mirror of https://github.com/axmolengine/axmol.git
221 lines
8.2 KiB
C
221 lines
8.2 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 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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#define FLUID_DENSITY 0.00014
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#define FLUID_DRAG 2.0
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char messageBuffer[1024];
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// Modified from chipmunk_private.h
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static inline cpFloat k_scalar_body(cpBody* body, cpVect point, cpVect n)
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{
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cpFloat rcn = cpvcross(cpvsub(point, cpBodyGetPosition(body)), n);
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return 1.0f / cpBodyGetMass(body) + rcn * rcn / cpBodyGetMoment(body);
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}
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static cpBool waterPreSolve(cpArbiter* arb, cpSpace* space, void* ptr)
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{
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CP_ARBITER_GET_SHAPES(arb, water, poly);
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cpBody* body = cpShapeGetBody(poly);
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// Get the top of the water sensor bounding box to use as the water level.
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cpFloat level = cpShapeGetBB(water).t;
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// Clip the polygon against the water level
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int count = cpPolyShapeGetCount(poly);
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int clippedCount = 0;
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#ifdef _MSC_VER
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// MSVC is pretty much the only compiler in existence that doesn't support variable sized arrays.
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cpVect clipped[10];
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#else
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cpVect clipped[count + 1];
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#endif
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for (int i = 0, j = count - 1; i < count; j = i, i++)
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{
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cpVect a = cpBodyLocalToWorld(body, cpPolyShapeGetVert(poly, j));
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cpVect b = cpBodyLocalToWorld(body, cpPolyShapeGetVert(poly, i));
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if (a.y < level)
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{
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clipped[clippedCount] = a;
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clippedCount++;
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}
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cpFloat a_level = a.y - level;
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cpFloat b_level = b.y - level;
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if (a_level * b_level < 0.0f)
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{
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cpFloat t = cpfabs(a_level) / (cpfabs(a_level) + cpfabs(b_level));
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clipped[clippedCount] = cpvlerp(a, b, t);
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clippedCount++;
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}
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}
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// Calculate buoyancy from the clipped polygon area
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cpFloat clippedArea = cpAreaForPoly(clippedCount, clipped, 0.0f);
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cpFloat displacedMass = clippedArea * FLUID_DENSITY;
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cpVect centroid = cpCentroidForPoly(clippedCount, clipped);
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ChipmunkDebugDrawPolygon(clippedCount, clipped, 5.0f, RGBAColor(0, 0, 1, 1), RGBAColor(0, 0, 1, 0.1f));
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ChipmunkDebugDrawDot(5, centroid, RGBAColor(0, 0, 1, 1));
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cpFloat dt = cpSpaceGetCurrentTimeStep(space);
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cpVect g = cpSpaceGetGravity(space);
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// Apply the buoyancy force as an impulse.
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cpBodyApplyImpulseAtWorldPoint(body, cpvmult(g, -displacedMass * dt), centroid);
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// Apply linear damping for the fluid drag.
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cpVect v_centroid = cpBodyGetVelocityAtWorldPoint(body, centroid);
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cpFloat k = k_scalar_body(body, centroid, cpvnormalize(v_centroid));
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cpFloat damping = clippedArea * FLUID_DRAG * FLUID_DENSITY;
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cpFloat v_coef = cpfexp(-damping * dt * k); // linear drag
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// cpFloat v_coef = 1.0/(1.0 + damping*dt*cpvlength(v_centroid)*k); // quadratic drag
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cpBodyApplyImpulseAtWorldPoint(body, cpvmult(cpvsub(cpvmult(v_centroid, v_coef), v_centroid), 1.0 / k), centroid);
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// Apply angular damping for the fluid drag.
