Texture Filtering

[forest tide]

Actually I managed to use two passes but I think they work consecutively? This is what I see with only the paletting pass

And this is what I see with two passes

[warm scroll]

Correct me if I'm wrong, but the reason why you do 4 samples is to simulate bilinear sampling?
Are these screenshots taken with the code that you shared earlier?

[forest tide]

Yea, the first screenshot is from that code. Honestly I'm not sure why we sample four times, this is an open source project and the shader was a contribution from someone not active anymore

sampler2D _MainTex;
sampler2D _PaletteTex;
float2 uTextSize;
float _Alpha;

fixed4 bilinearSample(sampler2D indexT, sampler2D LUT, float2 uv) {
    float2 TextInterval = 1.0 / uTextSize;

    float tlLUT = tex2D(indexT, uv).x;
    float trLUT = tex2D(indexT, uv + float2(TextInterval.x, 0.0)).x;
    float blLUT = tex2D(indexT, uv + float2(0.0, TextInterval.y)).x;
    float brLUT = tex2D(indexT, uv + TextInterval).x;

    float4 transparent = float4(0.5, 0.5, 0.5, 0.0);

    float4 tl = tlLUT == 0.0 ? transparent : float4(tex2D(LUT, float2(tlLUT, 1.0)).rgb, 1.0);
    float4 tr = trLUT == 0.0 ? transparent : float4(tex2D(LUT, float2(trLUT, 1.0)).rgb, 1.0);
    float4 bl = blLUT == 0.0 ? transparent : float4(tex2D(LUT, float2(blLUT, 1.0)).rgb, 1.0);
    float4 br = brLUT == 0.0 ? transparent : float4(tex2D(LUT, float2(brLUT, 1.0)).rgb, 1.0);

    float2 f = frac(uv.xy * uTextSize);
    float4 tA = lerp(tl, tr, f.x);
    float4 tB = lerp(bl, br, f.x);

    return lerp(tA, tB, f.y);
}

v2f vert(appdata v)
{ 
    //do nothing special
}

fixed4 frag(v2f i) : SV_Target
{
    fixed4 tex = bilinearSample(_MainTex, _PaletteTex, i.uv);
    if (tex.a == 0.0) {
        discard;
    }
    tex.a *= _Alpha;
    return tex;
}

isn't that code simply going to pick colors from the palette texture and interpolating them with the current position?

[warm scroll]

Yes. It's weird that there's no difference between the 2 screenshots.🤔

Is the uTextSize property set properly?

[forest tide]

I set it manually in a sample project

[warm scroll]

How are you setting it?

[forest tide]

If i change the texture filter to bilinear in the editor this happens

The second pass I was trying to use is this shader https://github.com/9D-Tony/UnitySmoothPixelFiltering/blob/main/Assets/Shader/JitterFree.shader. I can see it executes because the black background appears but it's running on top of the main texture not the result of the first pass

[warm scroll]

Yeah, won't do that.

[warm scroll]

Is that property declared properly in shaderlab?

Trying hardcoding a value right in the fragment shader instead.

[forest tide]

    Properties
    {
        _MainTex("Texture", 2D) = "white" {}
        _PaletteTex("Texture", 2D) = "white" {}
        _Alpha("Alpha", Range(0.0, 1.0)) = 1.0
        _Color("Tint", Color) = (1,1,1,1) 
        [ShowAsVector2] _uTextSize("Texture Size", Vector) = (0,0,0,0)
    }

If I do this float2 uTextSize = (32.0, 72.0);

[warm scroll]

Anything changes if you change the numbers(decreasing them)?

[forest tide]

if I do this

uTextSize = (32.0, 72.0);
fixed4 tex = bilinearSample(_MainTex, _PaletteTex, i.uv);

the shader goes nuts and yields this

[warm scroll]

Oh, so it does work.

Do these numbers correspond to the texture resolution?

Ah, I see what could be the issue. Can you test with a texture that only has 1 sprite? And set uTextSize to it's resolution(in the shader).

[forest tide]

yeah, will that with that will do that! Had to get back to work... can i ping you here in this thread later today?

[warm scroll]

Sure.

[forest tide]

if i set in the inspector, this happens

if I do this
fixed4 frag(v2f i) : SV_Target { uTextSize = (41.0, 77.0); fixed4 tex = bilinearSample(_MainTex, _PaletteTex, i.uv);

this happens

[warm scroll]

Yep looks correct.

[warm scroll]

The other issue is that you need to sample points around the current point.

Currently you're sampling point to the right, bottom and bottom-right.

Instead you need to sample 4(or even 8) points around the current position from all sides.

[forest tide]

Why is that when I change the value from the inspector it doesn't affect the result?

only when I did the manual assign to uTextSize

nevermind

the property was defined as _uTextSize and the var inside the shader was uTextSize

it looks like a bilinear filter now

thank you! that was very enlightening

[forest tide]

So I come with another question, the function works with a single sprite. Any ideias how I could make it work with a sprite atlas instead?

We must feed a sprite atlas

[warm scroll]

You'll need to feed in the sprite position and size within the atlas to the shader and use it to calculate the correct uvs before using them in your function.

[forest tide]

I have tried a few times and couldnt make it work... tried using the texel size + sending the rect info i used to unpack the texture (that one with 0.0 to 1.0 data) to inside the shader and a few other suggestions I found on the forums but none worked

Ended up creating a thread on the forum as well https://forum.unity.com/threads/bilinearsample-on-atlas-texture.1363159/

[forest tide]

Got it working by passing the atlas texture size instead of mapping the uv... So instead of passing the (41,77) I passed (1024,512) and it worked