mojo3d: attempted box physics not working!

[DruggedBunnyParticipant]

I can’t tell why this isn’t working: it builds static and dynamic bodies (CreateStaticBox/CreateDynamicBox) from a model passed to it, and everything renders OK, but my dynamic box body falls through the static ground body!

The method I use (using Model.Mesh.Bounds for New BoxCollider’s Boxf) works if I modify shapes.monkey2 to use ths method, so I don’t think that’s the problem, and hard-coding the sizes didn’t fix it (see commented-out returns in above functions)…

Monkey

#Import "<std>" #Import "<mojo3d>" #Import "<mojo3d-physics>" Using std.. Using mojo.. Using mojo3d.. ' ---------------------------------------- ' Application name... ' ---------------------------------------- Global AppName:String = "Physics test" ' ---------------------------------------- Function CreateStaticBox:StaticBody (model:Model) ' Build static body from model's mesh bounds (Boxf) and model... ' Works in shapes.monkey2 with line 74 modified as per: ' meshes[0]=Mesh.CreateBox( New Boxf( -1,-5,-1,1,5,1 ),1,1,1 ) ' colliders[0]=New BoxCollider(meshes[0].Bounds)'( New Boxf( -1,-5,-1,1,5,1 ) ) Return New StaticBody (New BoxCollider (model.Mesh.Bounds), model) ' Manual Boxf size doesn't do it... ' Return New StaticBody (New BoxCollider (New Boxf (-50, -0.5, -50, 50, 0.5, 50)), model) End Function CreateDynamicBox:DynamicBody (model:Model) ' Build dynamic body from model's mesh bounds (Boxf) and model... Return New DynamicBody (New BoxCollider (model.Mesh.Bounds), model) ' Return New DynamicBody (New BoxCollider (New Boxf (-0.5, -0.5, -0.5, 0.5, 0.5, 0.5)), model) End ' 1 x 1 x 1 box... gets resized after creation in demo below... Function CreateEasyBox:Model (color:Color = Color.Aluminum) Return New Model (Mesh.CreateBox (New Boxf (-0.5, -0.5, -0.5, 0.5, 0.5, 0.5)), New PbrMaterial (color)) End Class Game Extends Window ' Basic 3D scene requirements... Field scene:Scene Field camera:Camera Field light:Light Field ground:StaticBody Field box:DynamicBody Field phys_go:Bool Method New (title:String, width:Int, height:Int, flags:WindowFlags) Super.New (title, width, height, flags) scene = Scene.GetCurrent () camera = New Camera camera.Move (0, 5, -15) light = New Light light.Move (-50, 50, 0) ' Create mesh/entity... Local ground_model:Model = CreateEasyBox (Color.Green) ground_model.SetScale (100, 1, 100) ground_model.Move (0, -0.5, 0) ' Build static physics body from mesh/entity... ground = CreateStaticBox (ground_model) ' Create mesh/entity... Local box_model:Model = CreateEasyBox (Color.Red) box_model.SetScale (1, 1, 1) box_model.Move (0, 10, 0) box_model.Rotate (1, 2, 4) ' Build static physics body from mesh/entity... box = CreateDynamicBox (box_model) ' Light ground... light.PointAt (ground_model) ' Look at box... camera.PointAt (box_model) End Method ProcessInput:Void () If Keyboard.KeyHit (Key.Space) Then phys_go = True If Keyboard.KeyHit (Key.Escape) Then App.Terminate () If Keyboard.KeyDown (Key.A) camera.Move (0.0, 0.0, 0.5) End If Keyboard.KeyDown (Key.Z) camera.Move (0.0, 0.0, -0.5) End If Keyboard.KeyDown (Key.Left) camera.Rotate (0.0, 1.0, 0.0) End If Keyboard.KeyDown (Key.Right) camera.Rotate (0.0, -1.0, 0.0) End If Keyboard.KeyDown (Key.Up) camera.Rotate (1.0, 0.0, 0.0, True) End If Keyboard.KeyDown (Key.Down) camera.Rotate (-1.0, 0.0, 0.0, True) End End Method OnRender (canvas:Canvas) Override RequestRender () If phys_go World.GetDefault ().Update () Endif ProcessInput () scene.Render (canvas, camera) If Not phys_go canvas.DrawText ("Hit SPACE to start physics...", 20, 20) Endif End End Function Main () ' Windowed mode... Local width:Int = 640 Local height:Int = 480 Local flags:WindowFlags = WindowFlags.Center New AppInstance New Game (AppName, width, height, flags) App.Run () End

