mojo3d: set child to have no parent?

[DruggedBunnyParticipant]

I’m trying to create a child entity at a parent entity’s position, then remove the parent/child relationship to leave the child at the same scene hierarchy level as the parent.

Setting child.Parent to Null, however, removes it from the scene, as per Property Parent:Entity() -> Setter().

Logic here is that in Blitz3D, SetParent (entity, 0) would make the world/scene the child’s new parent, freeing it from the parent’s local space yet leaving it in the scene, in global space.

This test shows that ‘parent’ has no parent, yet isn’t removed from the scene, and I basically want ‘child’ to end up in that same state after positioning, ie. it then has no parent, but remains in the scene with equal relationship to scene as ‘parent’…

Monkey

#Import "<std>" #Import "<mojo>" #Import "<mojo3d>" Using std.. Using mojo.. Using mojo3d.. Class Game Extends Window Field scene:Scene Field light:Light Field cam_piv:Model Field camera:Camera Field parent:Model Field child:Model Method New (title:String, width:Int, height:Int, flags:WindowFlags) Super.New (title, width, height, flags) ' Create window SeedRnd (Millisecs ()) ' Init random seed SwapInterval = 1 ' V-sync on scene = Scene.GetCurrent () cam_piv = New Model camera = New Camera (cam_piv) light = New Light parent = Model.CreateBox (New Boxf (-0.5, -0.5, -0.5, 0.5, 0.5, 0.5), 1, 1, 1, New PbrMaterial (Color.Red)) child = Model.CreateBox (New Boxf (-0.25, -0.25, -0.25, 0.25, 0.25, 0.25), 1, 1, 1, New PbrMaterial (Color.Blue), parent) parent.Move (5, 0, 5) ' Position parent away from 0, 0, 0 child.Move (0, -1, 0) ' Position child 1 unit beneath parent End Method OnRender (canvas:Canvas) Override If Keyboard.KeyHit (Key.Space) Then child.Parent = Null ' Removes child from scene! If Keyboard.KeyHit (Key.Escape) Then App.Terminate () RequestRender () scene.Render (canvas, camera) If parent.Parent canvas.DrawText ("Parent (red) has a parent", 0, 0) Else canvas.DrawText ("Parent (red) has NO parent", 0, 0) Endif If child.Parent canvas.DrawText ("Child (blue) has a parent", 0, 20) Else canvas.DrawText ("Child (blue) has NO parent. Child has GONE!", 0, 20) Endif canvas.DrawText ("Press SPACE to set child's parent to Null", 0, 60) End End Function Run3D (title:String, width:Int, height:Int, flags:WindowFlags = WindowFlags.Center) New AppInstance New Game (title, width, height, flags) App.Run () End Function Main () Run3D ("3D Scene", 960, 540, WindowFlags.Center) ' 1/4 HD! ' Run3D ("3D Scene", 1920, 1080, WindowFlags.Fullscreen) End

