PMA Alpha Edge Artifacts in URP

Aisha

🧩 Problem Summary (in English):
Issue:
I’m experiencing unexpected white/gray seams or "halo" edges between image parts in my Spine character after importing into Unity (URP project).
These seams are especially visible around semi-transparent areas like lips or overlapping parts.

However, this issue does not exist in my previous Unity project using exactly the same exported Spine assets (.skel / .atlas / .png). So I’m confident the export settings and the assets themselves are correct.

✅ What I have already checked and confirmed:
✅ Using URP project

✅ Using latest spine-unity 4.2 from official GitHub UPM URL

✅ Installed both:

"com.esotericsoftware.spine.spine-csharp"

"com.esotericsoftware.spine.spine-unity"

"com.esotericsoftware.spine.urp-shaders"

✅ Shader in use is Spine/URP/Skeleton PMA Multiply

✅ Color space set to Gamma

✅ Straight Alpha Texture is set to false

✅ Texture import settings match previous working project:

sRGB: ✅ On

Alpha is Transparency: ❌ Off

Texture Type: Default

✅ Unity version is the same as previous project

✅ No warnings or material setup issues visible in SkeletonData component

✅ Other assets in the project display normally; issue only appears on Spine character

❌ What I tried (but didn't fix it):
❌ Re-exporting Spine JSON with "Premultiplied Alpha" unchecked

❌ Switching Shader to Skeleton PMA Additive, Straight, Screen, etc.

❌ Switching Color Space between Linear and Gamma

❌ Manually toggling “Straight Alpha Texture” flag in material

❌ Replacing .skel, .atlas, .png with known-good copies

❌ Following tutorials and fixes from YouTube (especially about shader or material mismatch) — didn’t help

❌ Completely deleting and re-installing spine-unity via GitHub UPM

💡 Hypothesis:
Since the exact same asset works correctly in the previous project, I suspect the cause lies in:

Either a subtle difference in URP shader setup or post-processing,

Or a Unity texture import pipeline difference triggered by the current project setup,

Or perhaps an invisible project setting difference I overlooked.

🙏 What I Need Help With:
Is there any known reason why PMA textures would show edge artifacts in URP despite correct setup?

Are there extra shader settings / customizations I may need to carry over from previous project?

Can you confirm if URP + PMA Multiply Shader still needs manual tweaks in certain Unity versions?

Let me know if you’d like me to attach comparison screenshots or Unity package files — I can provide both the working project and broken one.

Thank you so much in advance 🙏

Harald

Sorry to hear you're having troubles.

Aisha Shader in use is Spine/URP/Skeleton PMA Multiply

There is no shader Spine/URP/Skeleton PMA Multiply, what exact shader do you mean? The following shaders exist:
Universal Render Pipeline/Spine/Skeleton
Universal Render Pipeline/Spine/Blend Modes/Skeleton Multiply
If you used URP/Spine/Blend Modes/Skeleton Multiply, then note that this is a multiply blend mode (like in Photoshop) which is very likley not what you want.

If you export your atlas textures from Spine with PMA workflow, sRGB Color texture shall be enabled as shown and described here.

Aisha Is there any known reason why PMA textures would show edge artifacts in URP despite correct setup?

Note that your setup is not correctly following the documentation.

Aisha Can you confirm if URP + PMA Multiply Shader still needs manual tweaks in certain Unity versions?

There should be nothing that needs to be tweaked apart from setting the correct texture import settings and material settings as described in the documentation above.

Spinebot

The issue you're experiencing with white or gray seams around semi-transparent areas in your Spine character when using URP in Unity is likely related to the handling of premultiplied alpha (PMA) textures. Based on the information provided, it seems you've already checked most of the common causes, such as ensuring the correct shader and texture import settings. However, there are a few additional steps you can consider:

Check Shader Keywords: Sometimes, shader keywords from previous materials can cause unexpected behavior. Try resetting the material in the Inspector and reassigning the texture and properties to ensure no stray keywords are affecting the shader.
Verify URP Settings: Ensure that your URP settings are consistent with the previous project. This includes checking the render pipeline asset settings and any post-processing effects that might be applied.
Compare Project Settings: Since the same assets work in a previous project, compare the project settings between the two projects. Look for differences in graphics settings, quality settings, and any custom scripts or assets that might affect rendering.
Test with Minimal Project: Create a minimal Unity project with only the Spine assets and URP setup to isolate the issue. This can help determine if the problem is specific to the current project setup.
Contact Support: If the issue persists, consider sending a minimal Unity project that demonstrates the problem to Esoteric Software for further investigation. You can email it to contact@esotericsoftware.com, mentioning the context of your issue.

These steps should help you identify the root cause of the artifacts and resolve the issue.

Harald

@Aisha Also note that when using the URP 2D Renderer, you have to use the Spine URP 2D shaders instead of the URP 3D shaders respectively. This is described here:
https://esotericsoftware.com/spine-unity-rendering#URP-Shaders-Extension-Package