Initial revision; heightfield tracing code moved from ScEd.

This was SVN commit r250.
2026-07-09 07:24:37 +00:00 · 2004-05-22 16:44:39 +00:00
parent c7b6d0089f
commit 1721b0afa5
2 changed files with 225 additions and 0 deletions
@@ -0,0 +1,177 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+// Name:		HFTracer.cpp
+// Author:		Rich Cross
+// Contact:		rich@wildfiregames.com
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include "HFTracer.h"
+#include "terrain/Terrain.h"
+#include "terrain/Bound.h"
+#include "terrain/Vector3D.h"
+
+extern CTerrain g_Terrain;
+
+///////////////////////////////////////////////////////////////////////////////
+// CHFTracer constructor
+CHFTracer::CHFTracer(const u16* hf,u32 mapsize,float cellsize,float heightscale)
+	: m_Heightfield(hf), m_MapSize(mapsize), m_CellSize(cellsize), 
+	m_HeightScale(heightscale)
+{
+} 
+
+
+///////////////////////////////////////////////////////////////////////////////
+// RayTriIntersect: intersect a ray with triangle defined by vertices 
+// v0,v1,v2; return true if ray hits triangle at distance less than dist,
+// or false otherwise
+bool CHFTracer::RayTriIntersect(const CVector3D& v0,const CVector3D& v1,const CVector3D& v2,
+								const CVector3D& origin,const CVector3D& dir,float& dist) const
+{
+	const float EPSILON=0.00001f;
+
+	// calculate edge vectors
+	CVector3D edge0=v1-v0;
+	CVector3D edge1=v2-v0;
+
+    // begin calculating determinant - also used to calculate U parameter
+    CVector3D pvec=dir.Cross(edge1);
+
+    // if determinant is near zero, ray lies in plane of triangle
+    float det = edge0.Dot(pvec);
+    if (fabs(det)<EPSILON)
+        return false;
+
+    float inv_det = 1.0f/det;
+
+    // calculate vector from vert0 to ray origin
+    CVector3D tvec=origin-v0;
+
+    // calculate U parameter, test bounds
+    float u=tvec.Dot(pvec)*inv_det;
+    if (u<-0.01f || u>1.01f)
+        return false;
+
+    // prepare to test V parameter
+    CVector3D qvec=tvec.Cross(edge0);
+
+    // calculate V parameter and test bounds
+    float v=dir.Dot(qvec)*inv_det;
+    if (v<0.0f || u+v>1.0f)
+        return false;
+
+    // calculate distance to intersection point from ray origin
+    float d=edge1.Dot(qvec)*inv_det;
+    if (d>=0 && d<dist) {
+        dist=d;
+        return true;
+    }
+
+    return false;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+// CellIntersect: test if ray intersects either of the triangles in the given 
+// cell - return hit result, and distance to hit, if hit occurred
+bool CHFTracer::CellIntersect(int cx,int cz,CVector3D& origin,CVector3D& dir,float& dist) const
+{
+	bool res=false;
+
+	// get vertices for this cell
+	CVector3D vpos[4];
+	g_Terrain.CalcPosition(cx,cz,vpos[0]);
+	g_Terrain.CalcPosition(cx+1,cz,vpos[1]);
+	g_Terrain.CalcPosition(cx+1,cz+1,vpos[2]);
+	g_Terrain.CalcPosition(cx,cz+1,vpos[3]);
+
+	dist=1.0e30f;
+	if (RayTriIntersect(vpos[0],vpos[1],vpos[2],origin,dir,dist)) {
+		res=true;
+	}
+
+	if (RayTriIntersect(vpos[0],vpos[2],vpos[3],origin,dir,dist)) {
+		res=true;
+	}	
+
+	return res;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+// RayIntersect: intersect ray with this heightfield; return true if 
+// intersection occurs (and fill in grid coordinates of intersection), or false 
