vmap/radiant/winding.cpp

/*
   Copyright (C) 1999-2006 Id Software, Inc. and contributors.
   For a list of contributors, see the accompanying CONTRIBUTORS file.

   This file is part of GtkRadiant.

   GtkRadiant is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.

   GtkRadiant is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with GtkRadiant; if not, write to the Free Software
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */

#include "winding.h"

#include <algorithm>

#include "math/line.h"


inline double plane3_distance_to_point(const Plane3 &plane, const DoubleVector3 &point)
{
    return vector3_dot(point, plane.normal()) - plane.dist();
}

inline double plane3_distance_to_point(const Plane3 &plane, const Vector3 &point)
{
    return vector3_dot(point, plane.normal()) - plane.dist();
}

/// \brief Returns the point at which \p line intersects \p plane, or an undefined value if there is no intersection.
inline DoubleVector3 line_intersect_plane(const DoubleLine &line, const Plane3 &plane)
{
    return line.origin + vector3_scaled(
            line.direction,
            -plane3_distance_to_point(plane, line.origin)
            / vector3_dot(line.direction, plane.normal())
    );
}

inline bool float_is_largest_absolute(double axis, double other)
{
    return fabs(axis) > fabs(other);
}

/// \brief Returns the index of the component of \p v that has the largest absolute value.
inline int vector3_largest_absolute_component_index(const DoubleVector3 &v)
{
    return (float_is_largest_absolute(v[1], v[0]))
           ? (float_is_largest_absolute(v[1], v[2]))
             ? 1
             : 2
           : (float_is_largest_absolute(v[0], v[2]))
             ? 0
             : 2;
}

/// \brief Returns the infinite line that is the intersection of \p plane and \p other.
inline DoubleLine plane3_intersect_plane3(const Plane3 &plane, const Plane3 &other)
{
    DoubleLine line;
    line.direction = vector3_cross(plane.normal(), other.normal());
    switch (vector3_largest_absolute_component_index(line.direction)) {
        case 0:
            line.origin.x() = 0;
            line.origin.y() =
                    (-other.dist() * plane.normal().z() - -plane.dist() * other.normal().z()) / line.direction.x();
            line.origin.z() =
                    (-plane.dist() * other.normal().y() - -other.dist() * plane.normal().y()) / line.direction.x();
            break;
        case 1:
            line.origin.x() =
                    (-plane.dist() * other.normal().z() - -other.dist() * plane.normal().z()) / line.direction.y();
            line.origin.y() = 0;
            line.origin.z() =
                    (-other.dist() * plane.normal().x() - -plane.dist() * other.normal().x()) / line.direction.y();
            break;
        case 2:
            line.origin.x() =
                    (-other.dist() * plane.normal().y() - -plane.dist() * other.normal().y()) / line.direction.z();
            line.origin.y() =
                    (-plane.dist() * other.normal().x() - -other.dist() * plane.normal().x()) / line.direction.z();
            line.origin.z() = 0;
            break;
        default:
            break;
    }

    return line;
}


/// \brief Keep the value of \p infinity as small as possible to improve precision in Winding_Clip.
void Winding_createInfinite(FixedWinding &winding, const Plane3 &plane, double infinity)
{
    double max = -infinity;
    int x = -1;
    for (int i = 0; i < 3; i++) {
        double d = fabs(plane.normal()[i]);
        if (d > max) {
            x = i;
            max = d;
        }
    }
    if (x == -1) {
        globalErrorStream() << "invalid plane\n";
        return;
    }

    DoubleVector3 vup = g_vector3_identity;
    switch (x) {
        case 0:
        case 1:
            vup[2] = 1;
            break;
        case 2:
            vup[0] = 1;
            break;
    }


    vector3_add(vup, vector3_scaled(plane.normal(), -vector3_dot(vup, plane.normal())));
    vector3_normalise(vup);

    DoubleVector3 org = vector3_scaled(plane.normal(), plane.dist());

    DoubleVector3 vright = vector3_cross(vup, plane.normal());

    vector3_scale(vup, infinity);
    vector3_scale(vright, infinity);

