koobas.hobune.stream
How to get local position & rotation from not parent object
Hello,
My scene has three GameObjects, A, B and X.
X's parent is A.
B is unrelated to A, move and rotate uniquely.
I want to know local position & rotation if X's parent is B.
Therefore, first I set X's parent to B temporarily, get local positon & rotation, and set X's parent to A again. But cost of changing parent is large.
So second, I create dummy object and set it's parent to B. And set dummy's world positon & rotation equal to X's world position & rotation and get dummy's local positon & rotation. This way works fine, but cost is not small.
Is there a way more light?
Sorry my English is limited. I thank you for reading it through.
From memory, local position of X relative to B is B.inverseTransformPoint(X.position);.
For local rotation, you "subtract" B's rotation from X, so (this is probably wrong, but something like it works): Quaternion.Inverse(B.rotation)*X.rotation;.
Inverse is like using a "times -1" on the rotation, and * adds them together (math guys told us to use that symbol.) The order matters (so putting X.rotation first might be correct. I always have to experiment by testing at easy angles.)
Thanks Owen!
// get local position if B is X's parent
B.InverseTransformPoint(X.position);
// get local rotation if B is X's parent
Quaternion.Inverse(B.rotation) * X.rotation;
This way works fine.
$$anonymous$$oreover, this way is faster than the way copy position & rotation from dummy child object.
Thank you very much!
