1 | /* -*- mode: c++; c-basic-offset: 4; indent-tabs-mode: nil -*- */ |
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2 | /* |
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3 | * ---------------------------------------------------------------------- |
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4 | * ConvexPolygon.cpp: convex polygon class |
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5 | * |
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6 | * ====================================================================== |
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7 | * AUTHOR: Wei Qiao <qiaow@purdue.edu> |
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8 | * Purdue Rendering and Perceptualization Lab (PURPL) |
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9 | * |
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10 | * Copyright (c) 2004-2006 Purdue Research Foundation |
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11 | * |
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12 | * See the file "license.terms" for information on usage and |
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13 | * redistribution of this file, and for a DISCLAIMER OF ALL WARRANTIES. |
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14 | * ====================================================================== |
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15 | */ |
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16 | #include <assert.h> |
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17 | |
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18 | #include <GL/glew.h> |
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19 | |
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20 | #include "ConvexPolygon.h" |
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21 | #include "Trace.h" |
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22 | |
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23 | ConvexPolygon::ConvexPolygon(VertexVector newvertices) |
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24 | { |
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25 | vertices.insert(vertices.begin(), newvertices.begin(), newvertices.end()); |
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26 | } |
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27 | |
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28 | // Finds the intersection of the line through |
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29 | // p1 and p2 with the given plane, putting the |
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30 | // result in intersect. |
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31 | // |
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32 | // If the line lies in the plane, an arbitrary |
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33 | // point on the line is returned. |
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34 | // |
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35 | // http://astronomy.swin.edu.au/pbourke/geometry/planeline/ |
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36 | bool |
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37 | findIntersection(const Vector4& pt1, const Vector4& pt2, const Vector4& plane, Vector4& ret) |
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38 | { |
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39 | float a = plane.x; |
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40 | float b = plane.y; |
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41 | float c = plane.z; |
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42 | float d = plane.w; |
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43 | |
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44 | Vector4 p1 = pt1; |
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45 | p1.perspective_divide(); |
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46 | float x1 = p1.x; |
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47 | float y1 = p1.y; |
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48 | float z1 = p1.z; |
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49 | |
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50 | Vector4 p2 = pt2; |
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51 | p2.perspective_divide(); |
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52 | float x2 = p2.x; |
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53 | float y2 = p2.y; |
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54 | float z2 = p2.z; |
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55 | |
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56 | float uDenom = a * (x1 - x2) + b * (y1 - y2) + c * (z1 - z2); |
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57 | float uNumer = a * x1 + b * y1 + c * z1 + d; |
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58 | |
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59 | if (uDenom == 0){ |
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60 | //plane parallel to line |
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61 | ERROR("Unexpected code path: ConvexPolygon.cpp\n"); |
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62 | if (uNumer == 0){ |
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63 | ret = p1; |
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64 | return true; |
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65 | } |
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66 | return false; |
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67 | } |
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68 | |
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69 | float u = uNumer / uDenom; |
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70 | ret.x = x1 + u * (x2 - x1); |
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71 | ret.y = y1 + u * (y2 - y1); |
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72 | ret.z = z1 + u * (z2 - z1); |
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73 | ret.w = 1; |
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74 | return true; |
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75 | } |
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76 | |
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77 | void |
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78 | ConvexPolygon::transform(const Mat4x4& mat) |
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79 | { |
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80 | VertexVector tmp = vertices; |
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81 | vertices.clear(); |
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82 | |
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83 | for (unsigned int i = 0; i < tmp.size(); i++) { |
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84 | Vector4 vec = tmp[i]; |
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85 | vertices.push_back(mat.transform(vec)); |
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86 | } |
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87 | } |
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88 | |
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89 | void |
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90 | ConvexPolygon::translate(const Vector4& shift) |
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91 | { |
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92 | VertexVector tmp = vertices; |
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93 | vertices.clear(); |
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94 | |
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95 | for (unsigned int i = 0; i < tmp.size(); i++) { |
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96 | Vector4 vec = tmp[i]; |
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97 | vertices.push_back(vec+shift); |
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98 | } |
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99 | } |
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100 | |
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101 | void |
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102 | ConvexPolygon::clip(Plane& clipPlane, bool copy_to_texcoord) |
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103 | { |
