[gdal-dev] Coordinate system transfromations in dxf driver

[Pero Brbora]

Hi all,

I started with trying to solve ticket 5705, incorect ellipse reading  
when extrusion is [0,0,-1].

As always the easiest solution was looked last, that is RTFM. If you  
read dxf reference from autodesk you will see that everything is  
explained very well. Not all entities use OCS (object coordinate  
system, which is derived from extrusion vector). For ellipse its  
clearly stated, excerpt:
---
Ellipse group codes
Group codes, Description
10 Center point (in WCS). DXF: X value; APP: 3D point
20, 30 DXF: Y and Z values of center point (in WCS)
11 Endpoint of major axis, relative to the center (in WCS).
21, 31 DXF: Y and Z values of endpoint of major axis, relative to the  
center (in WCS)
---

Currently dxf driver blindly applies coordinate transformations to all  
supported entities, which is incorrect.

Note that angles need to be corrected with respect to OCS (right hand  
rule with counterclockwise direction).

RTFM, bye