    // project a really big  axis aligned box onto the plane

    DoubleLine r1, r2, r3, r4;
    r1.origin = vector3_added(vector3_subtracted(org, vright), vup);
    r1.direction = vector3_normalised(vright);
    winding.push_back(FixedWindingVertex(r1.origin, r1, c_brush_maxFaces));
    r2.origin = vector3_added(vector3_added(org, vright), vup);
    r2.direction = vector3_normalised(vector3_negated(vup));
    winding.push_back(FixedWindingVertex(r2.origin, r2, c_brush_maxFaces));
    r3.origin = vector3_subtracted(vector3_added(org, vright), vup);
    r3.direction = vector3_normalised(vector3_negated(vright));
    winding.push_back(FixedWindingVertex(r3.origin, r3, c_brush_maxFaces));
    r4.origin = vector3_subtracted(vector3_subtracted(org, vright), vup);
    r4.direction = vector3_normalised(vup);
    winding.push_back(FixedWindingVertex(r4.origin, r4, c_brush_maxFaces));
}


inline PlaneClassification Winding_ClassifyDistance(const double distance, const double epsilon)
{
    if (distance > epsilon) {
        return ePlaneFront;
    }
    if (distance < -epsilon) {
        return ePlaneBack;
    }
    return ePlaneOn;
}

/// \brief Returns true if
/// !flipped && winding is completely BACK or ON
/// or flipped && winding is completely FRONT or ON
bool Winding_TestPlane(const Winding &winding, const Plane3 &plane, bool flipped)
{
    const int test = (flipped) ? ePlaneBack : ePlaneFront;
    for (Winding::const_iterator i = winding.begin(); i != winding.end(); ++i) {
        if (test == Winding_ClassifyDistance(plane3_distance_to_point(plane, (*i).vertex), ON_EPSILON)) {
            return false;
        }
    }
    return true;
}

/// \brief Returns true if any point in \p w1 is in front of plane2, or any point in \p w2 is in front of plane1
bool Winding_PlanesConcave(const Winding &w1, const Winding &w2, const Plane3 &plane1, const Plane3 &plane2)
{
    return !Winding_TestPlane(w1, plane2, false) || !Winding_TestPlane(w2, plane1, false);
}

brushsplit_t Winding_ClassifyPlane(const Winding &winding, const Plane3 &plane)
{
    brushsplit_t split;
    for (Winding::const_iterator i = winding.begin(); i != winding.end(); ++i) {
        ++split.counts[Winding_ClassifyDistance(plane3_distance_to_point(plane, (*i).vertex), ON_EPSILON)];
    }
    return split;
}


#define DEBUG_EPSILON ON_EPSILON
const double DEBUG_EPSILON_SQUARED = DEBUG_EPSILON * DEBUG_EPSILON;

#define WINDING_DEBUG 0

/// \brief Clip \p winding which lies on \p plane by \p clipPlane, resulting in \p clipped.
/// If \p winding is completely in front of the plane, \p clipped will be identical to \p winding.
/// If \p winding is completely in back of the plane, \p clipped will be empty.
/// If \p winding intersects the plane, the edge of \p clipped which lies on \p clipPlane will store the value of \p adjacent.
void Winding_Clip(const FixedWinding &winding, const Plane3 &plane, const Plane3 &clipPlane, std::size_t adjacent,
                  FixedWinding &clipped)
{
    PlaneClassification classification = Winding_ClassifyDistance(
            plane3_distance_to_point(clipPlane, winding.back().vertex), ON_EPSILON);
    PlaneClassification nextClassification;
    // for each edge
    for (std::size_t next = 0, i = winding.size() - 1;
         next != winding.size(); i = next, ++next, classification = nextClassification) {
        nextClassification = Winding_ClassifyDistance(plane3_distance_to_point(clipPlane, winding[next].vertex),
                                                      ON_EPSILON);
        const FixedWindingVertex &vertex = winding[i];

