HFTracer.h

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/* Copyright (C) 2023 Wildfire Games.
 * This file is part of 0 A.D.
 *
 * 0 A.D. 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.
 *
 * 0 A.D. 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 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
 */
 
/*
 * Determine intersection of rays with a heightfield.
 */
 
#ifndef INCLUDED_HFTRACER
#define INCLUDED_HFTRACER
 
class CPatch;
class CVector3D;
class CTerrain;
 
///////////////////////////////////////////////////////////////////////////////
// CHFTracer: a class for determining ray intersections with a heightfield
class CHFTracer
{
public:
    // constructor; setup data
    CHFTracer(CTerrain& terrain);
 
    // intersect ray with this heightfield; return true if intersection
    // occurs (and fill in grid coordinates and point of intersection), or false otherwise
    bool RayIntersect(const CVector3D& origin, const CVector3D& dir, int& x, int& z, CVector3D& ipt) const;
 
    /**
     * Intersects ray with a single patch.
     * The ray is a half-infinite line starting at @p origin with direction @p dir
     * (not required to be a unit vector).. The patch is treated as a collection
     * of two-sided triangles, corresponding to the terrain tiles.
     *
     * If there is an intersection, returns true; and if @p out is not NULL, it
     * is set to the intersection point. This is guaranteed to be the earliest
     * tile intersected (starting at @p origin), but not necessarily the earlier
     * triangle inside that tile.
     *
     * This partly duplicates RayIntersect, but it only operates on a single
     * patch, and it's more precise (it uses the same tile triangulation as the
     * renderer), and tries to be more numerically robust.
     */
    static bool PatchRayIntersect(CPatch* patch, const CVector3D& origin, const CVector3D& dir, CVector3D* out);
 
private:
    // test if ray intersects either of the triangles in the given
    bool CellIntersect(int cx, int cz, const CVector3D& origin, const CVector3D& dir, float& dist) const;
 
    // The terrain we're operating on
    CTerrain& m_Terrain;
    // the heightfield were tracing
    const u16* m_Heightfield;
    // size of the heightfield
    size_t m_MapSize;
    // cell size - size of each cell in x and z
    float m_CellSize;
    // vertical scale - size of each cell in y
    float m_HeightScale;
};
 
#endif