| Re: IDLgrPolygon Leak? [message #69994 is a reply to message #69991] |
Wed, 03 March 2010 16:10   |
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Karl[1]
Messages: 79
Registered: October 2005
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On Mar 3, 1:24 pm, kBob <krd...@gmail.com> wrote:
> Not a memory leak, but a polygon leak.
>
> The 2010 IDL User Group meeting got me inspired to work with some
> object graphics mapping.
>
> However, I am running into some problems with adding a Shapefile to a
> object graphics window. When I call the IDLgrPOLYGON to draw and fill
> the shapefile vertices, there seems to be a leak or overflowing the
> polygon.
>
> Any thoughts on why. Sample code below. The IDLgrPOLYGON is set to
> work with vertices that only have one part. Anything else, the
> IDLgrPOLYLINE is used.
>
> Kelly Dean
> Fort Collins, CO
>
> =============== Test_PolyShp ===============
>
> ;+
> ;
> ; <P>Prepare Shapefile Entities for object model.
> ;
> ;----------------------------------------------------------- -----------
> PRO CountryModel, oModelSHP
>
> COMPILE_OPT DEFINT32, STRICTARR
>
> shpFile = FILEPATH( Subdirectory=['resource', 'maps', 'shape'],
> 'cntry02.shp' )
> oSHP = OBJ_NEW( 'IDLffShape', shpFile )
> IF ( OBJ_VALID( oSHP ) ) THEN BEGIN
> oModelSHP = OBJ_NEW( 'IDLgrModel' )
> oSHP -> GetProperty, N_ENTITIES = num_ent
> FOR entn = 0, num_ent-1 DO BEGIN
> ent = oSHP -> GetEntity( entn )
> IF ( ent.n_parts GE 2 ) THEN BEGIN
> cuts = [ (*ent.parts), ent.n_vertices ]
> FOR partn = 0, ent.N_parts-1 DO BEGIN
> ; oGon = OBJ_NEW('IDLgrPolygon', (*ent.vertices)[*,
> cuts[partn]:cuts[partn+1]-1] )
> oGon = OBJ_NEW('IDLgrPolyline', (*ent.vertices)[*,
> cuts[partn]:cuts[partn+1]-1] )
> oGon -> SetProperty, COLOR = [ 034, 139, 87 ] ; Forest Green
> oModelSHP -> ADD, oGon
> ENDFOR
> ENDIF ELSE IF ( ent.n_parts EQ 1 ) THEN BEGIN
> oGon = OBJ_NEW('IDLgrPolygon', (*ent.vertices) )
> oModelSHP -> ADD, oGon
> ENDIF ELSE BEGIN
> ENDELSE
> oSHP -> DestroyEntity, ent
> ENDFOR
> OBJ_DESTROY, oSHP
> ENDIF ELSE BEGIN
> ENDELSE
>
> END
> ;+
> ;
> ;
> ;----------------------------------------------------------- -----------
> PRO Test_PolyShp
>
> COMPILE_OPT DEFINT32, STRICTARR
>
> CountryModel, oModelCntry
> XOBJVIEW, oModelCntry
>
> ;WARNING: Big time memory leak
> ;Do IDL> HEAP_GC, /Verbose
>
> END
IDLgrPolygons need to be convex in order to render properly. (This is
the case for the underlying OpenGL as well)
I'm guessing that is what you mean by "leak". Drawing non-convex
polygons with grPolygon can sort of look like a leak.
It does not look like your code takes any steps to ensure that the
polygons are convex. It may be the case that your database consists
of only convex shapes, but I don't know that.
To solve this, look at IDLgrTesselator. It will take an arbitrary
input polygon and emit a covering set of triangles that can then be
stored in IDLgrPolygon.
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