cm_trace.c

quakeIII源码这个不用我多说吧

	float		t;
	vec3_t		startp;
	vec3_t		endp;

	enterFrac = -1.0;
	leaveFrac = 1.0;
	clipplane = NULL;

	if ( !brush->numsides ) {
		return;
	}

	c_brush_traces++;

	getout = qfalse;
	startout = qfalse;

	leadside = NULL;

	if ( tw->sphere.use ) {
		//
		// compare the trace against all planes of the brush
		// find the latest time the trace crosses a plane towards the interior
		// and the earliest time the trace crosses a plane towards the exterior
		//
		for (i = 0; i < brush->numsides; i++) {
			side = brush->sides + i;
			plane = side->plane;

			// adjust the plane distance apropriately for radius
			dist = plane->dist + tw->sphere.radius;

			// find the closest point on the capsule to the plane
			t = DotProduct( plane->normal, tw->sphere.offset );
			if ( t > 0 )
			{
				VectorSubtract( tw->start, tw->sphere.offset, startp );
				VectorSubtract( tw->end, tw->sphere.offset, endp );
			}
			else
			{
				VectorAdd( tw->start, tw->sphere.offset, startp );
				VectorAdd( tw->end, tw->sphere.offset, endp );
			}

			d1 = DotProduct( startp, plane->normal ) - dist;
			d2 = DotProduct( endp, plane->normal ) - dist;

			if (d2 > 0) {
				getout = qtrue;	// endpoint is not in solid
			}
			if (d1 > 0) {
				startout = qtrue;
			}

			// if completely in front of face, no intersection with the entire brush
			if (d1 > 0 && ( d2 >= SURFACE_CLIP_EPSILON || d2 >= d1 )  ) {
				return;
			}

			// if it doesn't cross the plane, the plane isn't relevent
			if (d1 <= 0 && d2 <= 0 ) {
				continue;
			}

			// crosses face
			if (d1 > d2) {	// enter
				f = (d1-SURFACE_CLIP_EPSILON) / (d1-d2);
				if ( f < 0 ) {
					f = 0;
				}
				if (f > enterFrac) {
					enterFrac = f;
					clipplane = plane;
					leadside = side;
				}
			} else {	// leave
				f = (d1+SURFACE_CLIP_EPSILON) / (d1-d2);
				if ( f > 1 ) {
					f = 1;
				}
				if (f < leaveFrac) {
					leaveFrac = f;
				}
			}
		}
	} else {
		//
		// compare the trace against all planes of the brush
		// find the latest time the trace crosses a plane towards the interior
		// and the earliest time the trace crosses a plane towards the exterior
		//
		for (i = 0; i < brush->numsides; i++) {
			side = brush->sides + i;
			plane = side->plane;

			// adjust the plane distance apropriately for mins/maxs
			dist = plane->dist - DotProduct( tw->offsets[ plane->signbits ], plane->normal );

			d1 = DotProduct( tw->start, plane->normal ) - dist;
			d2 = DotProduct( tw->end, plane->normal ) - dist;

			if (d2 > 0) {
				getout = qtrue;	// endpoint is not in solid
			}
			if (d1 > 0) {
				startout = qtrue;
			}

			// if completely in front of face, no intersection with the entire brush
			if (d1 > 0 && ( d2 >= SURFACE_CLIP_EPSILON || d2 >= d1 )  ) {
				return;
			}

			// if it doesn't cross the plane, the plane isn't relevent
			if (d1 <= 0 && d2 <= 0 ) {
				continue;
			}

			// crosses face
			if (d1 > d2) {	// enter
				f = (d1-SURFACE_CLIP_EPSILON) / (d1-d2);
				if ( f < 0 ) {
					f = 0;
				}
				if (f > enterFrac) {
					enterFrac = f;
					clipplane = plane;
					leadside = side;
				}
			} else {	// leave
				f = (d1+SURFACE_CLIP_EPSILON) / (d1-d2);
				if ( f > 1 ) {
					f = 1;
				}
				if (f < leaveFrac) {
					leaveFrac = f;
				}
			}
		}
	}

