mirror of https://github.com/axmolengine/axmol.git
123 lines
4.0 KiB
C
123 lines
4.0 KiB
C
/* Copyright (c) 2007 Scott Lembcke
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*/
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#include "chipmunk/chipmunk.h"
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#include "ChipmunkDemo.h"
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static cpBody* planetBody;
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static cpFloat gravityStrength = 5.0e6f;
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static void update(cpSpace* space, double dt)
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{
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cpSpaceStep(space, dt);
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}
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static void planetGravityVelocityFunc(cpBody* body, cpVect gravity, cpFloat damping, cpFloat dt)
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{
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// Gravitational acceleration is proportional to the inverse square of
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// distance, and directed toward the origin. The central planet is assumed
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// to be massive enough that it affects the satellites but not vice versa.
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cpVect p = cpBodyGetPosition(body);
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cpFloat sqdist = cpvlengthsq(p);
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cpVect g = cpvmult(p, -gravityStrength / (sqdist * cpfsqrt(sqdist)));
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cpBodyUpdateVelocity(body, g, damping, dt);
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}
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static cpVect rand_pos(cpFloat radius)
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{
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cpVect v;
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do
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{
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v = cpv(frand() * (640 - 2 * radius) - (320 - radius), frand() * (480 - 2 * radius) - (240 - radius));
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} while (cpvlength(v) < 85.0f);
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return v;
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}
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static void add_box(cpSpace* space)
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{
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const cpFloat size = 10.0f;
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const cpFloat mass = 1.0f;
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cpVect verts[] = {
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cpv(-size, -size),
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cpv(-size, size),
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cpv(size, size),
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cpv(size, -size),
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};
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cpFloat radius = cpvlength(cpv(size, size));
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cpVect pos = rand_pos(radius);
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cpBody* body = cpSpaceAddBody(space, cpBodyNew(mass, cpMomentForPoly(mass, 4, verts, cpvzero, 0.0f)));
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cpBodySetVelocityUpdateFunc(body, planetGravityVelocityFunc);
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cpBodySetPosition(body, pos);
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// Set the box's velocity to put it into a circular orbit from its
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// starting position.
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cpFloat r = cpvlength(pos);
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cpFloat v = cpfsqrt(gravityStrength / r) / r;
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cpBodySetVelocity(body, cpvmult(cpvperp(pos), v));
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// Set the box's angular velocity to match its orbital period and
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// align its initial angle with its position.
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cpBodySetAngularVelocity(body, v);
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cpBodySetAngle(body, cpfatan2(pos.y, pos.x));
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cpShape* shape = cpSpaceAddShape(space, cpPolyShapeNew(body, 4, verts, cpTransformIdentity, 0.0));
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cpShapeSetElasticity(shape, 0.0f);
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cpShapeSetFriction(shape, 0.7f);
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}
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static cpSpace* init(void)
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{
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// Create a rouge body to control the planet manually.
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cpSpace* space = cpSpaceNew();
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cpSpaceSetIterations(space, 20);
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planetBody = cpSpaceAddBody(space, cpBodyNewKinematic());
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cpBodySetAngularVelocity(planetBody, 0.2f);
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for (int i = 0; i < 30; i++)
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{
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add_box(space);
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}
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cpShape* shape = cpSpaceAddShape(space, cpCircleShapeNew(planetBody, 70.0f, cpvzero));
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cpShapeSetElasticity(shape, 1.0f);
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cpShapeSetFriction(shape, 1.0f);
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cpShapeSetFilter(shape, NOT_GRABBABLE_FILTER);
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return space;
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}
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static void destroy(cpSpace* space)
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{
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ChipmunkDemoFreeSpaceChildren(space);
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cpSpaceFree(space);
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}
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ChipmunkDemo Planet = {
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"Planet", 1.0 / 60.0, init, update, ChipmunkDemoDefaultDrawImpl, destroy,
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};
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