ThanCad

2dimensional cad for engineers

GENERAL

ThanCad is a 2dimensional cad, with raster inclusion capability and emphasis in engineering.
It is being written in Python and since it uses the Tkinter library, it is
platform independent! It will also be easy to translate it to various languages.
ThanCad is published under GPL.

DEVELOPMENT STEPS

The development will proceed with the following steps:

1. Store the drawing elements in memory so they can be accessed fast.
2. Visualize the drawing elements into screen.
3. Get interactive input from the user (mouse click drag, typed commands etc.).
4. Create simple elements and capabilities (points, lines, layers, colors etc.).
5. Implement layers.
6. Design the user interface so that it can easily be translated to various languages
(command line is necessary).
7. Store drawings to disk.
8. Plot drawings to plotters and printers.
9. Export to dxf (easy) and Import from dxf (difficult).
10. Insert raster into drawings.

CURRENT STATUS (September 6, 2008)

I am developing ThanCad in my free time, so the progress is slow. Right now steps 1-7, 9-10 are
ready or partially implemented. The drawing elements are stored in standard python data structures.
Element access is moderately fast for Python!
The GUI is split to 2 components. The first is library independent and deals with abstract windows,
menus etc. The second is library dependent and it implements windows, menus etc. Thus it is easy to
port the GUI to various libraries. Until version 0.0.2 wxPython was used as a library (wxPython is a
wxWindows wrapper). Later versions use Tkinter (Tkinter is the defacto library that comes along
with python). The reason for this change is that wxPython didn't seem, then, to work properly under
Linux. In the future the GUI may be ported to other libraries.
Right now the object snap perpendicular mode is being implemented.

FEATURES

At first be warned that ThanCad is slow because it is written in Python. Do not expect the speed that commercial CAD have. But because it is written in a very flexible high level language, its development is at least 10 times faster. In fact I do not think I would have the patience to make it in C++. I think that 3 features will make ThanCad better -well- than cad:
1. ThanCad is free. It is published under GPL, the GNU General Public License. This means that you don't pay anything for it, you can copy it as many times as you like, you can give it to a friend, and you can use it in your home and in your business. If you are a programmer, you can modify and/or extend ThanCad, or you can base your software on it. But if you intend to publish the modified/extended ThanCad (you may want to sell it), you must give your customers at least the rights that you have with ThanCad. Please see GPL for details.
2. ThanCad is written in python, so it is -at least it should be- platform independent. ThanCad should run unmodified in Windows 98/Me/NT/2000/XP, in Linux, in MACOS, Solaris etc. wherever python runs. I know of some companies that can not switch to Linux, although they have ported all software to Linux, because they depend on a commercially available CAD which runs only in a certain platform. ThanCad will free you to use the OS of your choice. ThanCad is currently being developed in OPEN SuSE Linux 11.0. From time to time I run it under Windows XP. It is sentimental to see the program behave the same way under Linux and Windows, without changing a single line of code!!!
3. ThanCad supports the "layer sublayer" concept. This means that a layer may contain sublayers and the sublayers may contain subsublayers etc. Each layer will have a set of attributes such as color, line type, visibility, draw order, transparency etc., which will be shared by all the elements the layer contains. The sublayers inherit the attributes of their parent by default. But you can overwrite any attribute if you want. For example imagine that you draw your house. Suppose you have a ground floor and a first floor. Naturally you create one layer for each floor. For the first floor you have the walls, the furniture, the various cables, the hydraulics. You can create a separate sublayer with different colors for each category. The same must be done for the ground floor. No problem, just copy the sublayer structure of the layer of the first floor to the layer of the second floor. The colors are already set. If you want to examine the first floor, make the layer of the ground floor invisible and all its sublayers are automatically made invisible too! Suppose you want to change the color of the furniture of the first and the ground floor. Select the common sublayers of the two layers and change the color of the sublayer of the furniture. Then you want to draw a garden. Create a layer "house" and put the layers of the ground and the first floor into it, as sublayers. Make this layer invisible, and you are free to draw the garden. Now try to do all the above with another CAD.

BUGS

- ThanCad is slower in Windows than in Linux. This is probably because Tkinter is slower in Windows than in Linux. Unfortunately newer version of Tkinter have not addressed this problem. Perhaps it is not possible.
- There is also a problem with the graphics in Windows 98 (the window flickers when the
mouse moves – not always. Windows XP does not have this problem.
- The font of the text is built in since Tkinter does not support rotated fonts. This means that standard X-fonts or Windows fonts are not available.
- The zoom all command sometimes does not zoom to the entire drawing. In this case
run regen and retry.
- Many of the objects which contain references to Tkinter widgets are not destroyed
when they are deleted because there are circular references. Spotting the circular references has proved to be difficult. The result is memory leaks.
- Finally I am sure there are many other bugs buried here and there in the code.

DOWNLOADS

ThanCad is usable if you care to save your work frequently. It can read and write dxf files, it can zoom and pan, and it can add lines, circles, points, images etc. interactively. Since layers are partially implemented all lines are continuous. The drawing may have various colors though. The latest code is published in sourceforge, as soon as I find the time to upload it!

