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/************************************************************************
Arcball rotation control. See the original article
"Arcball Rotation Control"
by Ken Shoemake <shoemake@graphics.cis.upenn.edu>
in "Graphics Gems IV", Academic Press, 1994.
for more details.
$Id: arcball.cxx 427 2004-09-27 04:45:31Z garland $
************************************************************************/
#include <gfx/arcball.h>
#include <gfx/gl.h>
#include <sstream>
namespace gfx
{
// Converts a unit quaternion to two points on the unit sphere
static void quat_to_sphere(const Quat& q, Vec3& from, Vec3& to)
{
const Vec3& v = q.vector();
double s = sqrt(v[0]*v[0] + v[1]*v[1]);
if( s==0.0 )
from = Vec3(0.0, 1.0, 0.0);
else
from = Vec3(-v[1]/s, v[0]/s, 0.0);
to[0] = q.scalar()*from[0] - v[2]*from[1];
to[1] = q.scalar()*from[1] + v[2]*from[2];
to[2] = v[0]*from[1] - v[1]*from[0];
if(q.scalar() < 0.0) from = -from;
}
// Converts to points on unit sphere into a unit quaternion
static Quat quat_from_sphere(const Vec3& from, const Vec3& to)
{
Vec3 v;
v[0] = from[1]*to[2] - from[2]*to[1];
v[1] = from[2]*to[0] - from[0]*to[2];
v[2] = from[0]*to[1] - from[1]*to[0];
double s = from*to;
return Quat(v, s);
}
Vec3 Arcball::proj_to_sphere(const Vec2& mouse)
{
Vec2 p = (mouse - ball_ctr) / ball_radius;
double mag = p*p;
if( mag > 1.0 )
{
double s = sqrt(mag);
return Vec3(p[0]/s, p[1]/s, 0.0);
}
else
{
return Vec3(p[0], p[1], sqrt(1-mag));
}
}
void Arcball::update()
{
// constrain v_from & v_to to axes here, if necessary
if( is_dragging )
{
q_drag = quat_from_sphere(v_from, v_to);
q_now = q_drag * q_down;
}
}
Arcball::Arcball()
{
ball_ctr = Vec2(0, 0);
ball_radius = 1.0;
q_now = Quat::ident();
q_down = Quat::ident();
q_drag = Quat::ident();
is_dragging = false;
}
bool Arcball::mouse_down(int *where, int which)
{
float vp[4];
glGetFloatv(GL_VIEWPORT, vp);
float W=vp[2], H=vp[3];
if( which==1 )
{
is_dragging = true;
Vec2 v( (2.0 * where[0] - W)/W, (H - 2.0 * where[1])/H );
v_from = proj_to_sphere(v);
v_to = v_from;
}
return true;
}
bool Arcball::mouse_up(int *where, int which)
{
is_dragging = false;
q_down = q_now;
q_drag = Quat::ident();
return false;
}
bool Arcball::mouse_drag(int *where, int *last, int which)
{
float vp[4];
glGetFloatv(GL_VIEWPORT, vp);
float W=vp[2], H=vp[3];
float diam = 2*radius;
if( which==1 )
{
Vec2 v( (2.0 * where[0] - W)/W, (H - 2.0 * where[1])/H );
v_to = proj_to_sphere(v);
}
else if( which==2 )
{
trans[0] += diam * (where[0] - last[0]) / W;
trans[1] += diam * (last[1] - where[1]) / H;
}
else if( which==3 )
{
trans[2] += 0.02*diam*(where[1] - last[1]);
}
else
return false;
return true;
}
void Arcball::apply_transform()
{
update();
curquat = conjugate(q_now);
Baseball::apply_transform();
}
void Arcball::update_animation()
{
}
void Arcball::get_transform(Vec3 & c, Vec3 &t, Quat & q)
{
c = ctr;
t = trans;
q = q_now;
}
void Arcball::set_transform(const Vec3 & c, const Vec3 &t, const Quat & q)
{
ctr = c;
trans = t;
q_now = q;
q_down = q;
q_drag = q;
}
void Arcball::write(std::ostream& out)
{
out << "arcball ";
out << ball_ctr << " " << ball_radius << " ";
out << q_now << " " << q_down << " " << q_drag << std::endl;
Baseball::write(out);
}
void Arcball::read(std::istream& in)
{
std::string name;
in >> name;
in >> ball_ctr >> ball_radius;
in >> q_now >> q_down >> q_drag;
Baseball::read(in);
}
} // namespace gfx
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