I use this which seems to be pretty accurate.
Displays quads at 2D screen coordinates using a pivot (pivot2d) which the mesh is attached to.
Credit to skidracer (pixies routine):
; Quads at 2D pixel locations
Const sw=640,sh=480
Const qwidth=180,qheight=120 ; quads width/height
Graphics3D sw,sh,0,2
SetBuffer BackBuffer()
HidePointer
Type quad
Field container ; container holding quad (surface)
Field vert ; quads first vertex in container
Field x,y ; quads x/y screen pos (in 2d pixels)
Field w,h ; quads width and height (in 2d pixels)
Field rotdir#
End Type
; init 3d display (camera + quads pivot)
spritecamera=CreateCamera()
pivot2d=CreatePivot(spritecamera)
aspect#=Float(GraphicsHeight())/Float(GraphicsWidth())
scale#=2.0/GraphicsWidth()
PositionEntity pivot2d,-1,aspect,1.0001
ScaleEntity pivot2d,scale,scale,scale
; create a quad container (surface to hold quads)
quadsurf=CreateQuadContainer(pivot2d)
; add quad to container pos(x,y) size(w,h) color(r,g,b)
quad1.quad=NewQuad(quadsurf , 0,0 , qwidth,qheight , 60,200,70)
MoveMouse 320,240
; MAIN LOOP
Repeat
mx=MouseX() : my=MouseY()
PositionQuad quad1,mx,my,0
RenderWorld
; just to confirm quad is displayed correctly
; let's draw a standard 2D rect (same pos/width)
Color 170,10,60
Rect mx,my,qwidth,qheight,0
; cursor
Color 200,200,200
Line mx,my+8,mx,my-8
Line mx+8,my,mx-8,my
Flip
Until KeyHit(1)
End
; create a container (surface) for holding quads
Function CreateQuadContainer(pivot)
Local quadmesh=CreateMesh(pivot)
Local surf=CreateSurface(quadmesh)
EntityFX quadmesh,1+2
ScaleEntity quadmesh,1,-1,1
PositionEntity quadmesh,-0.5,0.5,0
Return surf
End Function
; adds a new quad to an existing container
Function NewQuad.quad(surf,x,y,w,h,r=255,g=255,b=255)
q.quad=New quad
q\container=surf
q\x=x : q\y=y : q\w=w : q\h=h
q\vert=AddVertex(surf,x,y,0 ,0,0)
AddVertex surf,x+w,y,0 ,1,0
AddVertex surf,x,y+h,0 ,0,1
AddVertex surf,x+w,y+h,0 ,1,1
AddTriangle surf,q\vert+0,q\vert+1,q\vert+2
AddTriangle surf,q\vert+3,q\vert+2,q\vert+1
For o=0 To 3
VertexColor surf,q\vert+o,r,g,b
Next
Repeat
q\rotdir=Rnd(-2.5,2.5)+0.1
Until q\rotdir<>0
Return q
End Function
; position quad at 2d pixel coordinates
Function PositionQuad(q.quad,x,y,z#=1.0001)
Local s=q\container , v=q\vert
dx#=x-VertexX(s,v) : dy#=y-VertexY(s,v) : dz#=z-VertexZ(s,v)
For o=0 To 3
VertexCoords s,v+o,VertexX(s,v+o)+dx,VertexY(s,v+o)+dy,VertexZ(s,v+o)+dz
Next
q\x=VertexX(s,v) : q\y=VertexY(s,v)
End Function
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