MB_edit

Floor contact. Floor contact is a setup that prevents a character's feet (and hands) from going though a defined floor.

1. Make sure the character is facing the positive z-axis.

2. Create a plane as a reference for the floor level. To create a plane, find Plane in Asset Browser -> Templates -> Elements, and alt-drag Plane into the viewer. While the plane is selected go to Properties, move it to 0, 0, 0 (or anywhere you want) and scale it up. (You can rotate it too if you like.) If you skip Steps 2, 3, and 4, the xz-plane will be used as the floor.

3. Check if the floor plane (xz-plane) of the capture volume matches the floor plane in MotionBuilder. It doesn't if the L-frame was tilted on the floor and as the result the capture volume's axes were not set properly. (See System Calibration: a Wand and a L-frame). To check if the capture volume's floor plane is aligned with MotionBuilder's, find the data set in which the capture subject moves around extensively in the capture volume. Apply the data to Actor. Play the animation and look at the feet of the subject in the orthogonal side view (Ctrl+r) and front view (Ctrl+f): if the feet go through the floor at one end and float above the floor at the other end, then the capture volume's floor plane is tilted. Select the optical root, which is displayed a small sphere in Viewer. (Also the optical root is listed as C3D: Optical under Scene in Navigator.) Rotate the optical root (that rotates all the mocap data) to fix the tilt. Note: Ctrl+e lets you go back to the perspective view.

4. Associate the floor plane to a Character. In Navigator, select the Character you want to set up the floor contact for under Characters, and open Character Definition tab. Uncheck Characterize check box. Alt-drag the plane (created in Step 1) from the viewer to the Left and Right Foot Floor sections in Model column in Character Definition (shown in pink in the screen capture below). Characterize by checking Characterize check box.

5. Show Floor Contact. In Character Controls, click on Show and select Floor Contact in the pop-up window.

6. Adjust the foot floor markers. The foot floor markers define the contact areas (the heel and toes) and the bending section of a foot. Move the markers in the side view (Ctrl+r) and the front view (Ctrl+f). The positions of the foot floor markers in relation to the foot joints depend on the shapes of the skin geometries for the character's feet.

foot floor markers

7. Apply Plot Character... to Control Rigs's FK/IK.

8. Activate Feet Floor Contact. Select Character -> Character Settings -> Floor Contacts -> Feet Floor Contact.


With floor contact	Without floor contact

Note: Hand floor contact can be set up for hands in a similar manner.

Rigid body. When a marker disappears or jumps to a wrong location for a period of time that is too long to be filled in simply using spline, you may consider using a rigid body. The rigid body works well with rigid parts of our bodies, such as the head, hips, and rib cage.

1. Open Optical editor by clicking on any of the markers under Opticals -> C3D: optical in Navigator. Select Rigid Bodies tab (which is painted pink in the screen capture below.)

2. Find a frame in which the marker with a problem and two or three more markers near by exist. Ctrl-click them to select. Click on Add in Rigid Bodies pane. A red box that represents a rigid body appears in Viewer.

3. Select the marker with the problem. The graphs of the x, y, and z-rotation angles of the marker appear in Optical editor. Typing in an a shows the entire graphs in the editor. Use Split Segment where the problem starts. Use Split Segment again where the problem ends.

4. Move in time to be in the middle of the bad segment. The segment that you are in is green and all the other segments are in a pinkish color. Click on Remove Segment to remove the bad segment. Look at the Segment/Gap indicators (see the screen captures below) in the upper middle part of Navigator window and notice that Gap is now highlighted in light gray and Segment has turned white. Previously Segment was highlighted in light gray and Gap was white. This is because after the segment was removed, you have a gap there.

Before removing the segment	After removing the segment

5. If Auto-Rigid Body is selected (see above the graph area) as a fill method and if a rigid body has been created for the marker with a problem (Step 2 above), the gap is already filled using the rigid body. The marker problem should be fixed. If one of other fill methods (Auto-Constant, Auto-Linear, Auto-Bezier, Control Curve, or Sample Curve) is selected, click on that. A pop-up menu shows up. Select Auto-Rigid Body.


Auto-Rigid Body	Without a rigid body	With a rigid body

6. The quality of a rigid body can be monitored by selecting Settings tab and turning on Show Rigid Body Quality. A bar appears at the bottom of Optical editor. White is good, black is bad. See the screen capture below which shows four black areas where the qaulity of a rigid body is very poor.

The screen captured image below shows the rigid body created using the two back markers and the top chest marker because the top chest marker is occluded by the performer's torso, arms and head.

Sample data for editing with a rigid body. In the sample file, the top chest marker is occluded a couple of times.

Blending. Two motion clips may be seamlessly sequenced by blending them. For two motion clips to be blended seamlessly, in a certain number of frames of the clips the character must have similar spine shapes and have its weight on the same foot. In both motion clips, apply Plot Character in Character Settings to the skeleton and export .fbx files.

1. To import clips, right-click in the light gray area of Asset Browser's left pane, select Add favorite path from the pop-up menu (see the screen capture below left), and browse to the folder that contains your .fbx files. If you don't see your folder, right-click in Asset Browser's left pane again and this time select Refresh directory. You should see your folder listed. Click on it to open. The files in the folder show up in the right pane. Bring in the first motion clip by dragging it into Viewer. Make sure that you select the right clip name in the pop up menu (see the screen capture below middle). If you see C3D marker data as red boxes (see screen capture below right), go to the hierarchy (Ctrl-w) or turn on the selection mask for markers, select and delete them.


