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16
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1
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2 // written in the D programming language
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3
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4 module samples.Joints;
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5
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6 import chipmunkd.chipmunk;
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7
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8 import samples.ChipmunkDemo;
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9
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10 import std.math;
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11
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12 static cpSpace *space;
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13
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14 enum M_PI = PI;
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15 enum M_PI_2 = PI*0.5f;
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16
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17 static cpBody *
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18 addBall(cpVect pos, cpVect boxOffset)
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19 {
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20 cpFloat radius = 15.0f;
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21 cpFloat mass = 1.0f;
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22 cpBody *_body = cpSpaceAddBody(space, cpBodyNew(mass, cpMomentForCircle(mass, 0.0f, radius, cpvzero)));
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23 _body.p = cpvadd(pos, boxOffset);
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24
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25 cpShape *shape = cpSpaceAddShape(space, cpCircleShapeNew(_body, radius, cpvzero));
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26 shape.e = 0.0f; shape.u = 0.7f;
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27
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28 return _body;
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29 }
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30
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31 static cpBody *
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32 addLever(cpVect pos, cpVect boxOffset)
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33 {
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34 cpFloat mass = 1.0f;
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35 cpVect a = cpv(0, 15);
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36 cpVect b = cpv(0, -15);
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37
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38 cpBody *_body = cpSpaceAddBody(space, cpBodyNew(mass, cpMomentForSegment(mass, a, b)));
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39 _body.p = cpvadd(pos, cpvadd(boxOffset, cpv(0, -15)));
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40
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41 cpShape *shape = cpSpaceAddShape(space, cpSegmentShapeNew(_body, a, b, 5.0f));
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42 shape.e = 0.0f; shape.u = 0.7f;
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43
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44 return _body;
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45 }
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46
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47 static cpBody *
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48 addBar(cpVect pos, cpVect boxOffset)
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49 {
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50 cpFloat mass = 2.0f;
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51 cpVect a = cpv(0, 30);
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52 cpVect b = cpv(0, -30);
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53
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54 cpBody *_body = cpSpaceAddBody(space, cpBodyNew(mass, cpMomentForSegment(mass, a, b)));
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55 _body.p = cpvadd(pos, boxOffset);
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56
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57 cpShape *shape = cpSpaceAddShape(space, cpSegmentShapeNew(_body, a, b, 5.0f));
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58 shape.e = 0.0f; shape.u = 0.7f;
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59
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60 return _body;
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61 }
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62
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63 static cpBody *
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64 addWheel(cpVect pos, cpVect boxOffset)
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65 {
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66 cpFloat radius = 15.0f;
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67 cpFloat mass = 1.0f;
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68 cpBody *_body = cpSpaceAddBody(space, cpBodyNew(mass, cpMomentForCircle(mass, 0.0f, radius, cpvzero)));
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69 _body.p = cpvadd(pos, boxOffset);
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70
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71 cpShape *shape = cpSpaceAddShape(space, cpCircleShapeNew(_body, radius, cpvzero));
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72 shape.e = 0.0f; shape.u = 0.7f;
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73 shape.group = 1; // use a group to keep the car parts from colliding
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74
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75 return _body;
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76 }
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77
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78 static cpBody *
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79 addChassis(cpVect pos, cpVect boxOffset)
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80 {
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81 int num = 4;
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82 cpVect verts[] = [
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83 cpv(-40,-15),
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84 cpv(-40, 15),
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85 cpv( 40, 15),
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86 cpv( 40,-15),
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87 ];
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88
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89
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90 cpFloat mass = 5.0f;
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91 cpBody *_body = cpSpaceAddBody(space, cpBodyNew(mass, cpMomentForPoly(mass, num, verts.ptr, cpvzero)));
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92 _body.p = cpvadd(pos, boxOffset);
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93
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94 cpShape *shape = cpSpaceAddShape(space, cpPolyShapeNew(_body, num, verts.ptr, cpvzero));
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95 shape.e = 0.0f; shape.u = 0.7f;
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96 shape.group = 1; // use a group to keep the car parts from colliding
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97
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98 return _body;
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99 }
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100
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101 static cpSpace *
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102 init()
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103 {
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104 space = cpSpaceNew();
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105 space.iterations = 10;
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106 space.gravity = cpv(0, -100);
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107 space.sleepTimeThreshold = 0.5f;
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108
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109 cpBody *staticBody = &space.staticBody;
