112 lines
3.0 KiB
C
112 lines
3.0 KiB
C
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#include <vector>
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// Forward declarations
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struct Triangle;
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struct Vector {
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Vector(float coordinates[3]) : c(coordinates) {}
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Vector(float x, float y, float z) : c(new float[3]{x, y, z}) {}
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// Avoid having to write vector.c[index], instead allow vector[index]
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float operator[](int i) const { return c[i]; }
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float &operator[](int i) { return c[i]; }
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Vector operator+(const Vector &other) const {
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return Vector(c[0] + other.c[0], c[1] + other.c[1], c[2] + other.c[2]);
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}
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Vector operator-(const Vector &other) const {
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return Vector(c[0] - other.c[0], c[1] - other.c[1], c[2] - other.c[2]);
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}
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Vector operator*(float scalar) const {
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return Vector(c[0] * scalar, c[1] * scalar, c[2] * scalar);
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}
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Vector cross(const Vector &other) {
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return Vector(c[1] * other[2] - c[2] - other[1], c[2] * other[0] - c[0] * other[2],
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c[0] * other[1] - c[1] * other[0]);
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}
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float dot(const Vector &other) { return c[0] * other[0] + c[1] * other[1] + c[2] * other[2]; }
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float *c;
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};
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struct Point {
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Point(Vector pos, Triangle *triangle) : pos(pos), triangle(triangle) {}
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Vector pos;
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Triangle *triangle;
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};
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struct Triangle {
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Triangle(Vector p1, Vector p2, Vector p3) : p1(p1), p2(p2), p3(p3) {}
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std::vector<Point *> create_point_objects() {
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return std::vector<Point *>{new Point(p1, this), new Point(p2, this), new Point(p3, this)};
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}
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Vector p1;
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Vector p2;
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Vector p3;
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};
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struct Node {
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Node(int axis, Point *point, Node *left, Node *right)
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: axis(axis), point(point), left(left), right(right) {}
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int axis;
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Point *point;
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Node *left;
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Node *right;
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};
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struct Ray {
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Ray(Vector origin, Vector direction) : origin(origin), direction(direction) {}
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Vector origin;
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Vector direction;
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bool intersects_triangle(Triangle *triangle) {
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// Ray-triangle-intersection with the Möller–Trumbore algorithm
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// https://en.wikipedia.org/wiki/M%C3%B6ller%E2%80%93Trumbore_intersection_algorithm
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const float EPSILON = 0.0000001;
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Vector p1 = triangle->p1;
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Vector p2 = triangle->p2;
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Vector p3 = triangle->p3;
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Vector edge1 = p2 - p1;
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Vector edge2 = p3 - p1;
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Vector h = direction.cross(edge2);
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float a = edge1.dot(h);
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if (a > -EPSILON && a < EPSILON) return false; // This ray is parallel to this triangle.
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float f = 1.0 / a;
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Vector s = origin - p1;
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float u = f * s.dot(h);
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if (u < 0.0 || u > 1.0) return false;
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Vector q = s.cross(edge1);
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float v = f * direction.dot(q);
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if (v < 0.0 || u + v > 1.0) return false;
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// At this stage we can compute t to find out where the intersection point is on the
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// line.
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float t = f * edge2.dot(q);
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if (t > EPSILON) {
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return true;
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} else {
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// This means that there is a line intersection but not a ray intersection.
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return false;
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}
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}
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};
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