; AddTriangle Example
; -------------------

; AddTriangle connects three existing vertices into a solid triangle.
; Triangles are ONE-SIDED: a triangle is only visible from the side
; where its vertices appear in clockwise order. Space rebuilds this
; triangle with the opposite winding so you can see the difference.

Graphics3D 640,480
SetBuffer BackBuffer()

camera=CreateCamera()
PositionEntity camera,0,0,-4

mesh=CreateMesh()
surf=CreateSurface(mesh)

; Show vertex colours without needing a light
EntityFX mesh,2

clockwise=1
rebuild=1

While Not KeyDown(1)

    ; Space flips the winding order and rebuilds the triangle
    If KeyHit(57) Then clockwise=1-clockwise : rebuild=1

    If rebuild Then
        rebuild=0
        ClearSurface surf
        v0=AddVertex(surf,-1.5,-1,0)
        v1=AddVertex(surf,0,1.5,0)
        v2=AddVertex(surf,1.5,-1,0)
        VertexColor surf,v0,255,80,80
        VertexColor surf,v1,80,255,80
        VertexColor surf,v2,80,160,255
        If clockwise Then
            ; Clockwise as seen by the camera - the triangle is visible
            AddTriangle surf,v0,v1,v2
        Else
            ; Anticlockwise - the triangle faces AWAY and disappears
            AddTriangle surf,v0,v2,v1
        EndIf
    EndIf

    ; Arrow keys move the camera (walk round the back to see the other side)
    If KeyDown(200) Then MoveEntity camera,0,0,0.1
    If KeyDown(208) Then MoveEntity camera,0,0,-0.1
    If KeyDown(203) Then TurnEntity camera,0,1,0
    If KeyDown(205) Then TurnEntity camera,0,-1,0

    RenderWorld

    Text 0,0,"Space: flip winding order   Arrow keys: move camera   Esc: exit"
    If clockwise Then
        Text 0,20,"AddTriangle surf,v0,v1,v2 - clockwise, facing the camera"
    Else
        Text 0,20,"AddTriangle surf,v0,v2,v1 - anticlockwise, facing away!"
    EndIf

    Flip

Wend

End