Offset, Mounted Rotation...

There seems to be a little confusion over mounting objects and having the object rotate around another point other than its center. I've mentioned before that I'll be looking at that feature and the problems it causes for the physics/angular collision physics.

I've kinda gone over this a few too many times and perhaps I've not explained the situation very well so here's a graphical example of how to achieve it.

If you've got an object like this and you mount it, it would rotate around the center of the object (marked with a yellow cross) which isn't what you'd want as you want it to rotate around the little dark-grey disk so you'd simply organise your graphic like this and it would rotate around the correct point.

If you've got a single image and you want to rotate it around lots of different points on the image (cannot think of a reason to do this), only then would you need seperate art.

Until this is changed, stuff rotates around the images center. You can mount it to any point on the target object but it will always rotate around its center. As I've mentioned in other posts, rotating around any point other than the center adds complexity to the physics routines and I'll be looking at efficient methods to get around this. I won't just leave it as it is. It's EA guys. ;)

If this is totally unacceptable then there's an alternative but it involves an extra object. Don't forget that you can generate a fxSceneObject2D as these don't render anything but have all the core capabilities. You can mount this to the position on the target object and mount your object to this offset by a constant like "1 0" or whatever you like. The size of the invisible fxSceneObject2D then determines the offset from the center of the image.

Here's a code example...

// Show the bounding-boxes.
t2dSceneGraph.setDebugOn( BIT(1) );

// Create base sprite we want to mount to.	
new fxStaticSprite2D(testSprite1) { scenegraph = t2dSceneGraph; };
testSprite1.setSize( 10 );
testSprite1.setImageMap(tileMapImageMap);
// Move it so we can show we're mounted and not faking it.
testSprite1.setLinearVelocityX( 1 );

// Create hidden mount (articulation frame).
new fxSceneObject2D(hiddenMount) { scenegraph = t2dSceneGraph; };
// Use this size to control the offset.
hiddenMount.setSize( 10 );
hiddenMount.setAutoRotation( 90 );
hiddenMount.mount( testSprite1, "0 0", 0, false );

// Create our object we want to mount.	
new fxStaticSprite2D(testSprite2) { scenegraph = t2dSceneGraph; };
testSprite2.setSize( 10 );
testSprite2.setImageMap(tileMapImageMap,1);
testSprite2.mount( hiddenMount, "0 1" );

Here's an example of that working...

Hope this helps,

- Melv.