Vec3d Particle_source_cylinder::uniform_position_in_cylinder(
std::default_random_engine &rnd_gen )
{
// random point in cylinder along z
Vec3d cyl_axis = vec3d_init( ( axis_end_x - axis_start_x ),
( axis_end_y - axis_start_y ),
( axis_end_z - axis_start_z ) );
double cyl_axis_length = vec3d_length( cyl_axis );
double x, y, z;
double r, phi;
r = sqrt( random_in_range( 0.0, 1.0, rnd_gen ) ) * radius;
phi = random_in_range( 0.0, 2.0 * M_PI, rnd_gen );
z = random_in_range( 0.0, cyl_axis_length, rnd_gen );
//
x = r * cos( phi );
y = r * sin( phi );
z = z;
Vec3d random_pnt_in_cyl_along_z = vec3d_init( x, y, z );
// rotate:
// see https://en.wikipedia.org/wiki/Rodrigues'_rotation_formula
// todo: Too complicated. Try rejection sampling.
Vec3d random_pnt_in_rotated_cyl;
Vec3d unit_cyl_axis = vec3d_normalized( cyl_axis );
Vec3d unit_along_z = vec3d_init( 0, 0, 1.0 );
Vec3d rotation_axis = vec3d_cross_product( unit_along_z, unit_cyl_axis );
double rotation_axis_length = vec3d_length( rotation_axis );
if ( rotation_axis_length == 0 ) {
if ( copysign( 1.0, vec3d_z( unit_cyl_axis ) ) >= 0 ){
random_pnt_in_rotated_cyl = random_pnt_in_cyl_along_z;
} else {
random_pnt_in_rotated_cyl = vec3d_negate( random_pnt_in_cyl_along_z );
}
} else {
Vec3d unit_rotation_axis = vec3d_normalized( rotation_axis );
double rot_cos = vec3d_dot_product( unit_cyl_axis, unit_along_z );
double rot_sin = rotation_axis_length;
random_pnt_in_rotated_cyl =
vec3d_add(
vec3d_times_scalar( random_pnt_in_cyl_along_z, rot_cos ),
vec3d_add(
vec3d_times_scalar(
vec3d_cross_product( unit_rotation_axis,
random_pnt_in_cyl_along_z ),
rot_sin ),
vec3d_times_scalar(
unit_rotation_axis,
( 1 - rot_cos ) * vec3d_dot_product(
unit_rotation_axis,
random_pnt_in_cyl_along_z ) ) ) );
}
// shift:
Vec3d shifted = vec3d_add( random_pnt_in_rotated_cyl,
vec3d_init( axis_start_x, axis_start_y, axis_start_z ) );
return shifted;
}
static void space_body_update(Space *space,Body *body)
{
GList *it;
Cube a,b;
Body *other;
Vec3D stepVector;
Vec3D stepOffVector;
if ((!body) || (body->_done))return;
vec3d_scale(stepVector,body->velocity,space->stepFactor);
vec3d_negate(stepOffVector,stepVector);
vec3d_add(body->position,body->position,stepVector);
a.x = body->position.x + body->bounds.x;
a.y = body->position.y + body->bounds.y;
a.z = body->position.z + body->bounds.z;
a.w = body->bounds.w;
a.h = body->bounds.h;
a.d = body->bounds.d;
for (it = space->bodylist;it != NULL;it = g_list_next(it))
{
if (!it->data)continue;
if (it->data == body)continue;
/*check for collision*/
other = (Body *)it->data;
vec3d_cpy(b,other->position);
b.w = other->bounds.w;
b.h = other->bounds.h;
b.d = other->bounds.d;
vec3d_add(b,b,other->bounds);
if (cube_cube_intersection(a,b))
{
/*call touch functions*/
/*back the f**k off*/
//vec3d_cpy(body->_stepOffVector,stepOffVector);
//body->_done = 1;
// body->_needsBackoff = 1;
if (body->touch.function)
{
body->touch.function(body->touch.data,other);
}
}
}
}
