Motion Flow Mode

Select a biped > Motion panel > General rollout > Motion Flow Mode

The Transition Editor uses ghosts to represent the source (yellow) and destination (red) clips. Use these stick-figure ghosts to judge body position and set a likely start frame in both clips for the transition.

In Motion Flow mode, you combine .bip files, using either velocity-interpolated transitions or optimized transitions that compute minimum foot sliding, to create longer character animation. First, clips are added and referenced to .bip files in the Motion Flow Graph, these are then selected to create a Script on the Motion Flow Script rollout. The Transition Editor is used to adjust transitions between .bip files. Scripts, transitions, and clip references are saved in a Motion Flow Editor file (.mfe) for later editing or by using Save Segment on the General rollout to create one long .bip file based on the script.

Save Segment in Motion Flow mode does not save footsteps in the .bip file. Instead, feet are assigned an IK Blend value of 1 with the Object parameter on for the keys representing a footstep period (this puts the feet in world space). To extract footsteps from these .bip files, exit Motion Flow mode, load the .bip file and use Convert on the General rollout. Convert bases footstep extraction on foot IK Blend values.

Random Motion and Crowds

Random motions can be created for one or more bipeds using the Create Random Motion command. You can animate a crowd of bipeds for example. For a crowd you must share one motion flow among many bipeds.

If you are driving a crowd using delegates and behaviors, then rather that a completely random motion, the software picks appropriate clips based on the delegates speed and direction. If the delegate slows to a stop the software will find and use a clip that slows to a stop if one exists.

In all crowd simulations you must load clips and create transitions before synthesizing the crowd motion. Often many clips are used to synthesize crowds. Automatic transitions relieve you of having to create transitions between clips manually.

Two additional rollouts display in Motion Flow mode:

Note: In Motion Flow mode some character Studio controls are disabled.

Workflow: Getting Started with Clips and Transitions in Motion Flow mode

Create your own library of .bip files from imported motion capture data and from your own character animation. With a biped selected, turn on Motion Flow mode. Select Show Graph on the Motion Flow rollout to open the Motion Flow Graph. On the Motion Flow Graph, click Create Clip, and add clips in the Motion Flow dialog. Associate the clips to .bip files by first turning on Select Clips-Transitions on the Motion Flow Graph toolbar and then right-clicking a clip icon; a clip dialog appears, allowing you to browse for a clip.

Click Define Script on the Motion Flow Script rollout, then select a series of clips on the Motion Flow Graph. By left clicking on a clip it will appear in the list on the Motion Flow Script rollout. The clips are connected visually in the Motion Flow Graph with red arrows (active script) representing default transitions (Minimum Motion Loss). The default duration for a transition is 25 frames, which provides good results in many cases. Transitions by default use velocity interpolation between clips.

Use Edit Transition on the Motion Flow Script rollout to fine-tune the transitions between clips. Select a clip in the list of the Motion Flow Script rollout, then on the Motion Flow Script rollout, click Edit Transition; the Transition Editor displays, and the source and destination clip names are displayed at the top of the Transition Editor.

In the Source Clip area, Start Frame represents the frame in the source file where the transition starts. For example, if Source Clip Start Frame is 60, the transition from the source clip starts at frame 60. The duration of the transition is set in the Length field at the upper left; Length values are in frames. In this example, if Length is set to 10, the transition to the destination clip takes 10 frames. In the Destination Clip area, Start Frame represents the frame in the destination clip that the transition starts; a value of 80, for example, starts the transition at frame 80 of the destination clip. In this example, the source clip plays from 0 to 60, there is a 10 frame transition from frame 60 of the source clip to frame 90 of the destination clip (frames 80 to 90 cover the destination clip transition period), then the rest of the destination clip plays.

When the Transition Editor displays, the first things to try, before manually editing the transition, are the Optimized Transitions. Optimized transitions use a minimum foot sliding algorithm. The top right hand corner of the Transition Editor dialog is the icon for optimized transitions. If the optimized transition is not satisfactory try editing the transition manually.

Manual transition editing offers the most control; the Frame spinners in the Ghost areas of the Transition Editor allow you to scrub the source and destination clips while viewing two stick figures. Find a good start frame in both clips using the Frame spinners. Things to look for in both clips are similar supporting feet, body momentum that will appear natural, and arm motion similarities. If velocity changes between the clips are too abrupt, use the Length field to adjust the duration of the transition.

On the Motion Flow rollout, click Save to save your work as a .mfe file; transitions and scripts are saved. Use Save Segment on the General rollout to save a .bip file based on the current script. These .bip files contain no footsteps. Biped foot keys are saved with an IK Blend value of 1 for footsteps. To extract footsteps, exit Motion Flow mode, use Load File on the General rollout, and then click Convert on the General rollout. Convert looks at foot IK Blend values of 1 to extract footsteps.

Tip: The location of the referenced .bip files is saved in the .mfe file. If the .bip file cannot be found, the program looks to the motion flow directory specified in \plugcfg\biped.ini. By default, this setting is MoFlowDir=<maxdir>\cstudio\scripts

If a referenced .bip file cannot be found in its current location, you will need to move it to the specified Motion Flow directory. You can change the location of this directory at any time by editing your biped.ini file with a text editor. The new directory will be used the next time you restart 3D Studio MAX. You can also add multiple search paths to your biped.ini file by repeating the MoFloDir= line multiple times. The program will search the directories in the order they appear and will use the first instance of the file that it finds. When network rendering the filenames need to be UNC compatible.