void normal_at(Interpreter interp, SphereItem s, Vector4Item p)
{
// ( -- object_point )
interp.StackPush(s);
interp.Run("'transform' REC@ INVERSE");
interp.StackPush(p);
interp.Run("*");
// ( object_point -- object_normal )
interp.Run("0 0 0 Point -");
// ( object_normal -- world_normal )
interp.StackPush(s);
interp.Run("'transform' REC@ INVERSE TRANSPOSE SWAP * 0 'W' <REC! NORMALIZE");
}
ArrayItem intersections(Interpreter interp, SphereItem sphere, RayItem ray)
{
// Compute sphere_to_ray
interp.StackPush(ray);
interp.Run("'origin' REC@ 0 0 0 Point -");
Vector4Item sphere_to_ray = (Vector4Item)interp.StackPop();
// Compute a
interp.StackPush(ray);
interp.Run("'direction' REC@ DUP DOT");
DoubleItem a = (DoubleItem)interp.StackPop();
// Compute b
interp.StackPush(sphere_to_ray);
interp.StackPush(ray);
interp.Run("'direction' REC@ DOT 2 *");
DoubleItem b = (DoubleItem)interp.StackPop();
// Compute c
interp.StackPush(sphere_to_ray);
interp.Run("DUP DOT 1 -");
DoubleItem c = (DoubleItem)interp.StackPop();
float discriminant = b.FloatValue * b.FloatValue - 4.0f * a.FloatValue * c.FloatValue;
ArrayItem result = new ArrayItem();
if (discriminant < 0)
{
return(result);
}
else
{
double t1 = (-b.FloatValue - Math.Sqrt(discriminant)) / 2.0f / a.FloatValue;
double t2 = (-b.FloatValue + Math.Sqrt(discriminant)) / 2.0f / a.FloatValue;
result.Add(new IntersectionItem(t1, sphere));
result.Add(new IntersectionItem(t2, sphere));
return(result);
}
}