[XNA] - Problem with 'root bone translation' flipY

randeroo

Hi,

There was a recent change tagged as 1.7.08 in github (commit 2b241c3 from 16th Jan) which made the following change in some of the runtimes.

Previously...

worldY = (flipY && flipY != yDown) ? -y : y;

Now...

worldY = flipY != yDown ? -y : y;

I have only just updated my run-time to this version and this change seems to have caused some problems. For XNA the yDown is set to true (which sounds right because the origin is top left). So, I might set the location to be 500, 800 (800 pixels down the screen) and as long as my skeleton is less than 800 pixels tall then it will fit on the screen and not be poking off the top of the screen.

With the recent change (above) where flipY is false but yDown is true the worldY gets set to -800 which means the skeleton is not on screen.

I'm not actually sure what the flipY setting is meant to do? Is the intention that the root bone would stay in the same place but the skeleton would be mirrored in the vertical axis. (e.g. if the root bone was at the feet of the skeleton then setting flipY to true would display the mirror image of the skeleton as if the skeleton was stood on a mirror? Or does it do something else?

I did a few tests...

If I set the flipY to true on the skeleton then indeed the skeleton is mirrored about the root bone as I describe - this works for the old code and the new code in XNA. This makes sense because the code is effectively the same as flipY is true.

However if the flipY is set to false then the old code seems to work correctly (in my eyes) as the root bone location is the same but the skeleton is up the right way. But in the new code the skeleton is off the screen.

I hope the above makes sense. Could you take a look at some point Nate and see if this is a bug or if I have misunderstood what is going on?

Many thanks 🙂

randeroo

Pharan

The intention of flipX and flipY is so the whole skeleton gets flipped along its origin (its 0,0) regardless of where the root bone is. So if the root bone is really far away from the 0,0 point, flipping will cause the character to to jump to the opposite side.

This is why logical movements are supposed to be set on the Skeleton's x and y and not on the root bone. Any movements of the root bone are ideally purely visual/aesthetic like shaking or some rotation. Not something that affects game logic like moving across a level.

I think for XNA, you should ideally be updating logical coordinates to Skeleton.x and Skeleton.y.

Nate

Yup, Pharan is the man!

Setting the root bone position was the old way to do it, sorry about the confusion switching to using the skeleton x/y. I even confused myself when the examples were still using the root bone for positioning, which is why it took so long to fix all the runtimes. 😃

randeroo

Awesome guys - many thanks for explaining that. Tested this morning and confirmed that using skeleton.x and skeleton.y works.

I love the way I post a question just before going to bed and it is answered ready for when I wake up the next morning 🙂