	//
	// all planes have been checked, and the trace was not
	// completely outside the brush
	//
	if (!startout) {	// original point was inside brush
		tw->trace.startsolid = qtrue;
		if (!getout) {
			tw->trace.allsolid = qtrue;
			tw->trace.fraction = 0;
			tw->trace.contents = brush->contents;
		}
		return;
	}
	
	if (enterFrac < leaveFrac) {
		if (enterFrac > -1 && enterFrac < tw->trace.fraction) {
			if (enterFrac < 0) {
				enterFrac = 0;
			}
			tw->trace.fraction = enterFrac;
			tw->trace.plane = *clipplane;
			tw->trace.surfaceFlags = leadside->surfaceFlags;
			tw->trace.contents = brush->contents;
		}
	}
}

/*
================
CM_TraceThroughLeaf
================
*/
void CM_TraceThroughLeaf( traceWork_t *tw, cLeaf_t *leaf ) {
	int			k;
	int			brushnum;
	cbrush_t	*b;
	cPatch_t	*patch;

	// trace line against all brushes in the leaf
	for ( k = 0 ; k < leaf->numLeafBrushes ; k++ ) {
		brushnum = cm.leafbrushes[leaf->firstLeafBrush+k];

		b = &cm.brushes[brushnum];
		if ( b->checkcount == cm.checkcount ) {
			continue;	// already checked this brush in another leaf
		}
		b->checkcount = cm.checkcount;

		if ( !(b->contents & tw->contents) ) {
			continue;
		}

		CM_TraceThroughBrush( tw, b );
		if ( !tw->trace.fraction ) {
			return;
		}
	}

	// trace line against all patches in the leaf
#ifdef BSPC
	if (1) {
#else
	if ( !cm_noCurves->integer ) {
#endif
		for ( k = 0 ; k < leaf->numLeafSurfaces ; k++ ) {
			patch = cm.surfaces[ cm.leafsurfaces[ leaf->firstLeafSurface + k ] ];
			if ( !patch ) {
				continue;
			}
			if ( patch->checkcount == cm.checkcount ) {
				continue;	// already checked this patch in another leaf
			}
			patch->checkcount = cm.checkcount;

			if ( !(patch->contents & tw->contents) ) {
				continue;
			}
			
			CM_TraceThroughPatch( tw, patch );
			if ( !tw->trace.fraction ) {
				return;
			}
		}
	}
}

#define RADIUS_EPSILON		1.0f

/*
================
CM_TraceThroughSphere

get the first intersection of the ray with the sphere
================
*/
void CM_TraceThroughSphere( traceWork_t *tw, vec3_t origin, float radius, vec3_t start, vec3_t end ) {
	float l1, l2, length, scale, fraction;
	float a, b, c, d, sqrtd;
	vec3_t v1, dir, intersection;

	// if inside the sphere
	VectorSubtract(start, origin, dir);
	l1 = VectorLengthSquared(dir);
	if (l1 < Square(radius)) {
		tw->trace.fraction = 0;
		tw->trace.startsolid = qtrue;
		// test for allsolid
		VectorSubtract(end, origin, dir);
		l1 = VectorLengthSquared(dir);
		if (l1 < Square(radius)) {
			tw->trace.allsolid = qtrue;
		}
		return;
	}
	//
	VectorSubtract(end, start, dir);
	length = VectorNormalize(dir);
	//
	l1 = CM_DistanceFromLineSquared(origin, start, end, dir);
	VectorSubtract(end, origin, v1);
	l2 = VectorLengthSquared(v1);
	// if no intersection with the sphere and the end point is at least an epsilon away
	if (l1 >= Square(radius) && l2 > Square(radius+SURFACE_CLIP_EPSILON)) {
		return;
	}
	//
	//	| origin - (start + t * dir) | = radius
	//	a = dir[0]^2 + dir[1]^2 + dir[2]^2;
	//	b = 2 * (dir[0] * (start[0] - origin[0]) + dir[1] * (start[1] - origin[1]) + dir[2] * (start[2] - origin[2]));
	//	c = (start[0] - origin[0])^2 + (start[1] - origin[1])^2 + (start[2] - origin[2])^2 - radius^2;
	//
	VectorSubtract(start, origin, v1);
	// dir is normalized so a = 1
	a = 1.0f;//dir[0] * dir[0] + dir[1] * dir[1] + dir[2] * dir[2];
	b = 2.0f * (dir[0] * v1[0] + dir[1] * v1[1] + dir[2] * v1[2]);
	c = v1[0] * v1[0] + v1[1] * v1[1] + v1[2] * v1[2] - (radius+RADIUS_EPSILON) * (radius+RADIUS_EPSILON);

