Allow tiles to blend between two textures

assets/textures/terrain_blend/bricky_inner.png.import

@@ -0,0 +1,14 @@
+[remap]
+
+importer="image"
+type="Image"
+uid="uid://n7hbvgjiktlg"
+path="res://.godot/imported/bricky_inner.png-b94122a758411344f70f7c2760d21808.image"
+
+[deps]
+
+source_file="res://assets/textures/terrain_blend/bricky_inner.png"
+dest_files=["res://.godot/imported/bricky_inner.png-b94122a758411344f70f7c2760d21808.image"]
+
+[params]
+

assets/textures/terrain_blend/bricky_outer.png.import

@@ -0,0 +1,14 @@
+[remap]
+
+importer="image"
+type="Image"
+uid="uid://c8ntkfa6t0t4a"
+path="res://.godot/imported/bricky_outer.png-8d14c741e6e00049a6f23c5a7f0ba31a.image"
+
+[deps]
+
+source_file="res://assets/textures/terrain_blend/bricky_outer.png"
+dest_files=["res://.godot/imported/bricky_outer.png-8d14c741e6e00049a6f23c5a7f0ba31a.image"]
+
+[params]
+

assets/textures/terrain_blend/bricky_straight.png.import

@@ -0,0 +1,14 @@
+[remap]
+
+importer="image"
+type="Image"
+uid="uid://cl5gio1e8md5p"
+path="res://.godot/imported/bricky_straight.png-6b7be3b817156c5655dc51c502e77349.image"
+
+[deps]
+
+source_file="res://assets/textures/terrain_blend/bricky_straight.png"
+dest_files=["res://.godot/imported/bricky_straight.png-6b7be3b817156c5655dc51c502e77349.image"]
+
+[params]
+

assets/textures/terrain_blend/default.png.import

@@ -0,0 +1,14 @@
+[remap]
+
+importer="image"
+type="Image"
+uid="uid://bd65fhvitmpis"
+path="res://.godot/imported/default.png-16f623a6df352f7770c4e23ca5d9106b.image"
+
+[deps]
+
+source_file="res://assets/textures/terrain_blend/default.png"
+dest_files=["res://.godot/imported/default.png-16f623a6df352f7770c4e23ca5d9106b.image"]
+
+[params]
+

assets/textures/terrain_blend/grassy_inner.png.import

@@ -0,0 +1,14 @@
+[remap]
+
+importer="image"
+type="Image"
+uid="uid://cglldg71qap5f"
+path="res://.godot/imported/grassy_inner.png-dbbcf6e38e5a9f6ac5aa0bd1d57058a3.image"
+
+[deps]
+
+source_file="res://assets/textures/terrain_blend/grassy_inner.png"
+dest_files=["res://.godot/imported/grassy_inner.png-dbbcf6e38e5a9f6ac5aa0bd1d57058a3.image"]
+
+[params]
+

assets/textures/terrain_blend/grassy_outer.png.import

@@ -0,0 +1,14 @@
+[remap]
+
+importer="image"
+type="Image"
+uid="uid://cxwk1srj6obxh"
+path="res://.godot/imported/grassy_outer.png-23c05e3ec7820ad524433733076341dc.image"
+
+[deps]
+
+source_file="res://assets/textures/terrain_blend/grassy_outer.png"
+dest_files=["res://.godot/imported/grassy_outer.png-23c05e3ec7820ad524433733076341dc.image"]
+
+[params]
+

assets/textures/terrain_blend/grassy_straight.png.import

@@ -0,0 +1,14 @@
+[remap]
+
+importer="image"
+type="Image"
+uid="uid://cqgah04b0buil"
+path="res://.godot/imported/grassy_straight.png-f11f767de0d78d943ad64f3bc3a0dc4c.image"
+
+[deps]
+
+source_file="res://assets/textures/terrain_blend/grassy_straight.png"
+dest_files=["res://.godot/imported/grassy_straight.png-f11f767de0d78d943ad64f3bc3a0dc4c.image"]
+
+[params]
+

terrain/Terrain.cs

@@ -149,7 +149,13 @@ public partial class Terrain
 				var minDiff = Abs(sorted[0].Value.Y - sorted[2].Value.Y); // Difference between lowest and 3rd lowest point.
 				var maxDiff = Abs(sorted[3].Value.Y - sorted[1].Value.Y); // Difference between highest and 3rd highest point.
 
