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Draw Order when using multiple tracks unsupported?
We have a spine that uses multiple tracks -
track 1 - base animation. for idle, walking, etc.
track 2 - for special overrides when you have something equipped in your right hand
track 3 - for special overrides when you have something equipped in your left hand
for tracks 2 & 3, we've placed keyframes in some of these animations that nudge the draw order of slots
example: unsheathing a sword from behind your back should move the sword from behind the character to in front of it. if we want to unsheath two swords independently of each other, each track animation will have a keyframe to nudge the relevant slots around.
from what i've gathered, it seems spine doesn't handle this set up well. It seems that the draw order timeline for the highest track stomps on any draw order changes done by tracks beneath it. In other words, a keyframe that adjusts the draw order ends up being like an absolute snapshot of the draw order for the entire rig, instead of just relevant slots you want to move around.
It looks like the json for a spine only includes the relevant draw order changes for a keyframe, so I was thinking of doing something like this in DrawOrderTimeline.Apply -
for (int i = 0, n = drawOrderToSetupIndex.Length; i < n; i++)
{
if (drawOrderToSetupIndex[i] != i)
{
drawOrderItems[i] = slotsItems[drawOrderToSetupIndex[i]];
}
}basically i just tweaked this loop to only update the draw order if the draw order from the json is different (otherwise it will just use whatever draw order was set previously)
this kinda seems to work, but there's some loose ends and little bugs this introduces. for example, i often clear a track by calling SetEmptyAnimation on the track, but it unfortunately isn't resetting the draw order here.
I can try to chase down all the edgecases, but i figured I'd shoot a message here in case this is a solved problem already.
Thanks!
also i'm curious, is there an advantage to treating draw order the way spine does? opposed to just introducing a z axis? it feels very rigid, but i suppose it's simpler/more straightforward
You're right, when keying the draw order the entire draw order is applied. Spine doesn't know if you only want to key part of the draw order, or what would happen if one animation moves some slots below other slots, and another animation moves the other slots above.
As you suggest, if draw order was done using a numeric z-index it would give you the granular control you are looking for, but would mean you need to key each slot whose z-index changes. This would mean potentially a lot more timelines and is clunkier in the UI.
In the JSON or binary data the draw order is encoded as the changes necessary to modify the setup draw order to get the draw order for the key. After applying the changes, the entire keyed draw order is set on the timeline for the key. The changes can be seen in Spine as green or red arrows when you modify the draw order in animate mode. This may not be what you expect, eg if you move a slot down one this could be seen as that slot being moved down one or the slot below it being moved up one. For more complex draw order changes there can be many different ways to arrive at the keyed draw order and Spine chooses the simplest. I don't think it would solve your problems to rely on the change list.
It may be easiest for you to manipulate draw order at runtime. Eg, after applying animations, if animation X was applied then ensure these slots are above these other slots. This way you could still use draw order keys where keying the whole draw order list makes sense (eg on track 0), while still having other draw order changes on top of that.
Nate wroteIt may be easiest for you to manipulate draw order at runtime. Eg, after applying animations, if animation X was applied then ensure these slots are above these other slots.
I could try that. is there a method i can call to manipulate it at runtime? or do i just have to set up my own thing to adjust the order of Skeleton.drawOrder?
In some ways I could see that being kind of a pain in the butt to get right. We want to have the animation drive the draw order (i.e. allow the order to change at some arbitrary time mid-animation), so we'd probably have to use spine events. I'd guess the animator would need to supply the index as an event parameter to bump the slots. This could be fairly error prone since they can't really preview the outcome in the tool
Tangential question: If i pursue this, is there some way i can get the spine tool to treat draw order as we are intending to in Unity? Perhaps recompile a DLL and drop it in for the editor to use or something? 
quick follow up, i think i've fixed any edgecases i was seeing rather simply.
In Skeleton.cs, i build an ExposedList<Slot> of the original slot order at the same time the drawOrder list is being constructed. I then added a method ResetDrawOrder() that clears the current drawOrder and copies the values from the original slot order list.
From there, i just call ResetDrawOrder whenever i set a new animation or whenever i set an empty animation. Hopefully that's enough to get the job done 8)
chase-cc wroteis there a method i can call to manipulate it at runtime?
You just manipulate Skeleton drawOrder to have the slots in the order you want. Just be careful not to remove slots. Note that SkeletonData slots is the setup pose draw order. To reset the draw order to the setup pose draw order, you can clear the draw order, then add all the slots from the SkeletonData.
chase-cc wroteis there some way i can get the spine tool to treat draw order as we are intending to in Unity? Perhaps recompile a DLL and drop it in for the editor to use or something?
I'm afraid Spine doesn't have a scripting API or similar. Maybe you could set the draw order in animations, so you can see it correctly in the editor, then use that in the code (maybe process the draw order keys, extract the draw orders, then delete the keys/timelines), or write code that matches it (though I understand you said you'd like the animations to define the draw order).
I'm not sure just resetting the draw order to the setup pose will solve your problem of wanting to combine draw orders from multiple animations, but you have a better handle on the specifics of your situation.