Adding Samayun dynamic positionning - Thanks to Simon Rodriguez technique : http://blog.simonrodriguez.fr/articles/2015/06/un_ciel_dans_le_shader.html

maps/basic_setup.tscn

@@ -1,6 +1,7 @@
-[gd_scene load_steps=20 format=3 uid="uid://b8p2h0rmwy7qn"]
+[gd_scene load_steps=22 format=3 uid="uid://b8p2h0rmwy7qn"]
 
 [ext_resource type="Material" uid="uid://dpegsmygxcfmv" path="res://maps/materials/basic_ground.material" id="1_lodye"]
+[ext_resource type="Texture2D" uid="uid://b5jer2nm17ld" path="res://maps/textures/samayun_tex_001.png" id="1_thm7k"]
 [ext_resource type="PackedScene" uid="uid://cveshwnu272vf" path="res://maps/objects/ramp-complex.tscn" id="2_4eueh"]
 [ext_resource type="PackedScene" uid="uid://omess6wwwwcq" path="res://maps/objects/ramp-moving.tscn" id="3_bvbgo"]
 [ext_resource type="PackedScene" uid="uid://dvsl8x3lb1h4e" path="res://maps/objects/moutain.tscn" id="3_rbp35"]
@@ -15,10 +16,142 @@
 [ext_resource type="PackedScene" uid="uid://bfo13c5k8xu0x" path="res://maps/natural_ground.tscn" id="12_r7x73"]
 [ext_resource type="PackedScene" uid="uid://mdsxnqsijdqv" path="res://maps/dispensaire_01.tscn" id="13_ald41"]
 
