Code archives/3D Graphics - Mesh/AddMeshToSurface

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AddMeshToSurface by sswift
(Posted 24 years ago)
This function allows you to add a single surface mesh to a specific surface of another mesh.

This is extremely useful for optimizing your levels, because in Blitz, each surface you have affects your framerate significantly.

A surface is a collection of vertices within a mesh, and each mesh always has one surface.

So say you have a forest. If each tree were a seprate entity, you might have 100 surfaces! That's bad. In fact, if each tree uses two textures, one for the trunk, and one alpha mapped for the leaves, each tree might have TWO surfaces! That's even worse.

So what you should do is you should combine surfaces from diffrent entities which use the same texture into a single surface in a single entity.

For example, let's use that forest example again. If your trees are made from a solid trunk, and an alpha mapped top, then you should combine all your trees into one mesh with two surfaces, and put all the trunks in the first surface, and all the tops in the second.

However, because of the way alpha is sorted in Blitz, it might be better to keep the tops of the trees as seprate entites and just combine the trunks. You'll have to decide what is best for you.

You can also combine CLUMPS of trees into meshes, that way you can autofade out whole sections of forest for additional speedus.

Using that last method I was able to render a world with 50,000 2 poly trees on a terrain on realtively crappy hardware at a decent rate of speed. Such a feat would be impossible if they were seprate entities.

Anyhow, here is the code. Hope you find it useful! 
; -------------------------------------------------------------------------------------------------------------------
; This function copies a mesh with a single surface to a specific surface of another mesh.
;
; The function can optionally offset the mesh within the destination mesh as it copies it.
; The last six parameters may be omitted when calling the function if no transformation is desired.
; -------------------------------------------------------------------------------------------------------------------
Function AddMeshToSurface(SrcMesh, DestMesh, DestSurface, Voffsetx#=0, Voffsety#=0, Voffsetz#=0, Vpitch#=0, Vyaw#=0, Vroll#=0, Vscalex#=1, Vscaley#=1, VscaleZ#=1)

	; Determine if we can optimize the mesh copying.
	TransformVertices = True
	If (Vpitch#=0) And (Vyaw#=0) And (Vroll#=0) 
		TransformVertices = False
	EndIf


	; Make sure there's a surface to copy, because the mesh might be empty.
	If CountSurfaces(SrcMesh) > 0

		SrcSurface = GetSurface(SrcMesh, 1)

		DestVerts  = CountVertices(DestSurface)
		SrcVerts   = CountVertices(SrcSurface)
			
		; If we need to transform the vertices in a complex way...
		If TransformVertices

			; Do slower copy method because we need to rotate the vertices.

			; Create a pivot to do the transformations with.
			ThisPivot = CreatePivot()
			PositionEntity ThisPivot, Voffsetx#, Voffsety#, Voffsetz#, True
			RotateEntity ThisPivot, Vpitch#, Vyaw#, Vroll#, True
			ScaleEntity ThisPivot, Vscalex#, Vscaley#, Vscalez#

			; Copy all the vertices from the source mesh to the destination surface.
			For VertLoop = 0 To SrcVerts-1
					
				Vu#  = VertexU#(SrcSurface, VertLoop)
				Vv#  = VertexV#(SrcSurface, VertLoop)		
				Vw#  = VertexW#(SrcSurface, VertLoop)
				Vr   = VertexRed(SrcSurface, VertLoop)
				Vg   = VertexGreen(SrcSurface, VertLoop)
				Vb   = VertexBlue(SrcSurface, VertLoop)
			
				TFormPoint VertexX#(SrcSurface, VertLoop), VertexY#(SrcSurface, VertLoop), VertexZ#(SrcSurface, VertLoop), ThisPivot, 0
				Vx# = TFormedX#()
				Vy# = TFormedY#()
				Vz# = TFormedZ#()

				TFormNormal VertexNX#(SrcSurface, VertLoop), VertexNY#(SrcSurface, VertLoop), VertexNZ#(SrcSurface, VertLoop), ThisPivot, 0
				Vnx# = TFormedX#()
				Vny# = TFormedY#()
				Vnz# = TFormedZ#()
			
				AddVertex(DestSurface, Vx#, Vy#, Vz#, Vu#, Vv#, Vw#)
				VertexNormal(DestSurface, VertLoop+DestVerts, Vnx#, Vny#, Vnz#)
				VertexColor(DestSurface, VertLoop+DestVerts, Vr, Vg, Vb) 
	
			Next

			FreeEntity ThisPivot

		Else

			; Do the fast copy.
			; Fast copy can do offset and scaling, but not rotation.

			; Copy all the vertices from the source mesh to the destination surface.
			For VertLoop = 0 To SrcVerts-1

					
				Vx#  = VertexX#(SrcSurface, VertLoop)
				Vy#  = VertexY#(SrcSurface, VertLoop)
				Vz#  = VertexZ#(SrcSurface, VertLoop)
				Vu#  = VertexU#(SrcSurface, VertLoop)
				Vv#  = VertexV#(SrcSurface, VertLoop)		
				Vw#  = VertexW#(SrcSurface, VertLoop)
				Vnx# = VertexNX#(SrcSurface, VertLoop)
				Vny# = VertexNY#(SrcSurface, VertLoop)
				Vnz# = VertexNZ#(SrcSurface, VertLoop)						
				Vr   = VertexRed(SrcSurface, VertLoop)
				Vg   = VertexGreen(SrcSurface, VertLoop)
				Vb   = VertexBlue(SrcSurface, VertLoop)
		
				AddVertex(DestSurface, (Vx#*Vscalex#)+Voffsetx#, (Vy#*Vscaley#)+Voffsety#, (Vz#*Vscalez#)+Voffsetz#, Vu#, Vv#, Vw#)
				VertexNormal(DestSurface, VertLoop+DestVerts, Vnx#, Vny#, Vnz#)
				VertexColor(DestSurface, VertLoop+DestVerts, Vr, Vg, Vb) 
	
			Next

		EndIf


		; Copy all triangles from the source surface to the destination surface.	
		SrcTris  = CountTriangles(SrcSurface)
		For TriLoop = 0 To SrcTris-1
	
			V0 = TriangleVertex(SrcSurface, TriLoop, 0)
			V1 = TriangleVertex(SrcSurface, TriLoop, 1)
			V2 = TriangleVertex(SrcSurface, TriLoop, 2)
		
			AddTriangle(DestSurface, V0+DestVerts, V1+DestVerts, V2+DestVerts)
	
		Next
		
	EndIf

			
End Function