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#Import "<std>" #Import "<mojo3d>" #Import "<mojo3d-physics>" Using std.. Using mojo.. Using mojo3d.. ' ---------------------------------------- ' Application name... ' ---------------------------------------- Global AppName:String = "Physics test" ' ----------------------------------------   Function CreateStaticBox:StaticBody (model:Model)   ' Build static body from model's mesh bounds (Boxf) and model... ' Works in shapes.monkey2 with line 74 modified as per: ' meshes[0]=Mesh.CreateBox( New Boxf( -1,-5,-1,1,5,1 ),1,1,1 ) ' colliders[0]=New BoxCollider(meshes[0].Bounds)'(  New Boxf( -1,-5,-1,1,5,1 ) ) Return New StaticBody (New BoxCollider (model.Mesh.Bounds), model) ' Manual Boxf size doesn't do it... ' Return New StaticBody (New BoxCollider (New Boxf (-50, -0.5, -50, 50, 0.5, 50)), model) End   Function CreateDynamicBox:DynamicBody (model:Model)   ' Build dynamic body from model's mesh bounds (Boxf) and model... Return New DynamicBody (New BoxCollider (model.Mesh.Bounds), model) ' Return New DynamicBody (New BoxCollider (New Boxf (-0.5, -0.5, -0.5, 0.5, 0.5, 0.5)), model) End   ' 1 x 1 x 1 box... gets resized after creation in demo below...   Function CreateEasyBox:Model (color:Color = Color.Aluminum) Return New Model (Mesh.CreateBox (New Boxf (-0.5, -0.5, -0.5, 0.5, 0.5, 0.5)), New PbrMaterial (color)) End   Class Game Extends Window ' Basic 3D scene requirements... Field scene:Scene Field camera:Camera Field light:Light Field ground:StaticBody Field box:DynamicBody Field phys_go:Bool Method New (title:String, width:Int, height:Int, flags:WindowFlags) Super.New (title, width, height, flags) scene = Scene.GetCurrent () camera = New Camera camera.Move (0, 5, -15) light = New Light light.Move (-50, 50, 0) ' Create mesh/entity... Local ground_model:Model = CreateEasyBox (Color.Green)   ground_model.SetScale (100, 1, 100) ground_model.Move (0, -0.5, 0)   ' Build static physics body from mesh/entity... ground = CreateStaticBox (ground_model) ' Create mesh/entity... Local box_model:Model = CreateEasyBox (Color.Red)   box_model.SetScale (1, 1, 1) box_model.Move (0, 10, 0) box_model.Rotate (1, 2, 4)   ' Build static physics body from mesh/entity... box = CreateDynamicBox (box_model)   ' Light ground... light.PointAt (ground_model)   ' Look at box... camera.PointAt (box_model) End Method ProcessInput:Void () If Keyboard.KeyHit (Key.Space) Then phys_go = True If Keyboard.KeyHit (Key.Escape) Then App.Terminate () If Keyboard.KeyDown (Key.A) camera.Move (0.0, 0.0, 0.5) End If Keyboard.KeyDown (Key.Z) camera.Move (0.0, 0.0, -0.5) End If Keyboard.KeyDown (Key.Left) camera.Rotate (0.0, 1.0, 0.0) End If Keyboard.KeyDown (Key.Right) camera.Rotate (0.0, -1.0, 0.0) End If Keyboard.KeyDown (Key.Up) camera.Rotate (1.0, 0.0, 0.0, True) End If Keyboard.KeyDown (Key.Down) camera.Rotate (-1.0, 0.0, 0.0, True) End End Method OnRender (canvas:Canvas) Override RequestRender ()   If phys_go World.GetDefault ().Update () Endif ProcessInput () scene.Render (canvas, camera) If Not phys_go canvas.DrawText ("Hit SPACE to start physics...", 20, 20) Endif End End Function Main () ' Windowed mode... Local width:Int = 640 Local height:Int = 480 Local flags:WindowFlags = WindowFlags.Center New AppInstance New Game (AppName, width, height, flags) App.Run () End

Help!

[Mark SiblyKeymaster]

I think the problem here is that SetScale doesn’t currently affect the physics, only the rendering, so the ground box looks big but is still only actually a unit cube as far as the phyics is concerned.

I’ll have a think about how best to deal with this but for now thje BoxCollider size will need to be it’s ‘actual’ size.

[DruggedBunnyParticipant]

Hi Mark, I thought that, but I’m not actually convinced!

[IGNORE: See last post!]

See my second paragraph — it works when I use that same method in shapes.monkey2, I think because I:

1. create my box,
2. resize it,
3. pass that resized box (with, presumably, its resized .Bounds Boxf) to the collider setup.

So, collider setup should be using the .Bounds of the resized box model at that point, not scaling after creating the collider. Try this (modded shapes.monkey2):

[EDIT: See stripped-down version below.]

Also, using hard-coded values didn’t work — see the commented-out return values in CreateStatc/DynamicBox in first example.

[DruggedBunnyParticipant]

[IGNORE: See last post! But see comment about tweaking ANGLE const in this demo!]

