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