libcruft-util/geom/ellipse.cpp

112 lines
3.5 KiB
C++

/*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* Copyright 2015-2018 Danny Robson <danny@nerdcruft.net>
*/
#include "ellipse.hpp"
#include "ops.hpp"
#include "aabb.hpp"
#include "ray.hpp"
#include "sphere.hpp"
#include "point.hpp"
#include "../matrix.hpp"
using util::geom::ellipse;
///////////////////////////////////////////////////////////////////////////////
template <size_t S, typename T>
static bool
intersects (ellipse<S,T> e, util::point<S,T> p)
{
auto mag = (p - e.origin) * (p - e.origin) / (e.radius * e.radius);
return std::accumulate (mag.begin (), mag.end (), 0) <= 1;
}
//-----------------------------------------------------------------------------
template <size_t S, typename T, template <size_t,typename> class A, template <size_t,typename> class B>
bool
util::geom::intersects (A<S,T> a, B<S,T> b)
{
return ::intersects (a, b);
}
///////////////////////////////////////////////////////////////////////////////
template <size_t DimensionV, typename ValueT>
util::point<DimensionV,ValueT>
util::geom::project (util::geom::ray<DimensionV, ValueT> lhs,
util::geom::ellipse<DimensionV, ValueT> rhs)
{
return lhs.origin + lhs.direction * distance (lhs, rhs);
}
///////////////////////////////////////////////////////////////////////////////
// query a ray-ellipse distance by transforming spaces such that the ellipse is
// a sphere
template <size_t DimensionV, typename ValueT>
ValueT
util::geom::distance (ray<DimensionV,ValueT> r, ellipse<DimensionV,ValueT> e)
{
// find a transform that puts the ellipse at origin and scales it to a
// unit sphere.
auto const from_scaled = util::translation (e.origin.template as<vector> ()) *
util::scale (e.radius);
auto const to_scaled = inverse (from_scaled);
// transform the ray into this new space and query against a unit sphere
auto const scaled_r = to_scaled * r;
auto const scaled_d = distance (scaled_r, sphere<DimensionV,ValueT> {0, 1.f});
auto const scaled_p = scaled_r.at (scaled_d);
// transform the result back into the original space
return distance (r.origin, (from_scaled * scaled_p.homog ()).template redim<DimensionV> ());
}
///////////////////////////////////////////////////////////////////////////////
template <size_t S, typename T>
static util::geom::aabb<S,T>
bounds (ellipse<S,T> e)
{
return {
e.origin - e.radius,
e.origin + e.radius
};
}
//-----------------------------------------------------------------------------
template <size_t S, typename T, template <size_t,typename> class K>
util::geom::aabb<S,T>
util::geom::bounds (K<S,T> k)
{
return ::bounds (k);
}
///////////////////////////////////////////////////////////////////////////////
#define INSTANTIATE_S_T(S,T) \
template bool util::geom::intersects (ellipse<S,T>, util::point<S,T>); \
template util::point<S,T> util::geom::project(ray<S,T>, ellipse<S,T>); \
template util::geom::aabb<S,T> util::geom::bounds (ellipse<S,T>);
INSTANTIATE_S_T(2,float)
INSTANTIATE_S_T(3,float)