1 files changed, 48 insertions, 0 deletions
diff --git a/game/src/GameSession/TerrainMap.gdshader b/game/src/GameSession/TerrainMap.gdshader
new file mode 100644
index 0000000..a6774fd
--- /dev/null
+++ b/game/src/GameSession/TerrainMap.gdshader
@@ -0,0 +1,48 @@
+shader_type spatial;
+
+render_mode unshaded;
+
+// Cosmetic terrain texture
+uniform sampler2D terrain_tex: source_color, repeat_enable, filter_linear;
+// Province index texture
+uniform sampler2D province_index_tex : repeat_enable, filter_nearest;
+// Province colour texture
+uniform sampler2D province_colour_tex: source_color, repeat_enable, filter_nearest;
+// Position of the mouse over the map mesh in UV coords
+uniform vec2 hover_pos;
+// Position in UV coords of a pixel belonging to the currently selected province
+uniform vec2 selected_pos;
+
+uvec2 vec2_to_uvec2(vec2 v) {
+	return uvec2(v * 255.0);
+}
+
+uint uvec2_to_uint(uvec2 v) {
+	return (v.y << 8u) | v.x;
+}
+
+uvec2 read_uvec2(sampler2D tex, vec2 uv) {
+	return vec2_to_uvec2(texture(tex, uv).rg);
+}
+
+uint read_uint16(sampler2D tex, vec2 uv) {
+	return uvec2_to_uint(read_uvec2(tex, uv));
+}
+
+void fragment() {
+	uvec2 prov_idx_split = read_uvec2(province_index_tex, UV);
+
+	uint prov_index = uvec2_to_uint(prov_idx_split);
+	uint hover_index = read_uint16(province_index_tex, hover_pos);
+	uint selected_index = read_uint16(province_index_tex, selected_pos);
+
+	// Boost prov_colour's contribution if it matches hover_colour or selected_colour
+	float mix_val = float(prov_index == hover_index) * 0.3 + float(prov_index == selected_index) * 0.5;
+	// Don't mix if the province index is 0
+	mix_val *= float(prov_index != 0u);
+
+	vec3 terrain_colour = texture(terrain_tex, UV).rgb;
+	vec3 province_colour = texelFetch(province_colour_tex, ivec2(prov_idx_split), 0).rgb;
+
+	ALBEDO = mix(terrain_colour, province_colour, mix_val);
+}