ReactPhysics3D

MoKaLux · January 2020

I am exploring reactphysics3d.
I have a ship (from Paul

)

local ship = loadObj("3d", "ship.obj")
ship.shape = r3d.BoxShape.new(2, 1, 3)
local v2 = Viewport.new()
v2:setContent(ship)
v2:setPosition(0, 4, 0) -- min 2 for y
v2.body = world:createBody(v2:getMatrix())
v2.body:createFixture(ship.shape, nil, 100)
v2.body:enableGravity(false)

I have the game loop:

stage:addEventListener(Event.ENTER_FRAME, function(e)
	...
	local shipx = v2:getX()
	local shipy = v2:getY()
	local shipz = v2:getZ()
	if isright then shipx += 0.10 end
	if isleft then shipx -= 0.10 end
	if isup then shipy += 0.10 end
	if isdown then shipy -= 0.10 end
--	matrix:setPosition(shipx, shipy, shipz)
--	v2.body:setTransform(matrix)
--	v2:setPosition(shipx, shipy, shipz)
--	ship:setPosition(v2:getPosition())
	ship:setMatrix(v2.body:getTransform())
end)

The ship collides with the boxes but how can I move the ship please?
I am almost there (see the commented lines) but at some point the player crashes.

MoKaLux · January 2020

I think I found it

	if isright then v2.body:applyForce(32, 0, 0) end
	if isleft then v2.body:applyForce(-32, 0, 0) end
	if isup then v2.body:applyForce(0, 32, 0) end
	if isdown then v2.body:applyForce(0, -32, 0) end
	ship:setMatrix(v2.body:getTransform())

That works kind of like liquidfun (box2d).

MoKaLux · January 2020

another question please.
How can I move the ship in the direction it is facing?
I tried this but getRotationY() is always 0 so that doesn't work.

	if isup then
		matrix = v2.body:getTransform()
--		v2.body:applyForce(0, 0, 16*100)
		v2.body:applyForce(
			math.cos(^< matrix:getRotationY()) * 64*10,
			0,
			-math.sin(^< matrix:getRotationY()) * 64*10)
		print(matrix:getRotationX(), matrix:getRotationY(), matrix:getRotationZ())
	end
	if isdown then
--		v2.body:applyForce(0, 0, -16*100)
		v2.body:applyForce(
			-math.cos(^< matrix:getRotationY()) * 10*64,
			0,
			math.sin(^< matrix:getRotationY()) * 10*64)
		print(matrix:getRotationX(), matrix:getRotationY(), matrix:getRotationZ())
	end

Thank you for your help.
the project:

hgy29 · January 2020

Yes, you can’t always reverse a matrix to its Euler angles, so gideros don’t do it at all, although in the case of reactphysics it is always possible... but you can transform your direction vector by the matrix and normalize the result to get a new direction vector.

MoKaLux · January 2020

thank you for your feedback.
I am "rotating" the ship using torque:

	if istorqueleft then v2.body:applyTorque(0, -8*64, 0) end
	if istorqueright then v2.body:applyTorque(0, 8*64, 0) end

The ship is rotating as expected but I don't know if it changes the rotation of the ship or of the viewport or of the body. All of them don't seem to change, they are always 0. Will do more tests.

@hgy29 I remember the demo/game you did http://forum.giderosmobile.com/discussion/comment/60150/#Comment_60150. Do you mind sharing the code please?

hgy29 · January 2020

@MoKaLux, I wouldn't mind sharing it, but I'd need to refactor it before, since it uses various bits of code and assets all over my pc.
And it won't help you since in my demo, the ball was thrown in a known/fixed direction.

with reactphysics3d, it works pretty much the same as box2d: the collision engine change the transform matrix of the body, then your gideros code copy this matrix to the corresponding sprite. I think your issue is that setting the Matrix of a Sprite doesn't update its rotation/translation nor scale components, it only change its resulting matrix. thus you can't use getRotation() afterwise.

There are ways to compute back rotation angles from the matrix coeficients, but your problem is easier to solve since you don't need the angles, but the direction vector.

For example, if your untransformed ship is pointing toward 'z' axis, then you can get the transformed direction vector with the code below:

		local m=body:getTransform() -- or sprite:getMatrix()
		local ax,ay,az=m:transformPoint(0,0,0)
		local bx,by,bz=m:transformPoint(0,0,1)
		local dx,dy,dz=bx-ax,by-ay,bz-az

I hope that helps...

