mesh selection tool
allows to select surface elements by extending a key-colored
surface to its neighbours. This expansion can stop on various
criteria, meeting of an edge line or of a sharp enough angle,
or extend to all connected elements. Edge lines or conditional
lines enclosed or bordering selection can be selected too. The
selection is done by changing color of elements to key color.
Optionally, selection can be moved to the end of output LDraw
It is a simple console application, source code
is provided below to anyone willing to integrate it in a more
palatable interface. You may also use Michael Heidemann LETGUI front-end (highly recommended!).
package, including program for Windows, documentation,
source files (Visual C++ 6.0), example files.
V1.0: Initial release
Now limits expansion to main-colored
elements. -m option
Don't select bordering edge lines
if -b option is specified.
Return whole file (-d+)
or only key-colored elements to uncolored state (-d)
Bug correction: using discolor
(-d, -d+) implied -m option
Bordering condlines are no longer
selected if -b option
Prepare the input LDraw files. Selector only considers
surface and line elements (line type 2, 3, 4 or 5). Other
LDraw line types are ignored, including subparts or primitives
(Selector is mainly aiming meshes coming from LDD or other
Launch a command prompt.
Type the command line: selector [-p
<val>] [-k <val>] [c <val>] [-s][-x?][-a
<val>][-m][-d?][-b]LdrawFileIn LdrawFileOut. Selector will create LdrawFileOut,
containing the original file with selected elements colored
and optionally grouped at the end. Note that if file LdrawFileOut.
exists it will be overwritten without warning.
Here is a screen shot of a sample run:
- Input file is read and parsed, stored in an array.
- Except if -x- option
is activated (no expansion of key color) is specified, array
is scanned to find surfaces (triangles or quads) adjacent
to key-colored ones. These adjacent elements are colored
into key color if they are main-colored (color 16). This
process is repeated until no other surface gets colored.
The method is extremely inefficient, but seems fast enough
even with huge LDraw files... To allow expansion on surfaces
whose color is different from color 16, use -m
- This colored surface expansion is limited by default
on edge lines (-xl). If
the initial key-colored element is placed in an area completely
surrounded by edge lines (beware of leaks!), this area will
be completely selected. Alternatively, you can specify -x+ option. In this case, all
connected elements will be selected ("connected elements"=surfaces
that share a common edge). Expansion may be also limited
by sharp angle in surface. This is specified by using -a <angle>. Then all facet
junctions that have an angle sharper than <angle>
will be an expansion frontier. Note that adjusting the angle
value to select what you need may be tricky or impossible.
-a may be used at the same time to limit to edges
and sharp angles.
- After expansion, a new scan is done on lines (edge lines
and conditional lines). All the lines that border key-colored
element are colored. Optionnally, if -c
<color> is specified, lines that have a
key colored facet on only one side are colored using that
color instead of key color. The edge lines
condlines! in version 1.1) and condlines
(from version1.2) may also be omitted from selection if
-b option is used.
- If you use -s option,
all key colored elements will be grouped together at the
end of file. Bordering elements (if -c
option is used) come first, preceded by the comment "0
// Bordering edge lines" then "0 // Bordering
condlines". Then follows the rest of selected elements
is preceded by the comments "0 // Key Colored
edge lines", then "0 // Key Colored condlines"
and finally "0 // Key colored elements".
- -d option allows to
return all selected elements to their uncolored state (surfaces
into main color 16, lines to edge color 24). -d+
option goes one step further, and removes color from the
whole file. Of course, these options can be used only if
-s option is specified,
otherwise the whole selection process would be pointless
- -p <value> controls
the maximum distance between two points that Selector
will consider matching.
The following examples are based on this mesh,
a 3D capture from LDD 2421 part. This mesh is actually
composed of 4 non-connected areas, the bar, the
bar support, the brick and the stud. A few triangles
in each area have been colored using MLCad.
Using default options, cylindrical portion of
the bar is selected, since source file contained
there a dark pink triangle (default key color).
The edge lines bordering this area are also selected.
Command line: Selector 2921.dat sel1.dat
As you can see, conditional lines of the cylinder
are selected too.
option is used, the whole bar is selected. Non-connected
areas (no common edge) are not selected.
Command line: Selector -x+ 2921.dat sel2.dat
In LDD models (as in most LDraw ones!), studs
are simply laying on top surface, not connected
to it. When you adapt LDD 3D meshes to LDraw, the
studs need to be substituted with primitives. Selecting
the studs is easy, just color one triangle (here
red) in each stud, use -x+
option, and everything composing LDD stud (including
lines and conditional lines) can be selected and
deleted at once!
Command line: Selector -x+ -k 4 2921.dat sel3.dat
When the part contains many studs (eg. baseplates),
placing a colored triangle in each stud can be painful!
In this case, it is simpler to work negatively,
placing a key colored element in each area that
is not a stud. Here I will select all green
areas, and use -s
option to group selected elements to the end of
file. As opening huge files in MLCad can be very
slow (LDD baseplates reach several megabytes) it
may be convenient to remove studs using a text editor!
Command line: Selector -x+ -k 2 -s 2921.dat sel4.dat
Here we see the use of -c
<color> parameter. The edge line
bordering the selected area is now colored differently,
allowing to specifically select it.
Command line: Selector -c 1 2921.dat sel5.dat
Here is an example showing selection with limit
angle (example and image courtesy J.C. Tchang).
By limiting the expansion of facet with a 30°
angle, we are able to select side of LDD cow model.
Command line: Selector -a 30 64780.dat 64780b.dat
Another selection scenario, during conversion
of part 98585 from LDD mesh to LDraw. We need to
remove peg and axle holes to replace them with primitives.
As there are many areas separated by edge lines
in axle holes, it may seem a bit tedious to assign
a colored triangle in each area! So we are going
to use a bit twisted method to simplify things...
The first step will be to create a selection barrier
on top and bottom of part to "isolate"
the holes. 98585a is a quarter of the part (created
from LDD mesh using Symsplitter). One triangle on
top and one on bottom area is colored blue (key
color = 1).
We expand blue area...
Command line: Selector -k 1 98585a.dat 98585b.dat
Using MLCad, we add a dark pink element in each hole, result is 98585c
Now, we select dark pink areas (default key color)
to all connected elements (-x+). Expansion stops
when it meets a surface that is not main color,
so blue area will not be selected. Of course, since
we have used the sort option -s, we could have used
-d+ option to return all elements to uncolored state,
but the colored screenshots are more explicit...
Command line: Selector -x+ -s 98585c.dat 98585d.dat
We then remove the lines after "0 // Key
Colored elements", using LDDP od MLCad. Here
is the result (98585e.dat). The hole elements are
now completely removed, including condlines (always
tricky to remove manually).