# Weired Acis transformation matrix

This topic is 2739 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

## Recommended Posts

I have queried an ACIS solid in AutoCAD using autolisp and have extracted what appears to be a transformation matrix:

transform $-1 0.965925826289068 -0.258819045102521 0 0.258819045102521 0.965925826289068 0 0 0 1 -1.63832380999416 3.11204436836534 0 1 rotate no_reflect no_shear # [/quote] Dose anyone recognise this kind of entity? It sort of looks like a 4x4 transformation matrix (regarding the 0 0 0 1 line in the middle), but the arguments only have fourteen reals. #### Share this post ##### Link to post ##### Share on other sites Advertisement No documentation found, but a transform description can be anything (see e.g. the transform node of X3D). transform$-1 0.965925826289068 -0.258819045102521 0 0.258819045102521 0.965925826289068 0 0 0 1 -1.63832380999416 3.11204436836534 0 1 rotate no_reflect no_shear # [/quote]
I'd say that
0.965925826289068 -0.258819045102521 0
0.258819045102521 0.965925826289068 0
0 0 1
is a 3D rotation by 15 degree around the z axis, given as a affine matrix. I'd further assume that the subsequent
1.63832380999416 3.11204436836534 0
defines a affine position. I have no clue what the leading -1 and trailing 1 mean. The latter one may perhaps be a scaling factor, but then for uniform scaling only. If you want to investigate this w/o having access to a documentation, try to apply well known transformations and look at the resulting numbers.

##### Share on other sites

No documentation found, but a transform description can be anything (see e.g. the transform node of X3D).

transform \$-1 0.965925826289068 -0.258819045102521 0 0.258819045102521 0.965925826289068 0 0 0 1 -1.63832380999416 3.11204436836534 0 1 rotate no_reflect no_shear #

I'd say that
0.965925826289068 -0.258819045102521 0
0.258819045102521 0.965925826289068 0
0 0 1
is a 3D rotation by 15 degree around the z axis, given as a affine matrix. I'd further assume that the subsequent
1.63832380999416 3.11204436836534 0
defines a affine position. I have no clue what the leading -1 and trailing 1 mean. The latter one may perhaps be a scaling factor, but then for uniform scaling only. If you want to investigate this w/o having access to a documentation, try to apply well known transformations and look at the resulting numbers.
[/quote]

Thanks Haegarr,

That does sound very likely.

I have searched for documentation on this but have been unable to find any.

I'll do what you suggest and see if the numbers tally.

1. 1
2. 2
3. 3
Rutin
22
4. 4
5. 5

• 16
• 14
• 9
• 9
• 9
• ### Forum Statistics

• Total Topics
632928
• Total Posts
3009264
• ### Who's Online (See full list)

There are no registered users currently online

×