1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
|
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<title>libQGLViewer screenCoordSystem example</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<link href="../qglviewer.css" rel="stylesheet" type="text/css" />
<link rel="shortcut icon" href="../images/qglviewer.ico" type="image/x-icon" />
<link rel="icon" href="../images/qglviewer.icon.png" type="image/png" />
<script type="text/javascript">
var _gaq = _gaq || [];
_gaq.push(['_setAccount', 'UA-23223012-2']);
_gaq.push(['_trackPageview']);
(function() {
var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true;
ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js';
var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s);
})();
</script>
</head>
<body>
<div class="banner">
<a class="qindex" href="../index.html">Home</a>
<a class="qindex" href="../download.html">Download</a>
<a class="qindex highlight" href="index.html">Gallery</a>
<a class="qindex" href="../refManual/hierarchy.html">Documentation</a>
<a class="qindex" href="../developer.html">Developer</a>
</div>
<h1>The screenCoordSystem example</h1>
<center>
<img src="../images/screenCoordSystem.jpg" width="330" height="228" alt="screenCoordSystem"/>
</center>
<p>
A saucers control viewer that illustrates the screen coordinate system feature.
</p>
<p>
Use <code>startScreenCoordinatesSystem()</code> and <code>stopScreenCoordinatesSystem()</code> to
set this mode. Once this mode has been activated in <code>draw()</code>, the X,Y coordinates
correspond to the pixel units (origin in the lower left corner). Combined with the
<code>camera()->projectedCoordinatesOf()</code>, this feature enable the mix of 2D and 3D drawing.
</p>
<p>
In this example, the arrows that designate the saucers seem to be attached to the object. Of
course, such 2D drawing could have been computed in 3D, but this implies complex geometric
computations to make the arrow always face the camera and this method is much simpler.
</p>
<p>
Since we use gluCylinder
</p>
<h2>screenCoordSystem.h</h2>
<pre>
#include <QGLViewer/qglviewer.h>
#include <qcolor.h>
class Viewer : public QGLViewer {
protected:
virtual void init();
virtual void draw();
virtual QString helpString() const;
private:
void drawSaucer() const;
static const int nbSaucers = 10;
qglviewer::Frame saucerPos[nbSaucers];
QColor saucerColor[nbSaucers];
};
</pre>
<h2>screenCoordSystem.cpp</h2>
<pre>
#include "screenCoordSystem.h"
#include <stdio.h>
#include <stdlib.h> // RAND_MAX
using namespace qglviewer;
using namespace std;
void Viewer::init() {
for (int i = 0; i < nbSaucers; i++) {
Vec pos;
pos.x = rand() / static_cast<float>(RAND_MAX) - 0.5;
pos.y = rand() / static_cast<float>(RAND_MAX) - 0.5;
pos.z = rand() / static_cast<float>(RAND_MAX) - 0.5;
Quaternion ori(Vec(static_cast<float>(rand()) / RAND_MAX,
static_cast<float>(rand()) / RAND_MAX,
static_cast<float>(rand()) / RAND_MAX),
rand() / static_cast<float>(RAND_MAX) * M_PI);
saucerPos[i].setPosition(pos);
saucerPos[i].setOrientation(ori);
saucerColor[i].setRgb(int(255.0 * rand() / static_cast<float>(RAND_MAX)),
int(255.0 * rand() / static_cast<float>(RAND_MAX)),
int(255.0 * rand() / static_cast<float>(RAND_MAX)));
}
restoreStateFromFile();
help();
}
QString Viewer::helpString() const {
QString text("<h2>S c r e e n C o o r d S y s t e m</h2>");
text += "This example illustrates the <i>startScreenCoordinatesSystem()</i> "
"function ";
text += "which enables a GL drawing directly into the screen coordinate "
"system.<br><br>";
text += "The arrows are drawned using this method. The screen projection "
"coordinates ";
text += "of the objects is determined using "
"<code>camera()->projectedCoordinatesOf()</code>, ";
text += "thus <i>attaching</i> the 2D arrows to 3D objects.";
return text;
}
void Viewer::drawSaucer() const {
static GLUquadric *quadric = gluNewQuadric();
glTranslatef(0.0, 0.0, -0.014f);
gluCylinder(quadric, 0.015, 0.03, 0.004, 32, 1);
glTranslatef(0.0, 0.0, 0.004f);
gluCylinder(quadric, 0.03, 0.04, 0.01, 32, 1);
glTranslatef(0.0, 0.0, 0.01f);
gluCylinder(quadric, 0.05, 0.03, 0.02, 32, 1);
glTranslatef(0.0, 0.0, 0.02f);
gluCylinder(quadric, 0.03, 0.0, 0.003, 32, 1);
glTranslatef(0.0, 0.0, -0.02f);
}
void Viewer::draw() {
static Vec proj[nbSaucers];
int i;
// Draw 3D flying saucers
for (i = 0; i < nbSaucers; i++) {
glPushMatrix();
glMultMatrixd(saucerPos[i].matrix());
glColor4f(saucerColor[i].redF(), saucerColor[i].greenF(),
saucerColor[i].blueF(), saucerColor[i].alphaF());
drawSaucer();
glPopMatrix();
}
// Draw the arrows
glColor4f(foregroundColor().redF(), foregroundColor().greenF(),
foregroundColor().blueF(), foregroundColor().alphaF());
startScreenCoordinatesSystem();
for (i = 0; i < nbSaucers; i++) {
glBegin(GL_POLYGON);
proj[i] = camera()->projectedCoordinatesOf(saucerPos[i].position());
// The small z offset makes the arrow slightly above the saucer, so that it
// is always visible
glVertex3fv(proj[i] + Vec(-55, 0, -0.001f));
glVertex3fv(proj[i] + Vec(-17, -5, -0.001f));
glVertex3fv(proj[i] + Vec(-5, 0, -0.001f));
glVertex3fv(proj[i] + Vec(-17, 5, -0.001f));
glEnd();
}
stopScreenCoordinatesSystem();
// Draw text id
glDisable(GL_LIGHTING);
for (i = 0; i < nbSaucers; i++)
drawText(int(proj[i].x) - 62, int(proj[i].y) + 4, QString::number(i));
glEnable(GL_LIGHTING);
}
</pre>
<h2>main.cpp</h2>
<pre>
#include "screenCoordSystem.h"
#include <qapplication.h>
int main(int argc, char **argv) {
QApplication application(argc, argv);
Viewer viewer;
viewer.setWindowTitle("screenCoordSystem");
viewer.show();
return application.exec();
}
</pre>
<p>
Back to the <a href="index.html">examples main page</a>.
</p>
</body>
</html>
|
