Code archives/3D Graphics - Mesh/Mesh Clipping Demo

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Mesh Clipping Demo by big10p
(Posted 22 years ago)
Makes a copy of an existing mesh but cut in half (or whatever) along an arbitrary plane.

Could be used for various nifty in-game effects such as spawning etc., especially if used in conjuction with a decent particle system.

No media files required - therefore the demo meshes are a bit boring but try it on one of your own models!
Open in online IDE
;
; Mesh clip demo by big10p (A.K.A. Chris Chadwick) 2004.
;
; Written with Blitz3D v1.87
;
; Known issues:
; 1) copy_mesh_clip() attempts to paint the clipped mesh with the same brushes
;    that are applied to the mesh being copied. For multiple surface meshes,
;    GetSurfaceBrush() is used but only works if the mesh's surfaces have been
;    painted with PaintSurface(). If the multi surface mesh has been painted
;    en masse - using EntityTexture, EntityColor etc. - it doesn't work.
; 2) There seems to be a slight, noticeable color change when clipping tris that
;    are vertex colored. Not sure if this is down to a lack of precision with floats
;    or something I'm doing wrong. I'll have to investigate some more, I think. :)
; 3) I seem to get a much higher FPS (with frame locking turned off) if I turn off the
;    visible clipping plane. Not sure why it makes such a big difference as it's only
;    one surface with two triangles in!? :/
;


	Graphics3D 800,600,32

	; Create chequer pattern texture.
	Global tex = CreateTexture(64,64)
	SetBuffer TextureBuffer(tex)
	For y = 0 To 63 Step 4
		For x = 0 To 63 Step 2
			If c Then Color 255,255,255 Else Color 255,0,0
			c = Not c
			Rect x,y,2,4
		Next
		c = Not c
	Next
	SetBuffer BackBuffer()
	
	WireFrame 0
	AntiAlias 0

	SeedRnd MilliSecs()

	; Demo mesh info type.
	Type infoT
		Field mesh
		Field FX%
		Field vert_info%
	End Type
	
	; Frame timing and control.
	Global frame_count%
	Global fps%
	Global slowest_fps%
	Global fps_timeout%
	Global frame_time%
	Global slowest_frame%
	Global frame_start%
	fps_timer = CreateTimer(60)

	; Demo state flags.
	show_text% = True
	show_plane% = True
	rotate_plane% = True
	rotate_mesh% = True
	cull_backface% = False
	wiref% = False
	slowmo% = False
	frame_lock% = True

	; Flags to tell clip_tri functions the order to wind triangles.
	Const WIND_012% = 0
	Const WIND_102% = 1
	Const WIND_201% = 2

	; Flags to tell copy_mesh_clip() which vertex info to include when clipping.
	Const CLIP_NORMALS% = 1
	Const CLIP_UV_SET0% = 2
	Const CLIP_UV_SET1% = 4
	Const CLIP_RGBA%    = 8
	Const DEF_CLIP_INFO% = CLIP_NORMALS+CLIP_UV_SET0
	
	cam = CreateCamera()
	CameraRange cam,1,100
	PositionEntity cam,0,0,-3
	
	light = CreateLight()
	AmbientLight 100,100,100
	
	; Create the demo meshes.
	Dim mesh.infoT(0)
	create_meshes()
	current_mesh% = 0
			
	; Clipping plane.
	Const MAX_PLANE_DIST# = 1.3
	plane_pitch# = 0
	plane_yaw# = 0
	plane_dist# = -MAX_PLANE_DIST
	plane_move# = 0.01	
	plane_piv = CreatePivot()
	plane = CreateMesh(plane_piv)
	ps = CreateSurface(plane)
	AddVertex(ps,-2,0,2)
	AddVertex(ps,2,0,2)
	AddVertex(ps,-2,0,-2)
	AddVertex(ps,2,0,-2)
	AddTriangle(ps,0,1,2)
	AddTriangle(ps,1,3,2)
	EntityAlpha plane,.3
	EntityColor plane,0,0,200
	EntityFX plane,1+16
	PositionEntity plane,0,plane_dist,0
	RotateEntity plane_piv,plane_pitch,plane_yaw,0
	
	clip_mesh = copy_mesh_clip(mesh(current_mesh)\mesh,plane_dist,plane_pitch,plane_yaw,mesh(current_mesh)\vert_info)
	EntityFX clip_mesh,mesh(current_mesh)\FX Xor (cull_backface Shl 4)

	;
	; --- Main loop ---
	;
	
