@pixelmeat And note that the Universal Render Pipeline/Spine/Skeleton shader is for use with URP without a 2D Renderer, while Universal Render Pipeline/2D/Spine/Skeleton is for URP when using a 2D Renderer.

See the documentation here:
https://esotericsoftware.com/spine-unity-rendering#URP-Shaders-Extension-Package

pixelmeat Alright! Now I have configured the color space as Gamma and enabled PMA back. The warnings are gone and the character renders if I use the Spine/Skeleton shader.

Glad to hear you've decided to switch to Gamma color space! This will make many things behave more intuitively.

@pixelmeat Very glad to hear you've found the issue!

pixelmeat Just one more question for now. Are there versions of the outline shaders for the URP/2D category?

It's a bit more complicated currently, unfortunately there is no single-shader version available yet. This is planned in this issue ticket:
EsotericSoftware/spine-runtimes1824
However in the meantime you can use e.g. the RenderExistingMesh component and the Universal Render Pipeline/Spine/Outline/Skeleton-OutlineOnly shader as described here in the documentation.

You can find an outline URP example scene Outline Shaders URP.unity in the Samples of the Spine URP Shaders UPM package (installed via Package Manager under the Samples tab), there you can see this setup in action.

pixelmeat How can I make the outline object be mask-interactive?

By mask-interactive, do you mean the masks in the way of Inside-Mask Outside-Mask options of the Mask Interaction parameter of SkeletonAnimation? If so, that's the Stencil Comparison parameter (_StencilComp in the shader and in the Material properties under debug mode). Values are as follows (as names and parameter int-values):

• None - Inside and outside (Default): Always, 8
• Inside: LessEqual, 4
• Outside: Greater, 5

The integer values for each comparison operation can also be found under UnityEngine.Rendering.CompareFunction.

pixelmeat There's no info there about Stencil Comparison, not even if I look in debug mode. So I don't know how is it working correctly with the Sprite Mask.

Are you sure it's not there in debug mode, named _StencilComp? If you are switching from a previous shader, the keywords are carried over.

Your game looks so cute BTW! 8)

pixelmeat I was only looking under the "valid keywords" and "invalid keywords" not under "saved properties", my bad. Too many new things ^^

Keywords are for switching between shader variants (active shader branches), properties are actual value paramters.

pixelmeat Could I change this value somehow if I needed it?

Yes, you see it right in front of you. You can click on the 4 and replace it with e.g. 5 .

We have just exposed the Stencil Comparison parameter for all URP blend modes shaders (via this commit). These were indeed hidden as they don't use the same custom shader GUI code as built-in-RP blend modes shaders which exposes these properties. Thanks for reporting.

A new Spine URP Shaders UPM package is available for download:
https://esotericsoftware.com/spine-unity-download

pixelmeat Would it be possible to have a simpler version of this shader that, instead of modifying the texture color via a screen blending effect and an input color, just changed the color value of the texture to the same input color?

What do you mean by the last half of the sentence "just changed the color value of the texture to the same input color"? Do you want to output just the tint color in additive blend mode?

In general you can quite easily modify existing shaders if you just need to output a constant color. You can create a copy of the .shader file, and rename the name in the first line of the file to your desired name to be displayed in the Materials shader property.

Then you can change the line #pragma fragment frag which defines the following method from the included file "../../Include/Spine-Skeleton-ForwardPass-URP.hlsl" to be used:

half4 frag(VertexOutput i) : SV_Target{
	float4 texColor = tex2D(_MainTex, i.uv0);
#if defined(_ZWRITE)
	clip(texColor.a * i.color.a - _Cutoff);
#endif
#if defined(_TINT_BLACK_ON)
	return fragTintedColor(texColor, i.darkColor, i.color, _Color.a, _Black.a);
#else
	#if defined(_STRAIGHT_ALPHA_INPUT)
	texColor.rgb *= texColor.a;
	#endif
	return (texColor * i.color);
#endif
}

Now you can replace the used fragment program function like this in the .shader file:

 #pragma fragment yourFunction

and below the include statement add your function:

#include "../../Include/Spine-Skeleton-ForwardPass-URP.hlsl"

half4 yourFunction(VertexOutput i) : SV_Target {
	float4 texColor = tex2D(_MainTex, i.uv0);
#if defined(_ZWRITE)
	clip(texColor.a * i.color.a - _Cutoff);
#endif
	return float4(i.color.rgb, texColor.a * i.color.a);
}

pixelmeat I'd like the shader to output a single color from an input, without any blending, just the input color and the alpha from the character texture. And the shader should have the stencil interaction property.

Yes, that's exactly what should be achieved by the modifications that I proposed above .

pixelmeat I'll try to implement your suggestion and see how far my skills get me

Great. If it does not work, please re-read my posting and perform everything litterally as described .

pixelmeat I tried what you proposed. If I'm understanding correctly, by changing #pragma fragment frag to #pragma fragment constantColorFrag I'm telling the shader to use this new method to paint the image instead of the frag method found in ../../Include/Spine-Skeleton-ForwardPass-URP.hlsl, right?

Yes.

pixelmeat Just to clarify, I understand that I am not supposed to make any changes to the Spine-Skeleton-ForwardPass-URP.hlsl file.

Yes. The included Spine-Skeleton-ForwardPass-URP.hlsl file is shared with the original shader that you copied, you don't want to break the original shader.

The color is still performing some kind of additive effect

I thought you want to create a variant of Blend Modes/Skeleton Screen where there is only a constant color instead of the texture color used?

If you want to use normal blending and not screen blend mode, you could either replace the line:

Blend One OneMinusSrcColor

with this:

Blend One OneMinusSrcAlpha

You then also should remove /Blend Modes from the first line which defines the shader name and folder, as it's no blend-mode shader then. Alternatively you can also start from copying Spine-Skeleton-URP-2D.shader and applying the previous changes there.

I just noticed I forgot to premultiply the resulting color, so please also replace:

return float4(i.color.rgb, texColor.a * i.color.a);

with the following:

return i.color * texColor.a;