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1<HTML>
2<TITLE>Polylines, Markers and Text</title>
3<HEAD>
4</HEAD>
5<BODY>
6
7<TABLE WIDTH="100%" >
8<TR>
9<TD>
10</A>
11<A HREF="index.html">
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17</TD>
18
19<TD ALIGN="Right"><FONT COLOR="#238E23"><FONT SIZE=-1>
20<B>Geant4 User's Guide</B> <BR>
21<B>For Application Developers</B> <BR>
22<B>Visualization</B> </FONT></FONT> </TD>
23</TR>
24</TABLE>
25
26<CENTER><FONT COLOR="#238E23"><FONT SIZE=+3>
27<b>8.9 Polylines, Markers and Text</b><BR>
28</FONT></FONT></CENTER>
29<BR>
30
31<HR ALIGN="Center" SIZE="7%"><BR>
32
33<!-- ============================================== Section -->
34
35 Polylines, markers and text are defined in the <tt>graphics_reps</tt> category,
36 and are used only for visualization. Here we explain their definitions and usages.
37
38<h4>8.9.1 Polylines</h4>
39
40 A polyline is a set of successive line segments. It is defined with
41 a class <i>G4Polyline</i> defined in the <tt>graphics_reps</tt> category. A polyline
42 is used to visualize tracking steps, particle trajectories, coordinate
43 axes, and any other user-defined objects made of line segments.
44<P>
45 <i>G4Polyline</i> is defined as a list of <i>G4Point3D</i> objects, i.e., 
46 vertex positions. 
47 The vertex positions are set to a <i>G4Polyline</i> 
48 object with the <tt>push_back()</tt> method.
49 <P>
50 For example, an x-axis with length 5 cm and with red color is defined
51 in Source listing 8.9.1.
52<P>
53<center>
54<table border=2 cellpadding=10>
55<tr>
56<td>
57<PRE>
58 //----- C++ source codes: An example of defining a line segment
59// Instantiate an emply polyline object
60G4Polyline  x_axis;
61
62// Set red line colour
63G4Colour         red(1.0, 0.0, 0.0);
64G4VisAttributes  att(red);     
65x_axis.SetVisAttributes(&att);
66
67// Set vertex positions
68x_axis.push_back( G4Point3D(0., 0., 0.) );
69x_axis.push_back( G4Point3D(5.*cm, 0., 0.) );
70
71 //----- end of C++ source codes
72</PRE>
73</td>
74</tr>
75<tr>
76<td align=center>
77 Source listing 8.9.1<BR>
78 Defining an x-axis with length 5 cm and with colour red.
79</td>
80</tr>
81</table></center>
82<P>
83
84<h4>8.9.2 Markers</h4>
85
86 Here we explain how to use 3D markers in Geant4 Visualization.
87<p>
88<B>What are Markers?</B>
89<p>
90 Markers set marks at arbitrary positions in the 3D space. They are often
91 used to visualize hits of particles at detector components. A marker is
92 a 2-dimensional primitive with shape (square, circle, etc), color, and
93 special properties (a) of always facing the camera and (b) of having the
94 possibility of a size defined in screen units (pixels). Here "size" means
95 "overall size", e.g., diameter of circle and side of square (but diameter
96 and radius access functions are defined to avoid ambiguity).
97<P>
98 So the user who constructs a marker should decide whether or not it
99 should be visualized to a given size in world coordinates by setting the
100 world size. Alternatively, the user can set the screen size and the marker
101 is visualized to its screen size. Finally, the user may decide not to set
102 any size; in that case, it is drawn according to the sizes specified in
103 the default marker specified in the class <i>G4ViewParameters</i>.
104<P>
105 By default, "square" and "circle" are supported in Geant4 Visualization.
106 The former is described with class <i>G4Square</i>, and the latter with class
107 <i>G4Circle</i>:
108<p>
109<CENTER><TABLE BORDER=2 cellpadding=10>
110 <TR>
111 <TD><B>Marker Type</B></TD>
112 <TD><B>Class Name</B></TD>
113 </TR>
114 <TR>
115 <TD>circle</TD>
116 <TD><i>G4Circle</i></TD>
117 </TR>
118 <TR>
119 <TD>right square</TD>
120 <TD><i>G4Square</i></TD>
121 </TR>
122</TABLE></CENTER>
123<p>
124 These classes are inherited from class <i>G4VMarker</i>. They have constructors
125 as follows:
126<PRE>
127      //----- Constructors of G4Circle and G4Square
128      G4Circle::G4Circle (const G4Point3D&amp; pos );
129      G4Square::G4Square (const G4Point3D&amp; pos);
130</PRE>
131 Access functions of class <i>G4VMarker</i> are summarized below.
132<p>
133<b>Access functions of markers</B>
134<P>
135 Source listing 8.9.2 shows the access functions inherited from the base class <i>G4VMarker</i>.
136<P>
137<center>
138<table border=2 cellpadding=10>
139<tr>
140<td>
141<PRE>
142 //----- Set functions of G4VMarker
143 void G4VMarker::SetPosition( const G4Point3D&amp; );
144 void G4VMarker::SetWorldSize( G4double );
145 void G4VMarker::SetWorldDiameter( G4double );
146 void G4VMarker::SetWorldRadius( G4double );
147 void G4VMarker::SetScreenSize( G4double );
148 void G4VMarker::SetScreenDiameter( G4double );
149 void G4VMarker::SetScreenRadius( G4double );
150 void G4VMarker::SetFillStyle( FillStyle );
151 // Note: enum G4VMarker::FillStyle {noFill, hashed, filled};
152
153 //----- Get functions of G4VMarker
154 G4Point3D G4VMarker::GetPosition () const;
155 G4double G4VMarker::GetWorldSize () const;
156 G4double G4VMarker::GetWorldDiameter () const;
157 G4double G4VMarker::GetWorldRadius () const;
158 G4double G4VMarker::GetScreenSize () const;
159 G4double G4VMarker::GetScreenDiameter () const;
160 G4double G4VMarker::GetScreenRadius () const;
161 FillStyle G4VMarker::GetFillStyle () const;
162 // Note: enum G4VMarker::FillStyle {noFill, hashed, filled};
