Trying to find/write a shader to swap palettes on a SpineSprite (Godot 4.4))

Miles2650

I mostly blame my own inexperience with shaders, but I'm struggling to get a working shader that will allow me to swap out multiple colors in a SpineSprite. Or even a single color. I've found existing ones that work on a single texture, but so far I've failed to adapt them for SpineSprite. (Previously I have used GDScript to change the colors of individual SpineSlots at runtime. Unfortunately, this limits me to one color per Slot. I'd like to be able to have multiple colors on any given Slot and still be able to swap palettes.)

Has anyone created something like this that they're willing to share? Or have any links to resources that might help me?

Spinebot

To achieve palette swapping on a SpineSprite in Godot, you can use a custom shader that processes the entire sprite's texture. This approach allows you to change multiple colors across the sprite, rather than being limited to one color per slot. Here's a basic outline of how you might implement such a shader:

Create a ShaderMaterial: In Godot, create a new ShaderMaterial and assign it to your SpineSprite.
Write the Shader: The shader should take the original color and map it to a new color based on a palette. You can define the palette as a uniform array of colors.

Shader Code Example:

   shader_type canvas_item;

   uniform vec4 original_colors[4]; // Array of original colors to replace
   uniform vec4 new_colors[4]; // Array of new colors to use

   void fragment() {
       vec4 texColor = texture(TEXTURE, UV);
       for (int i = 0; i < 4; i++) {
           if (texColor.rgb == original_colors[i].rgb) {
               texColor.rgb = new_colors[i].rgb;
               break;
           }
       }
       COLOR = texColor;
   }

Assign Colors: In the Godot editor, assign the original and new colors in the shader parameters. This will allow you to swap colors dynamically.
Apply to SpineSprite: Ensure the ShaderMaterial is applied to the SpineSprite node. You can do this by setting the material in the Materials property section of the SpineSprite.

This shader will loop through the defined original colors and replace them with the corresponding new colors. You can expand the arrays to include more colors as needed.

Miles2650

Attempting Spinebot's example just made me realize that the problem wasn't actually my shader code. My mistake was trying to apply the ShaderMaterial under CanvasItem: Material when I should have been applying it under SpineSprite: Materials: Normal Material.

I am now suitably embarrassed, but will leave my post here in case it helps someone else in the future. Cheers!