1 files changed, 50 insertions, 0 deletions
diff --git a/game/src/Game/GameSession/TerrainMap.gdshader b/game/src/Game/GameSession/TerrainMap.gdshader
new file mode 100644
index 0000000..88e7019
--- /dev/null
+++ b/game/src/Game/GameSession/TerrainMap.gdshader
@@ -0,0 +1,50 @@
+shader_type spatial;
+
+render_mode unshaded;
+
+#include "res://src/GameSession/ProvinceIndexSampler.gdshaderinc"
+
+// Province colour texture
+uniform sampler2D province_colour_tex: source_color, repeat_enable, filter_nearest;
+// Index of the mouse over the map mesh
+uniform uint hover_index;
+// Index of the currently selected province
+uniform uint selected_index;
+// Cosmetic terrain textures
+uniform sampler2DArray terrain_tex: source_color, repeat_enable, filter_linear;
+// The number of times the terrain textures should tile vertically
+uniform float terrain_tile_factor;
+
+const vec3 highlight_colour = vec3(1.0);
+
+vec3 get_terrain_colour(vec2 uv, vec2 corner, vec2 half_pixel_size, vec2 terrain_uv) {
+	uvec3 province_data = read_uvec3(fma(corner, half_pixel_size, uv));
+	vec4 province_colour = texelFetch(province_colour_tex, ivec2(province_data.rg), 0);
+	vec3 terrain_colour = texture(terrain_tex, vec3(terrain_uv, float(province_data.b))).rgb;
+	vec3 mixed_colour = mix(terrain_colour, province_colour.rgb, province_colour.a);
+	uint index = uvec2_to_uint(province_data.rg);
+	float mix_val = 0.1 * (float(index == hover_index) + float(index == selected_index));
+	return mix(mixed_colour, highlight_colour, mix_val);
+}
+
+vec3 mix_terrain_colour(vec2 uv) {
+	vec2 map_size = vec2(textureSize(province_shape_tex, 0).xy) * province_shape_subdivisions;
+	vec2 pixel_offset = fract(fma(uv, map_size, vec2(0.5)));
+	vec2 half_pixel_size = 0.49 / map_size;
+
+	vec2 terrain_uv = uv;
+	terrain_uv.x *= map_size.x / map_size.y;
+	terrain_uv *= terrain_tile_factor;
+
+	return mix(
+		mix(get_terrain_colour(uv, vec2(-1, -1), half_pixel_size, terrain_uv),
+			get_terrain_colour(uv, vec2(+1, -1), half_pixel_size, terrain_uv), pixel_offset.x),
+		mix(get_terrain_colour(uv, vec2(-1, +1), half_pixel_size, terrain_uv),
+			get_terrain_colour(uv, vec2(+1, +1), half_pixel_size, terrain_uv), pixel_offset.x),
+			pixel_offset.y);
+}
+
+void fragment() {
+	vec3 terrain_colour = mix_terrain_colour(UV);
+	ALBEDO = terrain_colour;
+}