axmol/tests/cpp-tests/Classes/ChipmunkTestBed/demo/Unicycle.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* balance_body;
static cpFloat balance_sin = 0.0;
// static cpFloat last_v = 0.0;

static cpBody* wheel_body;
static cpConstraint* motor;

/*
        TODO:
        - Clamp max angle dynamically based on output torque.
*/

static inline cpFloat bias_coef(cpFloat errorBias, cpFloat dt)
{
    return 1.0f - cpfpow(errorBias, dt);
}

static void motor_preSolve(cpConstraint* motor, cpSpace* space)
{
    cpFloat dt = cpSpaceGetCurrentTimeStep(space);

    cpFloat target_x = ChipmunkDemoMouse.x;
    ChipmunkDebugDrawSegment(cpv(target_x, -1000.0), cpv(target_x, 1000.0), RGBAColor(1.0, 0.0, 0.0, 1.0));

    cpFloat max_v = 500.0;
    cpFloat target_v =
        cpfclamp(bias_coef(0.5, dt / 1.2) * (target_x - cpBodyGetPosition(balance_body).x) / dt, -max_v, max_v);
    cpFloat error_v    = (target_v - cpBodyGetVelocity(balance_body).x);
    cpFloat target_sin = 3.0e-3 * bias_coef(0.1, dt) * error_v / dt;

    cpFloat max_sin      = cpfsin(0.6);
    balance_sin          = cpfclamp(balance_sin - 6.0e-5 * bias_coef(0.2, dt) * error_v / dt, -max_sin, max_sin);
    cpFloat target_a     = asin(cpfclamp(-target_sin + balance_sin, -max_sin, max_sin));
    cpFloat angular_diff = asin(cpvcross(cpBodyGetRotation(balance_body), cpvforangle(target_a)));
    cpFloat target_w     = bias_coef(0.1, dt / 0.4) * (angular_diff) / dt;

    cpFloat max_rate = 50.0;
    cpFloat rate = cpfclamp(cpBodyGetAngularVelocity(wheel_body) + cpBodyGetAngularVelocity(balance_body) - target_w,
                            -max_rate, max_rate);
    cpSimpleMotorSetRate(motor, cpfclamp(rate, -max_rate, max_rate));
    cpConstraintSetMaxForce(motor, 8.0e4);
}

static void update(cpSpace* space, double dt)
{
    cpSpaceStep(space, dt);
}

static cpSpace* init(void)
{
    ChipmunkDemoMessageString =
        "This unicycle is completely driven and balanced by a single cpSimpleMotor.\nMove the mouse to make the "
        "unicycle follow it.";

    cpSpace* space = cpSpaceNew();
    cpSpaceSetIterations(space, 30);
    cpSpaceSetGravity(space, cpv(0, -500));

    {
        cpShape* shape     = NULL;
        cpBody* staticBody = cpSpaceGetStaticBody(space);

        shape = cpSpaceAddShape(space, cpSegmentShapeNew(staticBody, cpv(-3200, -240), cpv(3200, -240), 0.0f));
        cpShapeSetElasticity(shape, 1.0f);
        cpShapeSetFriction(shape, 1.0f);
        cpShapeSetFilter(shape, NOT_GRABBABLE_FILTER);

        shape = cpSpaceAddShape(space, cpSegmentShapeNew(staticBody, cpv(0, -200), cpv(240, -240), 0.0f));
        cpShapeSetElasticity(shape, 1.0f);
        cpShapeSetFriction(shape, 1.0f);
        cpShapeSetFilter(shape, NOT_GRABBABLE_FILTER);

        shape = cpSpaceAddShape(space, cpSegmentShapeNew(staticBody, cpv(-240, -240), cpv(0, -200), 0.0f));
        cpShapeSetElasticity(shape, 1.0f);
        cpShapeSetFriction(shape, 1.0f);
        cpShapeSetFilter(shape, NOT_GRABBABLE_FILTER);
    }

    {
        cpFloat radius = 20.0;
        cpFloat mass   = 1.0;

        cpFloat moment = cpMomentForCircle(mass, 0.0, radius, cpvzero);
        wheel_body     = cpSpaceAddBody(space, cpBodyNew(mass, moment));
        cpBodySetPosition(wheel_body, cpv(0.0, -160.0 + radius));

        cpShape* shape = cpSpaceAddShape(space, cpCircleShapeNew(wheel_body, radius, cpvzero));
        cpShapeSetFriction(shape, 0.7);
        cpShapeSetFilter(shape, cpShapeFilterNew(1, CP_ALL_CATEGORIES, CP_ALL_CATEGORIES));
    }

    {
        cpFloat cog_offset = 30.0;

        cpBB bb1 = cpBBNew(-5.0, 0.0 - cog_offset, 5.0, cog_offset * 1.2 - cog_offset);
        cpBB bb2 = cpBBNew(-25.0, bb1.t, 25.0, bb1.t + 10.0);

        cpFloat mass   = 3.0;
        cpFloat moment = cpMomentForBox2(mass, bb1) + cpMomentForBox2(mass, bb2);

        balance_body = cpSpaceAddBody(space, cpBodyNew(mass, moment));
        cpBodySetPosition(balance_body, cpv(0.0, cpBodyGetPosition(wheel_body).y + cog_offset));

        cpShape* shape = NULL;

        shape = cpSpaceAddShape(space, cpBoxShapeNew2(balance_body, bb1, 0.0));
        cpShapeSetFriction(shape, 1.0);
        cpShapeSetFilter(shape, cpShapeFilterNew(1, CP_ALL_CATEGORIES, CP_ALL_CATEGORIES));

        shape = cpSpaceAddShape(space, cpBoxShapeNew2(balance_body, bb2, 0.0));
        cpShapeSetFriction(shape, 1.0);
        cpShapeSetFilter(shape, cpShapeFilterNew(1, CP_ALL_CATEGORIES, CP_ALL_CATEGORIES));
    }

    cpVect anchorA  = cpBodyWorldToLocal(balance_body, cpBodyGetPosition(wheel_body));
    cpVect groove_a = cpvadd(anchorA, cpv(0.0, 30.0));
    cpVect groove_b = cpvadd(anchorA, cpv(0.0, -10.0));
    cpSpaceAddConstraint(space, cpGrooveJointNew(balance_body, wheel_body, groove_a, groove_b, cpvzero));
    cpSpaceAddConstraint(space, cpDampedSpringNew(balance_body, wheel_body, anchorA, cpvzero, 0.0, 6.0e2, 30.0));

    motor = cpSpaceAddConstraint(space, cpSimpleMotorNew(wheel_body, balance_body, 0.0));
    cpConstraintSetPreSolveFunc(motor, motor_preSolve);

    {
        cpFloat width  = 100.0;
        cpFloat height = 20.0;
        cpFloat mass   = 3.0;

        cpBody* boxBody = cpSpaceAddBody(space, cpBodyNew(mass, cpMomentForBox(mass, width, height)));
        cpBodySetPosition(boxBody, cpv(200, -100));

        cpShape* shape = cpSpaceAddShape(space, cpBoxShapeNew(boxBody, width, height, 0.0));
        cpShapeSetFriction(shape, 0.7);
    }

    return space;
}

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

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