	d = b * b - 4.0f * c;// * a;
	if (d > 0) {
		sqrtd = SquareRootFloat(d);
		// = (- b + sqrtd) * 0.5f; // / (2.0f * a);
		fraction = (- b - sqrtd) * 0.5f; // / (2.0f * a);
		//
		if (fraction < 0) {
			fraction = 0;
		}
		else {
			fraction /= length;
		}
		if ( fraction < tw->trace.fraction ) {
			tw->trace.fraction = fraction;
			VectorSubtract(end, start, dir);
			VectorMA(start, fraction, dir, intersection);
			VectorSubtract(intersection, origin, dir);
			#ifdef CAPSULE_DEBUG
				l2 = VectorLength(dir);
				if (l2 < radius) {
					int bah = 1;
				}
			#endif
			scale = 1 / (radius+RADIUS_EPSILON);
			VectorScale(dir, scale, dir);
			VectorCopy(dir, tw->trace.plane.normal);
			VectorAdd( tw->modelOrigin, intersection, intersection);
			tw->trace.plane.dist = DotProduct(tw->trace.plane.normal, intersection);
			tw->trace.contents = CONTENTS_BODY;
		}
	}
	else if (d == 0) {
		//t1 = (- b ) / 2;
		// slide along the sphere
	}
	// no intersection at all
}

/*
================
CM_TraceThroughVerticalCylinder

get the first intersection of the ray with the cylinder
the cylinder extends halfheight above and below the origin
================
*/
void CM_TraceThroughVerticalCylinder( traceWork_t *tw, vec3_t origin, float radius, float halfheight, vec3_t start, vec3_t end) {
	float length, scale, fraction, l1, l2;
	float a, b, c, d, sqrtd;
	vec3_t v1, dir, start2d, end2d, org2d, intersection;

	// 2d coordinates
	VectorSet(start2d, start[0], start[1], 0);
	VectorSet(end2d, end[0], end[1], 0);
	VectorSet(org2d, origin[0], origin[1], 0);
	// if between lower and upper cylinder bounds
	if (start[2] <= origin[2] + halfheight &&
				start[2] >= origin[2] - halfheight) {
		// if inside the cylinder
		VectorSubtract(start2d, org2d, dir);
		l1 = VectorLengthSquared(dir);
		if (l1 < Square(radius)) {
			tw->trace.fraction = 0;
			tw->trace.startsolid = qtrue;
			VectorSubtract(end2d, org2d, dir);
			l1 = VectorLengthSquared(dir);
			if (l1 < Square(radius)) {
				tw->trace.allsolid = qtrue;
			}
			return;
		}
	}
	//
	VectorSubtract(end2d, start2d, dir);
	length = VectorNormalize(dir);
	//
	l1 = CM_DistanceFromLineSquared(org2d, start2d, end2d, dir);
	VectorSubtract(end2d, org2d, v1);
	l2 = VectorLengthSquared(v1);
	// if no intersection with the cylinder and the end point is at least an epsilon away
	if (l1 >= Square(radius) && l2 > Square(radius+SURFACE_CLIP_EPSILON)) {
		return;
	}
	//
	//
	// (start[0] - origin[0] - t * dir[0]) ^ 2 + (start[1] - origin[1] - t * dir[1]) ^ 2 = radius ^ 2
	// (v1[0] + t * dir[0]) ^ 2 + (v1[1] + t * dir[1]) ^ 2 = radius ^ 2;
	// v1[0] ^ 2 + 2 * v1[0] * t * dir[0] + (t * dir[0]) ^ 2 +
	//						v1[1] ^ 2 + 2 * v1[1] * t * dir[1] + (t * dir[1]) ^ 2 = radius ^ 2
	// t ^ 2 * (dir[0] ^ 2 + dir[1] ^ 2) + t * (2 * v1[0] * dir[0] + 2 * v1[1] * dir[1]) +
	//						v1[0] ^ 2 + v1[1] ^ 2 - radius ^ 2 = 0
	//
	VectorSubtract(start, origin, v1);
	// dir is normalized so we can use a = 1
	a = 1.0f;// * (dir[0] * dir[0] + dir[1] * dir[1]);
	b = 2.0f * (v1[0] * dir[0] + v1[1] * dir[1]);
	c = v1[0] * v1[0] + v1[1] * v1[1] - (radius+RADIUS_EPSILON) * (radius+RADIUS_EPSILON);