+// otherwise
+bool CHFTracer::RayIntersect(CVector3D& origin,CVector3D& dir,int& x,int& z,CVector3D& ipt) const
+{
+	// intersect first against bounding box
+	CBound bound;
+	bound[0]=CVector3D(0,0,0);
+	bound[1]=CVector3D(m_MapSize*m_CellSize,65535*m_HeightScale,m_MapSize*m_CellSize);
+
+	float tmin,tmax;
+	if (!bound.RayIntersect(origin,dir,tmin,tmax)) {
+		// ray missed world bounds; no intersection
+		return false;
+	}
+
+	// project origin onto grid, if necessary, to get starting point for traversal
+	CVector3D traversalPt;
+	if (tmin>0) {
+		traversalPt=origin+dir*tmin;
+	} else {
+		traversalPt=origin;
+	}
+
+	// setup traversal variables
+	int sx=dir.X<0 ? -1 : 1;
+	int sz=dir.Z<0 ? -1 : 1;
+
+	float invCellSize=1.0f/float(m_CellSize);
+
+	float fcx=traversalPt.X*invCellSize;
+	int cx=int(fcx);
+
+	float fcz=traversalPt.Z*invCellSize;
+	int cz=int(fcz);
+
+	float invdx=float(1.0/fabs(dir.X));
+	float invdz=float(1.0/fabs(dir.Z));
+
+	float dist;
+	do {		
+		// test current cell
+		if (cx>=0 && cx<int(m_MapSize-1) && cz>=0 && cz<int(m_MapSize-1)) {
+			if (CellIntersect(cx,cz,origin,dir,dist)) {
+				x=cx;
+				z=cz;
+				ipt=origin+dir*dist;
+				return true;
+			}
+		} 
+
+		// get coords of current cell
+		fcx=traversalPt.X*invCellSize;
+		fcz=traversalPt.Z*invCellSize;
+
+		// get distance to next cell in x,z
+		float dx=(sx==-1) ? fcx-float(cx) : 1-(fcx-float(cx));
+		dx*=invdx;
+		float dz=(sz==-1) ? fcz-float(cz) : 1-(fcz-float(cz));
+		dz*=invdz;
+
+		// advance ..
+		float dist;
+		if (dx<dz) {
+			cx+=sx;
+			dist=dx;
+		} else {
+			cz+=sz;
+			dist=dz;
+		}
+
+		traversalPt+=dir*dist;
+	} while (traversalPt.Y>=0);
+	
+	// fell off end of heightmap with no intersection; return a miss
+	return false;
+}
@@ -0,0 +1,48 @@
+///////////////////////////////////////////////////////////////////////////////
+//
+// Name:		HFTracer.h
+// Author:		Rich Cross
+// Contact:		rich@wildfiregames.com
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#ifndef _HFTRACER_H
+#define _HFTRACER_H
+
+class CVector3D;
+
+#include "res/res.h"
+
+///////////////////////////////////////////////////////////////////////////////
+// CHFTracer: a class for determining ray intersections with a heightfield
+class CHFTracer
+{
+public:
+	// constructor; setup data
+	CHFTracer(const u16* hf,u32 mapsize,float cellsize,float heightscale);
+
+	// intersect ray with this heightfield; return true if intersection 
+	// occurs (and fill in grid coordinates and point of intersection), or false otherwise
+	bool RayIntersect(CVector3D& origin,CVector3D& dir,int& x,int& z,CVector3D& ipt) const;
+
+private:
+	// intersect a ray with triangle defined by vertices 
+	// v0,v1,v2; return true if ray hits triangle at distance less than dist,
+	// or false otherwise
+	bool RayTriIntersect(const CVector3D& v0,const CVector3D& v1,const CVector3D& v2,
+			const CVector3D& origin,const CVector3D& dir,float& dist) const;
+
+	// test if ray intersects either of the triangles in the given 
+	bool CellIntersect(int cx,int cz,CVector3D& origin,CVector3D& dir,float& dist) const;
+	
+	// the heightfield were tracing
+	const u16* m_Heightfield;
+	// size of the heightfield
+	u32 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