Mesh Outlines

Method to create outlines on meshes. Edge Detection and Outline Function, Need speeding up to be useful

Author: Birdie

;Edge detection functions
;(c)David Bird 2001
;Birdie
Graphics3D 640,480,0,2
SetBuffer BackBuffer()

cam=CreateCamera()
PositionEntity cam,0,0,-10
CameraClsColor cam,255,255,255

sphere=CreateSphere(10)
ScaleMesh sphere,5,3,2
EntityColor sphere,255,255,0

light1=CreateLight()
TurnEntity light1,45,45,0


While Not KeyDown(1)
    DeleteOutlines
    x#=Float(MouseYSpeed())/Float(2)
    y#=Float(MouseXSpeed())/Float(2)
    TurnEntity sphere,x,y,0,True

    OutlineMesh(sphere,cam)
    MoveMouse GraphicsWidth()/2,GraphicsHeight()/2
    UpdateWorld
    RenderWorld
    DrawOutlines()
    Color 0,0,0
    Text 320,0,"Edge Detection and Outline Function",1
    Text 320,15,"Need Speeding up to be useful.",1
    Text 320,47,"Move mouse to spin sphere.",1
    Flip
Wend

FreeEntity sphere
EndGraphics
End
;
;

Function Check_Cull_2D#(x1#,y1#,x2#,y2#,x3#,y3#)
     Return (x1-x2)*(y3-y2)-(y1-y2)*(x3-x2)
End Function

;
;

Type outside
    Field sx1,sy1
    Field sx2,sy2
End Type

Function OutLineMesh(mesh,cam,rr=0,gg=0,bb=0)
    For surfcnt=1 To CountSurfaces(mesh)
        ;
        ;Find matching tris
        ;
        surf=GetSurface(mesh,surfcnt)
        tricnt=CountTriangles(surf)
        For a=0 To tricnt-1
            TFormPoint VertexX(surf,TriangleVertex(surf,a,0)),VertexY(surf,TriangleVertex(surf,a,0)),VertexZ(surf,TriangleVertex(surf,a,0)),mesh,0
            CameraProject cam,TFormedX(),TFormedY(),TFormedZ()
            sx1=ProjectedX()
            sy1=ProjectedY()

            TFormPoint VertexX(surf,TriangleVertex(surf,a,1)),VertexY(surf,TriangleVertex(surf,a,1)),VertexZ(surf,TriangleVertex(surf,a,1)),mesh,0
            CameraProject cam,TFormedX(),TFormedY(),TFormedZ()
            sx2=ProjectedX()
            sy2=ProjectedY()

            TFormPoint VertexX(surf,TriangleVertex(surf,a,2)),VertexY(surf,TriangleVertex(surf,a,2)),VertexZ(surf,TriangleVertex(surf,a,2)),mesh,0
            CameraProject cam,TFormedX(),TFormedY(),TFormedZ()
            sx3=ProjectedX()
            sy3=ProjectedY()
            cull1#=Check_Cull_2d(sx1,sy1,sx2,sy2,sx3,sy3)

            ;Check edge 1 0-1
            edge=FindSecondTri(surf,a,TriangleVertex(surf,a,0),TriangleVertex(surf,a,1))
            If edge>0 Then  ;check culling of both tri's
                ;get screen coords of edge tri
                TFormPoint VertexX(surf,TriangleVertex(surf,edge,0)),VertexY(surf,TriangleVertex(surf,edge,0)),VertexZ(surf,TriangleVertex(surf,edge,0)),mesh,0
                CameraProject cam,TFormedX(),TFormedY(),TFormedZ()
                ex1=ProjectedX()
                ey1=ProjectedY()

                TFormPoint VertexX(surf,TriangleVertex(surf,edge,1)),VertexY(surf,TriangleVertex(surf,edge,1)),VertexZ(surf,TriangleVertex(surf,edge,1)),mesh,0
                CameraProject cam,TFormedX(),TFormedY(),TFormedZ()
                ex2=ProjectedX()
                ey2=ProjectedY()