MoKaLux · January 2020

that is working great

, I just need to play with the numbers now. Thank you very much for your answer. I noticed reactphysics3d was working like box2d. I will post the code here when I am done. Peace.

MoKaLux · January 2020

here is a video and the source file, please feel free to improve.
~~youtube.com/watch?v=cE1_uHiOArY~~
Code based on gideros 3d collisions demo (hgy29) + ship graphix from Paul.
main.lua = 146 lines of code

MoKaLux · January 2020

Some more questions please. This is how I set up a 3D object.

-- a ship
local objship = loadObj("3d/ship", "ship.obj")
objship.shape2 = r3d.CapsuleShape.new(2, 1)
local shipvp = Viewport.new()
shipvp:setContent(objship)
shipvp:setPosition(0, 10, 0) -- position the ship when starting the game
shipvp.body = world:createBody(shipvp:getMatrix())
shipvp.body:createFixture(objship.shape2, nil, 100)
--shipvp.body:enableGravity(false)

Now the capsule shape has no friction but we should be able to change the friction value using setMaterial and setFrictionCoefficient(0.5)
But I don't know how to access the setFrictionCoefficient

From the reactphysics doc it's written:

Here is how to get the material of a rigid body and how to modify some of its properties:
// Get the current material of the body
rp3d::Material& material = rigidBody ->getMaterial();
// Change the friction coefficient of the body
material.setFrictionCoefficient(rp3d::decimal(0.2));

And in the gideros github I see this:

int r3dBody_SetMaterial(lua_State* L) {
	Binder binder(L);
	rp3d::RigidBody* body = static_cast(binder.getInstance(
			"r3dBody", 1));
	rp3d::Material& mat = body->getMaterial();
	lua_getfield(L, 2, "frictionCoefficient");
	if (!lua_isnil(L,-1))
		mat.setFrictionCoefficient(luaL_checknumber(L, -1));
	lua_pop(L, 1);
}

https://github.com/gideros/gideros/blob/master/plugins/reactphysics3d/source/Common/reactbinder.cpp
I tried these but that don't work:
1- local mat = shipvp.body:getMaterial() mat:setFrictionCoefficient(0.5)
2- shipvp.body:setMaterial(setFrictionCoefficient(0.5))
3- shipvp.body:setFrictionCoefficient(0.5)
Thank you in advance for your help.

MoKaLux · January 2020

I found it

local mat = shipvp.body:getMaterial()
print(mat.frictionCoefficient) -- prints 0.3 
mat.frictionCoefficient = 0.75
print(mat.frictionCoefficient) -- prints 0.75
shipvp.body:setMaterial(mat) -- apply new material

MoKaLux · January 2020

another question please. I am creating a sphereshape and I would like to move it towards the front of the ship.

local objship = loadObj("3d/ship", "ship.obj")
objship.shape3 = r3d.SphereShape.new(1.5)
local shipvp = Viewport.new()
shipvp:setContent(objship)
shipvp:setPosition(0, 10, 0) -- position the ship when starting the game
shipvp.body = world:createBody(shipvp:getMatrix())
shipvp.body:createFixture(objship.shape3, nil, 100) -- shape, transform, mass

I know it has to do with the transform but what value does it take?
shipvp.body:createFixture(objship.shape3, nil, 100) -- shape, transform, mass

What I tried

:
1- objship.shape3:setTransform(0, 5, 10)
2- objship.shape3:setPosition(0, 5, 10)

MoKaLux · January 2020

edit: I think I found it? Is this the way to do it?

local m = Matrix.new(0, 10, 0)
shipvp.body:createFixture(objship.shape3, m, 64) -- shape, transform, mass

hgy29 · January 2020

Almost there, just create an empty Matrix and use setPosition on it. Then use the matrix in createFixture

MoKaLux · January 2020

that worked, thank you very much hgy29

.

