koobas.hobune.stream
On a twice nested object, how to get the local position in terms of the middle parent space
Hi,
So, imagine a cube. This is the larger parent. This cube is made up of a bunch of smaller cubes in a 3x3x3 formation. Each of these smaller cubes is a smaller parent made up of six faces. Large Cube > smaller cubes > faces.
I need the positions of the faces. transform.position gives me their world position, transform.localPosition gives me their position local to the smaller cubes. I want to get their local position in terms of the larger cube space.
If I have to I can take the local positions of the faces in terms of the smaller cubes and convert them with some math, but is there a simpler way?
Thanks!
That's quite simple. The process is always the same:
// given
Transform parentObj;
Transform nestedChild;
Vector3 localPointInNestedChild;
Vector3 worldPoint = nestedChild.TransformPoint( localPointInNestedChild );
Vector3 localPointInParent = parentObj.InverseTransformPoint( worldPoint );
If you just want the position of an object in local space of another object you can directly use:
parentObj.InverseTransformPoint( child.position );
edit
If you need to transform a lot points from one space to another you can simply create a conversion matrix by combining the right worldToLocal and localToWorld matrices.
Keep in mind that matrix multiplications work in reverse order. So if you have a source space and a destination space you would do:
Matrix4x4 m = dest.worldToLocal * source.localToWorld;
Now you just have to multiply each point with that matrix:
Vector3 pointInDest = m * pointInSource;
