Fade edges of 2D spline-mesh

Question

I'm re-writing my Unity game in Raylib and are trying to recreate a path/road-shader I made with Shader Graph.

The first picture is how it looks in Unity, with faded/blurred edges. The path is a 2D spline-mesh created as you can see in the second picture. The third image is a spline-mesh created the same way in Raylib.

Does anyone have an idea how to get faded edges with GLSL-code?

The Shader Graph looks like this:

I'm new to GLSL and have been at this for days. I would really appreciate any help!

Edit:

I also tried to manually convert the shader. Here is an example where I tried to convert the Shader Graph.

Vert:

in vec3 vertexPosition;
in vec2 vertexTexCoord;

uniform mat4 mvp;
uniform mat4 matModel;

out vec2 fragTexCoord;
out vec3 fragPosition;

void main() {
      fragTexCoord = vertexTexCoord;
      fragPosition = vertexPosition;

      gl_Position = mvp * vec4(vertexPosition,1.0);
}

Frag:

in vec2 fragTexCoord;
in vec3 fragPosition;

uniform sampler2D texture0;

uniform float width;
uniform float blur;

void main() 
{
      vec4 texColor = texture2D(texture0, fragPosition.xy);
      vec2 halfVec = vec2(0.5, 0.5);
      float dist = distance(fragTexCoord, halfVec);
      
      float smoothstep1 = smoothstep(width,blur,dist);

      gl_FragColor = vec4(texColor.xyz, smoothstep1);

}

The result is this:

Or this, depending on width- and blur-parameters

Edit 2:

I translated the Shader Graph-code node by node and the result was basically what I already wrote i GLSL. The part I can't figure out is this Shader Graph-generated code.

(I simplified it from 5 to 2 lines and shortened the variable names)

UnityTexture2D unityTex =  UnityBuildTexture2DStructNoScale(_Texture2D);
float4 texColor = SAMPLE_TEXTURE2D(unityTex.tex,UnityBuildSamplerStateStruct(SamplerState_Linear_Repeat).samplerstate, unityTex.GetTransformedUV((IN.WorldSpacePosition.xy) / _Size)); 

Does anyone know what GetTransformedUV does? I cant find any information on UnityTexture2D by googling.

Answer 1

I finally made it work with a kind of hack.

Because its 2D and unlit I don't need to use normals. So I saved the center of the spline in the normals of the mesh. Then I can fade the edges based on the distance between the center and each vertex.

I get the same result as the Shader Graph in Unity.

I guess It's possible to store the data and pass it to the shader some other way, but I couldn't think of any.