Computer Animation Ying Zhu Georgia State University Walk Cycle, Action Editor, and NLA Editor

Walk cycle A walk cycle generally consists of four key poses Contact Recoil Passing High-point See http://www.blender.org/documentation/htmlI/x8053.html Let Blender interpolate between these poses

Create a walk cycle The process At the start frame, create the “rest” pose. Select all the bones that have been moved, press I to insert a key frame. Increase frame number. Create the “Contact” pose. Select all the bones that have been moved, press I to insert a key frame. Increase frame number. Create the “recoil” pose. Insert a key frame. Increase frame number. Create the “passing” pose. Insert a key frame. Increase frame number. Create the “high-point” pose. Insert a key frame. Repeat the above process until the character reaches the original contact pose.

Create a walk cycle Select a bone (or bones), open the IPO Curve Editor Choose “Pose” IPO type You’ll see the IPO curves for the bones

Copy and paste poses In Pose mode, select Pose menu and choose Copy Current Pose Paste Pose Paste Flipped Pose “Paste Pose” is useful for copy and paste the same pose in a walk cycle “Paste Flipped Pose” is useful for creating mirrored pose in a walk cycle E.g. reversed leg position Can also use the copy/paste icons

Combine walk cycles with path Two ways to create a walk cycle Move the character forward while you create the walk cycle Create the walk cycle without move the character forward In latter case, you can attach the armature with a path Create a path Select armature and then the path, press ctrl + P Choose “normal parent” (not “follow path”) The character will walk along the path

Action Editor Three editors are used in creating complex character animation IPO Curve Editor Action Editor NLA Editor Each is built on top of another and handles a different level of task

Action Editor IPO Curve Editor deals with the animation of each bone A user creates a pose and insert a key frame An IPO curve interpolates between key frames In Action Editor, you can create individual “action” An action is a sequence of poses that serve a purpose (e.g. walk, wave hand, rest, etc.)

Action Editor To create an action you create a sequence of poses and insert key frames In Action Editor window you’ll see a number of channels Each channel represents a bone A diamond marker is a pose marker Each vertical line represents a complete pose Along the time line, pose markers are interpolated by the IPO curves to see them you need to switch to IPO curve editor

Action Editor If you see a pink strip between two markers, it means there is no change in pose between these two markers

Action Editor You can give each action a meaningful name To add a new action, click on the button next to the action name and select “ADD NEW” Then you create another set of poses and insert key frames, and so on.

Action Editor For a character, each action is defined by a set of bones and their individual IPO curves An IPO curve is defined by a set of key frames markers and the curve that interpolates them You can create many (simple) actions for a character

Action Editor Then you may want to composite these actions to create complex animations Configure the sequence of actions Decide when each action is played on the timeline Determine how the actions blend with each other To do this you need to use the Non-Linear Animation (NLA) editor

NLA Editor NLA stands for “Non-Linear Animation” NLA Editor is a level above the Action Editor It allows you to organize and mix the actions you created in the Action Editor Organize actions along time line (If you see a blank window when you enter NLA Editor, press Home or Shift + MMB to scroll the window up and down.)

NLA Editor Select an armature, move the green line to the starting frame, press Shift + A to add an action strip Choose an action from a list These are the actions you created in the Action Editor You can move and scale the action strip Press Shift + A to add more action strips Organize them along the time line to create a logical sequence of actions

NLA Editor Action strips may overlap at some point E.g. “wave hand” in the middle of a “walk cycle” In many cases, you want one action to ease into another action E.g. walk  run  walk  rest

“Ease in” and “Ease out” in NLA How to set up “ease in” and “ease out”? Place two action strips so that the end of one action overlaps with the start of the next action by a number of frames (e.g. 15-frame overlap) Right click to select the first action Press N to bring up the “Transform Propoerties” menu Press “Auto-Blending” In the “In” field, type in the number of overlapping frames (e.g. 15)

“Ease in” and “Ease out” in NLA How to set up “ease in” and “ease out”? (Cont.) Right click to select the second action Press N to bring up the “Transform Propoerties” menu Press “Auto-Blending” In the “Out” field, type in the number of overlapping frames (e.g. 15)

NLA Editor The active action is marked in yellow Right click on the strip to make it active There is a dot on the left side to indicate active strips The action strips are evaluated from top to bottom You can move the action strips up and down to change their priorities

Why use Action Editor and NLA Editor? You can create a complex animation by adjust posing and inserting key frames You have just one action sequence that contains all the poses But this is inflexible Difficult to make changes Or you can create a number of simple actions and then composite them in NLA Editor Much more flexible and adaptive

Why use Action Editor and NLA Editor? For example, you may want to create an animation sequence with a character waves, walks, and then runs Option #1: You can create a single long animation sequence that contains all above Option #2: You may create three separate actions: wave, walk and run. Then you composite them in the NLA editor

Why use Action Editor and NLA Editor? What if you change your mind and instead want to do a walk, wave and run sequence? It’s difficult to make the changes with option #1. It’s easy to make the changes with option #2.