	While Not KeyHit(1)

		frame_start = MilliSecs()
	
		If KeyHit(2) Then show_text = Not show_text
		If KeyHit(3)
			show_plane = Not show_plane
			If show_plane Then ShowEntity plane Else HideEntity plane
		EndIf
		If KeyHit(4)
			rotate_plane = Not rotate_plane
			plane_pitch = 0
			plane_yaw = 0
		EndIf
		If KeyHit(5) Then rotate_mesh = Not rotate_mesh
		If KeyHit(6) Then cull_backface = Not cull_backface
		If KeyHit(7) Then wiref = Not wiref : WireFrame wiref
		If KeyHit(8) Then slowmo = Not slowmo
		If KeyHit(9) Then frame_lock = Not frame_lock
		If KeyHit(57) Then current_mesh = (current_mesh + 1) Mod 5

		If rotate_mesh Then RotateMesh mesh(current_mesh)\mesh,1,0,1

		; Change clipping plane distance.
		plane_dist = plane_dist + plane_move
		If Abs(plane_dist) > MAX_PLANE_DIST Then plane_move = -plane_move
		
		; Rotate clipping plane.
		If rotate_plane
			plane_pitch = (plane_pitch + 1) Mod 360
			plane_yaw = (plane_yaw + .5) Mod 360
		EndIf
		
		; Create an updated, clipped version of the current mesh.
		FreeEntity clip_mesh
		clip_mesh = copy_mesh_clip(mesh(current_mesh)\mesh,plane_dist,plane_pitch,plane_yaw,mesh(current_mesh)\vert_info)
		EntityFX clip_mesh,mesh(current_mesh)\FX Xor (cull_backface Shl 4)

		; Position visible plane to match clipping plane.
		If show_plane
			PositionEntity plane,0,plane_dist,0
			RotateEntity plane_piv,plane_pitch,plane_yaw,0
		EndIf
		
		RenderWorld

		frame_time = MilliSecs() - frame_start	
		If show_text Then show_info()

		If frame_lock
			WaitTimer(fps_timer)
			Flip True
		Else
			Flip False
		EndIf

		If slowmo Then Delay 200

	Wend

	End


;
; Creates a copy of a mesh, clipped along the given plane.
; Note: this function can only really perform clipping along an XZ aligned plane.
;       To perform clipping on an arbitrary, rotated plane, we cheat :) - first
;       we align the mesh to the XZ plane, perform the clipping, then return
;       the mesh to it's original orientation.
;
; Params:
; source_mesh - Mesh to be copied (remains unaltered by this function).
; plane_y     - Y distance of clipping plane from mesh origin.
; plane_pitch - Pitch of clipping plane.
; plane_yaw   - Yaw of clipping plane.
; vert_info   - Bit flags defining vertex info to include when clipping.
;
; Returns:
; Handle of newly created, clipped mesh.
;
Function copy_mesh_clip(source_mesh,plane_y#,plane_pitch#,plane_yaw#,vert_info%=DEF_CLIP_INFO)

	surf_count = CountSurfaces(source_mesh)

	; Temporarily align source mesh to XZ clipping plane.
	; Note: doing yaw THEN pitch rotation separately is important!
	; Prevents gimble lock when returning the mesh back to it's original rotation.
	RotateMesh source_mesh,0,-plane_yaw,0
	RotateMesh source_mesh,-plane_pitch,0,0

	If surf_count=1
		; We can make a copy of single surface meshes more quickly using CopyMesh.
		; (Unfortunately, CopyMesh combines surfs unless they use different textures
		; so this method can't be used with multi surface meshes).
		dest_mesh = CopyMesh(source_mesh)

		; Kill tris but keep verts.
		ClearSurface GetSurface(dest_mesh,1),False,True

		brush = GetEntityBrush(source_mesh)
		PaintEntity dest_mesh,brush
		FreeBrush brush
	Else
		dest_mesh = CreateMesh()
	
		; Copy all surfaces and vertices from source_mesh into dest_mesh.
		;
		For ss=1 To surf_count
			
			source_surf = GetSurface(source_mesh,ss)
			brush = GetSurfaceBrush(source_surf)
			dest_surf = CreateSurface(dest_mesh,brush)
			FreeBrush brush
	
			For sv=0 To CountVertices(source_surf)-1
				vy# = VertexY(source_surf,sv)
				dv = AddVertex(dest_surf,VertexX(source_surf,sv),vy,VertexZ(source_surf,sv))
				
