[GRASS-dev] OGSF vector feature styling

Maris Nartiss maris.gis at gmail.com
Tue Sep 29 05:06:26 EDT 2009

Hello OGSF and NVIZ experts.
As I was trying to fix attribute dependent rendering in NVIZ for 6.x
releases, it turned to more serious change than expected. I have
commited to trunk (r39323) first small change for OGSF that should
help to rebuild attribute dependent vector feature styling in NVIZ for

Please take a look into gstypes.h change [1], as it's most important
thing. It affects future NVIZ memory consumption and available
features. My idea how it should work:
1) every vector feature set(map) has default style and highlighted
feature style;
2) every vector feature (point, line ...) has it's layer/Cat info;
3) every vector feature can have own style (color, size, symbol, fill,
orientation etc.);
4) thematic mapping is controled by vector map switch that stores info
about base layer used for thematic mapping.
If no thematic mapping is used, memory consumption is increased by
layer/cat struct ammount for every displayed feature. In such case per
feature styling is unset and thus should not increase memory
consumption. When thematic mapping is enabled, every feature gets
additional style struct overhead.
Applying thematic styling information will be slow, as all features
will have to be processed.

I would like to hear something back from our OGSF/C masters what
should be changed/improved to make solid base for futhurer

Yes, tcl/tk based NVIZ in trunk is broken (and I don't plan to fully
fix it. Can be hacked to work on request).


1. http://trac.osgeo.org/grass/changeset/39323/grass/trunk/include/gstypes.h

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