I've been trying to make one object orbiting another:
//childX,childY,childZ are my starting coordinates
//here I count distance to the middle of my coordinate plane
float r = (float) Math.sqrt(Math.pow(childX, 2)+Math.pow(childY, 2)+Math.pow(childZ,2));
//here i convert my angles to radians
float alphaToRad = (float) Math.toRadians(findParent(figure.parentId).rotate[1]);//up_down
float betaToRad = (float) Math.toRadians(findParent(figure.parentId).rotate[0]);//left_right
float newX = (float) (r*Math.cos(betaToRad)*Math.cos(alphaToRad));
float newY = (float) (r*Math.cos(betaToRad)*Math.sin(alphaToRad));
float newZ = (float) (r*Math.sin(betaToRad));'
I have coordinates of my starting point(5,5,0) and angles 0° and 0°, so it means, that coordinates shouldn't change after calculating the new ones. But the result is:
newX: 7.071068 newY: 0.0 newZ: 0.0
Every method I try to calculate new coordinates there is always this strange result. What is that 7.07 and how can I get correct result?
@edit
To make my new point relative to the old one I just added angles of old point to the new one:
float alphaToRad = (float) Math.toRadians(findParent(figure.parentId).rotate[1]) + Math.atan(childY/childX);
float betaToRad = (float) Math.toRadians(findParent(figure.parentId).rotate[0]) + Math.asin(childZ/r);
Everything now works like it should have. Solved
7.07 is the value of r in your code, which is the distance of your point from the origin:
sqrt(5 * 5 + 5 * 5) = sqrt(50) = 7.0711
With both angles being zero, all the cos() values will be 1.0, and the sin() values 0.0. Which means that newX becomes r, which is 7.07, and both newY and newZ become 0.0. Which is exactly what you got, so there is no mystery in this result.
What you're basically doing is place the point at a given direction and distance from the origin. The distance is the same as the original distance. The direction is given by the two angles, where both angles being 0.0 corresponds to the x-axis direction.
In other words, what you're missing is that you're not taking the original direction of the point relative to the origin into account. You're placing the point at an absolute direction, based on the two angles, instead of at a direction relative to the original direction of the point.
To rotate the point by the given angles, the easiest approach is to build rotation matrices from the angles, and apply them to your points.