How to change the center of mass / anchor point of a body?

[AndreasRef]

Hi

I want to be able to rotate a elongated rectangle not relative to its center, but relative to one of its end points.
I have looked at this similar issue:
#149

And it seems like I need to change the centre of mass of the rectangle to be at the pivot point

But how is that done? How do I set the anchor point (or change the center of mass) of a body? I cannot find it anywhere in the documentation.

[liabru]

Try this:

body.position.x += offset.x;
body.position.y += offset.y;
body.positionPrev.x += offset.x;
body.positionPrev.y += offset.y;

Where offset is the vector of the new centre, relative to the current body position (centre of mass). Maybe I should add this as a built in function, though I'm not sure if the result will be technically physically correct without a few other property updates (e.g. inertia) but should work fine for now.

[ajay1773]

@liabru what is the positionPrev here?

[ProgrammingLife]

Try this:

body.position.x += offset.x;
body.position.y += offset.y;
body.positionPrev.x += offset.x;
body.positionPrev.y += offset.y;

Where offset is the vector of the new centre, relative to the current body position (centre of mass). Maybe I should add this as a built in function, though I'm not sure if the result will be technically physically correct without a few other property updates (e.g. inertia) but should work fine for now.

Looks it doesn't work. Tried here: phaserjs/phaser#6442