                TFormPoint VertexX(surf,TriangleVertex(surf,edge,2)),VertexY(surf,TriangleVertex(surf,edge,2)),VertexZ(surf,TriangleVertex(surf,edge,2)),mesh,0
                CameraProject cam,TFormedX(),TFormedY(),TFormedZ()
                ex3=ProjectedX()
                ey3=ProjectedY()
                cull2#=Check_Cull_2d(ex1,ey1,ex2,ey2,ex3,ey3)
                If cull1<=0 And cull2>0 Then ;this is an edge
                    edge2d.outside=New outside
                    edge2d\sx1=sx1
                    edge2d\sy1=sy1
                    edge2d\sx2=sx2
                    edge2d\sy2=sy2
                End If
            End If
            ;Check edge 2 1-2
            edge=FindSecondTri(surf,a,TriangleVertex(surf,a,1),TriangleVertex(surf,a,2))
            If edge>0 Then  ;check culling of both tri's
                ;get screen coords of edge tri
                TFormPoint VertexX(surf,TriangleVertex(surf,edge,0)),VertexY(surf,TriangleVertex(surf,edge,0)),VertexZ(surf,TriangleVertex(surf,edge,0)),mesh,0
                CameraProject cam,TFormedX(),TFormedY(),TFormedZ()
                ex1=ProjectedX()
                ey1=ProjectedY()

                TFormPoint VertexX(surf,TriangleVertex(surf,edge,1)),VertexY(surf,TriangleVertex(surf,edge,1)),VertexZ(surf,TriangleVertex(surf,edge,1)),mesh,0
                CameraProject cam,TFormedX(),TFormedY(),TFormedZ()
                ex2=ProjectedX()
                ey2=ProjectedY()

                TFormPoint VertexX(surf,TriangleVertex(surf,edge,2)),VertexY(surf,TriangleVertex(surf,edge,2)),VertexZ(surf,TriangleVertex(surf,edge,2)),mesh,0
                CameraProject cam,TFormedX(),TFormedY(),TFormedZ()
                ex3=ProjectedX()
                ey3=ProjectedY()
                cull2#=Check_Cull_2d(ex1,ey1,ex2,ey2,ex3,ey3)
                If cull1<=0 And cull2>0 Then ;this is an edge
                    edge2d.outside=New outside
                    edge2d\sx1=sx2
                    edge2d\sy1=sy2
                    edge2d\sx2=sx3
                    edge2d\sy2=sy3
                End If
            End If
            ;Check edge 3 2-0
            edge=FindSecondTri(surf,a,TriangleVertex(surf,a,2),TriangleVertex(surf,a,0))
            If edge>0 Then  ;check culling of both tri's
                ;get screen coords of edge tri
                TFormPoint VertexX(surf,TriangleVertex(surf,edge,0)),VertexY(surf,TriangleVertex(surf,edge,0)),VertexZ(surf,TriangleVertex(surf,edge,0)),mesh,0
                CameraProject cam,TFormedX(),TFormedY(),TFormedZ()
                ex1=ProjectedX()
                ey1=ProjectedY()

                TFormPoint VertexX(surf,TriangleVertex(surf,edge,1)),VertexY(surf,TriangleVertex(surf,edge,1)),VertexZ(surf,TriangleVertex(surf,edge,1)),mesh,0
                CameraProject cam,TFormedX(),TFormedY(),TFormedZ()
                ex2=ProjectedX()
                ey2=ProjectedY()

                TFormPoint VertexX(surf,TriangleVertex(surf,edge,2)),VertexY(surf,TriangleVertex(surf,edge,2)),VertexZ(surf,TriangleVertex(surf,edge,2)),mesh,0
                CameraProject cam,TFormedX(),TFormedY(),TFormedZ()
                ex3=ProjectedX()
                ey3=ProjectedY()
                cull2=Check_Cull_2d(ex1,ey1,ex2,ey2,ex3,ey3)
                If cull1<=0 And cull2>0 Then ;this is an edge
                    edge2d.outside=New outside
                    edge2d\sx1=sx3
                    edge2d\sy1=sy3
                    edge2d\sx2=sx1
                    edge2d\sy2=sy1
                End If
            End If
        Next
    Next
    Return 
End Function

Function DrawOutlines(rr=0,gg=0,bb=0)
    Color rr,gg,bb
    For le.outside=Each outside
        Line le\sx1,le\sy1,le\sx2,le\sy2
    Next
End Function

Function DeleteOutlines()
    Delete Each outside
End Function

Function FindSecondtri(surf,this,ind1,ind2)
    For a=0 To CountTriangles(surf)-1
        If a<>this Then
            If TriangleVertex(surf,a,0)=ind2 And TriangleVertex(surf,a,1)=ind1 Then Return a
            If TriangleVertex(surf,a,1)=ind2 And TriangleVertex(surf,a,2)=ind1 Then Return a
            If TriangleVertex(surf,a,2)=ind2 And TriangleVertex(surf,a,0)=ind1 Then Return a
        End If
    Next
    Return -1
End Function