How to drag cpBody using UIPanGestureRecognizer coordinates?

[jvanbev1]

I am not using cocos2D, just straight up Chipmunk. When I drag using a UIPanGestureRecognizer, I want the cpBody to move where my finger is! Then when I raise my finger, it begins to drop (with some angular velocity in the direction I was dragging it). How do I do this?! I was looking at this...http://chipmunk-physics.net/forum/viewtopic.php?t=1598 But I feel it's not the best way.

Any advice would be great thanks!

As of now I have...

Code: Select all

    CGPoint location = [gesture locationInView:gesture.view.superview];
    
    if(gesture.state == UIGestureRecognizerStateBegan){
        mouse = cpMouseNew(space);
        cpMouseMove(mouse, cpv(location.x, location.y));
        cpMouseGrab(mouse, cpv(location.x, location.y));
    }
    else if (gesture.state == UIGestureRecognizerStateChanged) {
        //move the mouse to the click
        cpMouseMove(mouse, cpv(location.x, location.y));
        
        if(mouse->grabbedBody == nil){
            //if there's no associated grabbed object
            // try get one
            cpMouseGrab(mouse, cpv(location.x, location.y));
        }
    }
    else if (gesture.state == UIGestureRecognizerStateEnded){
        cpMouseRelease(mouse);
    }

and using cpMouse...

Code: Select all

/* Copyright (c) 2008 Tommy Thorsen
 *
 * 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 "cpMouse.h"
#include <stdlib.h>


static void
mouseUpdateVelocity(cpBody *body,
                    cpVect gravity,
                    cpFloat damping,
                    cpFloat dt)
{
    cpMouse *mouse = (cpMouse *)body->data;
    
    /*
     *  Calculate the velocity based on the distance moved since the
     *  last time we calculated velocity. We use a weighted average
     *  of the new velocity and the old velocity to make everything
     *  a bit smoother.
     */
    cpVect newVelocity = cpvmult(mouse->moved, 1.0f / dt);
    
    body->v = cpvadd(cpvmult(body->v, 0.7f),
                     cpvmult(newVelocity, 0.3f));
    
    mouse->moved = cpvzero;
}

static void
mouseUpdatePosition(cpBody *body,
                    cpFloat dt)
{
}

cpMouse *
cpMouseAlloc()
{
    return (cpMouse *)malloc(sizeof(cpMouse));
}

cpMouse *
cpMouseInit(cpMouse *mouse, cpSpace *space)
{
    mouse->space = space;
    mouse->grabbedBody = NULL;
    mouse->moved = cpvzero;
    
    mouse->body = cpBodyNew(INFINITY, INFINITY);
    mouse->body->velocity_func = mouseUpdateVelocity;
    mouse->body->position_func = mouseUpdatePosition;
    mouse->body->data = (void *)mouse;
    
    mouse->shape = cpCircleShapeNew(mouse->body, 3.0f, cpvzero);
    mouse->shape->layers = (unsigned int)(1 << 31);
    
    mouse->joint = NULL;
    
    cpSpaceAddBody(mouse->space, mouse->body);
    cpSpaceAddShape(mouse->space, mouse->shape);
    
    return mouse;
}

cpMouse *
cpMouseNew(cpSpace *space)
{
    return cpMouseInit(cpMouseAlloc(), space);
}

void
cpMouseDestroy(cpMouse *mouse)
{
    cpMouseRelease(mouse);
    
    cpSpaceRemoveShape(mouse->space, mouse->shape);
    cpSpaceRemoveBody(mouse->space, mouse->body);
    
    cpShapeFree(mouse->shape);
    cpBodyFree(mouse->body);
}

void
cpMouseFree(cpMouse *mouse)
{
    if (mouse) {
        cpMouseDestroy(mouse);
        free(mouse);
    }
}

cpVect
convertPointToCGPoint(cpVect originalPosition, int height)
{
    return cpv(originalPosition.x, originalPosition.y + height);
}

void
cpMouseMove(cpMouse *mouse, cpVect position)
{
    mouse->moved = cpvadd(mouse->moved,
                          cpvsub(position, mouse->body->p));
    mouse->body->p = position;
}

void
cpMouseGrab(cpMouse *mouse, cpVect point)
{
    cpMouseRelease(mouse);
    
    mouse->grabbedBody = NULL;
    
    cpShape *shape = cpSpacePointQueryFirst(mouse->space, point, (unsigned int)(1 << 31), 0);
    
    if (shape) {
        mouse->grabbedBody = shape->body;
        mouse->joint = cpPivotJointNew2(mouse->body,
                                        mouse->grabbedBody,
                                        cpvzero,
                                        cpBodyWorld2Local(mouse->grabbedBody, point));
        mouse->joint->maxForce = 30000.0f;
        //mouse->joint->biasCoef = 0.15f;
        cpSpaceAddConstraint(mouse->space, mouse->joint);
    }
}

void
cpMouseRelease(cpMouse *mouse)
{
    if (!mouse->joint) {
        return;
    }
    
    cpSpaceRemoveConstraint(mouse->space, mouse->joint);
    cpConstraintFree(mouse->joint);
    mouse->joint = NULL;
    
    mouse->grabbedBody = NULL;
}

But it's very jumpy and sometimes the bodies go out of the screen, sometimes they freeze...etc. Also there is a problem with converting the view location vs the shape location. I can't use the ccConvertPointToGL because I'm not using cocos2d.