axmol/tests/cpp-tests/Source/ChipmunkTestBed/demo/Tank.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"

static cpBody *tankBody, *tankControlBody;

static void update(cpSpace* space, double dt)
{
    // turn the control body based on the angle relative to the actual body
    cpVect mouseDelta = cpvsub(ChipmunkDemoMouse, cpBodyGetPosition(tankBody));
    cpFloat turn      = cpvtoangle(cpvunrotate(cpBodyGetRotation(tankBody), mouseDelta));
    cpBodySetAngle(tankControlBody, cpBodyGetAngle(tankBody) - turn);

    // drive the tank towards the mouse
    if (cpvnear(ChipmunkDemoMouse, cpBodyGetPosition(tankBody), 30.0))
    {
        cpBodySetVelocity(tankControlBody, cpvzero);  // stop
    }
    else
    {
        cpFloat direction = (cpvdot(mouseDelta, cpBodyGetRotation(tankBody)) > 0.0 ? 1.0 : -1.0);
        cpBodySetVelocity(tankControlBody, cpvrotate(cpBodyGetRotation(tankBody), cpv(30.0f * direction, 0.0f)));
    }

    cpSpaceStep(space, dt);
}

static cpBody* add_box(cpSpace* space, cpFloat size, cpFloat mass)
{
    cpFloat radius = cpvlength(cpv(size, size));

    cpBody* body = cpSpaceAddBody(space, cpBodyNew(mass, cpMomentForBox(mass, size, size)));
    cpBodySetPosition(
        body, cpv(frand() * (640 - 2 * radius) - (320 - radius), frand() * (480 - 2 * radius) - (240 - radius)));

    cpShape* shape = cpSpaceAddShape(space, cpBoxShapeNew(body, size, size, 0.0));
    cpShapeSetElasticity(shape, 0.0f);
    cpShapeSetFriction(shape, 0.7f);

    return body;
}

static cpSpace* init(void)
{
    ChipmunkDemoMessageString = "Use the mouse to drive the tank, it will follow the cursor.";

    cpSpace* space = cpSpaceNew();
    cpSpaceSetIterations(space, 10);
    cpSpaceSetSleepTimeThreshold(space, 0.5f);

    cpBody* 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);

    for (int i = 0; i < 50; i++)
    {
        cpBody* body = add_box(space, 20, 1);

        cpConstraint* pivot = cpSpaceAddConstraint(space, cpPivotJointNew2(staticBody, body, cpvzero, cpvzero));
        cpConstraintSetMaxBias(pivot, 0);         // disable joint correction
        cpConstraintSetMaxForce(pivot, 1000.0f);  // emulate linear friction

        cpConstraint* gear = cpSpaceAddConstraint(space, cpGearJointNew(staticBody, body, 0.0f, 1.0f));
        cpConstraintSetMaxBias(gear, 0);         // disable joint correction
        cpConstraintSetMaxForce(gear, 5000.0f);  // emulate angular friction
    }

    // We joint the tank to the control body and control the tank indirectly by modifying the control body.
    tankControlBody = cpSpaceAddBody(space, cpBodyNewKinematic());
    tankBody        = add_box(space, 30, 10);

    cpConstraint* pivot = cpSpaceAddConstraint(space, cpPivotJointNew2(tankControlBody, tankBody, cpvzero, cpvzero));
    cpConstraintSetMaxBias(pivot, 0);          // disable joint correction
    cpConstraintSetMaxForce(pivot, 10000.0f);  // emulate linear friction

    cpConstraint* gear = cpSpaceAddConstraint(space, cpGearJointNew(tankControlBody, tankBody, 0.0f, 1.0f));
    cpConstraintSetErrorBias(gear, 0);        // attempt to fully correct the joint each step
    cpConstraintSetMaxBias(gear, 1.2f);       // but limit it's angular correction rate
    cpConstraintSetMaxForce(gear, 50000.0f);  // emulate angular friction

    return space;
}

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

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