implement follow component + system

1 files changed, 27 insertions, 0 deletions

diff --git a/app/systems/rules/follow.rb b/app/systems/rules/follow.rb
new file mode 100644
index 0000000..0b5045e
--- /dev/null
+++ b/app/systems/rules/follow.rb
@@ -0,0 +1,27 @@
+FF::Scn::BoidRules.add(
+  FF::Sys.new('Follow', priority: 70) do
+    FF::Cmp::Follow.each do |follow|
+      boid = follow.entities[0].components[FF::Cmp::Boid][0]
+      target_coords = [0.0, 0.0]
+      case follow.target
+      when FF::Cmp::Boid
+        target_coords[0] = follow.target.x
+        target_coords[1] = follow.target.y
+      when Array
+        target_coords[0] = follow.target[0]
+        target_coords[1] = follow.target[1]
+      when :mouse
+        camera = FF::Cmp::SingletonCamera[0]
+        angle = camera.angle * (Math::PI / 180)
+        mouse = $gtk.args.inputs.mouse
+        half_width = $gtk.args.grid.w * 0.5
+        half_height = $gtk.args.grid.h * 0.5
+        target_coords[0] = (((mouse.x - half_width) / camera.zoom) * Math.cos(-angle)) - (((mouse.y - half_height) / camera.zoom) * Math.sin(-angle)) + camera.x
+        target_coords[1] = (((mouse.x - half_width) / camera.zoom) * Math.sin(-angle)) + (((mouse.y - half_height) / camera.zoom) * Math.cos(-angle)) + camera.y
+      end
+
+      boid.cx += (target_coords[0] - boid.x) / follow.strength.to_f
+      boid.cy += (target_coords[1] - boid.y) / follow.strength.to_f
+    end
+  end
+)