Fixed physics debug example and added description regarding collection proxy and slowing time for debugging. (#136)

Author: paweljarosz

debug/physics/collectionproxy.png

@@ -3,9 +3,21 @@ tags: debug
 title: Physics debug
 brief: This example allows you to toggle physics debug visualization as well as changing the time step so the simulation runs at one tenth of the speed.
 author: Defold Foundation
-scripts: physics.script
+scripts: physics.script, loader.script
+thumbnail: thumbnail.png
 ---
 
 With the physics visualization on, all collision object shapes are visible. In addition, at intersections the normals at the collision points are shown.
 
-![physics debug](physics.png)
+The example collection consists of:
+- 4 blocks with dynamic collision objects with Restituion 1.0, so they bounce forever,
+- 4 walls with static collision objects forming boundaries for the blocks,
+- game object `go` with:
+  - label with example description,
+  - a script `physics.script` included below.
+
+![physics debug](physics.png)
+
+This collection is additionally loaded via a `Collection Proxy` component in `main.collection`. Therefore, sending message `set_time_step` to its url `"main:/loader#physicsproxy"` is causing the proxy to have a different update time, causing e.g. the slow-motion effect, which might be helpful when debugging physics.
+
+![collection proxy](collectionproxy.png)

debug/physics/example.md

@@ -0,0 +1,11 @@
+function init(self)
+    msg.post(".", "acquire_input_focus")
+    msg.post("#physicsproxy", "load")
+end
+
+function on_message(self, message_id, message, sender)
+    if message_id == hash("proxy_loaded") then
+        msg.post(sender, "init")
+        msg.post(sender, "enable")
+    end
+end

debug/physics/example/loader.script

@@ -0,0 +1,57 @@
+name: "main"
+scale_along_z: 0
+embedded_instances {
+  id: "loader"
+  data: "components {\n"
+  "  id: \"loader\"\n"
+  "  component: \"/example/loader.script\"\n"
+  "  position {\n"
+  "    x: 0.0\n"
+  "    y: 0.0\n"
+  "    z: 0.0\n"
+  "  }\n"
+  "  rotation {\n"
+  "    x: 0.0\n"
+  "    y: 0.0\n"
+  "    z: 0.0\n"
+  "    w: 1.0\n"
+  "  }\n"
+  "  property_decls {\n"
+  "  }\n"
+  "}\n"
+  "embedded_components {\n"
+  "  id: \"physicsproxy\"\n"
+  "  type: \"collectionproxy\"\n"
+  "  data: \"collection: \\\"/example/physics.collection\\\"\\n"
+  "exclude: false\\n"
+  "\"\n"
+  "  position {\n"
+  "    x: 0.0\n"
+  "    y: 0.0\n"
+  "    z: 0.0\n"
+  "  }\n"
+  "  rotation {\n"
+  "    x: 0.0\n"
+  "    y: 0.0\n"
+  "    z: 0.0\n"
+  "    w: 1.0\n"
+  "  }\n"
+  "}\n"
+  ""
+  position {
+    x: 0.0
+    y: 0.0
+    z: 0.0
+  }
+  rotation {
+    x: 0.0
+    y: 0.0
+    z: 0.0
+    w: 1.0
+  }
+  scale3 {
+    x: 1.0
+    y: 1.0
+    z: 1.0
+  }
+}

debug/physics/example/main.collection

@@ -7,9 +7,9 @@ function on_input(self, action_id, action)
 	if action_id == hash("touch") and action.pressed then
 		msg.post("@system:", "toggle_physics_debug") -- <3>
 		if self.show_debug then -- <4>
-			msg.post("main:/loader", "set_time_step", { factor = 1, mode = 0 })
+			msg.post("main:/loader#physicsproxy", "set_time_step", { factor = 1, mode = 0 })
 		else
-			msg.post("main:/loader", "set_time_step", { factor = 0.1, mode = 1 })
+			msg.post("main:/loader#physicsproxy", "set_time_step", { factor = 0.1, mode = 1 })
 		end
 		self.show_debug = not self.show_debug -- <5>
 	end

debug/physics/example/physics.script

@@ -3,7 +3,7 @@ title = Defold-examples
 version = 0.1
 
 [bootstrap]
-main_collection = /example/physics.collectionc
+main_collection = /example/main.collectionc
 
 [input]
 game_binding = /builtins/input/all.input_bindingc