Tutorial 02: Using the VLFL-Toolbox for STL-File Export and Import

2014-11-18: Tim C. Lueth, MIMED - Technische Universität München, Germany (URL: http://www.sg-lib.org) - Last Change: 2019-06-11

Complete List of all Tutorials with Publishable MATLAB Files of this Solid-Geoemtries Toolbox

The following topics are covered an explained in the specific tutorials:

Tutorial 01: First Steps Using the VLFL-Toolbox for Solid Object Design
Tutorial 02: Using the VLFL-Toolbox for STL-File Export and Import
Tutorial 03: Closed 2D Contours and Boolean Operations in 2D
Tutorial 04: 2½D Design Using Boolean Operators on Closed Polygon Lists (CPL)
Tutorial 05: Creation, Relative Positioning and Merging of Solid Geometries (SG)
Tutorial 06: Relative Positioning and Alignment of Solid Geometries (SG)
Tutorial 07: Rotation of Closed Polygon Lists for Solid Geometry Design
Tutorial 08: Slicing, Closing, Cutting and Separation of Solid Geometries
Tutorial 09: Boolean Operations with Solid Geometries
Tutorial 10: Packaging of Sets of Solid Geometries (SG)
Tutorial 11: Attaching Coordinates Frames to Create Kinematik Models
Tutorial 12: Define Robot Kinematics and Detect Collisions
Tutorial 13: Mounting Faces and Conversion of Blocks into Leightweight-structures
Tutorial 14: Manipulation Functions for Closed Polygons and Laser Cutting (SVG)
Tutorial 15: Create a Solid by 2 Closed Polygons
Tutorial 16: Create Tube-Style Solids by Succeeding Polygons
Tutorial 17: Filling and Bending of Polygons and Solids
Tutorial 18: Analyzing and modifying STL files from CSG modeler (Catia)
Tutorial 19: Creating drawing templates and dimensioning from polygon lines
Tutorial 20: Programmatically Interface to SimMechanics Multi-Body Toolbox
Tutorial 21: Programmatically Convert Joints into Drives (SimMechanics)
Tutorial 22: Adding Simulink Signals to Record Frame Movements
Tutorial 23: Automatic Creation of a Missing Link and 3D Print of a Complete Model
Tutorial 24: Automatic Creation of a Joint Limitations
Tutorial 25: Automatic Creation of Video Titels, Endtitels and Textpages
Tutorial 26: Create Mechanisms using Universal Planar Links
Tutorial 27: Fourbar-Linkage: 2 Pose Syntheses and Linkage Export for 3D Printing
Tutorial 28: Fourbar-Linkage: 3 Pose Syntheses and Linkage Export for 3D Printing
Tutorial 29: Create a multi body simulation using several mass points
Tutorial 30: Creating graphical drawings using point, lines, surfaces, frames etc.
Tutorial 31: Importing 3D Medical DICOM Image Data and converting into 3D Solids
Tutorial 32: Exchanging Data with a FileMaker Database
Tutorial 33: Using a Round-Robin realtime multi-tasking system
Tutorial 34: 2D Projection Images and Camera Coordinate System Reconstruction
Tutorial 35: Creation of Kinematic Chains and Robot Structures
Tutorial 36: Creating a Patient-Individual Arm-Skin Protector-Shell
Tutorial 37: Dimensioning of STL Files and Surface Data
Tutorial 38: Some more solid geometry modelling function
Tutorial 39: HEBO Modules robot design
Tutorial 40: JACO Robot Simulation and Control
Tutorial 41: Inserting Blades, Cuts and Joints into Solid Geometries
Tutorial 42: Performing FEM Stress and Displacement Analysis and Structural Optimization of Solids
Tutorial 43: Performing FEM Structural Optimization (CAO) and Topological Optimization (SKO) of Solids
Tutorial 44: Creation of solids and kinematics from 3D curves and transformation matrices
Tutorial 45: Creation of Solids using the SG-Coder - SGofCPLcommand
Tutorial 46: Creating Fischertechnik compatible gear boxes using SGofCPLcommand
Tutorial 47: Creating four-joints by 3 pose synthesis

Motivation for this tutorial: (Originally SolidGeometry 1.1 required)

2. Import and export of STL-files in ASCII format and binary format

Often it is useful to import surface data fo solid volumes from STL-Files generated by other programs such as CATIA, ProEngineer, Solidworks etc. On the other hand we want to export our data for documentation, 3D-printing or the exchange with other users. The STL-File format is the most common file format for surface models. It supports ascii-text-format and binary formatted files. For export and import we need a couple of functions:

VLFLwriteSTL for writing STL-files in ascii file format.
VLFLwriteSTLb for writing STL-files in binary file format.

close all;

PL=PLcircle(10);

[VL,FL]=VLFLofPLz (PL,30);

VLFLplot(VL,FL); view (-30,30); grid on;

VLFLwriteSTL(VL,FL,'STL-ASCII','by My Name');
WRITING STL FILE /Users/timlueth/Desktop/Toolbox_test/STL-ASCII.STL in ASCII MODE
completed.
VLFLwriteSTLb(VL,FL,'STL-BINAR','by My Name');
WRITING STL (90 vertices, 176 facets) FILE /Users/timlueth/Desktop/Toolbox_test/STL-BINAR.STL in BINARY MODE
completed.