        // if first vertex of edge is ON
        if (classification == ePlaneOn) {
            // append first vertex to output winding
            if (nextClassification == ePlaneBack) {
                // this edge lies on the clip plane
                clipped.push_back(
                        FixedWindingVertex(vertex.vertex, plane3_intersect_plane3(plane, clipPlane), adjacent));
            } else {
                clipped.push_back(vertex);
            }
            continue;
        }

        // if first vertex of edge is FRONT
        if (classification == ePlaneFront) {
            // add first vertex to output winding
            clipped.push_back(vertex);
        }
        // if second vertex of edge is ON
        if (nextClassification == ePlaneOn) {
            continue;
        }
            // else if second vertex of edge is same as first
        else if (nextClassification == classification) {
            continue;
        }
            // else if first vertex of edge is FRONT and there are only two edges
        else if (classification == ePlaneFront && winding.size() == 2) {
            continue;
        }
            // else first vertex is FRONT and second is BACK or vice versa
        else {
            // append intersection point of line and plane to output winding
            DoubleVector3 mid(line_intersect_plane(vertex.edge, clipPlane));

            if (classification == ePlaneFront) {
                // this edge lies on the clip plane
                clipped.push_back(FixedWindingVertex(mid, plane3_intersect_plane3(plane, clipPlane), adjacent));
            } else {
                clipped.push_back(FixedWindingVertex(mid, vertex.edge, vertex.adjacent));
            }
        }
    }
}

std::size_t Winding_FindAdjacent(const Winding &winding, std::size_t face)
{
    for (std::size_t i = 0; i < winding.numpoints; ++i) {
        ASSERT_MESSAGE(winding[i].adjacent != c_brush_maxFaces, "edge connectivity data is invalid");
        if (winding[i].adjacent == face) {
            return i;
        }
    }
    return c_brush_maxFaces;
}

std::size_t Winding_Opposite(const Winding &winding, const std::size_t index, const std::size_t other)
{
    ASSERT_MESSAGE(index < winding.numpoints && other < winding.numpoints, "Winding_Opposite: index out of range");

    double dist_best = 0;
    std::size_t index_best = c_brush_maxFaces;

    Ray edge(ray_for_points(winding[index].vertex, winding[other].vertex));

    for (std::size_t i = 0; i < winding.numpoints; ++i) {
        if (i == index || i == other) {
            continue;
        }

        double dist_squared = ray_squared_distance_to_point(edge, winding[i].vertex);

        if (dist_squared > dist_best) {
            dist_best = dist_squared;
            index_best = i;
        }
    }
    return index_best;
}

std::size_t Winding_Opposite(const Winding &winding, const std::size_t index)
{
    return Winding_Opposite(winding, index, Winding_next(winding, index));
}

/// \brief Calculate the \p centroid of the polygon defined by \p winding which lies on plane \p plane.
void Winding_Centroid(const Winding &winding, const Plane3 &plane, Vector3 &centroid)
{
    double area2 = 0, x_sum = 0, y_sum = 0;
    const ProjectionAxis axis = projectionaxis_for_normal(plane.normal());
    const indexremap_t remap = indexremap_for_projectionaxis(axis);
    for (std::size_t i = winding.numpoints - 1, j = 0; j < winding.numpoints; i = j, ++j) {
        const double ai = winding[i].vertex[remap.x] * winding[j].vertex[remap.y] -
                          winding[j].vertex[remap.x] * winding[i].vertex[remap.y];
        area2 += ai;
        x_sum += (winding[j].vertex[remap.x] + winding[i].vertex[remap.x]) * ai;
        y_sum += (winding[j].vertex[remap.y] + winding[i].vertex[remap.y]) * ai;
    }

    centroid[remap.x] = static_cast<float>( x_sum / (3 * area2));
    centroid[remap.y] = static_cast<float>( y_sum / (3 * area2));
    {
        Ray ray(Vector3(0, 0, 0), Vector3(0, 0, 0));
        ray.origin[remap.x] = centroid[remap.x];
        ray.origin[remap.y] = centroid[remap.y];
        ray.direction[remap.z] = 1;
        centroid[remap.z] = static_cast<float>( ray_distance_to_plane(ray, plane));
    }
}