				; We don't need to bother with any other info for verts
				; in dest_mesh that are beyond the clipping plane.
				If Not vy<plane_y
					VertexNormal dest_surf,dv,VertexNX(source_surf,sv),VertexNY(source_surf,sv),VertexNZ(source_surf,sv)
					VertexTexCoords dest_surf,dv,VertexU(source_surf,sv,0),VertexV(source_surf,sv,0),0, 0
					VertexTexCoords dest_surf,dv,VertexU(source_surf,sv,1),VertexV(source_surf,sv,1),0, 1
					VertexColor dest_surf,dv,VertexRed(source_surf,sv),VertexGreen(source_surf,sv),VertexBlue(source_surf,sv),VertexAlpha(source_surf,sv)
				EndIf
			Next
		Next
	EndIf	

	; Process all surfaces in source_mesh...
	;
	For ss=1 To CountSurfaces(source_mesh)
		
		source_surf = GetSurface(source_mesh,ss)
		dest_surf = GetSurface(dest_mesh,ss)
		
		; Process all trinagles in source_surf...
		;
		For t=0 To CountTriangles(source_surf)-1

			v0 = TriangleVertex(source_surf,t,0)
			v1 = TriangleVertex(source_surf,t,1)
			v2 = TriangleVertex(source_surf,t,2)
			
			clip0 = VertexY(source_surf,v0) < plane_y
			clip1 = VertexY(source_surf,v1) < plane_y
			clip2 = VertexY(source_surf,v2) < plane_y
			
			Select clip0+clip1+clip2
			
			Case 0	; There are no 'bad' verts in this triangle...
			
				; Add this triangle so it's the same as it appears in source_surf.
				AddTriangle(dest_surf,v0,v1,v2)

			Case 1	; There is 1 'bad' vert in this triangle...
					
				;Find the 1 'bad' vert.
				;
				If clip0	 	; v0 is bad...

					clip_tri_1bad(source_surf,dest_surf,plane_y, v0,v1,v2, WIND_012, vert_info)

				ElseIf clip1	;v1 is bad...

					clip_tri_1bad(source_surf,dest_surf,plane_y, v1,v0,v2, WIND_102, vert_info)
				
				Else			;v2 is bad...

					clip_tri_1bad(source_surf,dest_surf,plane_y, v2,v0,v1, WIND_201, vert_info)
			
				EndIf
				
			Case 2	; There are 2 'bad' verts in this triangle...
			
				; Find the 1 'good' vert.
				;
				If Not clip0		; v0 is good...
				
					clip_tri_2bad(source_surf,dest_surf,plane_y, v0,v1,v2, WIND_012, vert_info)

				ElseIf Not clip1	; v1 is good...

					clip_tri_2bad(source_surf,dest_surf,plane_y, v1,v0,v2, WIND_102, vert_info)

				Else				; v2 is good...

					clip_tri_2bad(source_surf,dest_surf,plane_y, v2,v0,v1, WIND_201, vert_info)

				EndIf				

			End Select

		Next
		
	Next

	; Rotate source_mesh and dest_mesh to source_mesh's original rotation.
	RotateMesh source_mesh,plane_pitch,plane_yaw,0
	RotateMesh dest_mesh,plane_pitch,plane_yaw,0

	Return dest_mesh
	
End Function


;
; Creates a clipped triangle from a source_surf triangle that has 2 'bad' vertices. i.e. 2 of the
; triangles verts are beyond the clipping plane.
;
; Params:
; source_surf - Surface containing the triangle to be clipped.
; dest_surf   - Surface to build the clipped triangle in.
; plane_y     - Y distance of clipping plane from mesh origin.
; good_v      - Index of the one 'good' vertex in triangle.
; bad1_v      - Index of the first 'bad' vertex in the triangle.
; bad2_v      - Index of the second 'bad' vertex in the triangle.
; wind_order  - Flag indicating the order to wind the clipped triangle.
; vert_info   - Bit flags defining vertex info to include when clipping.
;
Function clip_tri_2bad(source_surf,dest_surf,plane_y#, good_v%,bad1_v%,bad2_v%, wind_order%, vert_info%)

	; Retrieve good/bad vert coords.
	good_vx# = VertexX(source_surf,good_v)
	good_vy# = VertexY(source_surf,good_v)
	good_vz# = VertexZ(source_surf,good_v)
	bad1_vx# = VertexX(source_surf,bad1_v)
	bad1_vy# = VertexY(source_surf,bad1_v)
	bad1_vz# = VertexZ(source_surf,bad1_v)
	bad2_vx# = VertexX(source_surf,bad2_v)
	bad2_vy# = VertexY(source_surf,bad2_v)
	bad2_vz# = VertexZ(source_surf,bad2_v)

