Stylish grass with urp with one shade

I want to make stylish grass for Unity-2022-3-LTS.5 URP with one shade of light and shadow that will spread throughout the entire mesh.

Therefore, I need to calculate the light and shadow as if all vertex were at one point at the base but have a view without changing, in Godot i used this trick:

varying vec3 model_origin;
void vertex() {
    model_origin = MODELVIEW_MATRIX[3].xyz;
}
void fragment() {
    VERTEX = model_origin;
    //light calculating path
}

How can I make same for unity?