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110 cpShape *shape;
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111
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112 shape = cpSpaceAddShape(space, cpSegmentShapeNew(staticBody, cpv(-320,240), cpv(320,240), 0.0f));
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113 shape.e = 1.0f; shape.u = 1.0f;
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114 shape.layers = NOT_GRABABLE_MASK;
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115
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116 shape = cpSpaceAddShape(space, cpSegmentShapeNew(staticBody, cpv(-320,120), cpv(320,120), 0.0f));
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117 shape.e = 1.0f; shape.u = 1.0f;
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118 shape.layers = NOT_GRABABLE_MASK;
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119
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120 shape = cpSpaceAddShape(space, cpSegmentShapeNew(staticBody, cpv(-320,0), cpv(320,0), 0.0f));
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121 shape.e = 1.0f; shape.u = 1.0f;
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122 shape.layers = NOT_GRABABLE_MASK;
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123
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124 shape = cpSpaceAddShape(space, cpSegmentShapeNew(staticBody, cpv(-320,-120), cpv(320,-120), 0.0f));
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125 shape.e = 1.0f; shape.u = 1.0f;
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126 shape.layers = NOT_GRABABLE_MASK;
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127
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128 shape = cpSpaceAddShape(space, cpSegmentShapeNew(staticBody, cpv(-320,-240), cpv(320,-240), 0.0f));
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129 shape.e = 1.0f; shape.u = 1.0f;
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130 shape.layers = NOT_GRABABLE_MASK;
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131
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132
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133 shape = cpSpaceAddShape(space, cpSegmentShapeNew(staticBody, cpv(-320,-240), cpv(-320,240), 0.0f));
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134 shape.e = 1.0f; shape.u = 1.0f;
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135 shape.layers = NOT_GRABABLE_MASK;
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136
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137 shape = cpSpaceAddShape(space, cpSegmentShapeNew(staticBody, cpv(-160,-240), cpv(-160,240), 0.0f));
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138 shape.e = 1.0f; shape.u = 1.0f;
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139 shape.layers = NOT_GRABABLE_MASK;
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140
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141 shape = cpSpaceAddShape(space, cpSegmentShapeNew(staticBody, cpv(0,-240), cpv(0,240), 0.0f));
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142 shape.e = 1.0f; shape.u = 1.0f;
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143 shape.layers = NOT_GRABABLE_MASK;
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144
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145 shape = cpSpaceAddShape(space, cpSegmentShapeNew(staticBody, cpv(160,-240), cpv(160,240), 0.0f));
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146 shape.e = 1.0f; shape.u = 1.0f;
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147 shape.layers = NOT_GRABABLE_MASK;
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148
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149 shape = cpSpaceAddShape(space, cpSegmentShapeNew(staticBody, cpv(320,-240), cpv(320,240), 0.0f));
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150 shape.e = 1.0f; shape.u = 1.0f;
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151 shape.layers = NOT_GRABABLE_MASK;
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152
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153 cpVect boxOffset;
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154 cpBody *body1;
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155 cpBody *body2;
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156
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157 cpVect posA = cpv( 50, 60);
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158 cpVect posB = cpv(110, 60);
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159
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160 // Pin Joints - Link shapes with a solid bar or pin.
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161 // Keeps the anchor points the same distance apart from when the joint was created.
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162 boxOffset = cpv(-320, -240);
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163 body1 = addBall(posA, boxOffset);
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164 body2 = addBall(posB, boxOffset);
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165 cpSpaceAddConstraint(space, cpPinJointNew(body1, body2, cpv(15,0), cpv(-15,0)));
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166
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167 // Slide Joints - Like pin joints but with a min/max distance.
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168 // Can be used for a cheap approximation of a rope.
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169 boxOffset = cpv(-160, -240);
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170 body1 = addBall(posA, boxOffset);
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171 body2 = addBall(posB, boxOffset);
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172 cpSpaceAddConstraint(space, cpSlideJointNew(body1, body2, cpv(15,0), cpv(-15,0), 20.0f, 40.0f));
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173
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174 // Pivot Joints - Holds the two anchor points together. Like a swivel.
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175 boxOffset = cpv(0, -240);
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176 body1 = addBall(posA, boxOffset);
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177 body2 = addBall(posB, boxOffset);
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178 cpSpaceAddConstraint(space, cpPivotJointNew(body1, body2, cpvadd(boxOffset, cpv(80,60))));
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179 // cpPivotJointNew() takes it's anchor parameter in world coordinates. The anchors are calculated from that
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180 // cpPivotJointNew2() lets you specify the two anchor points explicitly
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181
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182 // Groove Joints - Like a pivot joint, but one of the anchors is a line segment that the pivot can slide in
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183 boxOffset = cpv(160, -240);
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184 body1 = addBall(posA, boxOffset);
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185 body2 = addBall(posB, boxOffset);
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186 cpSpaceAddConstraint(space, cpGrooveJointNew(body1, body2, cpv(30,30), cpv(30,-30), cpv(-30,0)));
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187
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188 // Damped Springs
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189 boxOffset = cpv(-320, -120);
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190 body1 = addBall(posA, boxOffset);
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191 body2 = addBall(posB, boxOffset);
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192 cpSpaceAddConstraint(space, cpDampedSpringNew(body1, body2, cpv(15,0), cpv(-15,0), 20.0f, 5.0f, 0.3f));
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193
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194 // Damped Rotary Springs
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195 boxOffset = cpv(-160, -120);
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196 body1 = addBar(posA, boxOffset);
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197 body2 = addBar(posB, boxOffset);
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198 // Add some pin joints to hold the circles in place.