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cpVect cog = cpBodyLocalToWorld(body, cpBodyGetCenterOfGravity(body));
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cpFloat w_damping =
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cpMomentForPoly(FLUID_DRAG * FLUID_DENSITY * clippedArea, clippedCount, clipped, cpvneg(cog), 0.0f);
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cpBodySetAngularVelocity(body, cpBodyGetAngularVelocity(body) * cpfexp(-w_damping * dt / cpBodyGetMoment(body)));
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return cpTrue;
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}
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static cpSpace* init(void)
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{
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ChipmunkDemoMessageString = messageBuffer;
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cpSpace* space = cpSpaceNew();
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cpSpaceSetIterations(space, 30);
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cpSpaceSetGravity(space, cpv(0, -500));
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// cpSpaceSetDamping(space, 0.5);
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cpSpaceSetSleepTimeThreshold(space, 0.5f);
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cpSpaceSetCollisionSlop(space, 0.5f);
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cpBody *body, *staticBody = cpSpaceGetStaticBody(space);
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cpShape* shape;
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// Create segments around the edge of the screen.
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shape = cpSpaceAddShape(space, cpSegmentShapeNew(staticBody, cpv(-320, -240), cpv(-320, 240), 0.0f));
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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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shape = cpSpaceAddShape(space, cpSegmentShapeNew(staticBody, cpv(320, -240), cpv(320, 240), 0.0f));
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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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shape = cpSpaceAddShape(space, cpSegmentShapeNew(staticBody, cpv(-320, -240), cpv(320, -240), 0.0f));
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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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shape = cpSpaceAddShape(space, cpSegmentShapeNew(staticBody, cpv(-320, 240), cpv(320, 240), 0.0f));
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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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{
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// Add the edges of the bucket
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cpBB bb = cpBBNew(-300, -200, 100, 0);
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cpFloat radius = 5.0f;
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shape = cpSpaceAddShape(space, cpSegmentShapeNew(staticBody, cpv(bb.l, bb.b), cpv(bb.l, bb.t), radius));
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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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shape = cpSpaceAddShape(space, cpSegmentShapeNew(staticBody, cpv(bb.r, bb.b), cpv(bb.r, bb.t), radius));
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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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shape = cpSpaceAddShape(space, cpSegmentShapeNew(staticBody, cpv(bb.l, bb.b), cpv(bb.r, bb.b), radius));
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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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// Add the sensor for the water.
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shape = cpSpaceAddShape(space, cpBoxShapeNew2(staticBody, bb, 0.0));
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cpShapeSetSensor(shape, cpTrue);
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cpShapeSetCollisionType(shape, 1);
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}
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{
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cpFloat width = 200.0f;
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cpFloat height = 50.0f;
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cpFloat mass = 0.3 * FLUID_DENSITY * width * height;
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cpFloat moment = cpMomentForBox(mass, width, height);
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body = cpSpaceAddBody(space, cpBodyNew(mass, moment));
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cpBodySetPosition(body, cpv(-50, -100));
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cpBodySetVelocity(body, cpv(0, -100));
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cpBodySetAngularVelocity(body, 1);
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shape = cpSpaceAddShape(space, cpBoxShapeNew(body, width, height, 0.0));
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cpShapeSetFriction(shape, 0.8f);
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}
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{
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cpFloat width = 40.0f;
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cpFloat height = width * 2;
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cpFloat mass = 0.3 * FLUID_DENSITY * width * height;
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cpFloat moment = cpMomentForBox(mass, width, height);
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body = cpSpaceAddBody(space, cpBodyNew(mass, moment));
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cpBodySetPosition(body, cpv(-200, -50));
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cpBodySetVelocity(body, cpv(0, -100));
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cpBodySetAngularVelocity(body, 1);
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shape = cpSpaceAddShape(space, cpBoxShapeNew(body, width, height, 0.0));
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cpShapeSetFriction(shape, 0.8f);
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}
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cpCollisionHandler* handler = cpSpaceAddCollisionHandler(space, 1, 0);
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handler->preSolveFunc = (cpCollisionPreSolveFunc)waterPreSolve;
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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 Buoyancy = {
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"Simple Sensor based fluids.", 1.0 / 180.0, init, update, ChipmunkDemoDefaultDrawImpl, destroy,
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};
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