I just upgraded Spine from 3.6 to 3.7 and found that all my units are not rendering.

They all use RenderSeparator to separate character shadow and the character itself.
If I enable the main MechRenderer, it will show but of course with incorrect render order.

Below is the components setup that was working in 3.6 and not working after upgrade.

I was thinking if it is caused by using the old SkeletonAnimation class instead of SeletonMecaim class.
But than I have a few questions about changing the code to use SeletonMecaim.

1. the new create instance method now accept a T and I am not sure if I am doing it right.

mSpineSkeleton = SkeletonAnimation.NewSkeletonAnimationGameObject(dataAsset);  // 3.6
mSpineSkeleton =  SkeletonMecanim.NewSpineGameObject<SkeletonMecanim>(dataAsset); // like this?

2. the SkeletonAnimation has a AnimationState member that I can get and use it to control animations. e.g. SetAniamtion(), etc. Now it is gone. I don't know what to do about it.

mAnimState = mSpineSkeleton.AnimationState; // 3.6

I searched the code and found this from the runtime:

var animationStateComponent = (animator.GetComponent(typeof(IAnimationStateComponent))) as IAnimationStateComponent;
         state = animationStateComponent.AnimationState;

I tried the following but with null error.

var animationStateComponent = (mSpineSkeleton.GetComponent(typeof(IAnimationStateComponent))) as IAnimationStateComponent;
            mAnimState = animationStateComponent.AnimationState; // animationStateComponent is null

Also, is it normal to not seeing the character even in Editor (non-playing) state? I tested the separator renderer by hand and with separator renderers turned on and default renderer turned off, it doesn't show anything. Was it working before the upgrade? (3.6)

Both editor and play mode is not rendering.

I guess the issue maybe related to how I compose the spine game object by code which no longer work in 3.7.
I need to dynamically create the game object and add the components to make things more flexible and dynamic.

Here is part of the code how I add the Separator Renderer:

// SlotBlendModes
{
    var sbm = mSpineSkeleton.gameObject.AddComponent<SlotBlendModes>();
    sbm.multiplyMaterialSource = multiplyMaterialSource;
    sbm.screenMaterialSource = screenMaterialSource;
}

#region [ ========== SkeletonRenderSeparator ========== ]
{
    var srs = mSpineSkeleton.PrepareRenderSeparator();
    if (srs != null)
    {
        if (mSpineSkeleton.separatorSlots.Count == 1)
        {
            // shadow + unit
            srs.CreateSkeletonPartRenderer("shadow", -999);
            var spr = srs.CreateSkeletonPartRenderer("unit");
            mUnitRenderer = spr.GetComponent<Renderer>();
        }
        else if (mSpineSkeleton.separatorSlots.Count == 2)
        {
            // shadow + unit + effect
            srs.CreateSkeletonPartRenderer("shadow", -999);
            var spr = srs.CreateSkeletonPartRenderer("unit");
            mUnitRenderer = spr.GetComponent<Renderer>();
            srs.CreateSkeletonPartRenderer("effect", 999);
        }

    var mainRenderer = mSpineSkeleton.GetComponent<MeshRenderer>();
    mainRenderer.enabled = false;

    srs.enabled = true;
}
else
{
    Debug.LogWarningFormat(this, "Unit-{0} does not have layers separated.", unitID);
}
}
#endregion [ ========== SkeletonRenderSeparator (End) ========== ]

mSpineSkeleton.Initialize(false);

Here is the two extension function I used to the code above.

public static SkeletonRenderSeparator PrepareRenderSeparator(this SkeletonAnimation sa)
{
    var slots = sa.Skeleton.Data.Slots;

var detectedSeparators = new List<Spine.SlotData>();
foreach (var slot in slots)
{
    if (slot.Name.StartsWith("==="))    // all separator slot start with '==='
    {
        detectedSeparators.Add(slot);
    }
}

if (detectedSeparators.Count <= 0)
    return null;

var srs = sa.gameObject.AddComponent<SkeletonRenderSeparator>();
srs.SkeletonRenderer = sa;

sa.separatorSlots.Clear();
sa.separatorSlotNames = new string[detectedSeparators.Count];
int i = 0;
foreach (var slot in detectedSeparators)
{
    sa.separatorSlotNames[i] = slot.Name;
    sa.separatorSlots.Add(sa.skeleton.FindSlot(slot.Name));
    i++;
}
return srs;
}

public static SkeletonPartsRenderer CreateSkeletonPartRenderer(
                                this SkeletonRenderSeparator srs,
                                string name, int sortingOrder = 0)
{
    var go = new GameObject(name, typeof(MeshFilter), typeof(MeshRenderer));
    var spr = go.AddComponent<SkeletonPartsRenderer>();

go.transform.SetParent(srs.transform, false);


// Mesh 
{
    var meshFilter0 = srs.GetComponent<MeshFilter>();
    var meshFilter1 = go.GetComponent<MeshFilter>();
    meshFilter1.mesh = meshFilter0.mesh;
}

// Material
{
    var mr0 = srs.GetComponent<MeshRenderer>();
    var mr1 = go.GetComponent<MeshRenderer>();
    mr1.material = mr0.material;
}

spr.SetSortingOrder(sortingOrder);

srs.partsRenderers.Add(spr);

return spr;
}

Note that I changed the separatorSlotNames back to public to have the code compile because it is private in 3.7. But I guess some other changes in 3.7 make the code above not working anymore.

Thank you!
The characters are all visible in play mode now.
In the Scene panel it still not showing the character but I can see them in Game panel so it isn't a big issue.

I found another problem. One of my character doesn't have all the parts rendered.
Two parts of her hair is not rendering. I notice that those parts are all using "path". (Already re-exported from latest Spine 3.7 beta version)

Btw, you mentioned that SlotBlendMode is no longer needed. When blending like multiply is needed, can config the SkeletonDataAsset. Can this process be done automatically? e.g. detect if multiply or other blend mode used in skeleton and auto assign the data modifier?

My concern is, it is now requiring more actions to perform. In the original workflow, I only need to export the character to the project folder. The code and the SlotBlendMode will take care of the everything. I don't need to do anything to make it work which is very smooth in comparison.

Any updates on this?

Have you try to delete irrelevant bones leaving only the affected parts to test? That would help make tracing code much simpler.
Can also run both new/old functions in parallel at the same time and compare result systematically from code to test which function is having different output.