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199 cpSpaceAddConstraint(space, cpPivotJointNew(body1, staticBody, cpvadd(boxOffset, posA)));
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200 cpSpaceAddConstraint(space, cpPivotJointNew(body2, staticBody, cpvadd(boxOffset, posB)));
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201 cpSpaceAddConstraint(space, cpDampedRotarySpringNew(body1, body2, 0.0f, 3000.0f, 60.0f));
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202
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203 // Rotary Limit Joint
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204 boxOffset = cpv(0, -120);
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205 body1 = addLever(posA, boxOffset);
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206 body2 = addLever(posB, boxOffset);
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207 // Add some pin joints to hold the circles in place.
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208 cpSpaceAddConstraint(space, cpPivotJointNew(body1, staticBody, cpvadd(boxOffset, posA)));
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209 cpSpaceAddConstraint(space, cpPivotJointNew(body2, staticBody, cpvadd(boxOffset, posB)));
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210 // Hold their rotation within 90 degrees of each other.
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211 cpSpaceAddConstraint(space, cpRotaryLimitJointNew(body1, body2, -M_PI_2, M_PI_2));
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212
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213 // Ratchet Joint - A rotary ratchet, like a socket wrench
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214 boxOffset = cpv(160, -120);
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215 body1 = addLever(posA, boxOffset);
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216 body2 = addLever(posB, boxOffset);
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217 // Add some pin joints to hold the circles in place.
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218 cpSpaceAddConstraint(space, cpPivotJointNew(body1, staticBody, cpvadd(boxOffset, posA)));
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219 cpSpaceAddConstraint(space, cpPivotJointNew(body2, staticBody, cpvadd(boxOffset, posB)));
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220 // Ratchet every 90 degrees
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221 cpSpaceAddConstraint(space, cpRatchetJointNew(body1, body2, 0.0f, M_PI_2));
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222
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223 // Gear Joint - Maintain a specific angular velocity ratio
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224 boxOffset = cpv(-320, 0);
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225 body1 = addBar(posA, boxOffset);
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226 body2 = addBar(posB, boxOffset);
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227 // Add some pin joints to hold the circles in place.
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228 cpSpaceAddConstraint(space, cpPivotJointNew(body1, staticBody, cpvadd(boxOffset, posA)));
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229 cpSpaceAddConstraint(space, cpPivotJointNew(body2, staticBody, cpvadd(boxOffset, posB)));
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230 // Force one to sping 2x as fast as the other
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231 cpSpaceAddConstraint(space, cpGearJointNew(body1, body2, 0.0f, 2.0f));
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232
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233 // Simple Motor - Maintain a specific angular relative velocity
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234 boxOffset = cpv(-160, 0);
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235 body1 = addBar(posA, boxOffset);
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236 body2 = addBar(posB, boxOffset);
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237 // Add some pin joints to hold the circles in place.
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238 cpSpaceAddConstraint(space, cpPivotJointNew(body1, staticBody, cpvadd(boxOffset, posA)));
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239 cpSpaceAddConstraint(space, cpPivotJointNew(body2, staticBody, cpvadd(boxOffset, posB)));
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240 // Make them spin at 1/2 revolution per second in relation to each other.
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241 cpSpaceAddConstraint(space, cpSimpleMotorNew(body1, body2, M_PI));
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242
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243 // Make a car with some nice soft suspension
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244 boxOffset = cpv(0, 0);
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245 cpBody *wheel1 = addWheel(posA, boxOffset);
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246 cpBody *wheel2 = addWheel(posB, boxOffset);
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247 cpBody *chassis = addChassis(cpv(80, 100), boxOffset);
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248
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249 cpSpaceAddConstraint(space, cpGrooveJointNew(chassis, wheel1, cpv(-30, -10), cpv(-30, -40), cpvzero));
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250 cpSpaceAddConstraint(space, cpGrooveJointNew(chassis, wheel2, cpv( 30, -10), cpv( 30, -40), cpvzero));
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251
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252 cpSpaceAddConstraint(space, cpDampedSpringNew(chassis, wheel1, cpv(-30, 0), cpvzero, 50.0f, 20.0f, 1.5f));
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253 cpSpaceAddConstraint(space, cpDampedSpringNew(chassis, wheel2, cpv( 30, 0), cpvzero, 50.0f, 20.0f, 1.5f));
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254
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255 return space;
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256 }
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257
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258 static void
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259 update(int ticks)
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260 {
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261 cpSpaceStep(space, 1.0f/60.0f);
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262 }
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263
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264 static void
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265 destroy()
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266 {
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267 cpSpaceFreeChildren(space);
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268 cpSpaceFree(space);
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269 }
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270
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271 chipmunkDemo Joints = {
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272 "Joints and Constraints",
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273 null,
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274 &init,
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275 &update,
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276 &destroy,
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277 };
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