Here’s a stripped-down version of shapes.monkey2 showing mesh.bounds being used sucessfully for collider:

Monkey

Namespace myapp #Import "<std>" #Import "<mojo>" #Import "<mojo3d>" #Import "<mojo3d-physics>" #Import "assets/" Using std.. Using mojo.. Using mojo3d.. Const ANGLE:Float = 40 ' 10-20 for weirdness! Class MyWindow Extends Window Field _scene:Scene Field _camera:Camera Field _light:Light Field _ground:Model Method New( title:String="Simple mojo app",width:Int=640,height:Int=480,flags:WindowFlags=WindowFlags.Resizable ) Super.New( title,width,height,flags ) _scene=Scene.GetCurrent() 'create camera ' _camera=New Camera _camera.Move( 0,10,-10 ) 'create light ' _light=New Light _light.Move (-10, 10, 10) _light.RotateX( 90 ) 'aim directional light 'down'. 'create ground ' Local groundBox:=New Boxf( -60,-1,-60,60,0,60 ) _ground=Model.CreateBox( groundBox,16,16,16,New PbrMaterial( Color.Green ) ) Local gcollider:Collider=New BoxCollider( groundBox ) Local gbody:=New StaticBody( gcollider,_ground ) 'create some meshes/colliders Local mesh:=New Mesh Local collider:=New Collider mesh=Mesh.CreateBox( New Boxf( -1,-5,-1,1,5,1 ),1,1,1 ) collider=New BoxCollider(mesh.Bounds) ' USING MESH.BOUNDS ************ Local material:= New PbrMaterial (New Color (255, 0, 255)) Local model:=New Model( mesh,material ) model.Move( 0,10,0 ) model.Rotate (0, 0, ANGLE) Local body:=New DynamicBody( collider,model ) _light.PointAt (_ground) _camera.PointAt (_ground) End Method OnRender( canvas:Canvas ) Override If Keyboard.KeyHit (Key.Escape) Then App.Terminate () If Keyboard.KeyDown (Key.Up) Then _camera.Rotate (1.0, 0.0, 0.0, True) If Keyboard.KeyDown (Key.Down) Then _camera.Rotate (-1.0, 0.0, 0.0, True) RequestRender() World.GetDefault().Update() _scene.Render( canvas,_camera ) End End Function Main() New AppInstance New MyWindow App.Run() End

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Namespace myapp #Import "<std>" #Import "<mojo>" #Import "<mojo3d>" #Import "<mojo3d-physics>" #Import "assets/" Using std.. Using mojo.. Using mojo3d..   Const ANGLE:Float = 40 ' 10-20 for weirdness! Class MyWindow Extends Window Field _scene:Scene Field _camera:Camera Field _light:Light Field _ground:Model Method New( title:String="Simple mojo app",width:Int=640,height:Int=480,flags:WindowFlags=WindowFlags.Resizable ) Super.New( title,width,height,flags ) _scene=Scene.GetCurrent() 'create camera ' _camera=New Camera _camera.Move( 0,10,-10 ) 'create light ' _light=New Light _light.Move (-10, 10, 10) _light.RotateX( 90 ) 'aim directional light 'down'. 'create ground ' Local groundBox:=New Boxf( -60,-1,-60,60,0,60 ) _ground=Model.CreateBox( groundBox,16,16,16,New PbrMaterial( Color.Green ) ) Local gcollider:Collider=New BoxCollider( groundBox ) Local gbody:=New StaticBody( gcollider,_ground ) 'create some meshes/colliders Local mesh:=New Mesh Local collider:=New Collider mesh=Mesh.CreateBox( New Boxf( -1,-5,-1,1,5,1 ),1,1,1 ) collider=New BoxCollider(mesh.Bounds) ' USING MESH.BOUNDS ************   Local material:= New PbrMaterial (New Color (255, 0, 255)) Local model:=New Model( mesh,material ) model.Move( 0,10,0 ) model.Rotate (0, 0, ANGLE) Local body:=New DynamicBody( collider,model )   _light.PointAt (_ground) _camera.PointAt (_ground)   End Method OnRender( canvas:Canvas ) Override   If Keyboard.KeyHit (Key.Escape) Then App.Terminate () If Keyboard.KeyDown (Key.Up) Then _camera.Rotate (1.0, 0.0, 0.0, True) If Keyboard.KeyDown (Key.Down) Then _camera.Rotate (-1.0, 0.0, 0.0, True) RequestRender() World.GetDefault().Update() _scene.Render( canvas,_camera ) End End Function Main() New AppInstance New MyWindow App.Run() End

This demo also highlights some weirdness I noticed in the original sometimes — change const ANGLE at the top to 10-20 and watch it settle at a strange angle!

[DruggedBunnyParticipant]

Eek, maybe ignore all of this — my tweaked demo doesn’t use SetScale! Adding

Monkey

_ground.SetScale (100, 1, 100)

1	_ground.SetScale (100, 1, 100)

causes it to fall through. I assumed the bounds would be updated, then the collider built using that updated bounds (ie. thought you were referring to resizing not working after the collider is built), but apparently bounds stays fixed…

[Mark SiblyKeymaster]

SetScale is an algorithmic entity scale factor used by the renderer. It does not affect actual mesh vertex positions (as stored in memory) therefore does not affect mesh bounds either. If there was an Entity.Bounds, it would probably affect that though!

Mesh.TransformVertices and Mesh.FitVertices on the other hand *do* affect mesh vertex positions, so do affect  mesh bounds.

In general, my advice for now would be to avoid SetScale if you’re using physics and build all your meshes at the right size in the first place. You can also use Mesh.FitVertices if you want to physically scale a mesh to a certain size etc.

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