topic Block rotation around Y Axis changes the rotation value in the property window. in AutoCAD Forum

Block rotation around Y Axis changes the rotation value in the property window.

Anonymous — Tue, 27 Jul 2021 05:32:14 GMT

Hi there,

I have created a simple block(square). Inserted it to empty drawing at (10,10,0). Selected the block checked the rotation in the properties, it is zero as expected. Rotated in 3D via HOME->Rotate, selected based point as (10,10,0) then Y axis rotation (Green orbit) entered value of 10 degrees for rotation. It rotated the the block correctly but when I check the rotation value in the properties of the block it is 90 degrees!. If I do the same thing but for X Axis the rotation in the property does not changes (stay zero). As I understand, the rotation in the block properties should be around Z-Axis.

Does anyone know what the rotation in the block property exactly represents? Thanks,

Re: Block rotation around Y Axis changes the rotation value in the property window.

cheryl.buck — Tue, 27 Jul 2021 17:22:08 GMT

Hi @Anonymous,

That does sound unusual. I have not been able to reproduce the result, so I might have misunderstood one of your steps. Can you create a ScreenCast of your workflow to help us narrow down the cause?

All the best,

Re: Block rotation around Y Axis changes the rotation value in the property window.

leeminardi — Tue, 27 Jul 2021 18:18:14 GMT

The "rotation" property you refer to is a bit of a mystery to me. I rotated a block by 90° about the Y axis and the rotation property showed 270. I then rotated the block by 90° about the X axis and the Rotation property was 0!

Rotations in 3D can be difficult to determine and confusing to express in clear term. The order in which rotations are done will affect the final orientation. When working in 3D and I want to know the orientation of a 3D Block I find it best to use the VLISP function nentsel. For example, in the image below I have rotated a block to an isometric orientation (rotate3d about Y by 45° then about X by 35.2644°). Nentsel outputs the 4 row by 3 column transformation matrix of the block. The first vector (11.3197 3.52974 0.0) is the pick point for selecting the block. It is followed by the matrix where the first vector (0.707107 -0.408248 -0.57735) is a unit vector of the x axis of the block in world coordinates. The next vector (6.66134e-16 0.816496 -0.57735) is the unit Y axis. It is followed by the z vector and then a vector defining the location of the block.

Re: Block rotation around Y Axis changes the rotation value in the property window.

Anonymous — Tue, 27 Jul 2021 22:50:49 GMT

Hi @cheryl.buck ,

Thanks for your reply. Here it is https://autode.sk/3l6WJjA

Thanks,

Re: Block rotation around Y Axis changes the rotation value in the property window.

Anonymous — Tue, 27 Jul 2021 22:58:50 GMT

Hi @leeminardi

Thanks for your suggestion. Yes, you are the right the order of rotations is important. But I think, rotation (single value) defined in the block property is around Z-Axis, Kappa. From the 4x4 transformation matrix or 3x3 rotation matrix, kappa can be computed given the rotations order. The rotation(single value) in the block property (in my case) does not correspond to any of the rotation angles.

Thanks again.

Re: Block rotation around Y Axis changes the rotation value in the property window.

SEANT61 — Wed, 28 Jul 2021 02:58:09 GMT

The Rotation Property of a Block Reference is Governed by the Arbitrary Axis Algorithm.

About Arbitrary Axis Algorithm (DXF)

http://help.autodesk.com/cloudhelp/2016/ENU/AutoCAD-DXF/files/GUID-E19E5B42-0CC7-4EBA-B29F-5E1D595149EE.htm

If the attached block is 3d rotated around the "Y" axis by an amount greater than 0.89517 degrees, the Rotation property changes to 270.

Re: Block rotation around Y Axis changes the rotation value in the property window.

Anonymous — Thu, 29 Jul 2021 02:43:10 GMT

Hi @SEANT61 ,

Thanks a lot.