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