Get mesh polygon points world positions not using matrix maths?

Questions
1

I don’t wish to use any matrix maths as too costly, vector maths is fine though.

Any ideas?

Edit: I know it’s object world position + polygon point object position.
Can get the world position by:
object.matrixWorld.multiplyVector3(someWorldPositionVectorVariable);

Does that command use matrix stuff?

And how to get the polygon points local to the object?

3

I’m not 100% sure I understand your question. But you can extract the position (translation) portion of a 4x4 transformation matrix like this:

const position = new THREE.Vector3();

position.x = object.matrixWorld.elements[ 12 ];
position.y = object.matrixWorld.elements[ 13 ];
position.z = object.matrixWorld.elements[ 14 ];

I think adding the world position vector with each vertex position should do the trick.