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Tri.c - c

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typedef struct {
float x;
float y;
float z;
} Vector3;
typedef struct {
Vector3 a;
Vector3 b;
Vector3 c;
} Triangle;
typedef struct {
Vector3 p;
Vector3 normal;
} Plane;
// Dot product of two vectors
float dot (Vector3 *v1, Vector3 *v2) {
return v1->x * v2->x + v1->y * v2->y + v1->z * v2->z;
}
// Magnitude of a vector
float vectorMagnitude(Vector3 *v) {
return sqrt(v->x * v->x + v->y * v->y + v->z * v->z);
}
// Normalized version of a vector
Vector3 normalizedVector(Vector3 *v) {
float mag = vectorMagnitude(v);
Vector3 result = { v->x/mag, v->y/mag, v->z/mag };
return result;
}
// Multiply a vector by a float
Vector3 vectorMult(Vector3 *v, float f) {
Vector3 result = { v->x*f, v->y*f, v->z*f };
return result;
}
// Subtract v2 from v1
Vector3 vectorSubtr(Vector3 *v1, Vector3 *v2) {
Vector3 result = { v1->x-v2->x, v1->y-v2->y, v1->z-v2->z };
return result;
}
// Add a vector to another vector
Vector3 vectorAdd(Vector3 *v, Vector3 *p) {
Vector3 result = { v->x+p->x, v->y+p->y, v->z+p->z };
return result;
}
// Finds the point on a plane nearest the origin
Vector3 pointNearestOrigin (Plane *plane) {
float d = dot(&(plane->normal), &(plane->p));
Vector3 norm = normalizedVector(&(plane->normal));
Vector3 result = vectorMult(&norm, d);
return result;
}
// Project a vector in space onto a plane that intersects the origin.
Vector3 projectPointOnPlane(Vector3 *point, Plane *plane) {
Vector3 n = normalizedVector(&(plane->normal));
Vector3 u = vectorMult(&n, dot(point, &n));
Vector3 projected = vectorSubtr(point, &u);
projected = vectorAdd(&projected, &(plane->p));
return projected;
}
// Project a triangle onto a plane that intersects the origin.
Triangle projectOnPlane ( Triangle *t, Plane *p ) {
// for each point in the triangle we need to generate a vector to
// that point and project the vector onto the plane. The three
// resulting vectors point to the projected triangle points.
Vector3 a = projectPointOnPlane(&(t->a), p);
Vector3 b = projectPointOnPlane(&(t->b), p);
Vector3 c = projectPointOnPlane(&(t->c), p);
Vector3 displacement = pointNearestOrigin(p);
Triangle result = { vectorAdd(&a, &displacement), vectorAdd(&b, &displacement), vectorAdd(&c, &displacement) };
return result;
}
int main(int argc, char** argv) {
Vector3 planePoint = { -1.0, -1.0, -1.0 };
Vector3 planeNormal = { 0.1, 0.1, 0.1 };
Plane plane = { planePoint, planeNormal };
Vector3 p1 = { -2.0, 1.0, 1.0 };
Vector3 p2 = { 2.0, 1.0, 3.0 };
Vector3 p3 = { 6.0, 1.0, 4.0 };
Triangle triangle = { p1, p2, p3 };
Triangle projectedT = projectOnPlane(&triangle, &plane);
printf("(%f,%f,%f)\n(%f,%f,%f)\n(%f,%f,%f)\n", projectedT.a.x, projectedT.a.y, projectedT.a.z,
projectedT.b.x, projectedT.b.y, projectedT.b.z,
projectedT.c.x, projectedT.c.y, projectedT.c.z);
return 0;
}