By Jose Parrot

v 1.3, October, 21, 2008
v 1.2, October, 11, 2008
v 1.1, October, 10, 2008

Document version 1.0, October, 06, 2008

SOL3d is a solidus modeler and wire-frame renderer.

Introduction

This package was developed to create wire-frame drawings for line plotter output.

Windows version

I decided to port the package to Windows, by using .NET environment to allow execution in Windows xp

and Vista computers. Some improvements were made, as GUI, although maintaining the C style for the math. This new version is under development, and the menus are in English to make it easy to all to participate.

Basic principles

The world is defined by the following convention: positive X axis at your right, positive Z straight ahead and positive Y up.

As an example, the box shows the coordinates, to better demonstrate de coordinates system.

The perspective projection system

The perspective is determined by the intersection of the vectors from each object’s vertices P to the observer OBS with the Projection Plane.

For each point P(x,y,z) there is a projection point P’(Px,Py). The projection is determined in 2D coordinates, in the Projection Plane. The 2D system, at the Projection Plane, has its orign (0,0) in the center of the viewing window.

The center point of the viewing window in the Projection Plane is the intersection of such plane with the vector OBS-VIS. Such vector is perpendicular to the Projection Plane.

DIST is the distance from the observer OBS to the Projection Plane.

In the figures (a) and (b) below it is shown the vector P-OBS and its intersection P’ with the Projection Plane, (a) viewing from positive x axis and (b) viewing from the positive y axis.

Please note the following conventions:

OBS The observer or camera

VIS The point where the observer points to

P The point in 3D space

P’ The projected point in 2D space at the Projection Plane

File formats

.DAT

This file describes the objects (solidus). It uses 16-bit binary numbers, low endian.

N Number of models

(for each model m from 1 to N)

NP Number of points (vertices) of the model

(for each point)

X, y, z coordinates

NL Number of lines

(for each line)

L1, L2 indexes of the vertices of the line

NF Number of faces

(for each face)

NE Number of edges

(for each edge)

E1 …. ENE = indexes of the lines

.OBS

Text file describing the observer (camera) path, zoom, tilt.

N number of points

Xo, Yo, Zo coordinates of the points where the camera passes by

Xv, Yv, Zv coordinates of imaginary point where the camera points to

D distance of the projection plane (zoom effect)

T tilt angle

The program will determine a soft path, by calculating a Bezier like path.

Data structure

The data structure uses a non trivial approach which permits a huge number of objects. Instead of creating a set of objects (arrays arranged as matrices) it creates a single set of 3d points, a single set of lines, a single set of faces and a collection of pointers (arrays arranged as adjacency lists) to those primitives to define the objects. More details on data structure are found in this website.

Main targets

SOL3D project aims finish the porting to Windows, with the following objectives:

• Full functionalities implementation
• Code improvement for faster execution
• Clean code for better maintenance
• Good GUI
• Enhancements like line colors, face painting
• Animation output in AVI
• Documentation
• Interactive modeling
• Import from common 3D formats

The dream

I will be very happy if this simple application would help students to understand the 3D way of thinking, to learn 2D and 3D geometry,

Menus

File menu	Edit menu	Render menu

Dialog screenshots

Main dialog. Points tab	Lines tab	Faces tab

Transform dialog

Wire-frame plotting

Wire-frame plotting, with hidden line removal

A composite model, constructed with 64 primitives.

Source code and binaries

Both DOS C and Windows C++ versions are available to download. Please look at SOL3D package at sourceforge.net.

DOS version

The DOS version is all in Brazilian Portuguese and includes executables.

The code, with the exception of the graphics calls, is full portable to any C compiler, in any DOS, Windows or Linux environments.

The only minor adjusts are in the function argument definition, depending on the compiler and should be as in the below example:

Old C syntax

functionname()

type variable;

{

/* Function code */

}

Current C/C++ syntax

void functionname(type variable) // return type must be declared,

{ // arguments enclosed in parenthesis

// Function code

}

The few graphics functions (to set the graphics mode CGA, VGA and line plot) were developed by my own, in assembler and works well only in DOS machines.

To use it nowadays, we have two choices: call graphics functions available at the operating system API (Xwindow, Xfree, GDI, GDI+) or download a graphics toolkit elsewhere.

As the calls are really very simple, I strongly recommend using the graphics capabilities available in the operating system SDK.

The C source code includes output in HPGL language, thus allowing plot it in any line plotter, like the HP 7475.

You also port it to Java, in such case with a lot of more efforts.

Windows version

The Windows version is all in English and includes executables.

The source code is entirely in Microsoft Visual C++ environment. The code mixes both C and CLR syntaxes, although both are compatible with the complier.

The porting strategy was (1) to maintain as much as possible the original code (as it is very stable) for the core math calculations and for file I/O and (2) to create entirely new code for the GUI, by using the VC IDE resources, at same time providing a good and compatible interface, which works perfectly in both Windows xp and Vista computers.

For that reason, it needs the .NET 2.0 (or newer) run time dlls.