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/* 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 *planetBody;
static cpFloat gravityStrength = 5.0e6f;
static void
update(cpSpace *space, double dt)
{
cpSpaceStep(space, dt);
}
static void
planetGravityVelocityFunc(cpBody *body, cpVect gravity, cpFloat damping, cpFloat dt)
{
// Gravitational acceleration is proportional to the inverse square of
// distance, and directed toward the origin. The central planet is assumed
// to be massive enough that it affects the satellites but not vice versa.
cpVect p = cpBodyGetPosition(body);
cpFloat sqdist = cpvlengthsq(p);
cpVect g = cpvmult(p, -gravityStrength / (sqdist * cpfsqrt(sqdist)));
cpBodyUpdateVelocity(body, g, damping, dt);
}
static cpVect
rand_pos(cpFloat radius)
{
cpVect v;
do {
v = cpv(frand()*(640 - 2*radius) - (320 - radius), frand()*(480 - 2*radius) - (240 - radius));
} while(cpvlength(v) < 85.0f);
return v;
}
static void
add_box(cpSpace *space)
{
const cpFloat size = 10.0f;
const cpFloat mass = 1.0f;
cpVect verts[] = {
cpv(-size,-size),
cpv(-size, size),
cpv( size, size),
cpv( size,-size),
};
cpFloat radius = cpvlength(cpv(size, size));
cpVect pos = rand_pos(radius);
cpBody *body = cpSpaceAddBody(space, cpBodyNew(mass, cpMomentForPoly(mass, 4, verts, cpvzero, 0.0f)));
cpBodySetVelocityUpdateFunc(body, planetGravityVelocityFunc);
cpBodySetPosition(body, pos);
// Set the box's velocity to put it into a circular orbit from its
// starting position.
cpFloat r = cpvlength(pos);
cpFloat v = cpfsqrt(gravityStrength / r) / r;
cpBodySetVelocity(body, cpvmult(cpvperp(pos), v));
// Set the box's angular velocity to match its orbital period and
// align its initial angle with its position.
cpBodySetAngularVelocity(body, v);
cpBodySetAngle(body, cpfatan2(pos.y, pos.x));
cpShape *shape = cpSpaceAddShape(space, cpPolyShapeNew(body, 4, verts, cpTransformIdentity, 0.0));
cpShapeSetElasticity(shape, 0.0f);
cpShapeSetFriction(shape, 0.7f);
}
static cpSpace *
init(void)
{
// Create a rouge body to control the planet manually.
cpSpace *space = cpSpaceNew();
cpSpaceSetIterations(space, 20);
planetBody = cpSpaceAddBody(space, cpBodyNewKinematic());
cpBodySetAngularVelocity(planetBody, 0.2f);
for(int i=0; i<30; i++){
add_box(space);
}
cpShape *shape = cpSpaceAddShape(space, cpCircleShapeNew(planetBody, 70.0f, cpvzero));
cpShapeSetElasticity(shape, 1.0f);
cpShapeSetFriction(shape, 1.0f);
cpShapeSetFilter(shape, NOT_GRABBABLE_FILTER);
return space;
}
static void
destroy(cpSpace *space)
{
ChipmunkDemoFreeSpaceChildren(space);
cpSpaceFree(space);
}
ChipmunkDemo Planet = {
"Planet",
1.0/60.0,
init,
update,
ChipmunkDemoDefaultDrawImpl,
destroy,
};