Triangles and Vertices

Blitz3D Forums/Blitz3D Programming/Triangles and Vertices

_PJ_	(Posted 2011) [#1]

Not the best topic title, so sorry :)

I was wondering if there's an easy/specific (popular even?) metohod of identifying triangles which share vertices with a particular one, or perhaps, the triangles of which a particular vertex is 'part of' ?
So far, the only thing I have been able to come up with is to iterate through each triangle each and every time:

Graphics3D 800,600,32,6
SetBuffer BackBuffer()

;Wireframe True

Global Cam=CreateCamera()
MoveEntity Cam,0,0,-5

Global Sphere=CreateSphere()

EntityFX Sphere,34

Global TRI=GetRandomTriangle(Sphere)
ProcessTriangle(Sphere,GetSurface(Sphere,1),TRI)
	
While Not KeyDown(1)
	TurnEntity Sphere,0,1,0,True
	UpdateWorld
	RenderWorld
	Flip
Wend

Function GetRandomTriangle(Mesh)
	Local Triangle=Rand(0,CountTriangles(GetSurface(Mesh,1)))
	DebugLog "Triangle: "+Triangle
	Return Triangle
End Function

Function ProcessTriangle(Mesh,Surface,Triangle)
	Local IterVertices
		For IterVertices=0 To 2
			GetMatchingVertices(Sphere,GetSurface(Sphere,1),TRI,IterVertices)
		Next	
End Function

Function GetMatchingVertices(Mesh,Surface,Triangle,VertexIndex)
	Local Vertex=TriangleVertex(Surface,Triangle,VertexIndex)
	Local MatchTriangle
	For MatchTriangle=0 To CountTriangles(Surface)
		If (MatchTriangle<>Triangle)
			For MatchVertices=0 To 2
				If (TriangleVertex(Surface,MatchTriangle,MatchVertices)=Vertex)
					DebugLog "Vertex: "+VertexIndex
					DebugLog "Connects: "+MatchTriangle
					VertexColor Surface,Vertex,255,0,0,1.0
				End If
			Next
		End If		
	Next
End Function

Is there a simpler, or quicker method?

Rroff

(Posted 2011) [#2]

Short of pre-computing a lookup list at load (or design) time I don't know of any other approach other than what you've come up with - and you'd basically still have to do the same as what your doing it would just be faster on subsequent lookups.

Last edited 2011

_PJ_	(Posted 2011) [#3]

Thanks, Rroff. A pre-compiled lookup sounds good, at least, storing the intial triangle verts, though for complicated meshes of thousands of verts, that's a fair chunk of data duplicated, but as you say, it doesn't seem like there's much option...