	; Find Y distance from good vert to clipping plane.
	clip_y_dist# = good_vy-plane_y

	;
	; Calculate & add first new vert...
	;
	
	; Vector to bad vert 1 from good vert.
	xv# = bad1_vx-good_vx
	yv# = bad1_vy-good_vy
	zv# = bad1_vz-good_vz
	
	y_dist# = good_vy-bad1_vy
	side# = 1.0/y_dist
	ratio1# = clip_y_dist*side
	new1_v = AddVertex(dest_surf,good_vx+xv*ratio1,good_vy+yv*ratio1,good_vz+zv*ratio1)

	;
	; Calculate & add second new vert...
	;
	
	; Vector to bad vert 2 from good vert.
	xv# = bad2_vx-good_vx
	yv# = bad2_vy-good_vy
	zv# = bad2_vz-good_vz
	
	y_dist# = good_vy-bad2_vy
	side# = 1.0/y_dist
	ratio2# = clip_y_dist*side
	new2_v = AddVertex(dest_surf,good_vx+xv*ratio2,good_vy+yv*ratio2,good_vz+zv*ratio2)

	; Make the clipped triangle, wound in the specified way.
	Select wind_order
	Case WIND_012
		AddTriangle(dest_surf,good_v,new1_v,new2_v)
	Case WIND_102
		AddTriangle(dest_surf,new1_v,good_v,new2_v)
	Case WIND_201
		AddTriangle(dest_surf,new1_v,new2_v,good_v)
	End Select

	;
	; Update the requested settings for the 2 new verts...
	;
	
	If vert_info And CLIP_NORMALS
		; Retrieve original triangle's normals.
		good_nx# = VertexNX(source_surf,good_v)
		good_ny# = VertexNY(source_surf,good_v)
		good_nz# = VertexNZ(source_surf,good_v)
		bad1_nx# = VertexNX(source_surf,bad1_v)
		bad1_ny# = VertexNY(source_surf,bad1_v)
		bad1_nz# = VertexNZ(source_surf,bad1_v)
		bad2_nx# = VertexNX(source_surf,bad2_v)
		bad2_ny# = VertexNY(source_surf,bad2_v)
		bad2_nz# = VertexNZ(source_surf,bad2_v)
	
		; Calculate & set normals for the 2 new verts.
		nx# = good_nx + (bad1_nx-good_nx) * ratio1
		ny# = good_ny + (bad1_ny-good_ny) * ratio1
		nz# = good_nz + (bad1_nz-good_nz) * ratio1
		nl# = Sqr(nx*nx + ny*ny + nz*nz)
		VertexNormal dest_surf,new1_v,nx/nl,ny/nl,nz/nl
		nx# = good_nx + (bad2_nx-good_nx) * ratio2
		ny# = good_ny + (bad2_ny-good_ny) * ratio2
		nz# = good_nz + (bad2_nz-good_nz) * ratio2
		nl# = Sqr(nx*nx + ny*ny + nz*nz)
		VertexNormal dest_surf,new2_v,nx/nl,ny/nl,nz/nl
	EndIf

	If vert_info And CLIP_UV_SET0
		; Retrieve original triangle's set 0 UVs.
		good_tu# = VertexU(source_surf,good_v,0)
		good_tv# = VertexV(source_surf,good_v,0)
		bad1_tu# = VertexU(source_surf,bad1_v,0)
		bad1_tv# = VertexV(source_surf,bad1_v,0)
		bad2_tu# = VertexU(source_surf,bad2_v,0)
		bad2_tv# = VertexV(source_surf,bad2_v,0)
	
		; Calculate & set set 0 UVs for the 2 new verts.
		u# = good_tu + (bad1_tu-good_tu) * ratio1
		v# = good_tv + (bad1_tv-good_tv) * ratio1
		VertexTexCoords dest_surf,new1_v, u,v,0, 0
		u# = good_tu + (bad2_tu-good_tu) * ratio2
		v# = good_tv + (bad2_tv-good_tv) * ratio2
		VertexTexCoords dest_surf,new2_v, u,v,0, 0
	EndIf