IMPROVEMENTS

After the basic program is up and running, the following improvements might be considered:

1. Add new drawing elements (bezier curves, solids etc.).
2. Add utilities (trimming, extending, intersecting, dimensioning etc.).
3. Add raster editing.
4. Implement various algorithms (triangulation, contour lines etc.).
5. Add profession-specific capabilities (for example cross section of a highway,
profile of a conduit, circuit analysis, etc.).
6. Move the code to C and/or Fortran, for faster execution.

HISTORY

- Version 0.0.1 could only store elements in a structure, without graphical User Interface (GUI).
- Version 0.0.2 added a wxPython GUI. Lines, circles, and texts were implemented. Import
from dxf was partially implemented.
- Version 0.0.3 changed to Tkinter GUI. Export to dxf was implemented.
- Version 0.0.4 has better dxf import. Pan, zoom were greatly enhanced. Regenerations now
happen when it is necessary. Some bugs in the open/close commands were fixed. The
beginning of nested layers has been implemented. The quadtree structure was dropped
because the overhead was bigger than the gain in small to medium drawings.
- Version 0.0.5 has raster image support. Select window and select crossing has been
implemented. Layers have 2 working attributes; color and frozen. Creation of a topographic
grid was implemented - for engineers at last :)
The beginning of international translations was done.
Finally the drawing is saved in internal format, using Python's pickle. This overcomes
the deficiencies of dxf format.
- Version 0.0.6 has now a working command line. Object snap is quite implemented;
and it works fast - that was a surprise.
- Version 0.0.7 “Bond” has better and colored command line. The name of the commands
are now more “familiar”. So are the menus.
Another layer attribute, DrawOrder, was implemented which is an integer number; layers
with higher DrawOrder are drawn over the layers with lower DrawOrder.
The selection (or new definition) of layer colors is much better (and finalised).
Object snap now includes EndPoint, MidPoint, Center, Node, Quadrant, Intersection,
tangent, nearest modes; theres is also a nice window for the selection of object snap mode.
Right clicking when no command is running pops a menu with common commands.
Right clicking when zoom rt is active quits zoom and starts pan rt (and vice versa).
Semi-automatic line tracing of a bitmap (b/w) image is partially implemented.
The first steps to the units command were made.
The first unsuccessful steps to the nesting of commands were made.
The rectangle command is a convenience. It draws a closed line shaped as a rectangle.

- Version 0.0.8 “DoSomething” has so many enhancements that it is difficult to remember.
Here are some:
1. Massive changes in move,delete,scale,rotate commands.
2. Old select routines were deleted.
3. Plot (export) to raster image.
F3 toggles OSNAP on/off.
control arrowup/control arrowdown pans the drawing up/down.
control arrowleft/control arrowright pans the drawing left/right.
gray+/gray- zooms in / zooms out.
4. thanlcd font, thantimes font (not finished).
5. Import .shp font file.
6. Command select (element/window/crossing/previous).
7. Command list.
8. Command erase.
9. do/undo mechanism.
do/undo for erase command.
10. Added an option to insert a raster image as follows:
a. The insertion point is at -0.5, -0.5 user units
b. The scale is 1 pixel is 1 user unit.
This is needed for rectification of scanned topographic maps, which
have errors due to contraction of paper and scanner errors.
11. Command move and copy.
12. Zoom in/out can be done with middle wheel of the mouse.
13. Export to PIL has a GUI now (not finalised).
14. Command Rotate was cleaned and decorated with undo/redo functions.
15. Export to PIL image and then print as a workaround to print a drawing.
16. Command Scale was cleaned and decorated with undo/redo functions.
17. ThanCad was presented in EuroPython 2007, Vilnius, Lithuania.
18. Conversion to limited z capability. All elements accept z coordinates. In fact
ThanCad has now n-dimensional support. All adaptations to the code for the
z-coordinate also support arbitrary number of dimensions. Physicists this
CAD is for you!
19. New status bar supports view of pixel coordinates when the cursor is over
raster images. Toggle between world/pixel coordinates with F7.
20. Beginnings of GIS support (see educational menu).
21. Internal support for embedding other applications into ThanCad (for developers).

AUTHORS

Thanasis Stamos
----Residence: Athens, Greece, Europe.
----E-mail: cyberthanasis@excite.com

PAPERS ABOUT THANCAD (directly or indirectly)

1. ThanCad was presented in the EuroPython conference held in Vilnious, Lithuania, July 9-11, 2007.
The presentation is here.
2. The Binary Spatial Partitioning Tree data structure, which is used by ThanCad, was presented in The Sixth International Conference on Engineering Computational Technology, Athens, Greece, 2-5 September, 2008. 
The presentation is here

PROJECTS WHICH USE THANCAD (directly or indirectly)

ThanCad is used for commercial purposes!
- www.ktim.gr They use ThanCad to create private cadastre maps.

Last Updated: September 6, 2008