(trans) explained

Hi. Can i say that autolisp dont respect ucs at all and commands respect ucs by all means,?

Certain AutoLISP functions perform calculations relative to the current UCS, for example, inters.

If autolisp aknowladge ucs why the translstion is still required?

If autolisp aknowladge ucs why the translstion is still required?

Not all AutoLISP operations are performed relative to the active UCS.

Is there any reason?

From here:

To save space in the drawing database (and in the DXF file), the points associated with each entity are expressed in terms of the entity's own object coordinate system (OCS). With OCS, the only additional information needed to describe the entity's position in 3D space are the 3D vector describing the Z axis of the OCS and the elevation value.

as far as i know DXF are codes, now its being treated as a file? is it the DWG or part of it?

Hi

the doc say about UCS

User coordinate system—the working coordinate system. The user specifies a UCS to make drawing tasks easier. All points passed to AutoCAD commands, including those returned from AutoLISP routines and external functions, are points in the current UCS (unless the user precedes them with a * at the Command prompt). If you want your application to send coordinates in the WCS, OCS, or DCS to AutoCAD commands, you must first convert them to the UCS by calling the trans function.

this expression

(entmake (list (cons 0 "CIRCLE")            ;***
              (cons 6 "BYLAYER")
              (cons 8 "0")
              (cons 10 (list 0.0 0.0 0.0)1 0) ;***
              (cons 39 0.0)
              (cons 40 1.0)                ;***
              (cons 62 256)
              (cons 210 (list 0.0 0.0 1.0))))

will draw the circle on WCS origin ragedless of the active UCS

how come?

as far as i know DXF are codes, now its being treated as a file? is it the DWG or part of it?

AutoCAD DXF

this expression

(entmake (list (cons 0 "CIRCLE")            ;***
              (cons 6 "BYLAYER")
              (cons 8 "0")
              (cons 10 (list 0.0 0.0 0.0)1 0) ;***
              (cons 39 0.0)
              (cons 40 1.0)                ;***
              (cons 62 256)
              (cons 210 (list 0.0 0.0 1.0))))

will draw the circle on WCS origin ragedless of the active UCS

 

how come?

The expression as it stands will error as a result of this line:

(cons 10 (list 0.0 0.0 0.0)1 0)

Assuming the trailing 1 & 0 are removed, the circle will always be constructed at the WCS origin since the OCS origin = WCS origin, regardless of the active UCS. You already know this from your thread here.

AutoCAD DXF

 

 

 

The expression as it stands will error as a result of this line:

(cons 10 (list 0.0 0.0 0.0)1 0)

 

Assuming the trailing 1 & 0 are removed, the circle will always be constructed at the WCS origin since the OCS origin = WCS origin, regardless of the active UCS. You already know this from your thread here.

Hi

is the DXF is stands for a file format, DXF data structure is embedded into DWG, right?

User coordinate system—the working coordinate system. The user specifies a UCS to make drawing tasks easier. All points passed to AutoCAD commands, including those returned from AutoLISP routines and external functions, are points in the current UCS (unless the user precedes them with a * at the Command prompt). If you want your application to send coordinates in the WCS, OCS, or DCS to AutoCAD commands, you must first convert them to the UCS by calling the trans function.

why drawing database and DXF file are treated as two separate things?

as marked with bold, the guide claim all autolisp expressions returned points in UCS while in my case entmake ignores UCS

Hay everyone