cpPolyShape.c

/* 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 <stdlib.h>
#include <stdio.h>

#include "chipmunk.h"
#include "chipmunk_unsafe.h"

cpPolyShape *
cpPolyShapeAlloc(void)
{
	return (cpPolyShape *)cpcalloc(1, sizeof(cpPolyShape));
}

static void
cpPolyShapeTransformVerts(cpPolyShape *poly, cpVect p, cpVect rot)
{
	cpVect *src = poly->verts;
	cpVect *dst = poly->tVerts;
	
	for(int i=0; i<poly->numVerts; i++)
		dst[i] = cpvadd(p, cpvrotate(src[i], rot));
}

static void
cpPolyShapeTransformAxes(cpPolyShape *poly, cpVect p, cpVect rot)
{
	cpPolyShapeAxis *src = poly->axes;
	cpPolyShapeAxis *dst = poly->tAxes;
	
	for(int i=0; i<poly->numVerts; i++){
		cpVect n = cpvrotate(src[i].n, rot);
		dst[i].n = n;
		dst[i].d = cpvdot(p, n) + src[i].d;
	}
}

static cpBB
cpPolyShapeCacheData(cpShape *shape, cpVect p, cpVect rot)
{
	cpPolyShape *poly = (cpPolyShape *)shape;
	
	cpFloat l, b, r, t;
	
	cpPolyShapeTransformAxes(poly, p, rot);
	cpPolyShapeTransformVerts(poly, p, rot);
	
	cpVect *verts = poly->tVerts;
	l = r = verts[0].x;
	b = t = verts[0].y;
	
	// TODO do as part of cpPolyShapeTransformVerts?
	for(int i=1; i<poly->numVerts; i++){
		cpVect v = verts[i];
		
		l = cpfmin(l, v.x);
		r = cpfmax(r, v.x);
		
		b = cpfmin(b, v.y);
		t = cpfmax(t, v.y);
	}
	
	return cpBBNew(l, b, r, t);
}

static void
cpPolyShapeDestroy(cpShape *shape)
{
	cpPolyShape *poly = (cpPolyShape *)shape;
	
	cpfree(poly->verts);
	cpfree(poly->tVerts);
	
	cpfree(poly->axes);
	cpfree(poly->tAxes);
}

static int
cpPolyShapePointQuery(cpShape *shape, cpVect p){
	return cpBBcontainsVect(shape->bb, p) && cpPolyShapeContainsVert((cpPolyShape *)shape, p);
}

static void
cpPolyShapeSegmentQuery(cpShape *shape, cpVect a, cpVect b, cpSegmentQueryInfo *info)
{
	cpPolyShape *poly = (cpPolyShape *)shape;
	cpPolyShapeAxis *axes = poly->tAxes;
	cpVect *verts = poly->tVerts;
	int numVerts = poly->numVerts;
	
	for(int i=0; i<numVerts; i++){
		cpVect n = axes[i].n;
		cpFloat an = cpvdot(a, n);
		if(axes[i].d > an) continue;
		
		cpFloat bn = cpvdot(b, n);
		cpFloat t = (axes[i].d - an)/(bn - an);
		if(t < 0.0f || 1.0f < t) continue;
		
		cpVect point = cpvlerp(a, b, t);
		cpFloat dt = -cpvcross(n, point);
		cpFloat dtMin = -cpvcross(n, verts[i]);
		cpFloat dtMax = -cpvcross(n, verts[(i+1)%numVerts]);
		
		if(dtMin <= dt && dt <= dtMax){
			info->shape = shape;
			info->t = t;
			info->n = n;
		}
	}
}

static const cpShapeClass polyClass = {
	CP_POLY_SHAPE,
	cpPolyShapeCacheData,
	cpPolyShapeDestroy,
	cpPolyShapePointQuery,
	cpPolyShapeSegmentQuery,
};

int
cpPolyValidate(cpVect *verts, int numVerts)
{
	for(int i=0; i<numVerts; i++){
		cpVect a = verts[i];
		cpVect b = verts[(i+1)%numVerts];
		cpVect c = verts[(i+2)%numVerts];
		
		if(cpvcross(cpvsub(b, a), cpvsub(c, b)) > 0.0f)
			return 0;
	}
	
	return 1;
}

int
cpPolyShapeGetNumVerts(cpShape *shape)
{
	cpAssert(shape->klass == &polyClass, "Shape is not a poly shape.");
	return ((cpPolyShape *)shape)->numVerts;
}

cpVect
cpPolyShapeGetVert(cpShape *shape, int idx)
{
	cpAssert(shape->klass == &polyClass, "Shape is not a poly shape.");
	cpAssert(0 <= idx && idx < cpPolyShapeGetNumVerts(shape), "Index out of range.");
	
	return ((cpPolyShape *)shape)->verts[idx];
}


static void
setUpVerts(cpPolyShape *poly, int numVerts, cpVect *verts, cpVect offset)
{
	poly->numVerts = numVerts;

	poly->verts = (cpVect *)cpcalloc(numVerts, sizeof(cpVect));
	poly->tVerts = (cpVect *)cpcalloc(numVerts, sizeof(cpVect));
	poly->axes = (cpPolyShapeAxis *)cpcalloc(numVerts, sizeof(cpPolyShapeAxis));
	poly->tAxes = (cpPolyShapeAxis *)cpcalloc(numVerts, sizeof(cpPolyShapeAxis));
	
	for(int i=0; i<numVerts; i++){
		cpVect a = cpvadd(offset, verts[i]);
		cpVect b = cpvadd(offset, verts[(i+1)%numVerts]);
		cpVect n = cpvnormalize(cpvperp(cpvsub(b, a)));

		poly->verts[i] = a;
		poly->axes[i].n = n;
		poly->axes[i].d = cpvdot(n, a);
	}
}

cpPolyShape *
cpPolyShapeInit(cpPolyShape *poly, cpBody *body, int numVerts, cpVect *verts, cpVect offset)
{
	// Fail if the user attempts to pass a concave poly, or a bad winding.
	cpAssert(cpPolyValidate(verts, numVerts), "Polygon is concave or has a reversed winding.");
	
	setUpVerts(poly, numVerts, verts, offset);
	cpShapeInit((cpShape *)poly, &polyClass, body);

	return poly;
}

cpShape *
cpPolyShapeNew(cpBody *body, int numVerts, cpVect *verts, cpVect offset)
{
	return (cpShape *)cpPolyShapeInit(cpPolyShapeAlloc(), body, numVerts, verts, offset);
}

// Unsafe API (chipmunk_unsafe.h)

void
cpPolyShapeSetVerts(cpShape *shape, int numVerts, cpVect *verts, cpVect offset)
{
	cpAssert(shape->klass == &polyClass, "Shape is not a poly shape.");
	cpPolyShapeDestroy(shape);
	setUpVerts((cpPolyShape *)shape, numVerts, verts, offset);
}