I am currently working on a game in Godot which involves rendering countries on a globe. I have very little prior experience with Godot, but have experimented with it in the past.
I am using this data from Natural Earth for country borders, and have successfully gotten it to display on the globe using a line mesh. The data was originally in shapefile format, but I converted it to GeoJSON using mapshaper.org.
The data basically boils down to a list of points given in latitude and longitude, which I then converted into 3d points and created a mesh using SurfaceTool.
I am having trouble generating an actual surface for the mesh, however. Firstly, I am unable to find a built-in function to generate a triangle mesh from this data. I have looked into numerous solutions, including using the built-in Mesh.PRIMITIVE_TRIANGLE_FAN format, which doesn't work on concave shapes.
I have looked into triangulation algorithms such as delaunay triangulation, but have had little success implementing them.
My current plan is to generate a triangle mesh using the 2d data (x,y = longitude,latitude), and project it onto the surface of the sphere. In order to produce a curved surface, I will include the vertices of the sphere itself in the mesh (example).
I would like to know how to go about constructing a triangle mesh from this data. In essence, I need an algorithm that can do the following things:
- Create a triangle mesh from a concave polygon (country border)
- Connect the mesh to a series of points within this polygon
- Allow for holes within the polygon (for lakes, etc.)
Here is an example of the result I am looking for.
Again, I am quite new to Godot and I am probably over-complicating things. If there is an easier way to go about rendering countries on a globe, please let me know.
This is my current code:
extends Node
export var radius = 1
export var path = "res://data/countries.json"
func coords(uv):
return (uv - Vector2(0.5, 0.5)) * 360
func uv(coords):
return (coords / 360) + Vector2(0.5, 0.5)
func sphere(coords, r):
var angles = coords / 180 * 3.14159
return Vector3(
r * cos(angles.y) * sin(angles.x),
r * sin(angles.y),
r * cos(angles.y) * cos(angles.x)
)
func generate_mesh(c):
var mesh = MeshInstance.new()
var material = SpatialMaterial.new()
material.albedo_color = Color(randf(), randf(), randf(), 1.0)
var st = SurfaceTool.new()
st.begin(Mesh.PRIMITIVE_LINE_STRIP)
for h in c:
var k = sphere(h, radius)
st.add_normal(k / radius)
st.add_uv(uv(h))
st.add_vertex(k)
st.index()
mesh.mesh = st.commit()
mesh.set_material_override(material)
return mesh
func load_data():
var file = File.new()
file.open(path, file.READ)
var data = JSON.parse(file.get_as_text()).result
file.close()
for feature in data.features:
var geometry = feature.geometry
var properties = feature.properties
if geometry.type == "Polygon":
for body in geometry.coordinates:
var coordinates = []
for coordinate in body:
coordinates.append(Vector2(coordinate[0], coordinate[1]))
add_child(generate_mesh(coordinates))
if geometry.type == "MultiPolygon":
for polygon in geometry.coordinates:
for body in polygon:
var coordinates = []
for coordinate in body:
coordinates.append(Vector2(coordinate[0], coordinate[1]))
add_child(generate_mesh(coordinates))
func _ready():
load_data()