#include <stdio.h>
#include <chipmunk.h>
int main(void){
// cpVect is a 2D vector and cpv() is a shortcut for initializing them.
cpVect gravity = cpv(0, -100);
// Create an empty space.
cpSpace *space = cpSpaceNew();
cpSpaceSetGravity(space, gravity);
// Add a static line segment shape for the ground.
// We'll make it slightly tilted so the ball will roll off.
// We attach it to a static body to tell Chipmunk it shouldn't be movable.
cpShape *ground = cpSegmentShapeNew(cpSpaceGetStaticBody(space), cpv(-20, 5), cpv(20, -5), 0);
cpShapeSetFriction(ground, 1);
cpSpaceAddShape(space, ground);
// Now let's make a ball that falls onto the line and rolls off.
// First we need to make a cpBody to hold the physical properties of the object.
// These include the mass, position, velocity, angle, etc. of the object.
// Then we attach collision shapes to the cpBody to give it a size and shape.
cpFloat radius = 5;
cpFloat mass = 1;
// The moment of inertia is like mass for rotation
// Use the cpMomentFor*() functions to help you approximate it.
cpFloat moment = cpMomentForCircle(mass, 0, radius, cpvzero);
// The cpSpaceAdd*() functions return the thing that you are adding.
// It's convenient to create and add an object in one line.
cpBody *ballBody = cpSpaceAddBody(space, cpBodyNew(mass, moment));
cpBodySetPosition(ballBody, cpv(0, 15));
// Now we create the collision shape for the ball.
// You can create multiple collision shapes that point to the same body.
// They will all be attached to the body and move around to follow it.
cpShape *ballShape = cpSpaceAddShape(space, cpCircleShapeNew(ballBody, radius, cpvzero));
cpShapeSetFriction(ballShape, 0.7);
// Now that it's all set up, we simulate all the objects in the space by
// stepping forward through time in small increments called steps.
// It is *highly* recommended to use a fixed size time step.
cpFloat timeStep = 1.0/60.0;
for(cpFloat time = 0; time < 2; time += timeStep){
cpVect pos = cpBodyGetPosition(ballBody);
cpVect vel = cpBodyGetVelocity(ballBody);
printf(
"Time is %5.2f. ballBody is at (%5.2f, %5.2f). It's velocity is (%5.2f, %5.2f)\n",
time, pos.x, pos.y, vel.x, vel.y
);
cpSpaceStep(space, timeStep);
}
// Clean up our objects and exit!
cpShapeFree(ballShape);
cpBodyFree(ballBody);
cpShapeFree(ground);
cpSpaceFree(space);
return 0;
}