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#Import "<std>" #Import "<mojo>" #Import "<mojo3d>"   Using std.. Using mojo.. Using mojo3d..   Class Game Extends Window Field scene:Scene Field light:Light Field cam_piv:Model Field camera:Camera   Field parent:Model Field child:Model Method New (title:String, width:Int, height:Int, flags:WindowFlags)   Super.New (title, width, height, flags) ' Create window   SeedRnd (Millisecs ()) ' Init random seed SwapInterval = 1 ' V-sync on scene = Scene.GetCurrent () cam_piv = New Model camera = New Camera (cam_piv) light = New Light parent = Model.CreateBox (New Boxf (-0.5, -0.5, -0.5, 0.5, 0.5, 0.5), 1, 1, 1, New PbrMaterial (Color.Red)) child = Model.CreateBox (New Boxf (-0.25, -0.25, -0.25, 0.25, 0.25, 0.25), 1, 1, 1, New PbrMaterial (Color.Blue), parent) parent.Move (5, 0, 5) ' Position parent away from 0, 0, 0 child.Move (0, -1, 0) ' Position child 1 unit beneath parent   End Method OnRender (canvas:Canvas) Override   If Keyboard.KeyHit (Key.Space) Then child.Parent = Null ' Removes child from scene! If Keyboard.KeyHit (Key.Escape) Then App.Terminate () RequestRender () scene.Render (canvas, camera)   If parent.Parent canvas.DrawText ("Parent (red) has a parent", 0, 0) Else canvas.DrawText ("Parent (red) has NO parent", 0, 0) Endif   If child.Parent canvas.DrawText ("Child (blue) has a parent", 0, 20) Else canvas.DrawText ("Child (blue) has NO parent. Child has GONE!", 0, 20) Endif canvas.DrawText ("Press SPACE to set child's parent to Null", 0, 60)   End End Function Run3D (title:String, width:Int, height:Int, flags:WindowFlags = WindowFlags.Center) New AppInstance New Game (title, width, height, flags) App.Run () End   Function Main () Run3D ("3D Scene", 960, 540, WindowFlags.Center) ' 1/4 HD! ' Run3D ("3D Scene", 1920, 1080, WindowFlags.Fullscreen) End

[DruggedBunnyParticipant]

I guess I want to make it a member of Scene.RootEntities? Is it safe to just do Scene.RootEntities.Add (entity)? Feels like setting parent to Null should do that, though, like parent’s Null status, above.

EDIT: Nah, that’s not allowed, being private!

[Simon ArmstrongParticipant]

I got round this issue by creating a parentless entity (not a model) which I called hidden.

By parenting any models I didn’t want in the scene to this entity they became hidden and then could be used for templates and the like.

[DruggedBunnyParticipant]

Hmm, guess I could do that. Wondering if it’s intended, though, as it seems weird not to be able to place into same hierarchy level as default entities.

[DruggedBunnyParticipant]

That doesn’t do it for me — I create a nonentity:Entity and hit space to set as child’s parent, but it still just disappears:

Monkey

' Wall of boxes... #Import "<std>" #Import "<mojo>" #Import "<mojo3d>" Using std.. Using mojo.. Using mojo3d.. Class Game Extends Window Field scene:Scene Field light:Light Field cam_piv:Model Field camera:Camera Field nonentity:Entity Field parent:Model Field child:Model Method New (title:String, width:Int, height:Int, flags:WindowFlags) Super.New (title, width, height, flags) ' Create window SeedRnd (Millisecs ()) ' Init random seed SwapInterval = 1 ' V-sync on scene = Scene.GetCurrent () nonentity = New Entity cam_piv = New Model camera = New Camera (cam_piv) light = New Light parent = Model.CreateBox (New Boxf (-0.5, -0.5, -0.5, 0.5, 0.5, 0.5), 1, 1, 1, New PbrMaterial (Color.Red)) child = Model.CreateBox (New Boxf (-0.25, -0.25, -0.25, 0.25, 0.25, 0.25), 1, 1, 1, New PbrMaterial (Color.Blue), parent) parent.Move (5, 0, 5) ' Position parent away from 0, 0, 0 child.Move (0, -1, 0) ' Position child 1 unit beneath parent End Method OnRender (canvas:Canvas) Override If Keyboard.KeyHit (Key.Space) child.Parent = nonentity Endif If Keyboard.KeyHit (Key.Escape) Then App.Terminate () RequestRender () scene.Render (canvas, camera) If parent.Parent canvas.DrawText ("Parent (red) has a parent", 0, 0) Else canvas.DrawText ("Parent (red) has NO parent", 0, 0) Endif If child.Parent canvas.DrawText ("Child (blue) has a parent", 0, 20) Else canvas.DrawText ("Child (blue) has NO parent. Child has GONE!", 0, 20) Endif canvas.DrawText ("Press SPACE to set child's parent to Null", 0, 60) End End Function Run3D (title:String, width:Int, height:Int, flags:WindowFlags = WindowFlags.Center) New AppInstance New Game (title, width, height, flags) App.Run () End Function Main () Run3D ("3D Scene", 960, 540, WindowFlags.Center) ' 1/4 HD! ' Run3D ("3D Scene", 1920, 1080, WindowFlags.Fullscreen) End

