Linetrim, Line Trimmer
job of Linetrim is done much better by my new Intersector utility. I suggest you use it instead.
lines going through triangles or quads. Sets of lines and triangles
are provided to the utility as separate LDraw files. A third
file containing the cropped lines is created. Optionnally, a
fourth file containing everything but the lines of the first
file may be created.
It is a simple console application, source code
is provided below to anyone willing to integrate it in a more
This image shows the purpose of line trimmer:
even though the lines highlighting wheel spokes are placed below
rim surface, they bleed through it (left image) with some renderers
(here MLCad). Cutting the lines at their exact length provides
a clean result (right image).
parts are built from flat surfaces and have no clear inside.
The only information available is local orientation of facets
winding. Linetrim will remove
line portion which is on CCW side of intersecting polygon (that
is to say the side of triangle or quad where vertex order is
seen counter clock wise). A side effect is that Linetrim
is effective only when ends of lines are to be trimmed, it will
fail when the center part of a line should be removed, as shown
in the image below. Intended result could have be obtained by
splitting lines in half prior to using Linetrim.
package, including program for Windows and Macintosh,
documentation, source files (Visual C++ 6.0) and the following
spokes.dat contains lines to trim
outlining a few quads.
cyls.dat contains triangles/quads
against which lines will be trimmed
trimmed.dat is the resulting files
with lines cropped, output of Linetrim.
spokeslineless.dat is the optional
file created by Linetrim,
equal to spokes.dat stripped from all lines.
spokestrimmed.dat is the combination
of the two previous files
Note: Macintosh version (universal binary) courtesy
of Jim DeVona
Prepare the input LDraw files. Linetrim
lines against triangles or quads. Other LDraw line types
are ignored. Parts or primitives must be inlined down to
triangles and quads (LDDesignPad
does this very conveniently).
does not require input files to be BFC certified, it does
need the right winding of all trimming triangle and quads.
The simplest way is to add a 0 BFC CERTIFY CW at the beginning
of the trimming file and check using LDview
with BFC option + red and green faces coloring. Lines on
red side of polygons will be trimmed. If some polygons have
the red face on the wrong side, use LDDesignPad
to reverse windings of these polygons.
Launch a command prompt
Type the command line: Linetrim
LdrawTriQuadFile LdrawLineFile LdrawTrimmedLineFileOut [LdrawLineRemovedFile].
Linetrim will create LdrawTrimmedLineFileOut
containing the trimmed lines. Note that if file LdrawTrimmedLineFileOut
exists it will be overwritten without warning. Optionally,
LdrawLineRemovedFile with the same contents as LdrawLineFile
with all lines removed will be created.
output file with 6 digits after decimal point, this precision
is excessive for most usages and values should be rounded.
Here again, LDDesignPad
does that very well.
Here is a screen shot of a sample run:
- Both input files are read and parsed. Quads are split
into 2 triangles. Quads with bad winding ("bow-tie")
will not be properly processed. Lines from the first file
are stored in an array, triangles from second files are
stored in another.
- All lines from the first set are tested for intersection
with all triangle of the second set. If an intersection
is found, the end of the line that is on CCW side of the
triangle is replaced with this intersection. The line to
triangle intersection program is adapted from www.softsurfer.com
triangle intersection code.
- Output file is created.