Symmetry dilemna

for the life of me, I can’t figure which symmetry option to use! I have to experiment to determine which one I need. I can’t find anything that indicates which color is associated with which axis. That would be a nice start. 

Symmetry is specified for a particular axis, which confuses me, and may be part of my issue. I would assume symmetry would be applied across a plane, not an axis. If I have symmetry turned on for the X axis, and I’m drawing on the XY plane, I would imagine that I draw a line from 1,1,0 to 2,2,0, that it would be duplicated at 1,-1,0 to 2,-2,0 (x,y,z). What happens if I’m drawing parallel to the XY plane, but at a Z location of 1? If symmetry is really applied around the X axis, the duplicated line would start at Z = -1. But that isn’t what happens.

for the life of me, I can’t figure which symmetry option to use! I have to experiment to determine which one I need. I can’t find anything that indicates which color is associated with which axis. That would be a nice start. 

Symmetry is specified for a particular axis, which confuses me, and may be part of my issue. I would assume symmetry would be applied across a plane, not an axis. If I have symmetry turned on for the X axis, and I’m drawing on the XY plane, I would imagine that I draw a line from 1,1,0 to 2,2,0, that it would be duplicated at 1,-1,0 to 2,-2,0 (x,y,z). What happens if I’m drawing parallel to the XY plane, but at a Z location of 1? If symmetry is really applied around the X axis, the duplicated line would start at Z = -1. But that isn’t what happens.

0
5 comments

Official comment

Hello Gary, 

So to help you: 

Red = X

Green = Y

Blue = Z 

In 3D this is pretty standard coloring technique-- RGB = XYZ if that helps at all. 

Symmetry reflects over the axes-- which in themselves can be treated like planes. Think of a cube. Z is the length, X is the width, Y is the height. You could theoretically extrude surfaces perpendicular to the axes such that the Z axis you are reflecting over is a plane that is ZY, but things are reflected in the X direction,  the X axis is XY, but things are reflected in the Z direction,  and the Y axis is ZX and things are reflected in the Y direction. I know that is confusing, but that is correct.  If you reflect over Z, you are reflecting over the length axis, y, you are reflecting over the height (vertical) axis, and X you are reflecting over the width axis. 


In our quick tools, the order is ZYX. The reason for this is because due to the iPad's layout, and the way that a lot of design is done, the Z axis is used more frequently in symmetry than the X axis-- primarily because most of the time in industrial design, you will be reflecting elements over the long axis. 

Playing around a bit with the tools will help you get accustomed to them, and you will understand how they work better. If you are new to 3D, this can be a bit odd to understand at first, but you will be cruising along in no time. 

I hope that helps, 

 

Nyko

 

Sorry, in my example above, 1,1,0 > 2,2,0.  Would reflect to 1,-2,0 > 2,-2,0

If I assume symmetry is about an axis, from the pic above, I’m guessing red is the X axis, blue is Z, which leaves green for Y. How do you explain the duplicated lines with Y symmetry turned on? It looks like they were also reflected about the X axis.

That was my issue, I was interpreting symmetry about an axis as the exactly that, about an axis, when in fact it’s across a plane. Thanks for your reply!

Please sign in to leave a comment.