RichardCooper wrote:
I'm trying to determine the default method of rasterization used by
v.to
rast.
In the v.to.rast manual it states in relation to the -d option, that
'All
cells touched by the line will be set, not only those on the render
path',
but I'm not certain which method is being used by default.
I came across a paper by Biagi and Negretti
<http://geomatica.como.polimi.it/workbooks/n2/articoli/lbmn.pdf> *
which
describes how by default vectors are rasterized in GRASS 5. The
latter
authors refer to the 'center' method as being the standard GRASS
command in
5.0 (p. 4). Is this used in GRASS 7? From my observation (in the Map
Display), by default, vector area appear to be rasterized if the
center of
the grid cell falls within the area boundary?
I haven't checked through the code,
Hints:
grep -nr centroid * # inside the module's source code directory
Binary file OBJ.x86_64-unknown-linux-gnu/vect2rast.o matches
Binary file OBJ.x86_64-unknown-linux-gnu/do_lines.o matches
Binary file OBJ.x86_64-unknown-linux-gnu/do_areas.o matches
Binary file OBJ.x86_64-unknown-linux-gnu/support.o matches
do_areas.c:42: if (ISNULL(&cat)) { /* No centroid or no category
*/
do_areas.c:94: int i, centroid, nareas_selected;
do_areas.c:114: centroid = Vect_get_area_centroid(Map, i + 1);
do_areas.c:116: if (centroid <= 0) {
do_areas.c:117: G_debug(2,_("Area without centroid (OK for
island)"));
do_areas.c:120: Vect_read_line(Map, NULL, Cats, centroid);
do_areas.c:127: G_debug(2, _("Area centroid without
category"));
do_areas.c:131: /* field < 1, process all areas with centroid
*/
v.to.rast.html:41:Labeled areas and/or centroids will produce filled
raster coverages with edges
v.to.rast.html:49:Points and orphaned centroids will be converted into
single cells on the
vect2rast.c:219: /* maximum possible numer of areas: number of
centroids
vect2rast.c:221: * number of areas with centroid that are within
cat constraint
Nikos
but maybe someone has some knowledge on
the history of v.to.rast?
Cheers,
Richard
*http://geomatica.como.polimi.it/workbooks/n2/articoli/lbmn.pdf
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