Global Coordinate System

Global Coordinate System

I use Cheetah3D exclusively to create models for importing into Unity. A problem I run into every time is that Unity uses a global coordinate system, but Cheetah3D apparently does not. Some objects have the same coordinates in Cheetah and Unity, but others do not, making it difficult to make precise adjustments to the models. I have no idea why some are the same and some are not.

It looks like Cheetah doesn't use a global coordinate system. I can have two objects in the exactly the same position, same pivot point, same everything, but their transform values are different in Cheetah. However, when imported into Unity, which uses global coordinates, identical objects have identical transforms. It gets even more complicated with parent/child relationships.

It would simplify things greatly if I could know the actual coordinates of objects in the global space within Cheetah.

John B said:

Yeah, I always have trouble with Cheetah's idea of global coordinates. Apparently global is relative, to what I've never figured out.

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Now I´m confused.
Forgive my ignorance but did you accidentally move your objects in geometry mode rather then in object mode?

Cheers
Frank

frank beckmann said:

Now I´m confused.
Forgive my ignorance but did you accidentally move your objects in geometry mode rather then in object mode?

Cheers
Frank

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I don't know what geometry mode is and can't find a reference to it in the docs. So I'm guessing I didn't use it.

Sometimes, burning the transform does it. For example, I just tried it with a child object. The parent's position is 0.0, 0.0, 0.0 and its child's position is -0.3, 0.2, 0.0, relative to the parent. I select the child object and burn its transform. Now the child object, which has not moved, has coordinates 0.0, 0.0, 0.0. What coordinate system is that? It's not relative to the parent, it's not relative to the world. If I import into Unity, that child has the coordinates it had prior to burning the transform, that is, its position relative to its parent.

If an object's position coordinates can change without the object itself moving, then it's not using a consistent coordinate system. An object's position values should never change unless the object's position changes. There has to be some consistent, absolute point of reference. If an object is at 0, 0, 0, that should either be at the center of the world, or at the center of the parent's.

BTW, I see you found an old post of mine. I've obviously not gained any further understanding of Cheetah's system since that time.

John B said:

I don't know what geometry mode is and can't find a reference to it in the docs. So I'm guessing I didn't use it.

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You´re kidding right?
When you make a parametric object editable - select all it´s components (point/edges or faces) and move it around its pivot/origin point will stay at the same spot from where you start the translation/movement.

John B said:

Sometimes, burning the transform does it. For example, I just tried it with a child object. The parent's position is 0.0, 0.0, 0.0 and its child's position is -0.3, 0.2, 0.0, relative to the parent. I select the child object and burn its transform. Now the child object, which has not moved, has coordinates 0.0, 0.0, 0.0. What coordinate system is that?

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You did a reset by hitting "burn transform"! To get it´s global position hit "Center pivot point" followed by "Burn pivot point" - and there you have it - back&force.

frank beckmann said:

You did a reset by hitting "burn transform"! To get it´s global position hit "Center pivot point" followed by "Burn pivot point" - and there you have it - back&force.

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So it is possible to get back to actual coordinates, it just takes a few extra steps.

But that doesn't change the fact that two objects can be in the same position and show different coordinates. That should not be possible. Every other 3D program I've used has an absolute coordinate system - an object's XYZ position always shows where it is in the world independent of anything else.

John B said:

So it is possible to get back to actual coordinates, it just takes a few extra steps.

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Why would you need the steps when you already knows that the child ocject stays at -0.3, 0.2, 0.0

John B said:

But that doesn't change the fact that two objects can be in the same position and show different coordinates. That should not be possible. Every other 3D program I've used has an absolute coordinate system - an object's XYZ position always shows where it is in the world independent of anything else.

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Name 1. Maybe CAD software.
In every subdivsion-modeler I know you can move the mesh from its origin point when components are translated and not the object itself.

John B said:

.. an object's XYZ position always shows where it is in the world independent of anything else.

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Same thing in Cheetah3d - but you seem to like to move your objects components instead of the object itself - so what else?

Cheers
Frank