Tangents describe the entry and exit of curve segments from a key. This menu operates on the shape of curve segments around selected keys. Note that these settings affect only existing animation curves segments’ tangents.
Specifying a spline tangent creates an animation curve that is smooth between the key before and the key after the selected key. The tangents of the curve are co-linear (both at the same angle). This ensures that the animation curve smoothly enters and exits the key. When animating fluid movement, a spline tangent is an excellent place to start. You use a minimum number of keys to achieve your look.
Specifying a linear tangent creates an animation curve as a straight line joining two keys. If the in tangent type is linear, the curve segment before the key is a straight line. If the out-tangent type is linear, the curve segment after the key is a straight line. When animating the color of a heating element on a stove, you would use linear to achieve that gradual change in color from charcoal gray to burning hot red.
Specifying a clamped tangent creates an animation curve that has the characteristics of linear and spline curves.
The keys’ tangents will be splines unless the value of two adjacent keys are very close. In this case, the out tangent of the first key and the in tangent of the second key will be interpolated as linear.
When animating a skeleton in a walk-cycle, you may notice a slipping of the pelvic and foot joint position. This occurs because the value of the keys on the curve are either the same or close to (within tolerance of) the value of the other. Maya assigns a default spline tangent to describe what occurs between these keys. This is why you get the joint positions slipping.
By setting the tangent type to clamped for these keys, the slipping is corrected and the tangents becomes a combination of linear and spline.
In the Maya environment preferences, Clamped is the default tangent type.
Specifying a stepped tangent creates an animation curve whose out tangent is a flat curve.
The curve segment is flat (horizontal), so the value changes at the key without gradation.
The light from a strobe light turns on and off. To create a strobe-like effect, you would use a step tangent.
To get a quick preview of your animation as if all keys have Stepped tangents, right-click the Time Slider and toggle the Enable Stepped Preview option. When Enable Stepped Preview is on, playing back your animation lets you quickly view the position of objects as they hit each keyframe. Curves return
to their original tangent types when you turn off Enable Stepped Preview.
Specifying a fixed tangent allows a key’s tangents to remain unchanged as the key is edited.
When animating a ball, you may find the ball isn’t falling from a desired height, yet its impact with the floor and everything else is perfect. Using a fixed tangent lets you change the height of the ball while retaining the tangent’s angle. This is somewhat different from Edit > Keys > Bake Simulation.
This process is useful when you want to:
Plateau tangents ease animation curves in and out of their keyframes like spline tangents, but also flatten curve segments that occur between equal-valued keyframes like clamped tangents. The plateau tangent normally behaves like a spline tangent, but ensures that the minimum and maximum values along a curve are all at keyframes.
Plateau tangents are useful when you want the positions of your keyframes to be exact, because they ensure the maximum and minimum values (‘hills and valleys’) of the curve do not extend past their keyframes. For example, picture an animation of a ball rolling off a table, falling to the floor, and then rolling on the floor. With spline tangents, the ball falls through the floor, then comes back up to the floor. With plateau tangents, the ball will not fall through the floor. The tangents guarantee that your animation will not wander beyond the values you keyframed.
To do this, if a spline tangent would produce a minimum or maximum between two keyframes, the plateau tangent flattens the keyframes in question. Keyframes at local minimum and maximum points along the curve are also flattened. Finally, the first and last keyframe along a curve are always flattened if they have plateau tangents.
Auto tangents clamp curve values between frames to a maximum or minimum point based on the adjacent keyframe values. Auto tangents are the default type for new keys (set as the Default in tangent and Default out tangent in your Animation (Settings) preferences).
Specifying Auto tangents creates an animation curve where the first and last keyframes have flat tangents, and keyframes in between do not overshoot the neighboring keyframe value. This type of curve prevents issues with interpenetration of closely animated objects that can occur with other tangent types, such as Spline.
Lets you specify a type of tangent for the In Tangent only. The In Tangent defines the type of curve segment that comes before a key.
Lets you specify a type of tangent for the Out Tangent only. The Out Tangent defines the type of curve segment that comes after a key.
+ s + 
-click to display the marking menu.