Initial MoonModel implementation

lib/moon_model/mesh.rb

@@ -0,0 +1,98 @@
+# frozen_string_literal: true
+
+module MoonModel
+  class Mesh
+    attr_reader :name, :vertices, :triangles, :material
+
+    def initialize(name:, material: nil)
+      @name = name
+      @material = material
+      @vertices = []
+      @triangles = []
+    end
+
+    def vertex(point)
+      @vertices << point.map(&:to_f)
+      @vertices.length - 1
+    end
+
+    def triangle(a, b, c)
+      @triangles << [a, b, c]
+    end
+
+    def quad(a, b, c, d, flip: false)
+      flip ? (triangle(a, c, b); triangle(a, d, c)) : (triangle(a, b, c); triangle(a, c, d))
+    end
+
+    def add_box(center, size)
+      cx, cy, cz = center
+      sx, sy, sz = size.map { |v| v / 2.0 }
+      ids = [[-sx,-sy,-sz],[sx,-sy,-sz],[sx,sy,-sz],[-sx,sy,-sz],[-sx,-sy,sz],[sx,-sy,sz],[sx,sy,sz],[-sx,sy,sz]].map do |x,y,z|
+        vertex([cx+x, cy+y, cz+z])
+      end
+      quad(ids[0], ids[3], ids[2], ids[1]); quad(ids[4], ids[5], ids[6], ids[7])
+      quad(ids[0], ids[1], ids[5], ids[4]); quad(ids[1], ids[2], ids[6], ids[5])
+      quad(ids[2], ids[3], ids[7], ids[6]); quad(ids[3], ids[0], ids[4], ids[7])
+    end
+
+    def add_tapered_box(center, length, width_a, width_b, height)
+      cx, cy, cz = center
+      x0 = cx - length / 2.0; x1 = cx + length / 2.0
+      z0 = cz - height / 2.0; z1 = cz + height / 2.0
+      ids = [[x0,cy-width_a/2,z0],[x0,cy+width_a/2,z0],[x1,cy+width_b/2,z0],[x1,cy-width_b/2,z0],
+             [x0,cy-width_a/2,z1],[x0,cy+width_a/2,z1],[x1,cy+width_b/2,z1],[x1,cy-width_b/2,z1]].map { |p| vertex(p) }
+      quad(ids[0],ids[3],ids[2],ids[1]); quad(ids[4],ids[5],ids[6],ids[7])
+      quad(ids[0],ids[1],ids[5],ids[4]); quad(ids[1],ids[2],ids[6],ids[5])
+      quad(ids[2],ids[3],ids[7],ids[6]); quad(ids[3],ids[0],ids[4],ids[7])
+    end
+
+    def add_cylinder(center, radius, height, segments: 24)
+      cx, cy, cz = center
+      bottom = segments.times.map { |i| a = i * 2*Math::PI/segments; vertex([cx+radius*Math.cos(a), cy+radius*Math.sin(a), cz-height/2]) }
+      top = segments.times.map { |i| a = i * 2*Math::PI/segments; vertex([cx+radius*Math.cos(a), cy+radius*Math.sin(a), cz+height/2]) }
+      cb = vertex([cx,cy,cz-height/2]); ct = vertex([cx,cy,cz+height/2])
+      segments.times do |i|
+        j = (i+1)%segments
+        triangle(cb,bottom[j],bottom[i]); triangle(ct,top[i],top[j]); quad(bottom[i],bottom[j],top[j],top[i])
+      end
+    end
+
+    def add_annular_cylinder(center, inner_radius, outer_radius, z0, z1, segments: 32)
+      cx, cy = center
+      oi=[]; oo=[]; ti=[]; to=[]
+      segments.times do |i|
+        a=i*2*Math::PI/segments
+        oi << vertex([cx+inner_radius*Math.cos(a),cy+inner_radius*Math.sin(a),z0])
+        oo << vertex([cx+outer_radius*Math.cos(a),cy+outer_radius*Math.sin(a),z0])
+        ti << vertex([cx+inner_radius*Math.cos(a),cy+inner_radius*Math.sin(a),z1])
+        to << vertex([cx+outer_radius*Math.cos(a),cy+outer_radius*Math.sin(a),z1])
+      end
+      segments.times do |i|
+        j=(i+1)%segments
+        quad(oo[i],oo[j],to[j],to[i]); quad(oi[i],ti[i],ti[j],oi[j])
+        quad(oi[i],oi[j],oo[j],oo[i]); quad(ti[i],to[i],to[j],ti[j])
+      end
+    end
+
+    def add_tri_prism(outer, inner)
+      o = outer.map { |p| vertex(p) }
+      i = inner.map { |p| vertex(p) }
+      triangle(o[0], o[1], o[2]); triangle(i[0], i[2], i[1])
+      3.times { |n| quad(o[n], o[(n + 1) % 3], i[(n + 1) % 3], i[n]) }
+    end
+
+    def transform
+      vertices.map! { |point| yield(point) }
+      self
+    end
+
+    def bounds
+      axes = vertices.transpose
+      axes.map { |axis| [axis.min || 0.0, axis.max || 0.0] }
+    end
+
+    def valid?
+      !vertices.empty? && triangles.all? { |tri| tri.uniq.length == 3 && tri.all? { |i| i.between?(0, vertices.length - 1) } }
+    end
+  end
+end