Why won't my multiply shader work with a texture set to Point (no filter)?

Hey folks!

So, I’m working on my first shader - shader newbie here - which takes a greyscale section of a texture (UV) and multiplies it by a block of colour on the same texture (UV2). This works great, but I’m also hoping to get a retro-ish pixel-art effect with the texture - so I set the texture filter to ‘point’ (or ‘no filter’)…

Immediately the colour tinting stops working - the texture is sharp and pixelated, but it’s no-longer tinted by the color block.

Can anybody tell me how to get my tinting shader to work with a texture set to point (‘no filter’)?

Shader code follows…

Shader "OldSchool/TranspSkinTone"
{
	Properties
	{
		_MainTex ("Texture", 2D) = "white" {}
	}
	SubShader
	{
		Tags { "Queue"="Transparent" "RenderType"="Transparent" }
		LOD 100

		Pass
		{
			CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag
			// make fog work
			#pragma multi_compile_fog
			
			#include "UnityCG.cginc"

			struct appdata
			{
				float4 vertex : POSITION;
				float2 uv : TEXCOORD0;
				float2 uv2Tone : TEXCOORD1;
			};

			struct v2f
			{
				float2 uv : TEXCOORD0;
				float2 uv2 : TEXCOORD1;
				UNITY_FOG_COORDS(1)
				float4 vertex : SV_POSITION;
			};

			sampler2D _MainTex;
			float4 _MainTex_ST;
			
			v2f vert (appdata v)
			{
				v2f o;
				o.vertex = UnityObjectToClipPos(v.vertex);
				o.uv = TRANSFORM_TEX(v.uv, _MainTex);
				UNITY_TRANSFER_FOG(o,o.vertex);
				return o;
			}
			
			fixed4 frag (v2f i) : SV_Target
			{
				// sample the texture
				fixed4 col = tex2D(_MainTex, i.uv);
				fixed4 colTone = tex2D(_MainTex, i.uv2);
				col *= colTone;
				clip(col.a - 1);
				
				// apply fog
				UNITY_APPLY_FOG(i.fogCoord, col);
				return col;
			}
			ENDCG
		}
	}
}

Thanks in advance,

–Rev

Hey, I was given a solution by Skilfuldriver on the Unity Forums… I failed to initialise my second UV set in the Vertex program, so the fragment program was doing nothing with the second set.

As it turns out, filtering wasn’t the problem - which suggests that the tinting effect I was getting with my earlier code was… an error? Nonetheless, tinting works with a point texture using the following shader code:

Shader "OldSchool/TranspSkinTone"
{
	Properties
	{
		_MainTex ("Texture", 2D) = "white" {}
	}
	SubShader
	{
		Tags { "Queue"="Transparent" "RenderType"="Transparent" }
		LOD 100

		Pass
		{
			CGPROGRAM
			#pragma vertex vert
			#pragma fragment frag
			// make fog work
			#pragma multi_compile_fog
			
			#include "UnityCG.cginc"

			struct appdata
			{
				float4 vertex : POSITION;
				float2 uv : TEXCOORD0;
				float2 uv2Tone : TEXCOORD1;
			};

			struct v2f
			{
				float2 uv : TEXCOORD0;
				float2 uv2 : TEXCOORD1;
				UNITY_FOG_COORDS(2)
				float4 vertex : SV_POSITION;
			};

			sampler2D _MainTex;
			float4 _MainTex_ST;
			
			v2f vert (appdata v)
			{
				v2f o;
				o.vertex = UnityObjectToClipPos(v.vertex);
				o.uv = TRANSFORM_TEX(v.uv, _MainTex);
				o.uv2 = TRANSFORM_TEX(v.uv2Tone, _MainTex);
				UNITY_TRANSFER_FOG(o,o.vertex);
				return o;
			}
			
			fixed4 frag (v2f i) : SV_Target
			{
				// sample the texture
				fixed4 col = tex2D(_MainTex, i.uv);
				fixed4 colTone = tex2D(_MainTex, i.uv2);
				col *= colTone;
				clip(col.a - 1);
				
				// apply fog
				UNITY_APPLY_FOG(i.fogCoord, col);
				return col;
			}
			ENDCG
		}
	}
}

All the best,

–Rev