# Constraints

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Constraints | Constraints in Action

Constraints, at their most basic, are controllers controlling how one item relates to another. Constraints can serve many purposes, and when used in combination with each other can create very complex controllers and motions. Rich explains, by example, each and every one of modo's available constraints, providing an in-depth look at the fundamentals of automation in the rigging process. The 'Constrains' page goes over the constraints themselves, while the 'Constraints in Action' page shows some actual usage scenarios of constraints (selected above).

Users can jump ahead to a specific section by using the Chapter selection widget on the right side of the player or by directly clicking any of the Chapter Title links below.

Tab | Time | Chapter | Description
1 | 0:01:51 | Adding Constraints | Demonstration of the proper way to add a constrain to an item or multiple items.
2 | 0:07:12 | Removing Const. | Demonstration of how to remove a constrain form the scene.
3 | 0:11:50 | Direction | Demonstration of the Direction Constraint.
4 | 0:20:06 | Geometry | Demonstration of the Geometry Constraint.
5 | 0:33:59 | Path | Demonstration of the Path Constraint.
6 | 0:47:11 | Intersect | Demonstration of the Intersect Constraint.
4 | 0:57:15 | Intersect 2 | Additional demonstrations of the Intersect Constraint.
5 | 1:07:17 | Distance | Demonstration of the Distance Constraint.
6 | 1:12:03 | Extra Options | Reference of the options available to Constraints and their application.
| 1:23:41 | Total Video Time |

Frequently Asked Questions--

Q.) So, constraints are modifiers?

> A.) Yes the constraints are just modifiers with special UI to help deploying them easier, for more information on other modifiers types check out the modifiers section.

Q.) I see values going into the properties fields but nothing happens?

> A.) This is briefly explained in the video, but for more information on how the primary XYZ channels that you see in the properties panel relate to an items final position / rotation / scale check out the Transform Items section.

Q.) At one point it looked like he moved the scale tool instead of actually scaling it?

> A.) Yes he did, instead of clicking on the ring in the middle he clicked on the "axis" which allows you to place a tool in space where you want. Modo allows for a lot of flexibility in how a manipulator is positioned in the scene, to understand this idea more fully check out the Action Centers section.

Q.) You can have something named CUBE and cube in the scene, aren't they the same?

> A.) No. Modo looks at not only the letters themselves but also their "case" or if they capitalized or not. So in this example you could also have CUbe and CUBe in there and all four names would be considered different, or unique by the system.

Q.) It looks like sometimes you lose focus on the things you are working with in the properties tab, why?

> A.) The properties tab understands multiple selections so you can multi edit 3 items position Y at once for instance. This panel also understands different item types, and as they are added new tabs appear vertically to allow you to chose them. As you deselect and/or select new items this list will dynamically update which can cause which tab is active.

Q.) I have heard the term 'Up Vectors' before, what else are they used for?

> A.) That would be Inverse Kinematics... check out that section for more information.

Q.) He keeps using the work handy, why oh why can't he stop?

> A.) Its a sickness, he admits it... and that is the first step to recovery.

Q.) At one point he just drag an item onto another item to parent it, why didn't it move in the 3D scene?

> A.) That is because by default modo "Parents in Place". For more information on parenting and hierarchies check out the Parenting section.

Q.) He keeps mentioning a "Key Frame", what is that?

> A.) Key Frames are how modo and other 3D applications adjust values over time. To learn more about Key Frames check out the Keyframes and DopeSheet section.

Q.) What is "Draw Style" as it relates to a locator?

> A.) "Draw Style" describes modo's ability to customize how a locator might look in a scene. This is done for creating rigging interfaces as well as to just make a locator standout in a scene. See the Locator Display section for more info.

Q.) Is "Flipping" a curve like flipping a polygon's normal?

> A.) Yes and no, you select curves in polygon mode, so modo treats curves a lot like a polygon. They are different however and you are not flipping the curves normal but you are changing its direction.

Q.) What does "Point Order" mean?

> A.) An item's "Point Order" is the order in which modo stores the information that it then builds into the polygon, curve or surface. This is fixed, unless a modeling operation forces modo to add or remove points from its list; though modo does a very good job of not affecting the order of points that were unaffected by said modeling operation. Point order is a big concern for Morphs and how they work.

Q.) Some constraints create locators automatically, is there a way to have them use an existing item instead?

> A.) No. You also can't define a name for any auto-generated locators, so just be aware that they will be added in the root of your scene and then move them into the hierarchy where they are needed.

Resources--

Links to the modo in-line help system
Docs: Constraints
Docs: Action Centers
Docs: Statistics and Info Panel
Docs: Deformers
Docs: KeyFraming
Docs: Locator Draw Styles

Links to other pages in this training
Training: Modifiers
Training: Transformation Items
Training: Action Centers
Training: Inverse Kinematics
Training: Parenting and Hierarchies
Training: Schematic
Training: Deformers
Training: Keyframes and DopeSheet
Training: Locator and Mesh Display
Training: Curves

Files--

Links to the modo scenes used in the video
(click to open in modo)
File: Constraints_01.lxo
File: Constraints_02.lxo

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