/**
* graphene_triangle_contains_point:
* @t: a #graphene_triangle_t
* @p: a #graphene_point3d_t
*
* Checks whether the given triangle @t contains the point @p.
*
* Returns: `true` if the point is inside the triangle
*
* Since: 1.2
*/
bool
graphene_triangle_contains_point (const graphene_triangle_t *t,
const graphene_point3d_t *p)
{
graphene_vec3_t point, v1, v2, v3;
float dot_11, dot_12, dot_13;
float dot_22, dot_23;
float inv_denom, u, v;
graphene_point3d_to_vec3 (p, &point);
/* we use the barycoordinates from the given point to check
* if the point is inside the triangle.
*
* see: http://www.blackpawn.com/texts/pointinpoly/default.html
*/
graphene_vec3_subtract (&t->c, &t->a, &v1);
graphene_vec3_subtract (&t->b, &t->a, &v2);
graphene_vec3_subtract (&point, &t->a, &v3);
dot_11 = graphene_vec3_dot (&v1, &v1);
dot_12 = graphene_vec3_dot (&v1, &v2);
dot_13 = graphene_vec3_dot (&v1, &v3);
dot_22 = graphene_vec3_dot (&v2, &v2);
dot_23 = graphene_vec3_dot (&v2, &v3);
inv_denom = 1.f / (dot_11 * dot_22 - dot_12 * dot_12);
u = (dot_22 * dot_13 - dot_12 * dot_23) * inv_denom;
v = (dot_11 * dot_23 - dot_12 * dot_13) * inv_denom;
return (u >= 0.f) && (v >= 0.f) && (u + v < 1.f);
}
/**
* graphene_ray_get_distance_to_point:
* @r: a #graphene_ray_t
* @p: a #graphene_point3d_t
*
* Computes the distance from the origin of the given ray to the given point.
*
* Returns: the distance of the point
*
* Since: 1.4
*/
float
graphene_ray_get_distance_to_point (const graphene_ray_t *r,
const graphene_point3d_t *p)
{
graphene_vec3_t point;
graphene_vec3_t tmp;
float distance;
graphene_point3d_to_vec3 (p, &point);
graphene_vec3_subtract (&point, &r->origin, &tmp);
distance = graphene_vec3_dot (&tmp, &r->direction);
/* the point is behind the ray */
if (distance < 0)
{
graphene_vec3_subtract (&r->origin, &point, &tmp);
return graphene_vec3_length (&tmp);
}
/* get the position on the ray at the given distance */
graphene_vec3_scale (&r->direction, distance, &tmp);
graphene_vec3_add (&tmp, &r->origin, &tmp);
graphene_vec3_subtract (&tmp, &point, &tmp);
return graphene_vec3_length (&tmp);
}
/**
* graphene_triangle_get_area:
* @t: a #graphene_triangle_t
*
* Computes the area of the given #graphene_triangle_t.
*
* Returns: the area of the triangle
*
* Since: 1.2
*/
float
graphene_triangle_get_area (const graphene_triangle_t *t)
{
graphene_vec3_t v1, v2, tmp;
graphene_vec3_subtract (&t->c, &t->b, &v1);
graphene_vec3_subtract (&t->a, &t->b, &v2);
graphene_vec3_cross (&v1, &v2, &tmp);
return graphene_vec3_length (&tmp) * .5f;
}
/**
* graphene_matrix_project_point:
* @m: ...
* @p: ...
* @res: (out caller-allocates): ...
*
* ...
*
* Since: 1.0
*/
void
graphene_matrix_project_point (const graphene_matrix_t *m,
const graphene_point_t *p,
graphene_point_t *res)
{
graphene_vec3_t pa, qa;
graphene_vec3_t pback, qback, uback;
float p_z, u_z, t;
g_return_if_fail (m != NULL);
g_return_if_fail (p != NULL);
g_return_if_fail (res != NULL);
graphene_vec3_init (&pa, p->x, p->y, 0.0f);
graphene_vec3_init (&qa, p->x, p->y, 1.0f);
graphene_matrix_transform_vec3 (m, &pa, &pback);
graphene_matrix_transform_vec3 (m, &qa, &qback);
graphene_vec3_subtract (&qback, &pback, &uback);
p_z = graphene_vec3_get_z (&pback);
u_z = graphene_vec3_get_z (&uback);
t = -p_z / u_z;
graphene_point_init (res,
graphene_vec3_get_x (&pback) + t * graphene_vec3_get_x (&uback),
graphene_vec3_get_y (&pback) + t * graphene_vec3_get_y (&uback));
}
/**
* graphene_triangle_get_normal:
* @t: a #graphene_triangle_t
* @res: (out caller-allocates): return location for the normal vector
*
* Computes the normal vector of the given #graphene_triangle_t.
*
* Since: 1.2
*/
void
graphene_triangle_get_normal (const graphene_triangle_t *t,
graphene_vec3_t *res)
{
graphene_vec3_t v1, v2, tmp;
float length_sq;
graphene_vec3_subtract (&t->c, &t->b, &v1);
graphene_vec3_subtract (&t->a, &t->b, &v2);
graphene_vec3_cross (&v1, &v2, &tmp);
length_sq = graphene_vec3_dot (&tmp, &tmp);
if (length_sq > 0)
graphene_vec3_scale (&tmp, 1.f / sqrtf (length_sq), res);
else
graphene_vec3_init_from_vec3 (res, graphene_vec3_zero ());
}
/**
* graphene_ray_get_closest_point_to_point:
* @r: a #graphene_ray_t
* @p: a #graphene_point3d_t
* @res: (out caller-allocates): return location for the closest point3d
*
* Computes the point on the given #graphene_ray_t that is closest to the
* given point @p.
*
* Since: 1.4
*/
void
graphene_ray_get_closest_point_to_point (const graphene_ray_t *r,
const graphene_point3d_t *p,
graphene_point3d_t *res)
{
graphene_vec3_t point, result;
float distance;
graphene_point3d_to_vec3 (p, &point);
graphene_vec3_subtract (&point, &r->origin, &result);
distance = graphene_vec3_dot (&result, &r->direction);
if (distance < 0)
graphene_vec3_init_from_vec3 (&result, &r->origin);
else
{
graphene_vec3_scale (&r->direction, distance, &result);
graphene_vec3_add (&result, &r->origin, &result);
}
graphene_point3d_init_from_vec3 (res, &result);
}