-[sub_resource type="PhysicalSkyMaterial" id="PhysicalSkyMaterial_615c2"]
+[sub_resource type="Shader" id="Shader_av6ac"]
+code = "
+// NOTE: Shader automatically converted from Godot Engine 4.0.alpha5's PhysicalSkyMaterial.
+
+shader_type sky;
+
+uniform float rayleigh : hint_range(0, 64) = 2.0;
+uniform vec4 rayleigh_color : hint_color = vec4(0.3, 0.405, 0.6, 1.0);
+uniform float mie : hint_range(0, 1) = 0.005;
+uniform float mie_eccentricity : hint_range(-1, 1) = 0.8;
+uniform vec4 mie_color : hint_color = vec4(0.69, 0.729, 0.812, 1.0);
+
+uniform float turbidity : hint_range(0, 1000) = 10.0;
+uniform float sun_disk_scale : hint_range(0, 360) = 1.0;
+uniform vec4 ground_color : hint_color = vec4(0.1, 0.07, 0.034, 1.0);
+uniform float exposure : hint_range(0, 128) = 0.1;
+uniform float dither_strength : hint_range(0, 10) = 1.0;
+
+uniform sampler2D night_sky : hint_black_albedo;
+
+uniform sampler2D samayun : hint_albedo;
+uniform float samayun_scale : hint_range(0, 1.0) = 0.25;
+uniform vec3 samayun_position = vec3( 0.0, 0.5, 0.0 );
+
+const vec3 UP = vec3( 0.0, 1.0, 0.0 );
+
+// Sun constants
+const float SUN_ENERGY = 1000.0;
+
+// Optical length at zenith for molecules.
+const float rayleigh_zenith_size = 8.4e3;
+const float mie_zenith_size = 1.25e3;
+
+float henyey_greenstein(float cos_theta, float g) {
+	const float k = 0.0795774715459;
+	return k * (1.0 - g * g) / (pow(1.0 + g * g - 2.0 * g * cos_theta, 1.5));
+}
+
+// From: https://www.shadertoy.com/view/4sfGzS credit to iq
+float hash(vec3 p) {
+	p  = fract( p * 0.3183099 + 0.1 );
+	p *= 17.0;
+	return fract(p.x * p.y * p.z * (p.x + p.y + p.z));
+}
+
+
+
+void sky() {
+	if (LIGHT0_ENABLED) {
+		float zenith_angle = clamp( dot(UP, normalize(LIGHT0_DIRECTION)), -1.0, 1.0 );
+		float sun_energy = max(0.0, 1.0 - exp(-((PI * 0.5) - acos(zenith_angle)))) * SUN_ENERGY * LIGHT0_ENERGY;
+		float sun_fade = 1.0 - clamp(1.0 - exp(LIGHT0_DIRECTION.y), 0.0, 1.0);
+
+		// Rayleigh coefficients.
+		float rayleigh_coefficient = rayleigh - ( 1.0 * ( 1.0 - sun_fade ) );
+		vec3 rayleigh_beta = rayleigh_coefficient * rayleigh_color.rgb * 0.0001;
+		// mie coefficients from Preetham
+		vec3 mie_beta = turbidity * mie * mie_color.rgb * 0.000434;
+
+		// Optical length.
+		float zenith = acos(max(0.0, dot(UP, EYEDIR)));
+		float optical_mass = 1.0 / (cos(zenith) + 0.15 * pow(93.885 - degrees(zenith), -1.253));
+		float rayleigh_scatter = rayleigh_zenith_size * optical_mass;
+		float mie_scatter = mie_zenith_size * optical_mass;
+
+		// Light extinction based on thickness of atmosphere.
+		vec3 extinction = exp(-(rayleigh_beta * rayleigh_scatter + mie_beta * mie_scatter));
+
+		// In scattering.
+		float cos_theta = dot(EYEDIR, normalize(LIGHT0_DIRECTION));
+
+		float rayleigh_phase = (3.0 / (16.0 * PI)) * (1.0 + pow(cos_theta * 0.5 + 0.5, 2.0));
+		vec3 betaRTheta = rayleigh_beta * rayleigh_phase;
+
+		float mie_phase = henyey_greenstein(cos_theta, mie_eccentricity);
+		vec3 betaMTheta = mie_beta * mie_phase;
+
+		vec3 Lin = pow(sun_energy * ((betaRTheta + betaMTheta) / (rayleigh_beta + mie_beta)) * (1.0 - extinction), vec3(1.5));
+		// Hack from https://github.com/mrdoob/three.js/blob/master/examples/jsm/objects/Sky.js
+		Lin *= mix(vec3(1.0), pow(sun_energy * ((betaRTheta + betaMTheta) / (rayleigh_beta + mie_beta)) * extinction, vec3(0.5)), clamp(pow(1.0 - zenith_angle, 5.0), 0.0, 1.0));
+
+		// Hack in the ground color.
+		Lin  *= mix(ground_color.rgb, vec3(1.0), smoothstep(-0.1, 0.1, dot(UP, EYEDIR)));
+
+		// Solar disk and out-scattering.
+		float sunAngularDiameterCos = cos(LIGHT0_SIZE * sun_disk_scale);
+		float sunAngularDiameterCos2 = cos(LIGHT0_SIZE * sun_disk_scale*0.5);
+		float sundisk = smoothstep(sunAngularDiameterCos, sunAngularDiameterCos2, cos_theta);
+		vec3 L0 = (sun_energy * 1900.0 * extinction) * sundisk * LIGHT0_COLOR;
+		L0 += texture(night_sky, SKY_COORDS).xyz * extinction;
+
+		vec3 color = (Lin + L0) * 0.04;
+		COLOR = pow(color, vec3(1.0 / (1.2 + (1.2 * sun_fade))));
+		COLOR *= exposure;
+		// Make optional, eliminates banding.
+		COLOR += (hash(EYEDIR * 1741.9782) * 0.08 - 0.04) * 0.016 * dither_strength;
+	} else {
+		// There is no sun, so display night_sky and nothing else.
+		COLOR = texture(night_sky, SKY_COORDS).xyz * 0.04;
+		COLOR *= exposure;
+	}
+//	vec2 samayun_uv = uv_moon(samayun_position, samayun_scale, SKY_COORDS);
+//	COLOR += texture(samayun, samayun_uv).rgb;
+	if (length(EYEDIR - normalize(samayun_position)) < 0.5 ) { // we are in the area of the sky where samayun is placed
+		//We define a local plane tangent to the skydome at samayun_position
+        //We work with everything normalized
+        vec3 n1 = normalize(cross(samayun_position,vec3(0,1,0)));
+        vec3 n2 = normalize(cross(samayun_position,n1));
+		//We project EYEDIR on this plane
+        float x = dot(EYEDIR,n1) ;
+        float y = dot(EYEDIR,n2) ;
+        
+		COLOR += texture(samayun, vec2(x,y)+vec2(0.5)).rgb;
+		//COLOR = mix(COLOR, texture(samayun, vec2(x,y)+vec2(0.5)).rgb, clamp (samayun_position.y, 0.0, 1.0)) ;
+	}
+}
+"
+
+[sub_resource type="ShaderMaterial" id="ShaderMaterial_s2q0l"]
+shader = SubResource( "Shader_av6ac" )
+shader_param/rayleigh = 2.0
+shader_param/rayleigh_color = Color(0.3, 0.405, 0.6, 1)
+shader_param/mie = 0.005
+shader_param/mie_eccentricity = 0.8
+shader_param/mie_color = Color(0.69, 0.729, 0.812, 1)
+shader_param/turbidity = 10.0
+shader_param/sun_disk_scale = 1.0
+shader_param/ground_color = Color(0.1, 0.07, 0.034, 1)
+shader_param/exposure = 0.1
+shader_param/dither_strength = 1.0
+shader_param/samayun_scale = 0.201
+shader_param/samayun_position = Vector3(0.226, 0.161, 0.065)
+shader_param/samayun = ExtResource( "1_thm7k" )
 
 [sub_resource type="Sky" id="Sky_fa16p"]
-sky_material = SubResource( "PhysicalSkyMaterial_615c2" )
+sky_material = SubResource( "ShaderMaterial_s2q0l" )
 
 [sub_resource type="Environment" id="Environment_n5kgx"]
 background_mode = 2