axmol/tests/cpp-tests/Classes/ChipmunkTestBed/demo/Convex.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 "chipmunk/chipmunk.h"
#include "chipmunk/chipmunk_unsafe.h"

#include "ChipmunkDemo.h"

#define DENSITY (1.0 / 10000.0)

static cpShape* shape;

static void update(cpSpace* space, double dt)
{
    cpFloat tolerance = 2.0;

    if (ChipmunkDemoRightClick && cpShapePointQuery(shape, ChipmunkDemoMouse, NULL) > tolerance)
    {
        cpBody* body = cpShapeGetBody(shape);
        int count    = cpPolyShapeGetCount(shape);

        // Allocate the space for the new vertexes on the stack.
        cpVect* verts = (cpVect*)alloca((count + 1) * sizeof(cpVect));

        for (int i = 0; i < count; i++)
        {
            verts[i] = cpPolyShapeGetVert(shape, i);
        }

        verts[count] = cpBodyWorldToLocal(body, ChipmunkDemoMouse);

        // This function builds a convex hull for the vertexes.
        // Because the result array is the same as verts, it will reduce it in place.
        int hullCount = cpConvexHull(count + 1, verts, verts, NULL, tolerance);

        // Figure out how much to shift the body by.
        cpVect centroid = cpCentroidForPoly(hullCount, verts);

        // Recalculate the body properties to match the updated shape.
        cpFloat mass = cpAreaForPoly(hullCount, verts, 0.0f) * DENSITY;
        cpBodySetMass(body, mass);
        cpBodySetMoment(body, cpMomentForPoly(mass, hullCount, verts, cpvneg(centroid), 0.0f));
        cpBodySetPosition(body, cpBodyLocalToWorld(body, centroid));

        // Use the setter function from chipmunk_unsafe.h.
        // You could also remove and recreate the shape if you wanted.
        cpPolyShapeSetVerts(shape, hullCount, verts, cpTransformTranslate(cpvneg(centroid)));
    }

    cpSpaceStep(space, dt);
}

static cpSpace* init(void)
{
    ChipmunkDemoMessageString = "Right click and drag to change the blocks's shape.";

    cpSpace* space = cpSpaceNew();
    cpSpaceSetIterations(space, 30);
    cpSpaceSetGravity(space, cpv(0, -500));
    cpSpaceSetSleepTimeThreshold(space, 0.5f);
    cpSpaceSetCollisionSlop(space, 0.5f);

    cpBody *body, *staticBody = cpSpaceGetStaticBody(space);

    // Create segments around the edge of the screen.
    shape = cpSpaceAddShape(space, cpSegmentShapeNew(staticBody, cpv(-320, -240), cpv(320, -240), 0.0f));
    cpShapeSetElasticity(shape, 1.0f);
    cpShapeSetFriction(shape, 1.0f);
    cpShapeSetFilter(shape, NOT_GRABBABLE_FILTER);

    cpFloat width  = 50.0f;
    cpFloat height = 70.0f;
    cpFloat mass   = width * height * DENSITY;
    cpFloat moment = cpMomentForBox(mass, width, height);

    body = cpSpaceAddBody(space, cpBodyNew(mass, moment));

    shape = cpSpaceAddShape(space, cpBoxShapeNew(body, width, height, 0.0));
    cpShapeSetFriction(shape, 0.6f);

    return space;
}

static void destroy(cpSpace* space)
{
    ChipmunkDemoFreeSpaceChildren(space);
    cpSpaceFree(space);
}

ChipmunkDemo Convex = {
    "Convex.", 1.0 / 60.0, init, update, ChipmunkDemoDefaultDrawImpl, destroy,
};