Resize animation based on an externally defined bounding box

ssrun

I'm using a rendering system that let's you define a bounding box size where the asset gets rendered using that size and I'd like to know if Spine has a way to resize the animation based on the box size. For example, if I specify a 400x400 bounding box, I want to render my animation so that the largest extents never exceed 400.

ssrun

Nate

SkeletonData width and SkeletonData height give you the setup pose AABB. You can use that to scale your skeleton (on load or by scaling the root bone) to fit in any size box.

ssrun

I tried setting the scale on the root bone but it doesn't seem to change anything. Here is the code I'm using with the C++ generic runtime.

float widthRatio = newRect.GetWidth() / m_skeletonData->getWidth();
float heightRatio = newRect.GetHeight() / m_skeletonData->getHeight();
float scale = min(widthRatio, heightRatio);
spine::BoneData* boneData = m_skeletonData->findBone("root");
boneData->setScaleX(scale);
boneData->setScaleY(scale);

The size of the bounding box is 100x100 and I'm using the Spineboy sample which has a width and height of 419x686 so the scale calculated is about 0.145.

Nate

You'll need to either set the skeleton's scale (not skeleton data) or set the skeleton to the setup pose (so it gets the values from the skeleton data), and of course you'll need Skeleton updateWorldTransform. Setting it on the loader (SkeletonJson or SkeletonBinary) is probably better if you don't need to change it, and will work better if you have moved the root bone from 0,0.

ssrun

I've tried it and it doesn't work either. I'm wondering if changing the scale on SkeletonJson is allowed after I've already read in the data file. The size of the bounding box is given to me on a callback which happens after the atlas and json files are loaded. Would I need to reload everything after I receive the bounding box size callback?

Nate

Ah, sorry, of course you get the scale from the data returned by SkeletonJson. Yes, you would need to read the data again to use the loader scale. An alternative would be to read the JSON yourself to get the scale out, without building up the skeleton data. Or you could use a preprocessing step when you build your game to extract the scale to somewhere that is easily accessible when the game runs. Or you can set the scale on the root bone. Oh, you can set Skeleton scaleX and Skeleton scaleY. That is actually better than setting it on the root bone, as (like setting the loader scale) it will affect all bones, even those with disable inherit scale.

ssrun

Thank you. I used scaleX and scaleY on the Skeleton to achieve the goal.