-				mesh.SurfaceSetUV2(new(rnd.Next(4), 0.0f));
+// Randomly select two different textures and one blend texture.
+				mesh.SurfaceSetColor(new(
+					rnd.NextSingle(),
+rnd.NextSingle(),
+					rnd.NextSingle()
+));
+
 				var first = sorted[(minDiff > maxDiff) ? 0 : 3].Corner;
 				if (first is Corner.TopLeft or Corner.BottomRight) {
 					AddTriangle(corners.TopLeft    , new(0.0f, 0.0f),

terrain/terrain_material.tres

@@ -1,15 +1,28 @@
-[gd_resource type="ShaderMaterial" load_steps=7 format=4 uid="uid://doe8owgx4jeu1"]
+[gd_resource type="ShaderMaterial" load_steps=15 format=4 uid="uid://doe8owgx4jeu1"]
 
 [ext_resource type="Shader" path="res://terrain/terrain_shader.gdshader" id="1_mf55c"]
+
 [ext_resource type="Image" uid="uid://b0jp1dyxugbr7" path="res://assets/textures/terrain/grass.png" id="5_mau31"]
 [ext_resource type="Image" uid="uid://bpo7mkr6sctqr" path="res://assets/textures/terrain/dirt.png" id="6_xc3ue"]
 [ext_resource type="Image" uid="uid://dqyqg6yt7yk3k" path="res://assets/textures/terrain/rock.png" id="7_84wdo"]
 [ext_resource type="Image" uid="uid://bkwjxg6g2itag" path="res://assets/textures/terrain/sand.png" id="8_3fpcn"]
 
+[ext_resource type="Image" uid="uid://bd65fhvitmpis" path="res://assets/textures/terrain_blend/default.png" id="5_qdlds"]
+[ext_resource type="Image" uid="uid://cqgah04b0buil" path="res://assets/textures/terrain_blend/grassy_straight.png" id="6_s3ccy"]
+[ext_resource type="Image" uid="uid://cxwk1srj6obxh" path="res://assets/textures/terrain_blend/grassy_outer.png" id="7_wgbkx"]
+[ext_resource type="Image" uid="uid://cglldg71qap5f" path="res://assets/textures/terrain_blend/grassy_inner.png" id="8_dm7dx"]
+[ext_resource type="Image" uid="uid://cl5gio1e8md5p" path="res://assets/textures/terrain_blend/bricky_straight.png" id="9_fwpox"]
+[ext_resource type="Image" uid="uid://c8ntkfa6t0t4a" path="res://assets/textures/terrain_blend/bricky_outer.png" id="10_kq5au"]
+[ext_resource type="Image" uid="uid://n7hbvgjiktlg" path="res://assets/textures/terrain_blend/bricky_inner.png" id="11_0i2i8"]
+
 [sub_resource type="Texture2DArray" id="Texture2DArray_3nq13"]
 _images = Array[Image]([ExtResource("5_mau31"), ExtResource("6_xc3ue"), ExtResource("7_84wdo"), ExtResource("8_3fpcn")])
 
+[sub_resource type="Texture2DArray" id="Texture2DArray_3nq14"]
+_images = Array[Image]([ExtResource("5_qdlds"), ExtResource("6_s3ccy"), ExtResource("7_wgbkx"), ExtResource("8_dm7dx"), ExtResource("9_fwpox"), ExtResource("10_kq5au"), ExtResource("11_0i2i8")])
+
 [resource]
 render_priority = 0
 shader = ExtResource("1_mf55c")
 shader_parameter/textures = SubResource("Texture2DArray_3nq13")
+shader_parameter/blend_textures = SubResource("Texture2DArray_3nq14")

terrain/terrain_shader.gdshader

@@ -1,10 +1,22 @@
 shader_type spatial;
 render_mode blend_mix, depth_draw_opaque, cull_back, diffuse_burley, specular_schlick_ggx;
 
-uniform sampler2DArray textures : source_color, filter_linear_mipmap, repeat_enable;
+uniform sampler2DArray textures       : source_color, filter_linear_mipmap, repeat_enable;
+uniform sampler2DArray blend_textures : source_color, filter_nearest_mipmap, repeat_enable;
 
 void fragment() {
-	ALBEDO = texture(textures, vec3(UV, UV2.x)).rgb;
+	int num_textures       = textureSize(textures, 0).z;
+	int num_blend_textures = textureSize(blend_textures, 0).z;
+
+	float tex_primary_index   = COLOR.r * float(num_textures);
+	float tex_secondary_index = COLOR.g * float(num_textures);
+	float tex_blend_index     = COLOR.b * float(num_blend_textures);
+
+	vec4 tex_primary   = texture(textures, vec3(UV, tex_primary_index));
+	vec4 tex_secondary = texture(textures, vec3(UV, tex_secondary_index));
+
+	vec4 blend = texture(blend_textures, vec3(UV, tex_blend_index));
+	ALBEDO = mix(tex_secondary, tex_primary, blend.a).rgb;
 
 	METALLIC  = 0.0;
 	SPECULAR  = 0.5;