Palette swap based on light position

Unity Engine
1

Hello!

I’m trying to create this type of art style where dark areas gets its color swapped to a different one preserving only the edge/silhouette color.

In this example you can see the brick being lit has a greenish color and the unlit area has a dark tone:

I’ve tried to apply the concepts from these articles but couldn’t get it to work :frowning:

Shaders Case Study - Pixel Art Palette Swapping -https://www.youtube.com/watch?v=u4Iz5AJa31Q
Prime31 - SpriteLightKit - GitHub - prime31/SpriteLightKit: Blended lighting system for Unity that works with standard Sprites
Stencil Buffer Using the Stencil Buffer for Sprite Occlusion - prime31 blog - Game dev tips, tricks and random thoughts

2

Hi,

As I understand you cant make palette swap? or you have other conceptual problems?
I have a fork from RedBlue Games “Palette Swap” that I personally use. Be aware, that workflow is far prom polished.
Here the links:

3

Hi @vhman ! Thanks for sharing the links!

I’m trying to apply a different palette outside the mask like the images bellow:

982×880 29 KB

1940×1090 277 KB

This is the code used in the video:

using UnityEngine;

[ExecuteInEditMode]
public class PaletteSwapMatrix : MonoBehaviour
{
    public Color Color0;
    public Color Color1;
    public Color Color2;
    public Color Color3;

    Material _mat;

    void OnEnable()
    {
        Shader shader = Shader.Find("Hidden/PaletteSwapMatrix");
        if (_mat == null)
            _mat = new Material(shader);
    }

    void OnDisable()
    {
        if (_mat != null)
            DestroyImmediate(_mat);
    }

    void OnRenderImage(RenderTexture src, RenderTexture dst)
    {
        _mat.SetMatrix("_ColorMatrix", ColorMatrix);
        Graphics.Blit(src, dst, _mat);
    }

    Matrix4x4 ColorMatrix
    {
        get
        {
            Matrix4x4 mat = new Matrix4x4();
            mat.SetRow(0, ColorToVec(Color0));
            mat.SetRow(1, ColorToVec(Color1));
            mat.SetRow(2, ColorToVec(Color2));
            mat.SetRow(3, ColorToVec(Color3));

            return mat;
        }
    }

    Vector4 ColorToVec(Color color)
    {
        return new Vector4(color.r, color.g, color.b, color.a);
    }
}

// Upgrade NOTE: replaced 'mul(UNITY_MATRIX_MVP,*)' with 'UnityObjectToClipPos(*)'

Shader "Hidden/PaletteSwapMatrix"
{
    Properties
    {
        _MainTex ("Texture", 2D) = "white" {}
    }
    SubShader
    {
        Cull Off ZWrite Off ZTest Always

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
           
            #include "UnityCG.cginc"

            struct appdata
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
            };

            struct v2f
            {
                float4 vertex : SV_POSITION;
                float2 uv : TEXCOORD0;
            };

            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uv = v.uv;
                return o;
            }
           
            sampler2D _MainTex;
            half4x4 _ColorMatrix;

            fixed4 frag (v2f i) : SV_Target
            {
                fixed x = tex2D(_MainTex, i.uv).r;
                return _ColorMatrix[x * 3];
            }

            ENDCG
        }
    }
}
4

Hi,

I don’t have experience in Shaders. I assume it would be better to have two tilemaps with different palettes and use sprite mask

5

Good news!!! I’ve spent some time studying shaders and managed to get the effect

Using SpriteLightKit and make the RenderTexture full black and white we can compare the pixel color:

half4 frag( fragmentInput i ) : COLOR
{
    half4 main = tex2D( _MainTex, i.uv );
    half4 lights = tex2D( _LightsTex, i.uv );
        fixed x = tex2D(_MainTex, i.uv).r;
       
    return lights.r > 0.9 ? _MultiplicativeFactor * main * lights : _ColorMatrix[x * 3];
}

I’m checking if the current pixel from LightsText (Black/White) is white. In that case i’m going to render the original image. Otherwise I’ll apply the color swapping on black areas.

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