Walking Cycle Animation and Interpolation Rama Hoetzlein

Feb 21 st (Mon) Mar 2 nd (Wed) Mar 15th 9:00-12:00 (morning)13:00-16:40 (afternoon) DAILY TOPIC: Walking, Posing and Animation Keyframes, Auto keying Quick lab: Walk cyclesQuick lab: Walk cycles Muybridge, motion studiesPosing Walk cycle dynamics,Human dynamics KeyframingAssignment: Animation MORNING: AnimationAFTERNOON: Motion Capture Critique of animationsHistory and foundations Start on Motion Capture topicRotoscoping, camera tracking Current trends: Performace cap. Lab: Import of mo. cap data Assignment: Refine animations. OR import mo.cap data Motion Capture session with Stefania and Camilla Hagg - Full-body capture session Recap… Where are we

Today.. 1. Key frame (drawing) 2. Auto keys Quick lab: Walk cycle (#1) 3. Interpolation 4. Graph editor Quick lab: Walk cycle (#2)

“Gradually we developed a professional class of ‘clean up men’ who took pride in their work. It was their skill that made the pictures look so fine, yet for a number of years they never got screen credit, nor even the salary they deserved… An ideal group would include an assistant animator (simple changes), second assistant (still learning), breakdown man, and inbetweener who could double as a handyman. The last category included everything: threading the film, taking a test over to the cutter..” Assistant Animators

In computer animation, the software replaces the inbetweener with a mathematical process of interpolation. With interpolation, the computer automatically determines intermediate frames from the start and end frames. * As a mathematical process, interpolation may not give the results you expect… But it is easy to get started..

Turn Auto Key on Load the Timing panel here Set total frames Steps for Auto Keying

Select object first.. Right-click on any attribute and select Set Key. Usually this is done on Translate and Rotate of rig controllers.

Steps for Auto Keying Set time slider to desired time.. and move object to location for that time Notice lines tell you where you have keys.

Animating a Walk Cycle (first attempt) Use the Human rig provided. Or another if you like. 1. Use the Auto Key technique. 2. Set your total animation time to 25 frames (8 sec) 3. Hint: The time between strides is 1 second for full cycle (30 frames), ½ second per leg (15 frames) 4. Note the body translates at a constant rate in space

Go for it!

Keyframing using Interpolation Mathematical problem: Given a set of points, what are the most reasonable points in between?

Brief History of Computer Animation of Keyframes Linear interpolation…. just use a weighted average between points. Linear is discontinuous at the key points. Linear only account for two points.

In boat building, splines are thin pieces of wood that are bent to fit the key points set by clamps. The spline interpolates the clamp points. Splines

Bezier Curves Paul de Casteljau (1959), invented Bezier curves. Pierre Bezier used in automotive modeling. Key point Tangent point Bezier curves are continuous at the key points. Bezier curves interpolate the end key points (pass through them)

12 key points needed Only 4 of these interpolate the curve In practice the other 8 are made into tangent points. Bezier curves require non-interpolated points Polynomial Curves Bezier Curves Use all the points to create a fit curve. Does not need to pass through the key points. Computationally expensive.

Why is this important in animation? Difference between this… and this…

1974, Burtnyk & Wein “..simple linear animation between key frames will not produce a realistic result.” linear

Eadweard Muybridge ( ), Motion studies

Contact pose - Both legs are at their extreme point. Opposite arm is forward. Recoil - Weight falls on the recoil pose. Front foot fully touches. Body at lowest position, arms at extreme. Passing -Back leg passes the contact leg. Arms at sides. High point -Body at highest pose. Back leg is pushing body forward. Back toe peels off the ground. Contact – DOWN to – Recoil – UP to high-point – AND – Contact --..

World reference frame - Outside observer Local reference frame - View from camera following the character Contact foot is stationary on the ground. (otherwise you fall) Back foot advances quickly to catch next contact. Contact foot moves backward relative to body center. Back foot advances at same rate that contact trails.

World Reference Frame Incorrect version Can you tell what’s wrong with this? Can you tell which foot is which? Left foot, Right foot, and Body

World Reference Frame Left foot, Right foot, and Body Correct version What’s different? Why?

Contact foot stays planted on the ground. Linear interpolation keeps it flat. Back foot eases up to the forward location rapidly, but not linearly. Whole body translates forward linearly. Now back foot is contact foot.