Rectifier, LDraw file
scans a LDraw file and performs two kinds of optimization on
Convert adjacent triangles into a
quad. This conversion is done only if the resulting quad
is convex, flat enough (less than 1° warp) and if the
triangles have the same winding and color.
Convert rhombuses (quads that have
parallel opposite sides) bordered by at least one line into
a rect primitive. Rhombuses must be perfectly
flat to allow this conversion.
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), sample files.
V1.0: Initial release
V1.1: Corrected a stack size issue
that caused crash under Windows 2000.
V1.2: Rectifier now cares to BFC orientation
when replacing quads with rect primitives.
If no BFC orientation is specified in the input file, CCW
is assumed. Also tries to keep simple coefficients in rect
primitive transformation matrix when possible.
V1.3: Corrected a bug that caused
wrong coefficient in small rect
V1.4: Added -t option allowing to
choose the maximum angle formed by two triangles being merged
into a quad.
V1.5: Added -a option allowing to
prevent quad to rect conversion when the quad has adjacent
V1.6: Used dynamic memory allocation
to enable the use on big LDraw files.
V1.7: Manages direct color (code courtesy
of Nils Schmidt). Prevents creation of quads with too flat
V1.8: Corrected a bug introduced in
version 1.7 (wrong file output of edge lines).
V1.9: Simpler matrix coefficients
for generated rect primitive! The LDraw code
is even tighter. The program is simpler, too ;)
Prepare the input LDraw file. Rectifier works on any
LDraw file, but should be used in the end of authoring process,
before submitting parts to tracker.
Launch a command prompt
Type the command line: rectifier [-c]
[-q] [-r] [-a] [-t <value>] LdrawFileIn LdrawFileOut.
Rectifier will create optimized
LdrawFileOut. Note that if file LdrawFileOut exists it will
be overwritten without warning. -c, -q and -r are optional
parameters controlling the behavior of Rectifier.
These options will be detailed below.
Here is a screen shot of a sample run:
- Input file is read and parsed. Triangles, quads and
lines are stored in an array (limited by memory... or patience!).
- A first scan is done to locate triangles of the same
color that share a common side. For each candidate we check
if the formed quad would be convex and planar enough. If
a quad is found, it replaces the first triangle and the
second is deleted. We then search for a conditional line
that would have been set between the two triangles. If one
is found it is suppressed.
- We then scan again the array, this time looking for
rhombuses. They are identified by their diagonals which
must cross in their middle. When a rhombus is found, we
look for edge lines bordering the rhombus. According to
the configuration of these edge lines, we determine the
type of rect primitive to use among rect1,
rect2p, rect2a, rect3
and rect, as well as its orientation. Center
of the rhombus will become center of primitive, while length
and orientation of its sides determine the transformation
matrix of the primitive. Rect primitive will
be inserted in file at previous position of the rhombus,
lines (incorporated in rect) are deleted.
- Rectifier then writes
output file, changing only modified or deleted lines.
- Behaviour of Rectifier
can be controlled with the following command line parameters:
- -c: Converted triangles
are colored in yellow, newly formed rect
primitives are colored blue. This helps appreciating
the work of Rectifier.
- -q: Rectifier
does not attempt to transform triangles into quads.
- -a: Rectifier
does not convert quad to rect when the
quad has adjacent condline(s). This may improve smooth
shading of the part.
- -r: Rectifier
does not convert bordered rhombuses into rect
- -t <value>:
defines the maximum angle formed by two triangles to
be merged into a quad. Default value is 0.95°, matching
This file (64053.dat) was processed with Rectifier.
It located several adjacent triangles (yellow) and combined
some quads and lines into rect primitives.
As a result, the file is shrunk by 24%...
Command line: rectifier -c 64053.dat 64053r.dat