skydome.gd

func skyDomeLookup(vertices : Array, dv : Vector3):
	for idx in vertices.size():
		if vertices[idx].distance_squared_to(dv) < 0.0001:
			return idx
	var index : int = vertices.size()
	vertices.push_back(dv)
	return index

func createSkyDome(r_inner : float, r_outer : float):
	const numX = 16
	const numY = 4
	const total_points = (2 * numY + 1) * numX * 3 # triangles * 3

	# total number of vertices allocated to buffer:
	var vertices : Array
	var indices : Array
	var lookup : Array # Vector3 -> index

	# vertices for triangle strip:
	var va : Vector3
	var vb : Vector3
	var vc : Vector3
	var vd : Vector3

	var stepa  : float = PI * 2.0 / numX
	var startb : float = asin(r_inner / r_outer)
	var stepb  : float = (PI / 2.0 - startb) / 4.0

	for y in numY:
		var b : float = startb + stepb * y

		for x in numX:
			var a : float = stepa * x

			va = Vector3( sin(a)         * cos(b) * r_outer,         sin(b) * r_outer,         -cos(a)         * cos(b) * r_outer )
			vb = Vector3( sin(a + stepa) * cos(b) * r_outer,         sin(b) * r_outer,         -cos(a + stepa) * cos(b) * r_outer )
			vc = Vector3( sin(a + stepa) * cos(b + stepb) * r_outer, sin(b + stepb) * r_outer, -cos(a + stepa) * cos(b + stepb) * r_outer )
			vd = Vector3( sin(a)         * cos(b + stepb) * r_outer, sin(b + stepb) * r_outer, -cos(a)         * cos(b + stepb) * r_outer )

			# Find va, vb, vc, vd in the lookup hashmap and add their index to the indices vector
			# Triangle 1: va, vb, vc
			indices.push_back(skyDomeLookup(vertices, va));
			var va_idx = indices.back()
			indices.push_back(skyDomeLookup(vertices, vb));
			indices.push_back(skyDomeLookup(vertices, vc));
			var vc_idx = indices.back()
			# Triangle 2: vc, vd, va
			indices.push_back(vc_idx);
			indices.push_back(skyDomeLookup(vertices, vd));
			indices.push_back(va_idx);

	var b : float = startb + stepb * 3

	for x in numX:
		var a : float = stepa * x

		va = Vector3 ( sin(a)         * cos(b) * r_outer, sin(b) * r_outer, -cos(a)         * cos(b) * r_outer )
		vb = Vector3 ( sin(a + stepa) * cos(b) * r_outer, sin(b) * r_outer, -cos(a + stepa) * cos(b) * r_outer )
		vc = Vector3 ( 0.0, r_outer, 0.0 )

		indices.push_back(skyDomeLookup(vertices, va));
		indices.push_back(skyDomeLookup(vertices, vb));
		indices.push_back(skyDomeLookup(vertices, vc));

	assert(indices.size() == total_points)
	#print(vertices.size())