Similar it is possible to read the files in again

VLFLreadSTL for importing STL-files in ascii file format.
VLFLreadSTLb for importing STL-files in binary file format.

close all;

[VL,FL]=VLFLreadSTL ('STL-ASCII');

LOADING ASCII STL-File: /Users/timlueth/Desktop/Toolbox_test/STL-ASCII.STL scaling factor: 1 Processing 1234 lines: Finishing solid AOI-LIB:"STL-ASCII by My Name" 11-Jun-2019 13:49:41 11-Jun-2019 13:49:41

figure(1); VLFLplot(VL,FL,'b'); view (-30,30); grid on;

[VL,FL]=VLFLreadSTLb ('STL-BINAR');

LOADING BINARY STL-File: /Users/timlueth/Desktop/Toolbox_test/STL-BINAR.STL Binary Header: COLOR=RGBA,MATERIAL=AAAABBBBCCCCDDDD;SOLID "STL-BINAR by My Name" 11-Jun-2019 13 Color of solid defined as: "k" Alpha of solid defined as: 65.00 Number of facets: 176 0..

figure(2); VLFLplot(VL,FL,'g'); view (-30,30); grid on;

3. Checking surface volume data and STL-files

Especially, when reading in STL-Files that are generated by other programs and libraries it makes sense to check the data quality. For that purpose there is a function that will be explained later in more detail. This function is called at the end of each STL import.

VLFLchecker is used to analyze vertex list (VL) and facet list (FL)

VLFLchecker(VL,FL);     % Check the data structure
VLFLchecker: 90 vertices and 176 facets.
    0 FACET PROBLEMS DETECTED (ERRORS)
    0 VERTEX PROBLEMS DETECTED (OBSOLETE WARNING)
    0 EDGE PROBLEMS DETECTED (NON MANIFOLD WARNING)
    0 SOLID/EDGE PROBLEMS DETECTED (OPEN SOLID WARNING)
% There are some more procedures to view and analyze solid volumee data

BBofVL generates the bounding box dimensions of the solid
VLFLui is simple user interface to open an STL file
VLFLminimize eliminates doubles in VL and FL
VLFLnormf calucates norm vector direction and size
VLFLplot4 figure with 4 subplots
VLFLselect selected vertex list for a given facet list
VLFLseparate find different independen objects in VL and FL
VLFLshort remove unused vertices from VL
VLFLsurface returns only vertex list and facet list for one surface
VLFLvertexfusion shrinks vertex list by merging extremy near vertices

BBofVL(VL)

ans = 1×6

  -10.0000    9.9756   -9.9939    9.9939         0   30.0000

close all; VLFLplots4 (VL,FL,'g');

close all; VLFLseparate(VL,FL);

Analyzing 90 facets for separation z=[0.0mm|30.0mm] Object TEST-1 with 176 facets

MVL = 1×3

     0   -10     0

4. Generation of text, numbers, characters and formulas as solid volume

Often you want to write some numbers or code on top of a solid object. For that purpose there is a currently slow function that is able to convert a Matlab-string (even with LaTex-code) into a solid object.

VLFLtextimage writes a line using the text command and converts it into a solid volume
VLFLtext does the same for a very limited number of characters

close all;

[VL,FL]=VLFLtextimage('The lazy dog!');

VLFLplot (VL,FL,'g'); view (-30,30);

[VL,FL,d]=VLFLtext('TL-MMXI-XII-XVII');

VLFLwriteSTL (VL,FL,'exp_2011_12_17', 'by Tim C Lueth');

WRITING STL FILE /Users/timlueth/Desktop/Toolbox_test/exp_2011_12_17.STL in ASCII MODE completed.

