Move texture with mouse

This code has been declared by its author to be Public Domain code.

PickedUV / Move texture with mouse by Noobody

2011

Since B3D doesn't have functions for the UV coordinates at the intersection point of CameraPick/LinePick/etc. I wrote a function to do this. It works by first making a local 2D orthonormal coordinate system on the triangle and then converting the picked location to barycentric coordinates, allowing interpolation of UV coordinates within the triangle.

The sample code shows an application of this function by allowing the user to move a texture on a mesh using the mouse. The texel clicked by the user always stays at the mouse position, while the rest of the texture is moved around on the mesh (useful for editors, maybe?)

Graphics3D 800, 600, 0, 2
SetBuffer BackBuffer()

Global PickedU#, PickedV#


Local Cam = CreateCamera()
Local Texture = CreateFunkyTexture()
Local Mesh = CreateCone(64)
EntityPickMode Mesh, 2
EntityTexture Mesh, Texture

MoveEntity Cam, 0.0, 0.0, -3.0

Local Timer = CreateTimer(60)

Local OldPickedU#, OldPickedV#, OldPickedSurface

While Not KeyHit(1)
	TurnEntity Mesh, KeyDown(200) - KeyDown(208), KeyDown(205) - KeyDown(203), 0.0, True
	
	If MouseDown(1) Then
		CameraPick(Cam, MouseX(), MouseY())
		
		If PickedEntity() <> 0 And PickedSurface() <> 0 Then
			CalculatePickedUV()
			
			If PickedSurface() = OldPickedSurface Then
				DU# = PickedU# - OldPickedU#
				DV# = PickedV# - OldPickedV#
				
				Local Surface = PickedSurface()
				For Vertex = 0 To CountVertices(Surface) - 1
					Local U# = VertexU(Surface, Vertex)
					Local V# = VertexV(Surface, Vertex)
					
					VertexTexCoords Surface, Vertex, U# - DU#, V# - DV#
				Next
				
				PickedU# = PickedU# - DU#
				PickedV# = PickedV# - DV#
			Else
				OldPickedSurface = PickedSurface()
			EndIf
			
			OldPickedU# = PickedU#
			OldPickedV# = PickedV#
		Else
			OldPickedSurface = 0
		EndIf
	Else
		OldPickedSurface = 0
	EndIf
	
	RenderWorld
	
	Text 0, 0, "Click and drag the texture!"
	Text 0, 15, "Use arrow keys to turn the mesh"
	
	Flip 0
	WaitTimer Timer
Wend
End

Function CreateFunkyTexture()
	Local Texture = CreateTexture(256, 256, 1)
	
	SetBuffer TextureBuffer(Texture)
	LockBuffer()
	
	For X = 0 To 255
		For Y = 0 To 255
			WritePixelFast X, Y, (X*$010001) Xor (Y*$010101)
		Next
	Next
	
	UnlockBuffer()
	SetBuffer BackBuffer()
	
	Return Texture
End Function

Function CalculatePickedUV()
	Local Surface = PickedSurface()
	If Surface Then
		Local Mesh = PickedEntity()
		
		TFormPoint PickedX(), PickedY(), PickedZ(), 0, Mesh
		
		Local Triangle = PickedTriangle()
		
		Local V1 = TriangleVertex(Surface, Triangle, 0)
		Local V2 = TriangleVertex(Surface, Triangle, 1)
		Local V3 = TriangleVertex(Surface, Triangle, 2)
		
		Local DX1# = VertexX(Surface, V2) - VertexX(Surface, V1)
		Local DY1# = VertexY(Surface, V2) - VertexY(Surface, V1)
		Local DZ1# = VertexZ(Surface, V2) - VertexZ(Surface, V1)
		Local DX2# = VertexX(Surface, V3) - VertexX(Surface, V1)
		Local DY2# = VertexY(Surface, V3) - VertexY(Surface, V1)
		Local DZ2# = VertexZ(Surface, V3) - VertexZ(Surface, V1)
		
		Local NX# = DY1#*DZ2# - DY2#*DZ1#
		Local NY# = DX2#*DZ1# - DX1#*DZ2#
		Local NZ# = DX1#*DY2# - DY1#*DX2#
		Local UX# = NY #*DZ2# - DY2#*NZ #
		Local UY# = DX2#*NZ # - NX #*DZ2#
		Local UZ# = NX #*DY2# - NY #*DX2#
		
		Local InvLength1# = 1.0/Sqr(UX#*UX# + UY#*UY# + UZ#*UZ#)
		Local Length2# = Sqr(DX2#*DX2# + DY2#*DY2# + DZ2#*DZ2#)
		Local InvLength2# = 1.0/Length2#
		
		UX# = UX#*InvLength1#
		UY# = UY#*InvLength1#
		UZ# = UZ#*InvLength1#
		DX2# = DX2#*InvLength2#
		DY2# = DY2#*InvLength2#
		DZ2# = DZ2#*InvLength2#
		
		Local T1# = 0.0
		Local S1# = 0.0
		Local T2# = DX1#*UX # + DY1#*UY # + DZ1#*UZ #
		Local S2# = DX1#*DX2# + DY1#*DY2# + DZ1#*DZ2#
		Local T3# = 0.0
		Local S3# = Length2#
		Local T4# = (TFormedX() - VertexX(Surface, V1))*UX # + (TFormedY() - VertexY(Surface, V1))*UY # + (TFormedZ() - VertexZ(Surface, V1))*UZ #
		Local S4# = (TFormedX() - VertexX(Surface, V1))*DX2# + (TFormedY() - VertexY(Surface, V1))*DY2# + (TFormedZ() - VertexZ(Surface, V1))*DZ2#

		
		Local Denominator# = 1.0/((S2# - S3#)*(T1# - T3#) + (T3# - T2#)*(S1# - S3#))
		Local Lambda1# = ((S2# - S3#)*(T4# - T3#) + (T3# - T2#)*(S4# - S3#))*Denominator#
		Local Lambda2# = ((S3# - S1#)*(T4# - T3#) + (T1# - T3#)*(S4# - S3#))*Denominator#
		Local Lambda3# = 1.0 - Lambda1# - Lambda2#
		
		PickedU# = VertexU(Surface, V1)*Lambda1# + VertexU(Surface, V2)*Lambda2# + VertexU(Surface, V3)*Lambda3#
		PickedV# = VertexV(Surface, V1)*Lambda1# + VertexV(Surface, V2)*Lambda2# + VertexV(Surface, V3)*Lambda3#
	EndIf
End Function

Comments

Kryzon

2011

Thanks for sharing, it looks great!

Further references:

Fredborg also wrote PickedU\V\W() style functions: http://blitzbasic.com/codearcs/codearcs.php?code=515

You can also find something similar inside Blitz3D\samples\birdie\TexPaint\ (if I got the author's name right.)

Noobody

2011

Oh, I wasn't aware of either of them, thanks for mentioning :)

The other PickedU/V/W functions from the codearchives take a bit more code, but seem to work great! Replacing the PickedUV in this example with the code you linked gives the exact same behaviour.

The one from the birdie sample does the job as well, although it uses CameraProject, which is something I wanted to avoid; values get very inaccurate when parts of the triangle are off-screen or behind the camera.

BlitzSupport

2011

Nice one!

Charrua

2011

thank's so much

Juan

void

2013

Much thanks

Mikorians

2014

Oooh yeah...!!!

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