of the object. We should not do this unless
we expect not to need to modify any of those properties again.
That should sound mysterious, because the text has not explained what a base type is. That is the next discussion. The text lists five base object types, and explains our lessons will use two of them, shown in bold text below:
- editable mesh - This is the network of faces, edges, and vertices you see in a wireframe view of a 3D object. Making the object an editable mesh allows you to sculpt it at the vertex level.
- editable spline - An editable spline is like a wireframe for a Shape object. (Splines are 3D as well.)
- editable poly - Like an editable mesh, but with more features. To be covered in a later class.
- editable patch - A patch is a surface generated from a spline (a curve). Think of it as the next generation of editable spline
- NURBS (Non-Uniform Rational B-Splines) - Do you really want to know, after that name? A better definition than the one in the text is here. A better discussion is in this article.
So, the text is saying not to collapse the stack for an object that we might want to convert from one base type to another.
Exercise 2: Exercise 2 adds modifiers the water tower in the gas station scene. shows you how to modify
the angle snap setting, and shows what effect it has.
Question 1: Why do you only have to apply a modifer to one of the braces of the water tower, instead of applying it to all of them?
Exercise 3: This exercise shows you how to use modifers to make a more realistic looking cactus and some tumbleweeds.
Question 2: Which modifier is used to create random variation in the shape of an object?
Question 3: At the end of step 17, the cactus still look artificial. What modifier to you use to smooth out the angles on it?
Exercise 4: Exercise 4 takes us into new material: adding a sky to an existing scene.