114 lines
2.6 KiB
C++
114 lines
2.6 KiB
C++
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/**
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@file Box.cpp
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Box class
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@maintainer Morgan McGuire, http://graphics.cs.williams.edu
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@created 2001-06-02
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@edited 2008-12-27
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*/
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#include "G3D/Box2D.h"
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#include "G3D/CoordinateFrame.h"
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#include "G3D/Rect2D.h"
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namespace G3D {
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bool Box2D::overlaps1Way(const Box2D& other) const {
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for (int a = 0; a < 2; ++a) {
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float t = other.m_corner[0].dot(m_axisin[a]);
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// Find the extent of box 2 on m_axisin a
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float tMin = t;
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float tMax = t;
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for (int c = 1; c < 4; ++c) {
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t = other.m_corner[c].dot(m_axisin[a]);
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if (t < tMin) {
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tMin = t;
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} else if (t > tMax) {
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tMax = t;
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}
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}
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// We have to subtract off the origin
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// See if [tMin, tMax] intersects [0, 1]
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if ((tMin > 1 + origin[a]) || (tMax < origin[a])) {
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// There was no intersection along this dimension;
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// the boxes cannot possibly overlap.
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return false;
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}
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}
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// There was no dimension along which there is no intersection.
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// Therefore the boxes overlap.
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return true;
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}
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void Box2D::computeAxes() {
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m_axis[0] = m_corner[1] - m_corner[0];
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m_axis[1] = m_corner[3] - m_corner[0];
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// Make the length of each m_axisin = 1/edge length so we know any
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// dot product must be less than 1 to fall within the edge.
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float len[2];
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for (int a = 0; a < 2; ++a) {
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float lenSq = m_axis[a].squaredLength();
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m_axisin[a] = m_axis[a] / lenSq;
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origin[a] = m_corner[0].dot(m_axisin[a]);
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len[a] = sqrt(lenSq);
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m_axis[a] /= len[a];
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}
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// w * h
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m_area = len[0] * len[1];
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m_center = (m_corner[0] + m_corner[2]) * 0.5f;
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}
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Box2D::Box2D(const Vector2& center, float w, float h, float angle) {
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Vector2 X( cos(angle), sin(angle));
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Vector2 Y(-sin(angle), cos(angle));
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X *= w / 2;
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Y *= h / 2;
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m_corner[0] = center - X - Y;
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m_corner[1] = center + X - Y;
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m_corner[2] = center + X + Y;
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m_corner[3] = center - X + Y;
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computeAxes();
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}
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Box2D::Box2D(const AABox2D& b) {
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for (int i = 0; i < 4; ++i) {
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m_corner[i] = b.corner(i);
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}
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computeAxes();
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}
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Box2D::Box2D(const Vector2& min, const Vector2& max) {
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*this = Box2D(Rect2D::xyxy(min, max));
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}
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Box2D::Box2D(const CFrame& frame, Box2D& b) {
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for (int i = 0; i < 4; ++i) {
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m_corner[i] = frame.pointToWorldSpace(Vector3(b.corner(i), 0)).xy();
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}
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computeAxes();
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}
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} // G3D
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