Question

I want my sprite to move to a precise pixel location. I use the following code in the update method to move my sprite (kPlayerSpeed = 60.0f):

if (ccpDistance(self.position, requestedPosition) < kPlayerSpeed) {
            [self changeState:kStateWalking];
            return;
        }

switch (self.characterState) {
        case kStateWalkingUp:
            self.position = ccp(self.position.x, self.position.y + kPlayerSpeed * deltaTime);
            break;
        case kStateWalkingDown:
            self.position = ccp(self.position.x, self.position.y - kPlayerSpeed * deltaTime);
            break;
        case kStateWalkingLeft:
            self.position = ccp(self.position.x - kPlayerSpeed * deltaTime, self.position.y);
            break;
        case kStateWalkingRight:
            self.position = ccp(self.position.x + kPlayerSpeed * deltaTime, self.position.y);
            break;
        case kStateIdle:
            break;
        default:
            break;

if (ccpDistance(self.position, requestedPosition) < kPlayerSpeed)

With this code the player stops near but not exactly on the spot.

Answer 1

Andres, thanks for the reply.

I couldn’t quite get your code to work, so using your lead I did a bit more research and came up with this…

    float step = kPlayerSpeed * deltaTime;
    float dist = ccpDistance(self.position, requestedPosition);

    if (dist <= step) {
        self.position = requestedPosition;
    } else {
        CGPoint vectorBetweenAB = ccpSub(self.position, requestedPosition);
        CGPoint normVectorBetweenPositionAndEnd = ccpNormalize(vectorBetweenAB);
        CGPoint movementVectorForThisFrame = ccpMult(normVectorBetweenPositionAndEnd, step);
        if (self.position.x > movementVectorForThisFrame.x) {
            movementVectorForThisFrame.x = -movementVectorForThisFrame.x;
        }
        if (self.position.y > movementVectorForThisFrame.y) {
            movementVectorForThisFrame.y = -movementVectorForThisFrame.y;
        }
        self.position = ccpAdd(self.position, movementVectorForThisFrame);
    }

Is there a better way to do it than this?

Thanks