Add a path to your folder	Select the eright clip name	Delete marker data

2. Drag Character from Characters folder in Asset Browser onto the hips of the skeleton and characterize it as a biped.

3. In Transport Controls window, click on the take name box (the third box from the left in the top row, shown in pink in the screen capture below). In the drop-down menu select Take 002 (new) to create a new take. Say Yes to the question "Copy the data from the current take to the new take?" which pops up.

4. Make sure the new take is selected in Transport Controls. Bring in the second motion clip by dragging onto the hips of the skeleton. Make sure the new take is selected, and select FBX Replace Animation and the name of the take copied in Step 3 in the pop-up menu. Make sure that you drag the second motion clip onto the hips of the skeleton already in MotionBuilder so that you will not end up having two skeletons.

5. Open Motion Blend window by going to Window -> Motion Blend. Motion Blend Field should say No models. (See the screen capture below). Select the skeleton in Viewer and Alt-drag it into Motion Blend Field. A thin white line appears.

6. Select the name of the first take (firs motion clip) in the drop down menu that shows up when you click on the currently selected take name at the left side of the first track. (See the screen capture below). A narrow gray bar shows up indicating first the take.

7. Insert another track by clicking on Insert in Track pane. In the second track, select the name of the second take (second motion clip). Another narrow gray bar shows up, indicating the second take. (See the screen capture below.)

Note: In Motion Blend window, Shift-drag moves the tracks left and right. Ctrl-drag scales them up and down.

8. Move the clips by dragging over the frame number boxes (or typing numbers in the boxes) next to T (see the screen capture below) and overlap the clips.

9. Move the left and right ends of the colored bars (purple for the first take and orange for the second take) so that the right end of the purple bar and the left end of the orange bar overlap (See the screen capture below). These colored bars indicate the portions of the motion clips that will actually used. The portions of motion clips outside the colored bars (e.g., the portions of the narrower gray bars sticking out of colored bars) will be discarded.

10. Playback animation and repeat Steps 8 and 9 until you find a good place to blend. The skeleton animated by the first clip is in purple and the skeleton animated by the second clip is in orange in Viewer. Normally the shorter the duration of the clips used for blending, the better result you will get. If it's hard to see the blended motion because the three skeletons (the first clip's skeleton, second clip's skeleton, and blended clip's skeleton) are displayed, turn the the first and second clips' skeletons by clicking on the small purple and orange boxes labeled "Ghost". (See the screen capture below.)

11. If you want to use Match Pivot, select the joint that you want to use a pivot in Viewer and alt-drag it into the blending area of the blend track (bottom track). (See the screen capture below). Move the time indicator into the blending area (where the color is blended from purple to orange) in the resulting track. Match Pivot in Blend pane becomes available. Click on Match Pivot to apply.

12. Clicking on the blending area brings up Blend Editor. You may edit the curve which is a linear line by default. For instance, selecting Bezier as Tangent allows you to add ease-in and ease-out to the curve (See the screen captures below). You can go back to Motion Blend editor by clicking on Motion Blend on the left upper corner of Motion Blend window.

default linear blend curve

blend curve with ease-in & ease-out

13. In the bottom track create a new take by selecting Take 003 (new) from the drop down menu (see the screen capture below). Clicking on Process in the bottom track creates a new blended take.

14. Clicking Ghost in the first and second tracks hides the skeletons which are animated the clips before blending.

15. Characterize the skeleton animated by the new take (blended animation) by dragging Character onto the skeleton's hips.

16. Apply Plot Character in Character Settings to the skeleton and export as a .fbx file.

Sample data for blending. (The first 200 frames of this data cane be repeated by blending the end of the first copy and the beginning of the second copy.)

Retargeting. A joint can be moved to a specified location using IK and an auxiliary effector, over-riding the position in captured data. The position of the joint specified by an auxiliary effector and the position of the joint in captured data can be interpolated over time.

1. If it hasn't been characterized, drag Character from Characters folder in Asset Browser onto the hips of the skeleton and characterize it as a biped. Apply Plot Character... to Control Rigs's FK/IK.

2. Move to the frame in which retargeting reaches its goal. Right-click on the joint that you want to retarget in Character Controls. Select Create Aux Effector in the pop-up menu.

3. It is almost always wise to lock the translation of the hips to prevent weight shifting. You can lock it by selecting the hip in Character Controls and clicking on T and R in Effector Pinning pane in Character Controls.

4. Move in time to the frame in which retargeting starts. Set 0.0 to Reach T and Reach R, and key the frame by clicking on the K's.

5. Move forward in time to the frame in which retargeting reaches the goal. Set 0.0 to Reach T and Reach R, and key the frame by clicking on the K's.

6. Move forward in time to the frame in which retargeting ends. Set 0.0 to Reach T and Reach R, and key the frame by clicking on the K's.

7. Move back in time to the frame in which retargeting reaches the goal. Move the auxiliary effector (a green cube when selected) to the position where you want the limb to reach. Set 100.0 to Reach T and Reach R and key the frame by clicking on the K's. The screen captured image below shows the skeleton's leg (in light gray) reaching the auxiliary effector (a pink cube with orange corners) while the control rig's leg (in yellow with a blue ball and a red ball at joints) is staying at the original position.

8. Select FCurves tab and scroll down to find the f-curve for the auxiliary effector. You can edit the f-curve. For instance, the curve below can be edited by adding ease-in & ease-out and flatten the top.

Before editing the f-curve

After editing the f-curve

8. Apply Plot Character in Character Settings to the skeleton and export as a .fbx file.

Notes on Viewer: When Viewer window is selected, Ctrl-w lets you switch between the current 3D view (perspective or orthogonal view) and the schematic view (hierarchical view). Like in Maya, a frames all, f frames what is currently selected.