[SOLVED]Linear Fog shader only works with 2+ instances of the same object on-screen

Unity Engine
1

Hi,

I tried to change the sprite shader to produce a 2D linear fog effect where the shader lerps the color of the sprite to a predefined fog-color depending on the distance from the camera.
This works, however only if there are at least two instances of the same object with this shader on it on the screen.
The moment one of the instances leaves the screen, the fog-effect stops working.

I have added an image so you can see the problem. On the left, both instances of the tree are on-screen in game view. The shader works.
On the right, I moved one of the trees out of view.
It stopped working.

I have no idea what would cause this.

Here’s the code

Shader "Custom/FogSprite"
{
    Properties
    {
        [PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {}
        _Color ("Tint", Color) = (1,1,1,1)
        [MaterialToggle] PixelSnap ("Pixel snap", Float) = 0
        _FogColor ("Fog Color", Color) = (0.5, 0.5, 0.5, 1.0)
        _FogIntensity ("Fog Intensity", Range(0,1)) = 0
    }

    SubShader
    {
        Tags
        {
            "Queue"="Transparent"
            "IgnoreProjector"="True"
            "RenderType"="Transparent"
            "PreviewType"="Plane"
            "CanUseSpriteAtlas"="True"
        }

        Cull Off
        Lighting Off
        ZWrite Off
        Blend One OneMinusSrcAlpha

        Pass
        {
        CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            #pragma multi_compile _ PIXELSNAP_ON
            #include "UnityCG.cginc"
          
            struct appdata_t
            {
                float4 vertex   : POSITION;
                float4 color    : COLOR;
                float2 texcoord : TEXCOORD0;
            };

            struct v2f
            {
                float4 vertex   : SV_POSITION;
                fixed4 color    : COLOR;
                float2 texcoord  : TEXCOORD0;
                float depth : TEXCOORD1;
            };
          
            fixed3 worldpos;
            fixed4 _Color;
          
            v2f vert(appdata_t IN)
            {
                v2f OUT;
                OUT.vertex = UnityObjectToClipPos(IN.vertex);
                OUT.texcoord = IN.texcoord;
                OUT.color = IN.color * _Color;
                OUT.depth = IN.vertex.z;
                #ifdef PIXELSNAP_ON
                OUT.vertex = UnityPixelSnap (OUT.vertex);
                OUT.vertex = mul(_ObjectToWorld, IN.vertex);
                #endif

                return OUT;
            }

            sampler2D _MainTex;
            sampler2D _AlphaTex;
            float _AlphaSplitEnabled;
            fixed4 _FogColor;
            float _FogIntensity;

            fixed4 SampleSpriteTexture (float2 uv)
            {
                fixed4 color = tex2D (_MainTex, uv);

                #if UNITY_TEXTURE_ALPHASPLIT_ALLOWED
                if (_AlphaSplitEnabled)
                    color.a = tex2D (_AlphaTex, uv).r;
                #endif //UNITY_TEXTURE_ALPHASPLIT_ALLOWED

                return color;
            }

            fixed4 frag(v2f IN) : SV_Target
            {
                fixed4 c = SampleSpriteTexture (IN.texcoord) * IN.color;
                c.rgb = lerp(c, _FogColor, saturate(_FogIntensity * (IN.depth))).rgb;
                c.rgb *= c.a;
                return c;
                //return IN.vertex.z;
            }
        ENDCG
        }
    }
}

Thanks!

4822649--462515--shader issue.jpg
4822649--462515--shader issue.jpg1550×913 173 KB

2

can you test adding this to Tags?
“DisableBatching”=“True”

3

Thanks for the suggestion!
However, unfortunately, the shader completely stopped working now.

4

Your depth value in the vert shader is local space z. Sprites have no depth until they batch. You need to actually get the distance from the camera.

5

That worked, thanks a ton!