Can a LinePick be null yet return coords?

CameraPick is handy as you can pick empty space with it - ie:

If MouseHit(1) And entity=0
cube=CreateCube()
PositionEntity cube,world_pos_x, 1,world_pos_z
EndIf

You can calculate the 3D world coordiates via use of CameraProject, ProjectedX() and ProjectedY().

However, this is great if you don't move the overhead camera - as soon as you do you lose position accuracy. You can zoom in and out and preserve accuaracy - but as soon as you scroll the camera, bang goes the accuracy.

CameraPick is great for picking an entity as it works with the perspective of the camera - so it is great at what it does.

So, LinePick is surely the saviour as it couldn't care less about the perspective when picking a world position. However, I don't want to pick anything - I want to pick a position in 3D space.

How can I achieve this with LinePick? CameraPick can pick null (I'm not sure if it was designed to pick null, but you can force it).

Eh? What's the point of picking 'a position in 3D space' if you already know the coords of that point.

I don't really understand what you're trying to do, TBH.

CameraPick is designed to be used with the mouse in mind. Or for any other reason you'd need to choose the pick from a 2d location on the screen. Line pick is really for blind picking. When you want to find out if something is actually there.

For example, a platformer. You'd do a pick below the character to find out if he has something below his feet, but not yet touched the ground. Many uses :o)

oops - wrong thread

The coords are skewed by perspective - ie you can move a mouse pointer overhead and place a cube - but it doesn't appear at the point of the mouse pointer:

 Graphics3D 800,600,16,2

Global entity
Global ent
Global world_pos_x#
Global world_pos_z#


ground=CreatePlane()
EntityColor ground,0,200,0


Global cube1=CreateCube()
ScaleEntity cube1,.5,.5,.5
PositionEntity cube1,-2,1,-2
EntityPickMode cube1,2

Global cube2=CreateCube()
ScaleEntity cube2,.5,.5,.5
PositionEntity cube2,2,1,-2
EntityPickMode cube2,2

Global cube3=CreateCube()
ScaleEntity cube3,.5,.5,.5
PositionEntity cube3,0,1,0
EntityPickMode cube3,2

Global cube4=CreateCube()
ScaleEntity cube4,.5,.5,.5
PositionEntity cube4,-2,1,2
EntityPickMode cube4,2

Global cube5=CreateCube()
ScaleEntity cube5,.5,.5,.5
PositionEntity cube5,2,1,2
EntityPickMode cube5,2


light=CreateLight()
PositionEntity light,100,100,-100
PointEntity light,cube1


Global cam=CreateCamera()
CameraViewport cam,10,90,500,500
CameraProjMode cam,1
CameraZoom cam,2.5
CameraRange cam,.01,1000

PositionEntity cam,0,10,0 
RotateEntity cam,90,0,0


Repeat

	Cls
	
	If MouseHit(1) And entity<>0 ; something had to have been picked

	End If
	
	If MouseDown(1) And entity=0 ; basically picking empty space
		cube=CreateSphere()
		ScaleEntity cube,.25,.25,.25
		PositionEntity cube,world_pos_x,1,world_pos_z
	EndIf 
		
	If entity
		EntityColor entity,255,0,0
	EndIf	
		

; overhead camera
If KeyDown(16) Then TurnEntity cam,0,0,1 ; rotate cam left
If KeyDown(18) Then TurnEntity cam,0,0,-1 ; rotate cam right
If KeyDown(12) Then MoveEntity cam,0,0,.1 ; zoom in
If KeyDown(13) Then MoveEntity cam,0,0,-.1 ; zoom out
If KeyDown(17) Then MoveEntity cam,0,.1,0 ; forward
If KeyDown(31) Then MoveEntity cam,0,-.1,0 ; back
If KeyDown(30) MoveEntity cam,-.1,0,0 ; strafe left
If KeyDown(32) MoveEntity cam,.1,0,0 ; strafe right


UpdateWorld()

RenderWorld()

Project2DTo3DOrtho( MouseX() , MouseY() )

Text 10,10,"Entity Highlighted: "+entity
	
Flip

Until KeyDown(1)=1
ClearWorld()
End



Function Project2DTo3DOrtho(mx,my)

	;Check the mouse is in the 3d window 
	If mx>=10 And mx<=509 And my=>90 And my<=589
	
		;Get mouse position in relation to the 3d viewport
		vx=mx-10; 100
		vy=my-90; 100
		
		; draw the rectangle here as it relies on the mx and my coords
		Rect mx,my-3,1,7	
		Rect mx-3,my,7,1	
		
		;Get the 2d position of the origin
		CameraProject cam,0,0,0
		xx#=ProjectedX()
		yy#=ProjectedY()

				
		;Get the 2d position of 1,1,1
		CameraProject cam,1,1,1
		xx2#=ProjectedX()
		yy2#=ProjectedY()


		;Take one from the other to find the distance
		dx#=xx2-xx
		dy#=yy2-yy

		;World position is :
		world_pos_x#=(vx-xx)/dx
		world_pos_z#=(vy-yy)/dy
		
			
		ent=CameraPick(cam,vx,vy)
		If ent<>entity
		If entity Then EntityColor entity,255,255,255
			entity=ent
		EndIf
	
		Text 10,50,"Cursor is at World position X : "+world_pos_x
		Text 10,60,"                            Z : "+world_pos_z

	EndIf
End Function 

Click left mouse to insert a sphere.

This is fine when zooming in and out. It goes plop if you move the camera.

So I thought a sneaky LinePick would be great.

Changing this line from ...

CameraProject cam, 0,0,0

to

CameraProject cam,0,1,0

Fixes the problem. Your scaling is borked otherwise as you are positioning the sphere at y=1.

This kind of thing is what camerapick is designed to do - why aren't you using it?

Stevie

Ooooh.

I was pretty close though.

I have been out all day and was faffing about with this thing this morning - changing between Modes 1 and 2 - trying different things.

The reason why in this thread (and the other one) I seem caught in between two systems is because I am. I'm sort of trying to blend two methods into one.

The bog-standard CameraPick is ideal for selecting an entity - I like it - nothing wrong with it for my needs.

However, I also need to pick thin air - I'm not checking for a collision or checking for a mesh/surface/entity.

I'll admit, it is all somewhat advanced - considering, I am not showing exactly what I am doing - I've sort of dumbed it down a bit to make it more clear.

I have continue to reintegrate what I want to do into how Blitz3D will allow me to do what I want.

Still, I feel I will reach the promised land.

Pick thin air?

Why do you need to pick thin air? Why not just have a pickable plane?

ThinAir = createplane()
Entitypickmode ThinAir, 2
entityalpha ThinAir, 0

If pickedentity = ThinAir
etc......

Can you explain what your doing?

Yeh, I said it was advanced.

I already achieved what I want with banks of surfaces that do the job quite nicely. However, I pulled them out because it worked and I knew I wanted to do it differently.

The fact that I can already pick thin air is what drives me forward - dominance dripping all over the place - it's just great - picking thin air - awesome - it's total picking dominance - it is some kind of picking super-string - an event horizon of such Largeness that only the dominant will complete the journey.

Plus, this is just the first part of what I am doing - this is a building block.

OK, I think I'm done here...

Agreed, we'll leave you to do it the hard way.