update

shaders/011_circle/circle.gdshader

@@ -0,0 +1,17 @@
+shader_type spatial;
+render_mode cull_disabled;
+
+/*
+	We define the center position of our circle and then ask each pixel how far from that
+	center position it is. This will give the pixel a value between 0 – 1.
+	We can then ask the pixel if its value is lower or higher than a predefined value.
+	If it is higher we will set the pixel to white
+	and if it is lower we will set it to black.
+*/ 
+float circle(vec2 position, float radius, float feather) {
+	return smoothstep(radius, radius + feather, length(position - vec2(0.5)));
+}
+
+void fragment() {
+	ALBEDO.rgb = vec3( circle(UV, 0.3, 0.0) );
+}

shaders/011_circle/circle.tscn

@@ -0,0 +1,15 @@
+[gd_scene load_steps=4 format=3 uid="uid://cjcfr8tqdhbro"]
+
+[ext_resource type="Shader" path="res://shaders/011_circle/circle.gdshader" id="1_omahb"]
+
+[sub_resource type="ShaderMaterial" id="ShaderMaterial_iu8hm"]
+render_priority = 0
+shader = ExtResource("1_omahb")
+
+[sub_resource type="QuadMesh" id="QuadMesh_md0p6"]
+material = SubResource("ShaderMaterial_iu8hm")
+
+[node name="Circle" type="Node3D"]
+
+[node name="MeshInstance3D" type="MeshInstance3D" parent="."]
+mesh = SubResource("QuadMesh_md0p6")