MoKaLux · January 2020

some progress here!

to dos:
- ~~collision filtering~~DONE, better vehicle controls, better blender texturing!
- how to build levels? maybe in tiled?
- make games/apps

PS: the code is dirty

MoKaLux · January 2020

building a 3D map for the levels using TILED (objects) = OK

MoKaLux · January 2020

I managed to "build" levels using tiled

I tried getting the ship move like a car, no success

I tried getting the ship move like a ship, no success

I tried for days getting the controls right with no success, I would need some help here please!
I am almost ready to do some tutorials to bring some attention to gideros but I would like to get the controls done before

PS: I removed the factory buildings because it was too large for the zip file.

hgy29 · January 2020

To move like a ship, I'd do it that way:

	local gv=0	
	if isleft then gv=1 end
	if isright then gv=-1 end
	if isup then shipbody:applyForce(dx * force, 0, dz * force,ax+dz*gv,ay,az-dx*gv) end
	if isdown then shipbody:applyForce(-dx * force, 0, -dz * force,ax+dz*gv,ay,az-dx*gv) end

It will only rotate if you accelerate at the same time. The idea is to apply the force on the right or left side of the ship when you want to turn, and on the center if you don't, as if the propellers power was being adjusted to allow turning your ship.

MoKaLux · January 2020

nope that doesn't work, I still get the never ending sliding effects.
I asked the question on reactphysics3d github:
https://github.com/DanielChappuis/reactphysics3d/issues/119
@PaulH could you also please help here

?

I also tried to convert this box2d pdf to reactphysics. My goal would be to kill the lateral velocity.

In b2d, b2dot =

inline float32 b2Dot(const b2Vec2& a, const b2Vec2& b)
{
return a.x * b.x + a.y * b.y;
}

hgy29 · January 2020

It was working for me (i tried before replying), but I assumed it was a spaceship, in which case you’d want to keep lateral velocity since there are no frictions in space. Maybe you can query the current velocity, extract the lateral component and apply an opposite force to attenuate it ?

MoKaLux · January 2020

thank you very much for your help hgy29, your code is working of course

what I wanted to say is that the ship keeps sliding even if we have changed direction. I hope to make the ship slide only a little and then go to the correct direction. I tried everything I could. I will try some more the b2d way see what I get (cf:killing lateral velocity). Once again thank you very much for your help

.

hgy29 · January 2020

BTW I noticed that current plugin doesn't expose functions to query velocity and set/get damping. I added them for next release and I can send you an updated .dll if you wish.

MoKaLux · January 2020

oh yes I would gratefully want it

. I tried to join you on slack but the link above the forum doesn't work anymore.

hgy29 · January 2020

Thanks for flagging, I fixed it. You were already in the slack group though

MoKaLux · January 2020

THAT WORKED

Now simply using this to control the ship (vehicle)

	if isup then shipbody:applyForce(dx * force, 0, dz * force) end
	if isdown then shipbody:applyForce(-dx * force, 0, -dz * force) end
	if isleft then shipbody:applyTorque(0, -torque, 0) end
	if isright then shipbody:applyTorque(0, torque, 0) end

and the magic happens here:

	shipbody:setLinearDamping(0.3)

Thank you very much hgy29.
Now some tutorials!

PS: one little issue with lighting and android. I have this message:
FragmentShader:
0:19: L0003: Keyword 'sampler2DShadow' is reserved

stack traceback:
3dbase/3DLighting.lua:74: in function 'getShader'
3dbase/3DLighting.lua:109: in function 'setSpriteMode'
3dbase/3DShapes.lua:35: in function 'updateMode'
3d_factory/plane.lua:35: in function 'PLANE_3D'
main.lua:33: in main chunk

MoKaLux · February 2020

~~I am struggling doing some tuts~~

.
I have started

MoKaLux · February 2020

I have one more question regarding r3d. I don't know if I should start a new post?
My question is: can we get the position of a r3d body on only 1 axis?
I would like to access the position on a certain axis only (for example the body position on the x axis):

	for k, v in pairs(world.missiles) do
		v.body:applyForce(0, 0, missilespeed)
		print(v.body:getTransform()[1])
--		k:setMatrix(v.body:getTransform()[1])
--		k:setZ(v.body:getZ())
	end

Alternatively, would it be difficult to get the body matrix instead of its transform?
Transform doesn't take into account the scale, that would be pretty handy.