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104 | if (vertices.size() == 0) { |
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105 | //ERROR("ConvexPolygon: polygon has no vertices\n"); |
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106 | return; |
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107 | } |
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108 | |
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109 | VertexVector clippedVerts; |
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110 | clippedVerts.reserve(2 * vertices.size()); |
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111 | |
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112 | // The algorithm is as follows: for each vertex |
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113 | // in the current poly, check to see which |
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114 | // half space it is in: clipped or retained. |
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115 | // If the previous vertex was in the other |
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116 | // half space, find the intersect of that edge |
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117 | // with the clip plane and add that intersect |
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118 | // point to the new list of vertices. If the |
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119 | // current vertex is in the retained half-space, |
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120 | // add it to the new list as well. |
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121 | |
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122 | Vector4 intersect; |
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123 | Vector4 plane = clipPlane.get_coeffs(); |
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124 | |
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125 | bool prevRetained = is_retained(vertices[0], plane); |
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126 | if (prevRetained) |
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127 | clippedVerts.push_back(vertices[0]); |
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128 | |
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129 | for (unsigned int i = 1; i < vertices.size(); i++) { |
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130 | bool retained = is_retained(vertices[i], plane); |
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131 | if (retained != prevRetained) { |
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132 | bool found = findIntersection(vertices[i - 1], vertices[i], |
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133 | plane, intersect); |
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134 | assert(found); |
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135 | clippedVerts.push_back(intersect); |
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136 | } |
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137 | if (retained) { |
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138 | clippedVerts.push_back(vertices[i]); |
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139 | } |
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140 | prevRetained = retained; |
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141 | } |
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142 | |
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143 | bool retained = is_retained(vertices[0], plane); |
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144 | if (retained != prevRetained) { |
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145 | bool found = findIntersection(vertices[vertices.size() - 1], |
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146 | vertices[0], plane, intersect); |
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147 | assert(found); |
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148 | clippedVerts.push_back(intersect); |
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149 | } |
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150 | |
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151 | vertices.clear(); |
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152 | vertices.insert(vertices.begin(), |
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153 | clippedVerts.begin(), |
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154 | clippedVerts.end()); |
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155 | |
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156 | if (copy_to_texcoord) |
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157 | copy_vertices_to_texcoords(); |
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158 | } |
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159 | |
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160 | void |
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161 | ConvexPolygon::copy_vertices_to_texcoords() |
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162 | { |
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163 | if (texcoords.size() > 0) |
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164 | texcoords.clear(); |
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165 | |
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166 | for (unsigned int i = 0; i < vertices.size(); i++) { |
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167 | texcoords.push_back(vertices[i]); |
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168 | } |
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169 | } |
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170 | |
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171 | void |
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172 | ConvexPolygon::Emit(bool use_texture) |
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173 | { |
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174 | if (vertices.size() >= 3) { |
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175 | for (unsigned int i = 0; i < vertices.size(); i++) { |
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176 | if(use_texture) { |
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177 | glTexCoord4fv((float *)&(texcoords[i])); |
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178 | //glTexCoord4fv((float *)&(vertices[i])); |
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179 | } |
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180 | glVertex4fv((float *)&(vertices[i])); |
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181 | } |
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182 | } |
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183 | } |
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184 | |
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185 | void |
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186 | ConvexPolygon::Emit(bool use_texture, const Vector3& shift, const Vector3& scale) |
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187 | { |
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188 | if (vertices.size() >= 3) { |
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189 | for (unsigned int i = 0; i < vertices.size(); i++) { |
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190 | if (use_texture) { |
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191 | glTexCoord4fv((float *)&(vertices[i])); |
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192 | } |
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193 | Vector4 tmp = (vertices[i]); |
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194 | Vector4 shift_4d = Vector4(shift.x, shift.y, shift.z, 0); |
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195 | tmp = tmp + shift_4d; |
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196 | tmp.x = tmp.x * scale.x; |
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197 | tmp.y = tmp.y * scale.y; |
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198 | tmp.z = tmp.z * scale.z; |
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199 | glVertex4fv((float *)(&tmp)); |
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200 | } |
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201 | } |
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202 | } |
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