axmol/tests/cpp-tests/Source/ChipmunkTestBed/demo/Chains.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 "ChipmunkDemo.h"

#define CHAIN_COUNT 8
#define LINK_COUNT 10

static void BreakablejointPostStepRemove(cpSpace* space, cpConstraint* joint, void* unused)
{
    cpSpaceRemoveConstraint(space, joint);
    cpConstraintFree(joint);
}

static void BreakableJointPostSolve(cpConstraint* joint, cpSpace* space)
{
    cpFloat dt = cpSpaceGetCurrentTimeStep(space);

    // Convert the impulse to a force by dividing it by the timestep.
    cpFloat force    = cpConstraintGetImpulse(joint) / dt;
    cpFloat maxForce = cpConstraintGetMaxForce(joint);

    // If the force is almost as big as the joint's max force, break it.
    if (force > 0.9 * maxForce)
    {
        cpSpaceAddPostStepCallback(space, (cpPostStepFunc)BreakablejointPostStepRemove, joint, NULL);
    }
}

static void update(cpSpace* space, double dt)
{
    cpSpaceStep(space, dt);
}

static cpSpace* init(void)
{
    cpSpace* space = cpSpaceNew();
    cpSpaceSetIterations(space, 30);
    cpSpaceSetGravity(space, cpv(0, -100));
    cpSpaceSetSleepTimeThreshold(space, 0.5f);

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

    // 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);

    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);

    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);

    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 mass   = 1;
    cpFloat width  = 20;
    cpFloat height = 30;

    cpFloat spacing = width * 0.3;

    // Add lots of boxes.
    for (int i = 0; i < CHAIN_COUNT; i++)
    {
        cpBody* prev = NULL;

        for (int j = 0; j < LINK_COUNT; j++)
        {
            cpVect pos = cpv(40 * (i - (CHAIN_COUNT - 1) / 2.0), 240 - (j + 0.5) * height - (j + 1) * spacing);

            body = cpSpaceAddBody(space, cpBodyNew(mass, cpMomentForBox(mass, width, height)));
            cpBodySetPosition(body, pos);

            shape = cpSpaceAddShape(space, cpSegmentShapeNew(body, cpv(0, (height - width) / 2.0),
                                                             cpv(0, (width - height) / 2.0), width / 2.0));
            cpShapeSetFriction(shape, 0.8f);

            cpFloat breakingForce = 80000;

            cpConstraint* constraint = NULL;
            if (prev == NULL)
            {
                constraint = cpSpaceAddConstraint(
                    space, cpSlideJointNew(body, staticBody, cpv(0, height / 2), cpv(pos.x, 240), 0, spacing));
            }
            else
            {
                constraint = cpSpaceAddConstraint(
                    space, cpSlideJointNew(body, prev, cpv(0, height / 2), cpv(0, -height / 2), 0, spacing));
            }

            cpConstraintSetMaxForce(constraint, breakingForce);
            cpConstraintSetPostSolveFunc(constraint, BreakableJointPostSolve);
            cpConstraintSetCollideBodies(constraint, cpFalse);

            prev = body;
        }
    }

    cpFloat radius = 15.0f;
    body           = cpSpaceAddBody(space, cpBodyNew(10.0f, cpMomentForCircle(10.0f, 0.0f, radius, cpvzero)));
    cpBodySetPosition(body, cpv(0, -240 + radius + 5));
    cpBodySetVelocity(body, cpv(0, 300));

    shape = cpSpaceAddShape(space, cpCircleShapeNew(body, radius, cpvzero));
    cpShapeSetElasticity(shape, 0.0f);
    cpShapeSetFriction(shape, 0.9f);

    return space;
}

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

ChipmunkDemo Chains = {
    "Breakable Chains", 1.0 / 180.0, init, update, ChipmunkDemoDefaultDrawImpl, destroy,
};