C# OpenTK - Getting world coordinates of points that are altered by matrices

Question

I have written a skeletal animation system for a game I am working on. To draw lines that represent a skeleton, I use the GL matrix, and multiply it by each bone a long the body. For example before drawing the left hand, GL.multMatrix has been called for the lower back, upper back, left shoulder, left upper arm and left lower arm.

Currently I am now trying to deal with hitboxes. After this series of matrix transformations have been made, I am drawing a box with the local coordinates of -2,-2,-2 to 2,2,2. This works fine, the animated skeleton has a box around the hand.

However I've reached the stage of actually needing to use the hitbox, to check if it collides with another hitbox. I've worked out the algorithms I shall use for checking if there is a collision, but I first need to change those coordinates from their local to the hand coordinates, into coordinates I can use against other things in the world.

For example the left hand hitbox has the same local coordinates as the right hand hitbox, but how could I change that all back to global coordinates so I can get their proper world coordinates?

Answer 1

OpenGL stores its model matrix and view matrix together. As far as i know, you can't separate them once they are together.

To solve this, i simply ended up storing my own model matrix, which i then used GL.MultMatrix() to combine with the view matrix when it came time to draw. To access coordinates all i had to do then was to get M41, M42 and M43 (x, y and z) from the model matrix, and to get offset coordinates for a box, creating a translation of the offset of each vertex gave me the new coordinates of each respective vertex.