Animated Characters

by Justin Hong

This is my final project for Dr. Sueda's CSCE 489 Computer Animation course. In this project, I implemented skinning and keyframes to animate character walking. There are seven keyframes placed and rotated at arbitrary locations then drew Catmull-Rom splines in between each of the seven keyframes. Then using these keyframes, I drew the character model to interpolate between the keyframes and animated her walking along the splines that I drew. The character can walk along the loop normally, in reverse, freeze for a moment, disappear abruptly and teleport along the splines too.

I downloaded skinned characters with a walking animation from www.mixamo.com, then borrowed Dr. Sueda's FBX extractor to convert a .fbx file into .obj files. Then using a software called Blender, I extracted the character's textures into a .jpg file. The main model I used for developing was the Kachujin model, but my project also works with the Big Vegas model and Akai model too.

What Techniques did I use?

Linear Blend Skinning Techniques

Download character that walks in place to convert it from .fbx to .obj file
Write a parser that takes in a .txt file that parses input data to load in skeleton and skin data
Implement the skinning equation to update each bone at each frame
Utilize the skinning equation implementation and calculate results on the CPU

Keyframed Animation Techniques

Place 7 different keyframes at arbitrary points
Draw splines between each keyframe
Carefully rotate quaternions so that character appears to be walking along the spline
Implement arc-length parameterization so that character's speed is not depend on where the keyframes are located
Added time control to make character appear to walk backwards, freeze in place, disappear or teleport

What libraries did I utilize?

I wrote most of my code using C++. However, I also used OpenGL in order to draw the .obj files for the character, and draw the keyframes and splines. A little bit of GLSL was also used for shading.

Controls

Space bar - start or pause the walking animation
K key - toggle the keyframes and splines visible or invisible
S key - toggle between the various time controls implemented
Escape key - quit the program to reload animation with different character

Binding Pose

Kachujin's Loop

Big Vegas Character

Akai Character