I'm working with 3D models from an existing game with its own proprietary file formats, however the way they work is pretty standard:
- Skeleton is defined as a set of bones, each bone either has a parent bone or not (in which case it's the root of the model) and a matrix which moves the bone into the coordinate space of its parent (if I am using the right terminology).
- Skin is defined as a set of vertices and faces. Each vertex links to 1 or more bones, each with a weighting value that adds up to 1.
- Animation keyframes store values for each bone as translations (x, y, z) and quaternions (x, y, z, w).
I have the source code for the graphics engine, and by combining it with LearnOpenGL's Skeletal Animation (and a lot of trial and error) I was able to render the animation keyframes in wireframes.
What I'm trying to achieve is a visual editor to be able to define my own animation keyframes. I don't need to edit the skeleton/bone structure, relations or matrices, or edit the skin vertices/faces/weights.
So my question is, how can you do this in a visual way? How can you "draw" a quaternion on the screen and let the user move it around with the mouse? It's just a bunch of numbers - by my understanding the (x, y, z) defines a vector and thereby the plane that is perpendicular to that vector, and the w defines the angle of rotation in that plane. That's well and good as a mathematical explanation, but nobody can type in numbers for that vector/angle and get the result they want. They think in terms of "move the leg right a bit" or so on, but that small movement would likely change all 4 values in the quaternion. How do mainstream 3D editors handle this?
Many thanks!