163</PRE>
164</td>
165</tr>
166<tr>
167<td align=center>
168 Source listing 8.9.2<BR>
169 The access functions inherited from the base class <i>G4VMarker</i>.
170</td>
171</tr>
172</table></center>
173<P>
174 Source listing 8.9.3 shows sample C++ source code to define a very small red circle,
175 i.e., a dot with diameter 1.0 pixel. Such a dot is often used to visualize
176 a hit.
177<P>
178<center>
179<table border=2 cellpadding=10>
180<tr>
181<td>
182<PRE>
183 //----- C++ source codes: An example of defining a red small maker
184 G4Circle circle(position); // Instantiate a circle with its 3D
185                            // position. The argument "position"
186                            // is defined as G4Point3D instance
187 circle.SetScreenDiameter (1.0); // Should be circle.SetScreenDiameter
188                                 //  (1.0 * pixels) - to be implemented
189 circle.SetFillStyle (G4Circle::filled); // Make it a filled circle
190 G4Colour colour(1.,0.,0.);              // Define red color
191 G4VisAttributes attribs(colour);        // Define a red visualization attribute
192 circle.SetVisAttributes(attribs);       // Assign the red attribute to the circle
193 //----- end of C++ source codes
194</PRE>
195</td>
196</tr>
197<tr>
198<td align=center>
199 Source listing 8.9.3<BR>
200 Sample C++ source code to define a very small red circle.
201</td>
202</tr>
203</table></center>
204<P>
205
206<h4>8.9.3 Text</h4>
207
208 Text, i.e., a character string, is used to visualize various kinds of description,
209 particle name, energy, coordinate names etc. Text is described by the class
210 <i>G4Text</i> . The following constructors are supported:
211<PRE>
212     //----- Constructors of G4Text
213     G4Text (const G4String&amp; text);
214     G4Text (const G4String&amp; text, const G4Point3D&amp; pos);
215</PRE>
216
217 where the argument <tt>text</tt> is the text (string) to be visualized, and <tt>pos</tt> 
218 is the 3D position at which the text is visualized.
219<P>
220 Note that class <i>G4Text</i> also inherits <i>G4VMarker</i>. Size of text is recognized
221 as "font size", i.e., height of the text. All the access functions defined
222 for class <i>G4VMarker</i> mentioned above are available. In addition, the following
223 access functions are available, too:
224<PRE>
225     //----- Set functions of G4Text
226     void G4Text::SetText ( const G4String&amp; text ) ;
227     void G4Text::SetOffset ( double dx, double dy ) ;
228
229     //----- Get functions of G4Text
230     G4String G4Text::GetText () const;
231     G4double G4Text::GetXOffset () const;
232     G4double G4Text::GetYOffset () const;
233</PRE>
234
235 Method <tt>SetText()</tt> defines text to be visualized, and <tt>GetText()</tt> returns the
236 defined text. Method <tt>SetOffset()</tt> defines x (horizontal) and y (vertical)
237 offsets in the screen coordinates. By default, both offsets are zero, and
238 the text starts from the 3D position given to the constructor or to the
239 method <tt>G4VMarker:SetPosition()</tt>. Offsets should be given with the same units
240 as the one adopted for the size, i.e., world-size or screen-size units.
241<P>
242 Source listing 8.9.4 shows sample C++ source code to define text with the following properties:
243
244 <UL>
245  <LI>Text: "Welcome to Geant4 Visualization"</LI>
246  <LI>Position: (0.,0.,0.) in the world coordinates</LI>
247  <LI>Horizontal offset: 10 pixels</LI>
248  <LI>Vertical offset: -20 pixels</LI>
249  <LI>Colour: blue (default)</LI>
250 </UL>
251
252<P>
253<center>
254<table border=2 cellpadding=10>
255<tr>
256<td>
257<PRE>
258 //----- C++ source codes: An example of defining a visualizable text
259
260 //----- Instantiation
261 G4Text text ;
262 text.SetText ( "Welcome to Geant4 Visualization");
263 text.SetPosition ( G4Point3D(0.,0.,0.) );
264 // These three lines are equivalent to:
265 //  G4Text text ( "Welcome to Geant4 Visualization",
266 //                 G4Point3D(0.,0.,0.) );
267
268 //----- Size (font size in units of pixels)
269 G4double fontsize = 24.; // Should be 24. * pixels - to be implemented.
270 text.SetScreenSize ( fontsize );
271
272 //----- Offsets
273 G4double x_offset = 10.; // Should be 10. * pixels - to be implemented.
274 G4double y_offset = -20.; // Should be -20. * pixels - to be implemented.
275 text.SetOffset( x_offset, y_offset );
276
277 //----- Color (Blue is the default setting, and so the codes below are omissible)
278 G4Colour blue( 0., 0., 1. );
279 G4VisAttributes att ( blue );
280 text.SetVisAttributes ( att );
281
282 //----- end of C++ source codes
283</PRE>
284</td>
285</tr>
286<tr>
287<td align=center>
288 Source listing 8.9.4<BR>
289 An example of defining text.
290</td>
291</tr>
292</table></center>
293<P>
294
295<HR>
296  <A HREF="makingamovie.html">Next section</A><BR>
297  <A HREF="index.html">Back to contents</A>
298
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