vector rotations for branches of a 3d tree
- by freefallr
I'm attempting to create a 3d tree procedurally. I'm hoping that someone can check my vector rotation maths, as I'm a bit confused.
I'm using an l-system (a recursive algorithm for generating branches).
The trunk of the tree is the root node. It's orientation is aligned to the y axis.
In the next iteration of the tree (e.g. the first branches), I might create a branch that is oriented say by +10 degrees in the X axis and a similar amount in the Z axis, relative to the trunk.
I know that I should keep a rotation matrix at each branch, so that it can be applied to child branches, along with any modifications to the child branch.
My questions then:
for the trunk, the rotation matrix - is that just the identity matrix * initial orientation vector ?
for the first branch (and subsequent branches) - I'll "inherit" the rotation matrix of the parent branch, and apply x and z rotations to that also.
e.g.
using glm::normalize;
using glm::rotateX;
using glm::vec4;
using glm::mat4;
using glm::rotate;
vec4 vYAxis = vec4(0.0f, 1.0f, 0.0f, 0.0f);
vec4 vInitial = normalize( rotateX( vYAxis, 10.0f ) );
mat4 mRotation = mat4(1.0);
// trunk rotation matrix = identity * initial orientation vector
mRotation *= vInitial;
// first branch = parent rotation matrix * this branches rotations
mRotation *= rotate( 10.0f, 1.0f, 0.0f, 0.0f ); // x rotation
mRotation *= rotate( 10.0f, 0.0f, 0.0f, 1.0f ); // z rotation
Are my maths and approach correct, or am I completely wrong?
Finally, I'm using the glm library with OpenGL / C++ for this. Is the order of x rotation and z rotation important?
