Tint Black and Transparency with URP 3D rendering

Yimec

I have Spine characters in a 3D space using a custom shader to project shadows through the system defined by our game's technical artist. Programming has implemented a “flash” system (using Spine’s tint black) to provide impact feedback, for example.

However, it is currently not possible to use this tinting within animations created in Spine itself (for example, setting keyframes that return the sprite to white), and transparency is not being rendered either (although this is a smaller issue and not as important for us to solve).

What we would really like is to be able to restore the tint back to white whenever the animations require it.

Is there something we might be overlooking? How could we solve this?

We have also tried Spine’s default URP shaders, both 2D and 3D (in the case of the 3D shader, the sprites turn pink).

Harald

Yimec However, it is currently not possible to use this tinting within animations created in Spine itself (for example, setting keyframes that return the sprite to white),

Could you please describe in more detail why it's not possible? What have you tried, what was the expected outcome and what did you receive instead?

[..] and transparency is not being rendered either (although this is a smaller issue and not as important for us to solve).

Again, could you please describe what code you used to change transparency, and what material and shader settings you're using?

Yimec What we would really like is to be able to restore the tint back to white whenever the animations require it.

What do you mean by "when the animations require it"? In general you can set any tint you want, and add set tint via animations, or use animation events to set or clear a tint.

Yimec We have also tried Spine’s default URP shaders, both 2D and 3D (in the case of the 3D shader, the sprites turn pink).

Which exact version of the spine-unity runtime are you using (name of the unitypackage or version in the Package Manager), and which version of the Spine URP UPM package?

Are you using URP with a 3D renderer, or a 2D Renderer? What do you mean by "default" URP shader? There are three 2D and 3D shaders each, and all of them provide support for tint black.

If with a URP 3D shader the material is displayed as pink, are you sure youre using URP with a 3D renderer under Graphics settings?

Spinebot

Based on my knowledge, the issue you're experiencing is related to shader support for tint black functionality. Here's what you need to know:

Tint Black Support in Shaders

Currently, tint black (the feature allowing you to darken colors in addition to the regular tint) is only fully supported by the unlit shader Spine/Skeleton Tint Black in the built-in render pipeline. The URP shaders have limited support for this feature, which is why you're experiencing issues when trying to animate tint black values in your Spine animations.

For Your Specific Setup

Since you're using:

URP 3D rendering
A custom shader for shadow projection
Tint black for flash effects

You have a few options:

Extend Your Custom Shader: Your custom shader would need to implement tint black support similar to how the Spine/Skeleton Tint Black shader does. This means:
- Supporting vertex color-based tint black functionality
- Ensuring the shader properly reads and applies both the regular tint (Color) and dark tint (Dark Color) properties
Enable Tint Black at the Component: Make sure you have enabled Advanced - Tint Black at your SkeletonRenderer (or SkeletonAnimation) component. Without this enabled, the tint black data won't be passed to your shader properly.
Verify Transparency Settings: For the transparency issue, ensure your texture import settings match your export settings from Spine. Check that you're using the correct alpha workflow (straight alpha vs premultiplied alpha) and that your shader's blend mode is set up correctly for transparency.

Why the Default URP Shaders Don't Work

The pink color you're seeing with the URP 3D shader suggests a shader compilation error or missing shader properties. The URP 2D and 3D shaders may not fully support tint black animation, which is why your animated tint black keyframes aren't working as expected.

Recommended Solution

Work with your technical artist to add tint black support to your custom shader by referencing the implementation in Spine/Skeleton Tint Black. The shader needs to:

Read both _Color and _Black properties
Apply them correctly in the fragment shader
Support vertex colors for per-slot tinting

Yimec

Thanks for the detailed response.

We are using:

spine-csharp runtime 4.2.37
spine-unity runtime 4.2.118
Spine URP Shaders package 4.2.49

We are using URP with a 3D Renderer.

After more investigation, we managed to solve the issue, but we are still unsure whether this is the correct/safest long-term approach or if there is something important we should take into account to avoid future incompatibilities.

To clarify the original problem:

The expected result was that some animations had their first frame keyed with a white tint (resetting a previous black tint flash), but no tint change was being applied at all from Spine keyframes. However, changing tint black directly from Unity code worked correctly.

So when I said “when the animation requires it”, I meant “when there are keyframes modifying tint black values inside Spine animations”.

The issue seems related to our custom shader not implementing the Spine tint black logic correctly.

Using the Spine 2D URP shader actually works correctly, even under a 3D Renderer setup.

