chipmunk几何算法

/* Copyright (c) 2007 Scott Lembcke
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
*/

#include <stdio.h>
#include <string.h>
#include <stdarg.h>

#include "chipmunk_private.h"

void
cpMessage(const char *condition, const char *file, int line, cpBool isError, cpBool isHardError, const char *message, ...)
{
fprintf(stderr, (isError ? "Aborting due to Chipmunk error: " : "Chipmunk warning: "));

va_list vargs;
va_start(vargs, message); {
vfprintf(stderr, message, vargs);
fprintf(stderr, "\n");
} va_end(vargs);

fprintf(stderr, "\tFailed condition: %s\n", condition);
fprintf(stderr, "\tSource:%s:%d\n", file, line);

if(isError) abort();
}

#define STR(s) #s
#define XSTR(s) STR(s)

const char *cpVersionString = XSTR(CP_VERSION_MAJOR)"."XSTR(CP_VERSION_MINOR)"."XSTR(CP_VERSION_RELEASE);

void
cpInitChipmunk(void)
{
cpAssertWarn(cpFalse, "cpInitChipmunk is deprecated and no longer required. It will be removed in the future.");
}

//MARK: Misc Functions

cpFloat
cpMomentForCircle(cpFloat m, cpFloat r1, cpFloat r2, cpVect offset)
{
return m*(0.5f*(r1*r1 + r2*r2) + cpvlengthsq(offset));
}

cpFloat
cpAreaForCircle(cpFloat r1, cpFloat r2)
{
return (cpFloat)M_PI*cpfabs(r1*r1 - r2*r2);
}

cpFloat
cpMomentForSegment(cpFloat m, cpVect a, cpVect b)
{
cpVect offset = cpvmult(cpvadd(a, b), 0.5f);
return m*(cpvdistsq(b, a)/12.0f + cpvlengthsq(offset));
}

cpFloat
cpAreaForSegment(cpVect a, cpVect b, cpFloat r)
{
return r*((cpFloat)M_PI*r + 2.0f*cpvdist(a, b));
}

cpFloat
cpMomentForPoly(cpFloat m, const int numVerts, const cpVect *verts, cpVect offset)
{
cpFloat sum1 = 0.0f;
cpFloat sum2 = 0.0f;
for(int i=0; i<numVerts; i++){
cpVect v1 = cpvadd(verts[i], offset);
cpVect v2 = cpvadd(verts[(i+1)%numVerts], offset);

cpFloat a = cpvcross(v2, v1);
cpFloat b = cpvdot(v1, v1) + cpvdot(v1, v2) + cpvdot(v2, v2);

sum1 += a*b;
sum2 += a;
}

return (m*sum1)/(6.0f*sum2);
}

cpFloat
cpAreaForPoly(const int numVerts, const cpVect *verts)
{
cpFloat area = 0.0f;
for(int i=0; i<numVerts; i++){
area += cpvcross(verts[i], verts[(i+1)%numVerts]);
}

return -area/2.0f;
}

cpVect
cpCentroidForPoly(const int numVerts, const cpVect *verts)
{
cpFloat sum = 0.0f;
cpVect vsum = cpvzero;

for(int i=0; i<numVerts; i++){
cpVect v1 = verts[i];
cpVect v2 = verts[(i+1)%numVerts];
cpFloat cross = cpvcross(v1, v2);

sum += cross;
vsum = cpvadd(vsum, cpvmult(cpvadd(v1, v2), cross));
}

return cpvmult(vsum, 1.0f/(3.0f*sum));
}

void
cpRecenterPoly(const int numVerts, cpVect *verts){
cpVect centroid = cpCentroidForPoly(numVerts, verts);

for(int i=0; i<numVerts; i++){
verts[i] = cpvsub(verts[i], centroid);
}
}

cpFloat
cpMomentForBox(cpFloat m, cpFloat width, cpFloat height)
{
return m*(width*width + height*height)/12.0f;
}

cpFloat
cpMomentForBox2(cpFloat m, cpBB box)
{
cpFloat width = box.r - box.l;
cpFloat height = box.t - box.b;
cpVect offset = cpvmult(cpv(box.l + box.r, box.b + box.t), 0.5f);

// TODO NaN when offset is 0 and m is INFINITY
return cpMomentForBox(m, width, height) + m*cpvlengthsq(offset);
}

//MARK: Quick Hull

void
cpLoopIndexes(cpVect *verts, int count, int *start, int *end)
{
(*start) = (*end) = 0;
cpVect min = verts[0];
cpVect max = min;

for(int i=1; i<count; i++){
cpVect v = verts[i];

if(v.x < min.x || (v.x == min.x && v.y < min.y)){
min = v;
(*start) = i;
} else if(v.x > max.x || (v.x == max.x && v.y > max.y)){
max = v;
(*end) = i;
}
}
}

