Finding default unit vectors in 3D modelling

In summary, when modelling elements like tubes, the local x-axis is defined along the tube's length. If a unit vector for the z-axis is not applied, the software defaults to a coordinate system where the local zx-plane is parallel with the global zx-plane. This can cause confusion when the local x-axis is perpendicular to the global zx-plane, as the software must handle this case differently.
  • #1
dr.fea
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When you are modelling elements like tubes, the local x-axis is defined along the tubes length.

If a unit vector for the z-axis is not applied, modelling softwares defaults to a coordinate system where the local zx-plane is parallel with the global zx-plane.

I'm not sure what that means exactly, since the zx planes obviously can't be literally parallel if the local and global x-axis isn't pointing in the same direction.

Could someone please explain? My goal is to make a transformation matrix from the default coordinate system to an arbitrary one, but since I don't see how the default one is found, I'm quite stuck..
 
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  • #2
dr.fea said:
If a unit vector for the z-axis is not applied, modelling softwares defaults to a coordinate system where the local zx-plane is parallel with the global zx-plane.

Sounds like they mean to say the local z-axis is parallel to the global zx plane.

However, when the local x-axis is perpendicular to the global zx plane that rule can't define the orientation. The software must treat that case in some other way.
 

1. What are unit vectors in 3D modelling?

Unit vectors in 3D modelling are vectors with a magnitude of 1 unit. They are used to represent direction and orientation in 3D space.

2. Why is it important to find default unit vectors in 3D modelling?

Finding default unit vectors in 3D modelling is important because they serve as a reference point for other vectors in the model. They help maintain consistency and accuracy in the model's orientation and direction.

3. How do you find default unit vectors in 3D modelling?

Default unit vectors in 3D modelling can be found by using the right-hand rule. The x-axis is represented by the thumb, the y-axis by the index finger, and the z-axis by the middle finger. These three fingers form the default unit vectors in the model.

4. Can default unit vectors in 3D modelling be changed?

Yes, default unit vectors in 3D modelling can be changed depending on the needs of the model. However, it is important to maintain consistency and follow the right-hand rule to avoid confusion in the orientation and direction of the model.

5. How are default unit vectors in 3D modelling used in practical applications?

Default unit vectors in 3D modelling are used in various practical applications such as computer graphics, game development, and engineering design. They help define the orientation and direction of objects in 3D space, making it easier to manipulate and interact with the model.

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