godot4.2 C#与 shander通讯

shader代码:

shader_type canvas_item;
uniform float a : hint_range(0.0, 1.0)     ;
void vertex() {
    // Called for every vertex the material is visible on.
}

void fragment() {
    COLOR.a = a;
}

C#代码:

public override void _Ready()
    { 
　　　　((ShaderMaterial)Material).SetShaderParameter("a", .5);

    }