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' Wall of boxes...   #Import "<std>" #Import "<mojo>" #Import "<mojo3d>"   Using std.. Using mojo.. Using mojo3d..   Class Game Extends Window Field scene:Scene Field light:Light Field cam_piv:Model Field camera:Camera   Field nonentity:Entity Field parent:Model Field child:Model Method New (title:String, width:Int, height:Int, flags:WindowFlags)   Super.New (title, width, height, flags) ' Create window   SeedRnd (Millisecs ()) ' Init random seed SwapInterval = 1 ' V-sync on scene = Scene.GetCurrent () nonentity = New Entity cam_piv = New Model camera = New Camera (cam_piv) light = New Light parent = Model.CreateBox (New Boxf (-0.5, -0.5, -0.5, 0.5, 0.5, 0.5), 1, 1, 1, New PbrMaterial (Color.Red)) child = Model.CreateBox (New Boxf (-0.25, -0.25, -0.25, 0.25, 0.25, 0.25), 1, 1, 1, New PbrMaterial (Color.Blue), parent) parent.Move (5, 0, 5) ' Position parent away from 0, 0, 0 child.Move (0, -1, 0) ' Position child 1 unit beneath parent   End Method OnRender (canvas:Canvas) Override   If Keyboard.KeyHit (Key.Space) child.Parent = nonentity Endif If Keyboard.KeyHit (Key.Escape) Then App.Terminate () RequestRender () scene.Render (canvas, camera)   If parent.Parent canvas.DrawText ("Parent (red) has a parent", 0, 0) Else canvas.DrawText ("Parent (red) has NO parent", 0, 0) Endif   If child.Parent canvas.DrawText ("Child (blue) has a parent", 0, 20) Else canvas.DrawText ("Child (blue) has NO parent. Child has GONE!", 0, 20) Endif canvas.DrawText ("Press SPACE to set child's parent to Null", 0, 60)   End End Function Run3D (title:String, width:Int, height:Int, flags:WindowFlags = WindowFlags.Center) New AppInstance New Game (title, width, height, flags) App.Run () End   Function Main () Run3D ("3D Scene", 960, 540, WindowFlags.Center) ' 1/4 HD! ' Run3D ("3D Scene", 1920, 1080, WindowFlags.Fullscreen) End

[DruggedBunnyParticipant]

Not actually trying to hide things here, by the way — I want child to pick up parent’s position/rotation in the world, then be freed from parent: as in create bullet at end of gun, then free from parent so I can fire independent of parent’s future movement.

In my case, ‘gun’ means 5 units in front of current camera position at current rotation!

[Mark SiblyKeymaster]

There are basically 2 problems here.

Base Entity class defaults to hidden so ‘nonentity’ (and all it’s children) are hidden. I will probably add a ‘Pivot’ style subclass shows itself, but in the meantime if you’re using an entity as a pivot you’ll need to manually set entity.Visible=True. It’s useful right now for entities to default to hidden for various reasons.

Also, mojo3d isn’t really thinking about what an entities matrix should be after changing it’s parent. I’ll probably change this so if you set an entities parent to null, it retains it’s world matrix and if you set it to non-null it retains its local matrix – make sense?

With this is mind, this works for me in v1.1.09:

Monkey

If Keyboard.KeyHit (Key.Space) Local matrix:=child.Matrix child.Parent=Null child.Matrix=matrix Endif

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If Keyboard.KeyHit (Key.Space) Local matrix:=child.Matrix child.Parent=Null child.Matrix=matrix Endif

This stuff should be fixed soon.

[DruggedBunnyParticipant]

In my last version, adding the nonentity.Visible = True suggestion doesn’t actually work (still disappears), though your last matrix code seems to do it.

But, yeah, I think what you’re saying there regarding keeping the world matrix is what I was after!

[Author]

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