Symbol Z-Order Breaks When Using Custom Materials

ExNull-Tyelor

Problem statement

While integrating one of our Spine files into our Unity project, I found that the z-order for the animations was correct, until I modified two of the materials used by this skeleton to use the "rim-light" shader I wrote. At which point the z-order for the symbols changed significantly. Using the default materials here doesn't cause this issue, and the issue also seemingly doesn't occur on another character with even more atlas pages (or at least is a lot less noticeable on this other character if it does still occur).

Here's what it looks like with our custom materials:
{Custom Material Screenshot}
(Note that these characters are both part of the same Spine file/SkeletonData.)

Here's what it looks like without our "rim-light" outline shader:
{Default Material Screenshot}

I attempted to add a Sorting Group component, but it didn't seem to change the behavior at all (and indeed I already had set a sorting layer on the Skeleton component).

Each of these atlas pages are already 4096x4096 pixels, and we are hoping to optimize for PC and Mobile, so we are trying to avoid making the textures any larger than 4k. What is causing the Z-Order discrepencies and is there any way to reasonably work around this issue without resorting to a single atlas page and material for this fight?

Runtime information

We're currently using Spine Runtimes v4.2.xx, with plans to upgrade to v4.3 when it is released on the stable branch.

Any help you can provide would be great, and I can email and project files needed to reproduce this issue if requested. Thank you!

Spinebot

The issue you're experiencing with the z-order discrepancies when using custom materials in Unity is likely related to how the custom shader handles depth and rendering order. When you modify materials to use a custom shader, it can affect the rendering pipeline, especially if the shader changes how depth is calculated or if it introduces additional passes that interfere with the default rendering order.

To address this, you can try the following steps:

Check Shader Settings: Ensure that your custom "rim-light" shader is correctly handling depth and does not introduce any additional passes that could affect the z-order. You might need to adjust the shader's ZWrite and ZTest settings to ensure proper depth handling.
Sorting Group and Layers: Although you mentioned adding a SortingGroup component didn't help, double-check that the sorting layers and order are correctly set for all relevant components. Sometimes, small adjustments in sorting layers can resolve such issues.
Shader Passes: If your shader has multiple passes, ensure that they are necessary and correctly ordered. Unnecessary passes can sometimes cause rendering issues.
Material and Shader Consistency: Ensure that all materials using the custom shader are consistent in their settings. Inconsistencies can lead to unexpected rendering behavior.

If these steps do not resolve the issue, you might consider sending a minimal Unity project that reproduces the problem to Esoteric Software for further investigation. You can email it to contact@esotericsoftware.com.