What finally made it work in our shader was adding the following:

In the vertex shader:

#if defined(_TINT_BLACK_ON)
   OUT.darkColor = half3(IN.tintBlackRG.r, IN.tintBlackRG.g, IN.tintBlackB.r) + (_Black.rgb * IN.color.a);
#endif

And in the fragment shader:

#if defined(_TINT_BLACK_ON)
    texColor.rgb = fragTintedColor(texColor, IN.darkColor, IN.color, _Color.a, _Black.a);
    texColor.rgb = texColor.a < 0.001 ? texColor.rgb : texColor.rgb / texColor.a;
#endif

Using these includes:

#include "Packages/com.esotericsoftware.spine.urp-shaders/Shaders/Include/SpineCoreShaders/Spine-Common.cginc"
#include "Packages/com.esotericsoftware.spine.urp-shaders/Shaders/Include/Spine-Common-URP.hlsl"
#include "Packages/com.esotericsoftware.spine.urp-shaders/Shaders/Include/SpineCoreShaders/Spine-Skeleton-Tint-Common.cginc"

Our concern now is mostly about compatibility/future-proofing.

Our shader is written in HLSL, but Spine’s tint support still depends on CG includes. As long as Unity keeps supporting CG includes this should probably be fine, but we are slightly worried about future Unity versions eventually dropping CG support entirely.

Also, using those CG includes in some specific passes can generate issues.

So mainly we would like to know:

Is this the intended/correct way to support Spine tint black in a custom URP shader?
Is there a more future-proof approach recommended by Spine for fully-HLSL custom shaders in URP?

Harald

Yimec To clarify the original problem:

The expected result was that some animations had their first frame keyed with a white tint (resetting a previous black tint flash), but no tint change was being applied at all from Spine keyframes.

Did you enable Advanced - Tint Black at the SkeletonRenderer component?

However, changing tint black directly from Unity code worked correctly.

Did you change a Slot's dark color, or the material's Dark Color material property? Please note that these are two different values entirely, the latter tinting the whole skeleton which will not be reset by animations which are tinting slots.

The issue seems related to our custom shader not implementing the Spine tint black logic correctly.
Yimec What finally made it work in our shader was adding the following: [..]

Glad you've figure it out. Please always test with officially provided Spine shaders first. When they work as expected but your custom shaders don't you quickly know where the problem lies.

Using the Spine 2D URP shader actually works correctly, even under a 3D Renderer setup.

Please always describe precisely which shader you mean, there is no real default here. There are three URP 2D shaders provided:

Universal Render Pipeline/2D/Spine/Skeleton
Universal Render Pipeline/2D/Spine/Skeleton Lit
Universal Render Pipeline/2D/Spine/Sprite

If you mean that the Universal Render Pipeline/2D/Spine/Skeleton shader displays under a URP 3D Renderer setup, then please note that this might break on some devices, under some lighting setups, or in the future. Even when it displays correctly in the Unity Editor for now, it is not recommended to use URP 2D shaders with URP 3D Renderer and vice versa. This is documented here as well:
https://esotericsoftware.com/spine-unity-rendering#URP-Shaders-Extension-Package

I also see no reason why you would want to use the Universal Render Pipeline/2D/Spine/Skeleton shader when the Universal Render Pipeline/Spine/Skeleton shader provides additional properties like Depth Write and an additional shadow caster pass which are both missing in the 2D variant.

Yimec Our concern now is mostly about compatibility/future-proofing.

Our shader is written in HLSL, but Spine’s tint support still depends on CG includes. As long as Unity keeps supporting CG includes this should probably be fine, but we are slightly worried about future Unity versions eventually dropping CG support entirely.

I assume it's just the file extension .cginc and some macros which you're worried about. It's all HLSL code anyway. Or did you find anything really problematic?

Also, using those CG includes in some specific passes can generate issues.

Which did you find problematic? Which includes do you mean by "those CG includes"? Do you mean these:

#include "Packages/com.esotericsoftware.spine.urp-shaders/Shaders/Include/SpineCoreShaders/Spine-Common.cginc"
#include "Packages/com.esotericsoftware.spine.urp-shaders/Shaders/Include/SpineCoreShaders/Spine-Skeleton-Tint-Common.cginc"

If so, what makes them problematic?

Yimec Is this the intended/correct way to support Spine tint black in a custom URP shader?

Yes, just one or multiple depending on whether you need tinting together with a lit or unlit shader. In general you can always see the provided Spine shaders as a reference. You then need to decide which of the provided shaders is similar to what you need.

Is there a more future-proof approach recommended by Spine for fully-HLSL custom shaders in URP?

See above. We may rename files from .cginc to .hlsl in the next beta and replace any CGPROGRAM macro with HLSL if that helps.