#define SWAP(__A__, __B__) {cpVect __TMP__ = __A__; __A__ = __B__; __B__ = __TMP__;}

static int
QHullPartition(cpVect *verts, int count, cpVect a, cpVect b, cpFloat tol)
{
if(count == 0) return 0;

cpFloat max = 0;
int pivot = 0;

cpVect delta = cpvsub(b, a);
cpFloat valueTol = tol*cpvlength(delta);

int head = 0;
for(int tail = count-1; head <= tail;){
cpFloat value = cpvcross(delta, cpvsub(verts[head], a));
if(value > valueTol){
if(value > max){
max = value;
pivot = head;
}

head++;
} else {
SWAP(verts[head], verts[tail]);
tail--;
}
}

// move the new pivot to the front if it's not already there.
if(pivot != 0) SWAP(verts[0], verts[pivot]);
return head;
}

static int
QHullReduce(cpFloat tol, cpVect *verts, int count, cpVect a, cpVect pivot, cpVect b, cpVect *result)
{
if(count < 0){
return 0;
} else if(count == 0) {
result[0] = pivot;
return 1;
} else {
int left_count = QHullPartition(verts, count, a, pivot, tol);
int index = QHullReduce(tol, verts + 1, left_count - 1, a, verts[0], pivot, result);

result[index++] = pivot;

int right_count = QHullPartition(verts + left_count, count - left_count, pivot, b, tol);
return index + QHullReduce(tol, verts + left_count + 1, right_count - 1, pivot, verts[left_count], b, result + index);
}
}

// QuickHull seemed like a neat algorithm, and efficient-ish for large input sets.
// My implementation performs an in place reduction using the result array as scratch space.
int
cpConvexHull(int count, cpVect *verts, cpVect *result, int *first, cpFloat tol)
{
if(result){
// Copy the line vertexes into the empty part of the result polyline to use as a scratch buffer.
memcpy(result, verts, count*sizeof(cpVect));
} else {
// If a result array was not specified, reduce the input instead.
result = verts;
}

// Degenerate case, all poins are the same.
int start, end;
cpLoopIndexes(verts, count, &start, &end);
if(start == end){
if(first) (*first) = 0;
return 1;
}

SWAP(result[0], result[start]);
SWAP(result[1], result[end == 0 ? start : end]);

cpVect a = result[0];
cpVect b = result[1];

if(first) (*first) = start;
int resultCount = QHullReduce(tol, result + 2, count - 2, a, b, a, result + 1) + 1;
cpAssertSoft(cpPolyValidate(result, resultCount),
"Internal error: cpConvexHull() and cpPolyValidate() did not agree."
"Please report this error with as much info as you can.");
return resultCount;
}

//MARK: Alternate Block Iterators

#if defined(__has_extension)
#if __has_extension(blocks)

static void IteratorFunc(void *ptr, void (^block)(void *ptr)){block(ptr);}

void cpSpaceEachBody_b(cpSpace *space, void (^block)(cpBody *body)){
cpSpaceEachBody(space, (cpSpaceBodyIteratorFunc)IteratorFunc, block);
}

void cpSpaceEachShape_b(cpSpace *space, void (^block)(cpShape *shape)){
cpSpaceEachShape(space, (cpSpaceShapeIteratorFunc)IteratorFunc, block);
}

void cpSpaceEachConstraint_b(cpSpace *space, void (^block)(cpConstraint *constraint)){
cpSpaceEachConstraint(space, (cpSpaceConstraintIteratorFunc)IteratorFunc, block);
}

static void BodyIteratorFunc(cpBody *body, void *ptr, void (^block)(void *ptr)){block(ptr);}

void cpBodyEachShape_b(cpBody *body, void (^block)(cpShape *shape)){
cpBodyEachShape(body, (cpBodyShapeIteratorFunc)BodyIteratorFunc, block);
}

void cpBodyEachConstraint_b(cpBody *body, void (^block)(cpConstraint *constraint)){
cpBodyEachConstraint(body, (cpBodyConstraintIteratorFunc)BodyIteratorFunc, block);
}

void cpBodyEachArbiter_b(cpBody *body, void (^block)(cpArbiter *arbiter)){
cpBodyEachArbiter(body, (cpBodyArbiterIteratorFunc)BodyIteratorFunc, block);
}

static void NearestPointQueryIteratorFunc(cpShape *shape, cpFloat distance, cpVect point, cpSpaceNearestPointQueryBlock block){block(shape, distance, point);}
void cpSpaceNearestPointQuery_b(cpSpace *space, cpVect point, cpFloat maxDistance, cpLayers layers, cpGroup group, cpSpaceNearestPointQueryBlock block){
cpSpaceNearestPointQuery(space, point, maxDistance, layers, group, (cpSpaceNearestPointQueryFunc)NearestPointQueryIteratorFunc, block);
}

static void SegmentQueryIteratorFunc(cpShape *shape, cpFloat t, cpVect n, cpSpaceSegmentQueryBlock block){block(shape, t, n);}
void cpSpaceSegmentQuery_b(cpSpace *space, cpVect start, cpVect end, cpLayers layers, cpGroup group, cpSpaceSegmentQueryBlock block){
cpSpaceSegmentQuery(space, start, end, layers, group, (cpSpaceSegmentQueryFunc)SegmentQueryIteratorFunc, block);
}

void cpSpaceBBQuery_b(cpSpace *space, cpBB bb, cpLayers layers, cpGroup group, cpSpaceBBQueryBlock block){
cpSpaceBBQuery(space, bb, layers, group, (cpSpaceBBQueryFunc)IteratorFunc, block);
}

static void ShapeQueryIteratorFunc(cpShape *shape, cpContactPointSet *points, cpSpaceShapeQueryBlock block){block(shape, points);}
cpBool cpSpaceShapeQuery_b(cpSpace *space, cpShape *shape, cpSpaceShapeQueryBlock block){
return cpSpaceShapeQuery(space, shape, (cpSpaceShapeQueryFunc)ShapeQueryIteratorFunc, block);
}

#endif
#endif

#include "chipmunk_ffi.h"