Thank you

PS: I see in r3d.cpp file this code:

static void toTransform(lua_State *L, int n, rp3d::Transform &transform) {
	Binder binder(L);
	lua_pushvalue(L, n);
	if (binder.isInstanceOf("Matrix", -1)) {
		float mat[16];
		lua_getfield(L, -1, "getMatrix");
		lua_pushvalue(L, -2);
		lua_call(L, 1, 16);
		for (size_t k = 0; k < 16; k++)
			mat[k] = luaL_optnumber(L, -16 + k, 0);
		lua_pop(L, 17);
		transform.setFromOpenGL(mat);
	}
}

transform.setFromOpenGL(mat) OpenGL doesn't take the scale?

hgy29 · February 2020

1) You can use

body:getTransform():getX()

2) You actually get a Matrix from getTransform(), unfortunately reactphysics3d don't handle scaling. https://github.com/DanielChappuis/reactphysics3d/issues/103

MoKaLux · February 2020

perfect, thank you very much hgy29

For the scaling I do it this way when I create the obj:<pre class="CodeBlock">

	-- the obj
	self.obj = loadObj(xobjpath, xobjname)
	local minx, miny, minz = self.obj.min[1], self.obj.min[2], self.obj.min[3]
	local maxx, maxy, maxz = self.obj.max[1], self.obj.max[2], self.obj.max[3]
	local width, height, length = maxx - minx, maxy - miny, maxz - minz
	local matrix = self.obj:getMatrix()
	matrix:setPosition(params.x,params.y,params.z)
	matrix:setRotationX(0)
	matrix:setRotationY(0)
	matrix:setRotationZ(0)
	matrix:setScale(3,3,3) -- HERE IT IS
	self.obj:setMatrix(matrix)
	-- the obj body
	self.body = xworld:createBody(self.obj:getMatrix())
	-- the obj shape
	self.shape = r3d.SphereShape.new(height / 2 * self.obj:getScaleY()) -- AND I APPLY THE SCALE HERE TOO
	-- the obj fixture
	self.body:createFixture(self.shape, nil, 16) -- shape, transform, mass

MoKaLux · February 2020

MoKaLux said:
PS: one little issue with lighting and android. I have this message:
FragmentShader:
0:19: L0003: Keyword 'sampler2DShadow' is reserved

stack traceback:
3dbase/3DLighting.lua:74: in function 'getShader'
3dbase/3DLighting.lua:109: in function 'setSpriteMode'
3dbase/3DShapes.lua:35: in function 'updateMode'
3d_factory/plane.lua:35: in function 'PLANE_3D'
main.lua:33: in main chunk

I found a solution, you can comment these lines (3dbase/3DLighting.lua:74)

--			v=Shader.new(
--				ccode..D3._V_Shader,
--				ccode..D3._F_Shader,
--				Shader.FLAG_FROM_CODE,
--				LightingShaderConstants,LightingShaderAttrs)
--			v:setConstant("lightPos",Shader.CFLOAT4,1,Lighting.light[1],Lighting.light[2],Lighting.light[3],1)
--			v:setConstant("ambient",Shader.CFLOAT,1,Lighting.light[4])
--			v:setConstant("cameraPos",Shader.CFLOAT4,1,Lighting.camera[1],Lighting.camera[2],Lighting.camera[3],1)
--			Lighting._shaders[lcode]=v

and that works great on android!
Or you could check if it runs on android first with an if else statement.

			if application:getDeviceInfo() == "Android" then
			else
				v=Shader.new(
					ccode..D3._V_Shader,
					ccode..D3._F_Shader,
					Shader.FLAG_FROM_CODE,
					LightingShaderConstants,LightingShaderAttrs)
				v:setConstant("lightPos",Shader.CFLOAT4,1,Lighting.light[1],Lighting.light[2],Lighting.light[3],1)
				v:setConstant("ambient",Shader.CFLOAT,1,Lighting.light[4])
				v:setConstant("cameraPos",Shader.CFLOAT4,1,Lighting.camera[1],Lighting.camera[2],Lighting.camera[3],1)
				Lighting._shaders[lcode]=v
			end

I don't know if it can be fixed but we could add the if android statement in github so it works out of the box!?
Tested on html5 export and that works fine, no lighting errors, so that's only for android (maybe ios too?)
PEACE.

hgy29 · February 2020

@MoKaLux, it seems like a device specific issue, can you tell me what Gideros writes about OpenGL support when you run your poject ? There are afew 'print' lines at the top of 3DLighting to give opengl version and what extensions are supported

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