Pixel perfect sampling in surface shader

Questions & Answers
1

I’m creating procedural texture, with something like:

int texSize = 20;
Texture2D tex = new Texture2D (texSize, texSize, TextureFormat.RGBA32, false, false);
tex.filterMode = FilterMode.Point;

for (int i = 0; i < tex.width; i++)
{
	for(int j = 0; j < tex.height; j++)
	{
		if(i == 2 && j == 3)
		     tex.SetPixel(i, j, new Color(1.0f, 0.0f, 0.0f));
        if(i == 2 && j == 4)
             tex.SetPixel(i, j, new Color(1.0f, 0.0f, 0.0f));
	}
}

tex.Apply();

then in shader i want to sample pixel from this texture

Shader "Custom/Terrain" 
{
Properties 
{
	_TexData ("HexData", 2D) = "white" {}
}
SubShader 
{
	Tags { "RenderType"="Opaque" }
	LOD 200
	//Cull off
	
	CGPROGRAM
	#pragma surface surf Lambert finalcolor:mycolor
	#pragma target 3.0

	sampler2D _TexData;

    void surf(Input IN, inout SurfaceOutput o) 
    {
	    o.Albedo = grass; 
	    o.Alpha = 1.0;
    }

    void mycolor (Input IN, SurfaceOutput o, inout fixed4 color)
    {
        color.rgb = tex2D(_TexData, float2(	3 / 20.0f, 4 / 20.0f));// returns correctly red
        //or
        color.rgb = tex2D(_TexData, float2(	3 / 20.0f, 5 / 20.0f));// returns white
    }

	ENDCG
} 
FallBack "Diffuse"
}

i’m getting right values when sampling 3 / textSize, 4 / textSize, but wrong for 3 / textSize, 5 / textSize.

i’m saving texture to disk for testing and it looks good:
32319-test.png

is there a way to sample texture by pixel, or fix my pixel to text coord calculation?

2

manage to figure this out, problem was that texture wasn’t power of 2