Opening large DXF file

See,

http://forum.librecad.org/open-big-DXF-file-td5709234.html

Out of curiosity with somebody with auto cad. How fast does the full drawing pan on screen. That is when all circles are visible?

background: We are working on a new version of LibreCAD and have been looking in area's where we can optimise performance. One of the way to do this is using a QuadTree (http://en.wikipedia.org/wiki/Quadtree)
However, no matter how you look at it, when all entities are drawn on screen you will have to iterate over all entities to draw them.
Arguably you can leave small entities out and you can do this by asking the QuadTree implementation to only return all entities up-untill some depth level. LibreCAD 3 can do this using a level indicator (see http://wiki.librecad.org/lc3doc/lckernel/html/classlc_1_1_quad_tree_sub.html#a5e98edfcecde70c3ec4fbea6148ce52a)
However, the drawing is constructed such that we have many many small circles into each other not having a 'small' enough circle to not draw it.
Also when you 'zoom in' you can ask the QuadTree to only return the entities that are possibly visible on screen. The retrieve function supports a 'area' that will only return all entities within a specific area note: QuadTree does this roughly, we have more refined functions for exact matching in EntityContainer

I can compare ourselves with DraftSight, and the large file is also very very slow on DS. However, I cannot compare with AutoCAD because I don't have such license.

Just curious...

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