CCSprite scale and physics problem

[jjxtra]

Changing scale of CCSprite AFTER it is added to a physics node or a sprite batch node that is inside a physics node does not update physics body

[condor304]

+1 I have the same problem.

[rabzu]

+1

[slembcke]

This is actually intentional. There isn't a good way to apply a non-rigid transform to a rigid body and get a reasonable physically correct response. It's also quite expensive to do.

If you force the body into contact with another body by changing its, it will resolve the overlap in a very mushy, non-rigid way. It is possible to handle this in Chipmunk using collision handler callbacks and surface velocities, both of which are exposed by CCPhysics. It will probably never be implemented directly in Chipmunk because it's expensive and hard to generalize.

It is possible to re-sync the shape if you really want by calling the [CCShape rescaleShape:] method with the transform from the CCNode.nonRigidTransform property. Both of these are private, though I've been considering exposing a public method on CCPhysicsBody to allow re-syncing physics shapes to the node transforms manually. Would that be sufficient?

[DSalko]

slembcke, thank you for answer. I think exposing re-sync method is a good idea.

[jjxtra]

Re-sync will be sufficient, thanks!

[jjxtra]

Most uses cases would not be called every frame, only in cases where a game object changes size - say the player drinks a potion to grow big or small for example.

[cocojoe]

The private methods are perfect for that as I use them for exactly that
situation, shrink/grow powerups. Not had any problems at all.

On 19 February 2014 20:18, Jeff Johnson notifications@github.com wrote:

Most uses cases would not be called every frame, only in cases where a
game object changes size - say the player drinks a potion to grow big or
small for example.

Reply to this email directly or view it on GitHubhttps://github.com//issues/594#issuecomment-35543437
.

Martin

[DSalko]

cocojoe, can you please post some code, how you do it via private methods? Do you need to change cocos source for this? Thanks.

[cocojoe]

I rocked this in 2.1 with the following:

// Scale Circle Shapes
        for(ChipmunkCircleShape* newShape in self.chipmunkObjects)
        {
            if([newShape isKindOfClass:[ChipmunkCircleShape class]]) {
                cpCircleShapeSetRadius([newShape shape],[newShape radius]*scale); // Unsafe Resize
                cpCircleShapeSetOffset([newShape shape],ccpMult([newShape offset],scale));
            }
        }

Not tried in v3 yet.

[DSalko]

cocojoe, thanks. I had no luck with this in v3, following works for me ( suggested by slembcke )

CCPhysicsShape* shape = self.physicsBody.shapeList; 
[shape rescaleShape: [self nonRigidTransform]];

But I had to expose rescaleShape, nonRigidTransform and shapeList.