Added Box2d Lua module #8712

JCash · 2024-03-25T19:23:40Z

This allows you to get a physics body and manipulate its forces, velocities and other properties.

Example:

local id = factory.create("#factory", position)
local url = msg.url(nil, id, "collisionobject") -- get the collision object in the spawned object
self.body = b2d.get_body(url) -- get the b2body object
b2d.body.dump(self.body) -- debug print

-- add an impulse
local pos = b2d.body.get_position(self.body)
b2d.body.apply_linear_impulse(self.body, vmath.vector3(300,200,0), pos + vmath.vector3(16,16,0))

A full list of functions is available in the reference api for b2d and b2d.body.
Note that this was a first step. Next up is adding the missing structs, e.g. world, joints, fixtures and shapes support.

Fixes #8256
Fixes #8101
Fixes #5405
Fixes #3191
Fixes #3120

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Start with the user facing changes. This will end up in the release notes.
Add one of the GitHub approved closing keywords
Optionally also add the technical changes made. This is information that might help the reviewer. It will not show up in the release notes. Technical changes are identified by a line starting with one of these:
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There was a anomaly in the carbon chroniton propeller, introduced in version 8.10.2. This fix will make sure to reset the phaser collector on application startup.

Fixes #1234

### Technical changes
* Pay special attention to line 23 of phaser_collector.clj as it contains some interesting optimizations
* The propeller code was not taking into account a negative phase.

JCash · 2024-03-25T19:29:04Z

engine/engine/src/engine.cpp

@@ -1305,6 +1305,7 @@ namespace dmEngine
        script_lib_context.m_HidContext      = engine->m_HidContext;
        script_lib_context.m_GraphicsContext = engine->m_GraphicsContext;
        script_lib_context.m_JobThread       = engine->m_JobThreadContext;
+        script_lib_context.m_ConfigFile      = engine->m_Config;


To allow for reading game properties, like physics.scale

JCash · 2024-03-25T19:30:24Z

engine/gamesys/src/gamesys/scripts/script_box2d.cpp

+    void PushWorld(struct lua_State* L, class b2World* world)
+    {
+        lua_pushlightuserdata(L, world);
+    }


todo: add script_box2d_world.cpp with proper user type.

JCash · 2024-03-25T19:31:38Z

engine/gamesys/src/gamesys/scripts/script_box2d.cpp

+        dmGameObject::GetComponentUserDataFromLua(L, index, collection, COLLISION_OBJECT_EXT, (uintptr_t*)comp, 0, comp_world);
+    }
+
+    static int B2D_GetWorld(lua_State* L)


These parts should be moved to a world specific .cpp file

JCash · 2024-03-25T19:32:32Z

engine/gamesys/src/gamesys/scripts/script_box2d.cpp

+        SETCONSTANT(b2BodyType, b2_staticBody);
+        SETCONSTANT(b2BodyType, b2_kinematicBody);
+        SETCONSTANT(b2BodyType, b2_dynamicBody);
+        lua_setfield(L, -2, "b2BodyType");


They'll show up as box2d.b2bodyType.b2_staticBody

JCash · 2024-03-25T19:33:31Z

engine/physics/src/physics/physics.h

+    void* GetWorldContext2D(HWorld2D world);
+    void* GetCollisionObjectContext2D(HCollisionObject2D collision_object);


We need to resolve the glue between our physics engine and box2d

JCash · 2024-03-25T19:42:41Z

engine/gamesys/src/gamesys/scripts/script_box2d_body.cpp

+        //{"get_user_data", Body_GetUserData}, - could return the game object id ?
+        //{"set_user_data", Body_SetUserData}, - could attach the body to a game object?


Getting the id of the game object is useful, and it should be possible to set the id as well, with some extra component functions to make sure that the game+physics objects life times are considered.

JCash · 2024-03-25T19:45:07Z

engine/gamesys/src/gamesys/scripts/script_box2d.cpp

+        b2Body* body = dmGameSystem::CompCollisionObjectGetBox2DBody(component);
+
+        if (body)
+            PushBody(L, body);


I need to make this more robust, as it currently contains an internal pointer, and the game object may be deleted directly after (and along with is the collision object).

E.g. if this has a game object id set, then we need to check it before doing any operations on the body.

JCash · 2024-03-25T19:50:00Z

engine/gamesys/src/gamesys/scripts/script_box2d_body.cpp

+        {"__tostring", Body_tostring},
+        {"__eq", Body_eq},
+
+        {"get_position", Body_GetPosition},


The previous extension, uses the Box2D naming style: GetPosition().
Here I'm using the naming style in Defold.

Yay, or nay?

JCash · 2024-03-25T19:50:12Z

engine/gamesys/src/gamesys/scripts/script_box2d_body.cpp

+        // {"get_mass_data", Body_GetMassData},
+        // {"set_mass_data", Body_SetMassData},
+        // {"reset_mass_data", Body_ResetMassData},
+        // {"synchronize_fixtures", SynchronizeFixtures},
+        // SynchronizeSingle(b2Shape* shape, int32 index)


JCash · 2024-03-25T19:50:59Z

engine/gamesys/src/gamesys/scripts/script_box2d_body.cpp

+ * @name b2body
+ */
+
+/**


Copied all documentation, but set some to "undocumented" /** until they're implemented.

