Animation Exercise

Animation

Animation is the change of a property of an object over time. In 3DS Max, this is supported through keys and the animation bar as well as the curve editor and dope sheet. The curve editor and the dope sheet are more advanced so we will focus on the animation bar.

Animation Bar

This is the animation bar. Note the following colorized areas:

  • Blue: The animation slider/timeline where we can see and set our current frame.
  • Red: Keyframe controls.
    • Set Key toggle puts 3DS Max into keyframe mode. You could reposition assets or set properties in the scene and set/update keyframes in this mode.
    • Key Icon creates a keyframe for the currently selected object/property in the current frame
  • Yellow: VCR-style timeline controls including play/pause, fast forward, reverse, previous frame, next frame, and timeline properties (bottom right)

Animating Properties

In 3DS Max, animation involves creating a keyframe for the value of a property on a particular frame then creating other keyframes on other frames with different values for the property.

Basic Animation Exercise

Let's practice this with basic properties like position and rotation.

  1. Create a sphere and a box somewhere in your scene then enter set key mode.
  2. Move the timeline slider to frame 23 then select both objects.
  3. Add a keyframe for both objects by clicking the key icon in the keyframing tools area. Notice that this visibly creates a keyframe for these objects at the current frame. You could always see the keyframes created for a particular object by selecting that object; the timeline will refresh to show the keyframes set for that object only.
  4. Move the slider to frame 45, move, rotate, and scale the box only, then create a keyframe for the box.
  5. Move the slider to frame 37, move, rotate, and scale the sphere only, then create a keyframe for the sphere. Notice that as you move the slider, the box animates even though it is not the selected object.
  6. We can copy keyframes as well. Select the sphere, hold shift, then drag the keyframe over in frame 23 to frame 45. This should create a copy of that frame in frame 45.
  7. Adjust the current animation segment by opening the animation properties dialog (VCR controls, bottom-right button).
  8. Set the start time to 23 and the end time to 45 then hit ok. Notice that the timeline has now changed to only show that segment. Data outside this segment has not been deleted, it is only hidden.
  9. Let's preview our animation by hitting the play button. Notice that 3DS Max now moves the timeline on its own at the rate of however many frames per second that was indicated in the animation properties dialog (by default, 30).

Other Properties Exercise

We could also animate other properties than transformation.

  1. Add a taper modifier to the sphere. Make sure that 3DS Max is no longer auto looping.
  2. Go to frame 23. Click the button that says Key Filters and update the key filters so everything is off except modifiers then close the dialog.
  3. Having the sphere selected and on frame 23, click the key icon and notice the colour of the keyframe change to a dark green.
  4. Go to frame 34. Update the taper amount to 10. Click the key icon. Notice that another dark green keyframe is now created here.
  5. Copy the sphere's frame 23 to frame 45. Notice that if you play the animation now, the sphere animates through its taper keys.

Object Linking/Parenting/Hierarchy

In class, we will look at the transformation hierarchy. This is crucial to understanding how the skin modifier works which we will look at next class.

Skin

Skinning is how we can connect parts of a mesh to a skeleton. For today's exercise, we will create a simple skeleton made of 5 bones. Let's start with this:

  1. Create 5 dummies:
    • root
    • left
    • right
    • spine1
    • spine2
    • Attach them such that root is left, right, and spine1's parent and spine1 is spine2's parent. Position them as you see in the image, use the grid squares to tell you the position of each dummy:
  2. Create a mesh as you see in the following two pictures:
  3. Add the skin modifier to the mesh. Click the Add Bones button, select all bones in the dialog that comes up, then click the Select button in the dialog.
  4. In the skin modifier, now that the bones have been added, we can edit their envelopes. Click the Edit Envelopes button.

Skinning Types

There are two ways to skin a vertex onto a skeletal system. We will look at these two ways and look at the use cases that these skinning types apply to.

Note: You will see me refer to bones where we used dummies before. A bone is a generic name for a part of a skeletal system. Fun fact: You could create skeletal systems out of almost any type of object in 3DS Max, including meshes, as long as you use attach and link to form a system out of them.

Envelopes

Envelopes are capsule sections surrounding a bone that appear when a bone is selected in edit envelopes mode. They are composed of two capsules:

  • Inner capsule
  • Outer capsule

The inner capsule represents the volume where the bone's influence is strongest while the outer capsule represents where the bone's influence is weakest. Vertices caught within the influence volume of a bone are affected by a bone's transformations. If a vertex lies within the intersection of the influences of two or more bones, the weight of each bone on the vertex is a ratio between all of the intersecting bones according to the strength of the influence of each bone based on the position of the vertex within the bones' respective influence volumes.

Editing Envelopes

The components of each envelope could be edited by selecting that part and moving it. For the following, select the relevant bone firstt.

  • Envelope End: Used to modify the overall length of the envelope. Can be selected by selecting the end of the bone's describing axis.
  • Inner Capsule End: Used to modify the size of the inner capsule at a side. Can be selected by picking the inner capsule disk or one of its vertices.
  • Outer Capsule End: Similar to inner capsule end but modifies the outer capsule.

Let's try putting some vertices in the influence between the root and the left bone. Modify the envelopes as follows:

Notice how the vertices imbetween are now colored orange when each of those two bones is selected implying that the vertex' influence is partial between the two bones.

Let's try moving the left bone around to see how the influence is reflected:

Notice how moving the left bone only partially influenced the vertices imbetween while practically completely influencing the vertices closest to the bone. This is great for organic characters. What if we want to force the weight values of vertices?

Explicit Bone Weight

We also have access to the set bone weight tool. Click the Wrench Icon; this is the weight tool.

Notice that this tool is currently inactive. We must select vertices in order to activate it. Scroll up in the skin modifier rollout, deselect envelopes and cross-sections then select vertices.

We can continue to show envelopes of bones by selecting the desired bone's name in the bone list. When vertex selection is on, we can select vertices. In this case, I've selected the highlighted vertex by creating a marquee selection around (selection box). Notice that in the bone tool the weights are displayed as 0.5 root and 0.5 left.

Set it to 1.0 root by selecting root in the weight tool, typing 1.0 in the set-weight box and clicking set-weight.

Notice how immediately the vertex falls into total influence of the root. We use the weight tool to control the weights of vertices that don't need to have shared influence across multiple bones. This is very useful for mechanical objects that don't need to bend.