How does UV mapping work with surfacetool in Godot? - terrain

Question

I'm coding a terrain generator in Godot. I generate the Mesh using SurfaceTool and triangle strips. The geometry works fine — but the UV mapping doesn't, as each triangle repeats the texture instead of the full mesh covering the texture once:
Normalizing the UV-Coordinates to fit into the 0,0 - 1,1 dimensions is what should work, but doesn't, as it makes only one pair of triangles have the full texture and the rest is blank:
extends MeshInstance
export var terrain_width = 16
export var terrain_depth = 16
export var terrain_height = 1
export var terrain_scale = 1
#Noise Generation
var terrain_noise = OpenSimplexNoise.new()
var terrain_heightmap = ImageTexture.new()
var terrain_texture = Texture.new()
var terrain_material = SpatialMaterial.new()
var terrain_mesh = Mesh.new()
var surfacetool = SurfaceTool.new()
func _ready():
generate_heightmap()
generate_mesh()
func generate_heightmap():
#Setup the noise
terrain_noise.seed = randi()
terrain_noise.octaves = 4
terrain_noise.period = 20.0
terrain_noise.persistence = 0.8
#Make the texture
terrain_heightmap.create_from_image(terrain_noise.get_image(terrain_width+1, terrain_depth+1))
terrain_texture = terrain_heightmap
func generate_mesh():
#Set the material texture to the heightmap
terrain_material.albedo_texture = terrain_texture
# This is where the uv-mapping occurs, via the add_uv function
for z in range(0,terrain_depth):
surfacetool.begin(Mesh.PRIMITIVE_TRIANGLE_STRIP)
for x in range(0,terrain_width):
surfacetool.add_uv(Vector2((terrain_width-x)/terrain_width,z/terrain_depth))
surfacetool.add_vertex(Vector3((terrain_width-x)*terrain_scale, terrain_noise.get_noise_2d(x,z)*terrain_height*terrain_scale, z*terrain_scale))
surfacetool.add_uv(Vector2((terrain_width-x)/terrain_width,(z+1)/terrain_depth))
surfacetool.add_vertex(Vector3((terrain_width-x)*terrain_scale, terrain_noise.get_noise_2d(x,z+1)*terrain_height*terrain_scale, (z+1)*terrain_scale))
surfacetool.generate_normals()
surfacetool.index()
surfacetool.commit(terrain_mesh)
#Set the texture and mesh on the MeshInstance
self.material_override = terrain_material
self.set_mesh(terrain_mesh)
self.set_surface_material(0, terrain_texture)
I expect each triangle to cover only the corresponding coordinates in the texture.
It seems as if each triangle is considered as a separate surface.

Answer 1

You have lots of integer divisions there. There are many ways to fix that. Here's a quick one: Just add .0 after your exported variable's default values:
export var terrain_width = 16.0
export var terrain_depth = 16.0
export var terrain_height = 1.0
export var terrain_scale = 1.0
And here's a more explicit way:
export(float) var terrain_width = 16
export(float) var terrain_depth = 16
export(float) var terrain_height = 1
export(float) var terrain_scale = 1
Assuming you don't have any other bugs, this should fix the issue.