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Rotating objects can be a very awkward affair, especially when they don't behave as you expect.
This tutorial aims to show you why things don't always behave as they should and what you can do to fix it.
Each object has a reference point, a point of origin if you will. This location affects the object's location, rotation and is also the point that other objects will target when they are set to 'Point At' it.
It would make sense to look at some of the basic props that come with poser whilst learning about the origin.
I've included an image of 8 of the basic props with their origins shown as a green crosshair. The centre of the crosshair, or the location where the two lines cross, is the origin for the object.
I've shown the ball, the box, the cone, the cylinder, the two squares (one sided and two sided for good measure), the torus and the cane.
As you can see, most of the objects have the origin at their base. The only exceptions are the torus which has the origin in the centre and the cane which has the origin at the top of the handle.
Now we'll concentrate on a single prop whilst we play with the origin. I've loaded a single ball prop into the scene, turned the ground plane guide on (Display menu, Guides, Ground Plane), and turned the origin display on for the ball (select the ball, Object menu, Properties, tick the 'display origin' option).
Then, so that I can see what's going on, I changed the view to hidden line.
We can see by this image that the origin is on the floor, underneath the ball. When you move an object around the scene, the xTran, yTran, and zTran settings determine where the origin of the object will be.
To show that the ball will rotate around it's origin, we'll rotate the ball around the Z axis, 90 degrees should do it. I've shown two images, the first for a 45 degree change, the second for the 90 degree change. Just so you can see how it moves.
As you can see, the ball rotated from the origin, essentially falling to the side. Now, I'll put it back to it's starting position and we'll try something else.
Right, to move the origin you first need to display it, but we've done that already. Once the origin is displayed, you'll see three extra dials, OriginX, OriginY, and OriginZ. These dials obviously move the origin around, but not in the same way that you would move an object around.
When you move an objects xTran, yTran, and zTran dials, you are moving it to an absolute position in the scene. When you move the Origin around, you are moving it around in relation to it's object, nothing more.
We'll move the OriginY value to 0.050 which happens to be the centre of the ball.
I've popped the next image in the wireframe display style rather than hidden line as otherwise we'd not see the origin.
Right, so now we have the origin in the right place, I'll try the rotations again, one at 45 degrees and one at 90 degrees. I've gone back to the hidden line view basically because it's a little less confusing.
There we go, the object is now rotating by itself, or around it's own centre. Much better.
I hope that this tutorial has explained what the origin of an object is and how to manipulate it so that objects behave as you expect.