5. Turning and mirroring of solids by manipulating the vertex lists (VL)

Turning an object and mirroring is quite simple by exchanging a column of the vertex list to change the sign of a column. To show the use of the functions we generate first a simple roman date string as solid volume.

close all;

[VL,FL,d]=VLFLtext('TL-MMXI-XII-XVII'); VLFLplot(VL,FL,'r'); view(-30,30);

The functions for mirroring solid objects by manipulating the vertex list are the following:

VLswapX mirrors the solid at the x-axis (y/z-plane).
VLswapY mirrors the solid at the y-axis (x/z-plane).
VLswapZ mirrors the solid at the z-axis (x/y-plane).

close all, view (-30,30); grid on;

VLFLplot(VLswapX(VL),FL,'b'); % mirror at x-axis

VLFLplot(VLswapY(VL),FL,'y'); % mirror at y-axis

VLFLplot(VLswapZ(VL),FL,'m'); % mirror at z-axis

The functions for turning solid objects by manipulating the vertex list are the following:

VLswapXY turn the x-axis to the y-axis.
VLswapXZ turn the x-axis to the z-axis.
VLswapYX turn the y-axis to the x-axis.
VLswapYZ turn the y-axis to the z-axis.
VLswapZX turn the z-axis to the x-axis.
VLswapZY turn the z-axis to the y-axis.

close all, view (-30,30); grid on

VLFLplot(VL,FL,'r'); % original solid

VLFLplot(VLswapXY(VL),FL,'b'); % turn the x-axis to the y-axis

VLFLplot(VLswapXZ(VL),FL,'m'); % turn the x-axis to the z-axis

VLFLplot(VLswapYZ(VL),FL,'y'); % turn the y-axis to the z-axis

VLFLplot(VLswapZY(VL),FL,'c'); % turn the z-axis to the y-axis

VLFLplot(VLswapZX(VL),FL,'g'); % turn the z-axis to the x-axis

VLFLplot(VLswapYX(VL),FL,'w'); % turn the y-axis to the x-axis

6. Spatial transformation of solids by manipulating the vertex lists (VL)

All solid objects consisting of vertices and facets can be moved and rotated by only manipulating the vertex list (VL). Since the facet list is an index list, the facet list (FL) is not affected by a transformation of the vertex list. The following example generates a cylinder and perform different postion and orientation transformations.

closeall;

VLFLviewer([]);

PL=PLcircle(10); % define a base-contour

[VL,FL]=VLFLofPLz (PL,30); % extrude to a solid volume

VL=VLswapZX (VL); % swap X and X axis

VLFLplot(VL,FL); view (-30,30); grid on; % plot as red cylinder

In detail, there are five basic transformation functions for manipulation a vertex list (VL)

VLtrans0 for translating the solid in the coordiante system origin.
VLtrans1 for translating the solid into quadrant 1.
VLtransP for translating the solid using a translation vector.
VLtransR for rotation the solid using a rotation matrix.
VLtransT for transformating using an homogenous transformation matrix.

In addition to the already existing matlab functions rotx, roty, and rotz, two new functions are useful.

rot for generating a 3x3 rotation matrix for x y z given in rad.
rotdeg for generating a 3x3 rotation matrix for x y z given in degree.

VL=VLtrans0 (VL); % Transformation into the origin (blue)

VLFLplot(VL,FL,'b'); view (-30,30);

VL=VLtrans1 (VL); % Transformation into quadrant 1 (black)

VLFLplot(VL,FL,'k'); view (-30,30);

VL=VLtransP (VL,[0 ;0; 30]); % Transformation upwards 30 mm (yellow)

VLFLplot(VL,FL,'y'); view (-30,30);

VL=VLtransR (VL,rotdeg(0,30,15)); % Rotate 30 degree around y and 15 around z (magenta)

VLFLplot(VL,FL,'m'); view (-30,30);

T=[rotdeg(0,30,15), [20;0;0];[0 0 0 1]] % define a homogenous transformation matrix (green)

T = 4×4

    0.8365   -0.2241    0.5000   20.0000
    0.2588    0.9659         0         0
   -0.4830    0.1294    0.8660         0
         0         0         0    1.0000

VL=VLtransT (VL,T); % Transformation using an HT matrix

VLFLplot(VL,FL,'g'); view (-30,30); grid on;

VLFLplotlight (1,0.9); grid on;

Final remarks on toolbox version and execution date

VLFLlicense
This VLFL-Lib, Rel.  (2019-Jun-11), is for limited non commercial educational use only!
Licensee: Tim Lueth (Development Version)!
Please contact Tim Lueth, Professor at TU Munich, Germany!
WARNING: This VLFL-Lib (Rel. ) license will exceed at 14-Mar-2074 13:49:48!
Executed 11-Jun-2019 13:49:50 by 'timlueth' using Matlab 9.6.0.1114505 (R2019a) Update 2 on a MACI64
======================================== Used Matlab products: ======================================
database_toolbox
image_toolbox
map_toolbox
matlab
robotics_system_toolbox
simmechanics
simscape
simulink
=====================================================================================================

Tim Lueth, tested and compiled on OSX 10.7.5 with Matlab 2014b on 2014-11-19
Tim Lueth, executed and published on 64 Bit PC using Windows with Matlab 2014b on 2014-11-19