; TriangleVertex Example
; ----------------------

; TriangleVertex is the reverse of AddTriangle: it reads back which
; vertex index forms a given corner (0, 1 or 2) of a triangle.
; Space cycles through the corners; a marker highlights the vertex
; that TriangleVertex reports.

Graphics3D 640,480
SetBuffer BackBuffer()

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

mesh=CreateMesh()
surf=CreateSurface(mesh)

; One triangle with a distinct colour per corner
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
tri=AddTriangle(surf,v0,v1,v2)

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

; A marker sphere highlights the reported vertex
marker=CreateSphere()
ScaleEntity marker,0.12,0.12,0.12
EntityColor marker,255,0,255
EntityFX marker,1

corner=0

While Not KeyDown(1)

    ; Space cycles corner 0 -> 1 -> 2
    If KeyHit(57) Then corner=(corner+1) Mod 3

    ; The documented command: which vertex forms this corner?
    v=TriangleVertex(surf,tri,corner)

    ; Park the marker on that vertex using its stored position
    PositionEntity marker,VertexX(surf,v),VertexY(surf,v),VertexZ(surf,v)

    ; Arrow keys move the camera
    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: next corner   Arrow keys: move camera   Esc: exit"
    Text 0,20,"TriangleVertex(surf,"+tri+","+corner+") = vertex "+v

    Flip

Wend

End