AGulev

I like it a lot!

A couple of small things should be fixed in docs.

tests are still red.

AGulev · 2024-03-30T08:11:03Z

engine/gamesys/src/gamesys/scripts/box2d/script_box2d_body.cpp

+ * Set the position of the body's origin and rotation.
+ * This breaks any contacts and wakes the other bodies.
+ * Manipulating a body's transform may cause non-physical behavior.
+ * @name body:set_transform


documentation still uses body:* syntax

AGulev · 2024-03-30T08:14:10Z

engine/gamesys/src/gamesys/scripts/box2d/script_box2d_body.cpp

+
+/*# Get the user data pointer that was provided in the body definition.
+ * @name body:get_user_data
+ * @return id [type: hash] the game object id this body is connected to


this function isn't implemented, should be hidden from docs

AGulev · 2024-03-30T08:15:38Z

engine/gamesys/src/gamesys/scripts/box2d/script_box2d_body.cpp

+/** Get the total force currently applied on this object
+ * @name body:get_force
+ * @note Defold Specific
+ * @return force [type: vmath.vector3]


it seems like this function is already implemented but it's commented (as I understand /** - comment out function, and /*# - added function?)

Jhonnyg · 2024-04-02T08:11:22Z

engine/gamesys/src/gamesys/scripts/box2d/script_box2d.cpp

+// #define SETCONSTANT(NS, NAME) \
+//         lua_pushnumber(L, (lua_Number) NS :: NAME); \
+//         lua_setfield(L, -2, #NAME);
+
+
+//         lua_newtable(L);
+//         SETCONSTANT(b2Shape, e_circle);
+//         SETCONSTANT(b2Shape, e_edge);
+//         SETCONSTANT(b2Shape, e_polygon);
+//         SETCONSTANT(b2Shape, e_chain);
+//         lua_setfield(L, -2, "b2Shape");
+
+//         lua_newtable(L);
+//         SETCONSTANT(b2JointType, e_unknownJoint)
+//         SETCONSTANT(b2JointType, e_revoluteJoint)
+//         SETCONSTANT(b2JointType, e_prismaticJoint)
+//         SETCONSTANT(b2JointType, e_distanceJoint)
+//         SETCONSTANT(b2JointType, e_pulleyJoint)
+//         SETCONSTANT(b2JointType, e_mouseJoint)
+//         SETCONSTANT(b2JointType, e_gearJoint)
+//         SETCONSTANT(b2JointType, e_wheelJoint)
+//         SETCONSTANT(b2JointType, e_weldJoint)
+//         SETCONSTANT(b2JointType, e_frictionJoint)
+//         SETCONSTANT(b2JointType, e_ropeJoint)
+//         lua_setfield(L, -2, "b2JointType");
+
+// #undef SETCONSTANT


Is this dead code, debug code, or a todo?

Kind of both. I'll remove it.

JCash added 7 commits March 19, 2024 08:13

Added first version of a box2d specific Lua module

b2cc818

Added object methods to the b2body representation

823b2b3

Added some more functions

97f4090

Added more functions

1201393

Moved functions into _body.cpp

5087b2d

Added documentation

f332390

path fix for installation of box2d headers

8636bf4

JCash requested review from Jhonnyg and AGulev March 25, 2024 19:28

JCash commented Mar 25, 2024

View reviewed changes

JCash added 4 commits March 25, 2024 21:30

typo

f44a54f

Renamed scripting api after review discussion

031f986

Added more robust check if the body's game object is still alive

ae93009

Moved box2d script files into separate folder

0cc3dff

AGulev previously approved these changes Mar 30, 2024

View reviewed changes

Jhonnyg previously approved these changes Apr 2, 2024

View reviewed changes

JCash added 3 commits April 2, 2024 11:40

Updated documentation to b2d.body. format

7a63b31

review fixes

cdd2034

test fix

1e6dc8a

JCash dismissed stale reviews from Jhonnyg and AGulev via 1e6dc8a April 2, 2024 10:05

Fix forward declaration for b2World/b2Body to use correct (no) namespace

c64d604

JCash merged commit acdd78d into dev Apr 3, 2024
22 checks passed

JCash deleted the script-box2d branch April 3, 2024 09:18

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Added Box2d Lua module #8712

Added Box2d Lua module #8712

JCash commented Mar 25, 2024 •

edited by AGulev

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JCash Apr 2, 2024

Jhonnyg Apr 2, 2024

JCash Apr 2, 2024

		void* GetWorldContext2D(HWorld2D world);
		void* GetCollisionObjectContext2D(HCollisionObject2D collision_object);

		//{"get_user_data", Body_GetUserData}, - could return the game object id ?
		//{"set_user_data", Body_SetUserData}, - could attach the body to a game object?

Added Box2d Lua module #8712

Added Box2d Lua module #8712

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JCash commented Mar 25, 2024 • edited by AGulev

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JCash commented Mar 25, 2024 •

edited by AGulev