	d = b * b - 4.0f * c;// * a;
	if (d > 0) {
		sqrtd = SquareRootFloat(d);
		// = (- b + sqrtd) * 0.5f;// / (2.0f * a);
		fraction = (- b - sqrtd) * 0.5f;// / (2.0f * a);
		//
		if (fraction < 0) {
			fraction = 0;
		}
		else {
			fraction /= length;
		}
		if ( fraction < tw->trace.fraction ) {
			VectorSubtract(end, start, dir);
			VectorMA(start, fraction, dir, intersection);
			// if the intersection is between the cylinder lower and upper bound
			if (intersection[2] <= origin[2] + halfheight &&
						intersection[2] >= origin[2] - halfheight) {
				//
				tw->trace.fraction = fraction;
				VectorSubtract(intersection, origin, dir);
				dir[2] = 0;
				#ifdef CAPSULE_DEBUG
					l2 = VectorLength(dir);
					if (l2 <= radius) {
						int bah = 1;
					}
				#endif
				scale = 1 / (radius+RADIUS_EPSILON);
				VectorScale(dir, scale, dir);
				VectorCopy(dir, tw->trace.plane.normal);
				VectorAdd( tw->modelOrigin, intersection, intersection);
				tw->trace.plane.dist = DotProduct(tw->trace.plane.normal, intersection);
				tw->trace.contents = CONTENTS_BODY;
			}
		}
	}
	else if (d == 0) {
		//t[0] = (- b ) / 2 * a;
		// slide along the cylinder
	}
	// no intersection at all
}

/*
================
CM_TraceCapsuleThroughCapsule

capsule vs. capsule collision (not rotated)
================
*/
void CM_TraceCapsuleThroughCapsule( traceWork_t *tw, clipHandle_t model ) {
	int i;
	vec3_t mins, maxs;
	vec3_t top, bottom, starttop, startbottom, endtop, endbottom;
	vec3_t offset, symetricSize[2];
	float radius, halfwidth, halfheight, offs, h;

	CM_ModelBounds(model, mins, maxs);
	// test trace bounds vs. capsule bounds
	if ( tw->bounds[0][0] > maxs[0] + RADIUS_EPSILON
		|| tw->bounds[0][1] > maxs[1] + RADIUS_EPSILON
		|| tw->bounds[0][2] > maxs[2] + RADIUS_EPSILON
		|| tw->bounds[1][0] < mins[0] - RADIUS_EPSILON
		|| tw->bounds[1][1] < mins[1] - RADIUS_EPSILON
		|| tw->bounds[1][2] < mins[2] - RADIUS_EPSILON
		) {
		return;
	}
	// top origin and bottom origin of each sphere at start and end of trace
	VectorAdd(tw->start, tw->sphere.offset, starttop);
	VectorSubtract(tw->start, tw->sphere.offset, startbottom);
	VectorAdd(tw->end, tw->sphere.offset, endtop);
	VectorSubtract(tw->end, tw->sphere.offset, endbottom);

	// calculate top and bottom of the capsule spheres to collide with
	for ( i = 0 ; i < 3 ; i++ ) {
		offset[i] = ( mins[i] + maxs[i] ) * 0.5;
		symetricSize[0][i] = mins[i] - offset[i];
		symetricSize[1][i] = maxs[i] - offset[i];
	}
	halfwidth = symetricSize[ 1 ][ 0 ];
	halfheight = symetricSize[ 1 ][ 2 ];
	radius = ( halfwidth > halfheight ) ? halfheight : halfwidth;
	offs = halfheight - radius;
	VectorCopy(offset, top);
	top[2] += offs;
	VectorCopy(offset, bottom);
	bottom[2] -= offs;
	// expand radius of spheres
	radius += tw->sphere.radius;
	// if there is horizontal movement
	if ( tw->start[0] != tw->end[0] || tw->start[1] != tw->end[1] ) {
		// height of the expanded cylinder is the height of both cylinders minus the radius of both spheres
		h = halfheight + tw->sphere.halfheight - radius;
		// if the cylinder has a height
		if ( h > 0 ) {
			// test for collisions between the cylinders
			CM_TraceThroughVerticalCylinder(tw, offset, radius, h, tw->start, tw->end);
		}
	}
	// test for collision between the spheres
	CM_TraceThroughSphere(tw, top, radius, startbottom, endbottom);
	CM_TraceThroughSphere(tw, bottom, radius, starttop, endtop);
}

/*
================
CM_TraceBoundingBoxThroughCapsule

bounding box vs. capsule collision
================
*/
void CM_TraceBoundingBoxThroughCapsule( traceWork_t *tw, clipHandle_t model ) {