java quaternion 3D rotation implementation
- by MRM
I made a method to rotate a list of points using quaternions, but all i get back as output is the same list i gave to rotate on. Maybe i did not understood corectly the math for 3d rotations or my code is not implemented the right way, could you give me a hand?
This is the method i use:
public static ArrayList<Float> rotation3D(ArrayList<Float> points, double angle, int x, int y, int z)
{
ArrayList<Float> newpoints = points;
for (int i=0;i<points.size();i+=3)
{
float x_old = points.get(i).floatValue();
float y_old = points.get(i+1).floatValue();
float z_old = points.get(i+2).floatValue();
double[] initial = {1,0,0,0};
double[] total = new double[4];
double[] local = new double[4];
//components for local quaternion
//w
local[0] = Math.cos(0.5 * angle);
//x
local[1] = x * Math.sin(0.5 * angle);
//y
local[2] = y * Math.sin(0.5 * angle);
//z
local[3] = z * Math.sin(0.5 * angle);
//components for final quaternion Q1*Q2
//w = w1w2 - x1x2 - y1y2 - z1z2
total[0] = local[0] * initial[0] - local[1] * initial[1] - local[2] * initial[2] - local[3] * initial[3];
//x = w1x2 + x1w2 + y1z2 - z1y2
total[1] = local[0] * initial[1] + local[1] * initial[0] + local[2] * initial[3] - local[3] * initial[2];
//y = w1y2 - x1z2 + y1w2 + z1x2
total[2] = local[0] * initial[2] - local[1] * initial[3] + local[2] * initial[0] + local[3] * initial[1];
//z = w1z2 + x1y2 - y1x2 + z1w2
total[3] = local[0] * initial[3] + local[1] * initial[2] - local[2] * initial[1] + local[3] * initial[0];
//new x,y,z of the 3d point using rotation matrix made from the final quaternion
float x_new = (float)((1 - 2 * total[2] * total[2] - 2 * total[3] * total[3]) * x_old
+ (2 * total[1] * total[2] - 2 * total[0] * total[3]) * y_old
+ (2 * total[1] * total[3] + 2 * total[0] * total[2]) * z_old);
float y_new = (float) ((2 * total[1] * total[2] + 2 * total[0] * total[3]) * x_old
+ (1 - 2 * total[1] * total[1] - 2 * total[3] * total[3]) * y_old
+ (2 * total[2] * total[3] + 2 * total[0] * total[1]) * z_old);
float z_new = (float) ((2 * total[1] * total[3] - 2 * total[0] * total[2]) * x_old
+ (2 * total[2] * total[3] - 2 * total[0] * total[1]) * y_old
+ (1 - 2 * total[1] * total[1] - 2 * total[2] * total[2]) * z_old);
newpoints.set(i, x_new);
newpoints.set(i+1, y_new);
newpoints.set(i+2, z_new);
}
return newpoints;
}
For rotation3D(points, 50, 0, 1, 0) where points is:
0.0, 0.0, -9.0;
0.0, 0.0, -11.0;
20.0, 0.0, -11.0;
20.0, 0.0, -9.0;
i get back the same list.
