Blender Beginner for Beginner Tutorial: Mech Model Part 4: Animating
24th June 2010 – Blender 2.47
Once the mech model is rigged as in the previous tutorial, the bones can be used to help animate the mech. Here we will create a simple walk cycle for the rigged mech. This is the last tutorial in this series on using Blender to create a mech model. The final result of this tutorial, and thus the entire series, is shown in the video below.
Firstly, Blender needs to be set up with windows appropriate to animation. Go to the 1-Animation screen using the dropdown box at the top of the Blender windows. It will bring up windows organised like the below image, with the exception that the right hand window is an Ipo Curve Editor. Change it to an Action Editor window so it matches the image below. The open windows are now (from left to right, top to bottom):
Outliner – this shows all the objects in the scene. In this scene there are just the mech and armature, but it can be useful for navigating around larger scenes.
3D View – this is the same window as used for modelling and should be familiar by now.
Action Editor – this shows the keyframes for the bones – a diamond represents a keyframe on the appropriate bone at that frame. A keyframe on a bone at a frame means that the bone will be in that position and orientation at that frame when replayed in an animation.
Timeline – this shows the timeline of the animation. The Start value is the first frame of the animation and the End value is the last frame – the number to the right of that is the current frame number. Above those numbers is a graphical display of the same information – the lighter part is in between the Start and End frames, the green line is the current frame, and the other blue lines are those frames with keyframes.
Panels – this is the same as used for modelling and should be familiar by now.
Ensure the armature is visible by setting the X-ray option on the Armature subpanel of the Editing panel (F9). Also make sure the mech is selected and in pose mode. Press the record icon in the Timeline window. The record icon is the small red circle – like the record button on old video or cassette players. This starts automatic keyframing so that any moved bone will automatically be keyframed for the current frame. Use ALT-G and ALT-R to remove transformations on the mech. Now we are ready to animate a walk cycle.
When animating the walk cycle initially the mech won’t actually go forward, it will just walk on the spot. The mech body should stay is the same position in the X & Y axes – although it is ok for it to move up or down (the Z axis). Imagine a camera filming the mech walking from the side while it moves at the same speed as the mech. Set the frame counter on the Timeline to frame 1, this will be the contact pose – the point where the leading leg first touches the ground. Position the front foot as if it is just touching the ground on a forward step and position the back leg as if it is just about to move off the ground to start moving forward (as shown below). Posing the mech should automatically store the pose as keyframes on the timeline (as record was pressed in the earlier step).
The mid-point of the walk cycle is the mirror reverse of the contact pose. Select all the bones (A-KEY) and go to the 3D View menu option Pose → Copy Current Pose and move to frame 21, then Pose → Paste Flipped Pose. The end of the cycle is the same as the start so go to frame 41 and click Pose→ Paste Pose. Also set the length of the animation to 41 frames (by setting the End value on the Timeline to 41). Press play on the Timeline window and let the animation play a few times. The start of a walk is there, but it definitely needs more work. We just add more posed frames until Blender can correctly interpret the cycle better.
To improve the walk add a few more poses. On frame 3 (with a flipped version on frame 23) pose the point at wich the front leg takes the weight of the mech and the rear leg lifts off the ground (see left image below). On frame 11 (with a flipped version on frame 31) pose the highest point on the rear leg’s path to becoming the front leg (see right image below). With these extra points the walk looks much better. Add in more poses as required until happy with the cycle. Some helpful commands are ALT-G and ALT-R: to remove translations or rotations (this may require a manual keyframe afterwards). Use the I-KEY to manually set a keyframe on a bone. It is also possible to move the keyframes around in the Action Editor window with the G-KEY or delete them with the X-KEY.
Now to make the mech move. Go to frame 1. Select the master bone and press I-KEY and select Loc from the provided options. This keyframes the position of the whole mech at the start. Also place the 3D cursor on the tip of the front toe on the leading leg where it touches the ground (the Y-axis). Now move forward through the frames to the point that same toe is just about to leave the ground (frame 21 for me). As the mech is walking in place this toe is now far behind the mech. Move the master bone in the Y axis only (thus moving the entire mech) so that the tip of the toe is once again on the cursor (the image below shows this pose). Repeat this step with the current front toe. Once a toe touches the ground it should not move forward or backward until it leaves the ground. The cursor marks this unchanging point. Use the master bone to move the mech such that this constraint holds. This should complete the walkcycle, although more poses can be added if you like. Rename this action in Action Editor header, to something like Walkcycle. The animation is done, let’s produce a short video of the walk.
Turn record off by pressing the record button on the timeline. Make the left window an NLA editor. This window allows animations to be repeated, scaled, blended with other actions, and more. It is worth investigating further, but for now we just want the single walk animation repeated. So convert the walkcycle into a NLA strip by pressing the C-KEY in the NLA window. Then press N-KEY to bring up the Transforms panel. Here we can set the size of the strip. Set the Repeat value to 5. This will make the mech repeat the walk cycle 5 times. Press Play and the mech will move very fast! Increase the strip size by setting the Strip End to frame 200. To make the mech start each animation at the point it ended the previous one, put the name of the Master bone in the OffsBone box in the properties.
This is the point the blender file stops, but if you want to know how to record an animation like the video above, carry on. Position a camera to view the animation and some lights so you can see it. You can use the camera view (NUMPAD10) to see what the animation will look like when you play it. When happy, go to the Scene panel (F10), and chose an appropriate format (the above video was Quicktime) and press Anim. Blender will slowly render all the frames and you can play them back with the Play button. Not the best render, but this is a beginner tutorial (and I’m a beginner too) – we’ll learn how to do better later.