	If vert_info And CLIP_UV_SET1
		; Retrieve original triangle's set 1 UVs.
		good_tu# = VertexU(source_surf,good_v,1)
		good_tv# = VertexV(source_surf,good_v,1)
		bad1_tu# = VertexU(source_surf,bad1_v,1)
		bad1_tv# = VertexV(source_surf,bad1_v,1)
		bad2_tu# = VertexU(source_surf,bad2_v,1)
		bad2_tv# = VertexV(source_surf,bad2_v,1)
	
		; Calculate & set set 1 UVs for the 2 new verts.
		u# = good_tu + (bad1_tu-good_tu) * ratio1
		v# = good_tv + (bad1_tv-good_tv) * ratio1
		VertexTexCoords dest_surf,new1_v, u,v,0, 1
		u# = good_tu + (bad2_tu-good_tu) * ratio2
		v# = good_tv + (bad2_tv-good_tv) * ratio2
		VertexTexCoords dest_surf,new2_v, u,v,0, 1
	EndIf

	If vert_info And CLIP_RGBA
		; Retrieve original triangle's vert colors.
		good_r# = VertexRed(source_surf,good_v)
		good_g# = VertexGreen(source_surf,good_v)
		good_b# = VertexBlue(source_surf,good_v)
		bad1_r# = VertexRed(source_surf,bad1_v)
		bad1_g# = VertexGreen(source_surf,bad1_v)
		bad1_b# = VertexBlue(source_surf,bad1_v)
		bad2_r# = VertexRed(source_surf,bad2_v)
		bad2_g# = VertexGreen(source_surf,bad2_v)
		bad2_b# = VertexBlue(source_surf,bad2_v)
	
		; Retrieve original triangle's vert alpha.
		good_a# = VertexAlpha(source_surf,good_v)
		bad1_a# = VertexAlpha(source_surf,bad1_v)
		bad2_a# = VertexAlpha(source_surf,bad2_v)
	
		; Calculate & set color and alpha for the 2 new verts.
		r# = good_r + (bad1_r-good_r) * ratio1
		g# = good_g + (bad1_g-good_g) * ratio1
		b# = good_b + (bad1_b-good_b) * ratio1
		a# = good_a + (bad1_a-good_a) * ratio1
		VertexColor dest_surf,new1_v,r,g,b,a
		r# = good_r + (bad2_r-good_r) * ratio2
		g# = good_g + (bad2_g-good_g) * ratio2
		b# = good_b + (bad2_b-good_b) * ratio2
		a# = good_a + (bad2_a-good_a) * ratio2
		VertexColor dest_surf,new2_v,r,g,b,a
	EndIf

End Function


;
; Creates a clipped triangle from a source_surf triangle that has 1 'bad' vertex. i.e. 1 of the
; triangles verts is beyond the clipping plane.
; Note: this actually requires us to make a quad out of 2 tris.
;
; Params:
; source_surf - Surface containing the triangle to be clipped.
; dest_surf   - Surface to build the clipped triangle in.
; plane_y     - Y distance of clipping plane from mesh origin.
; bad_v       - Index of the one 'bad' vertex in triangle.
; good1_v     - Index of the first 'good' vertex in the triangle.
; good2_v     - Index of the second 'good' vertex in the triangle.
; wind_order  - Flag indicating the order to wind the clipped triangle(s).
; vert_info   - Bit flags defining vertex info to include when clipping.
;
Function clip_tri_1bad(source_surf,dest_surf,plane_y#, bad_v%,good1_v%,good2_v%, wind_order%, vert_info)

	; Retrieve good/bad vert coords.
	bad_vx#   = VertexX(source_surf,bad_v)
	bad_vy#   = VertexY(source_surf,bad_v)
	bad_vz#   = VertexZ(source_surf,bad_v)
	good1_vx# = VertexX(source_surf,good1_v)
	good1_vy# = VertexY(source_surf,good1_v)
	good1_vz# = VertexZ(source_surf,good1_v)
	good2_vx# = VertexX(source_surf,good2_v)
	good2_vy# = VertexY(source_surf,good2_v)
	good2_vz# = VertexZ(source_surf,good2_v)

	;
	; Calculate & add first new vert...
	;

	; Find Y distance from good vert 1 to clipping plane.
	clip_y_dist# = good1_vy-plane_y

	; Vector to bad vert from good vert 1.
	xv# = bad_vx-good1_vx
	yv# = bad_vy-good1_vy
	zv# = bad_vz-good1_vz
	
	y_dist# = good1_vy-bad_vy
	side# = 1.0/y_dist
	ratio1# = clip_y_dist*side
	new1_v = AddVertex(dest_surf,good1_vx+xv*ratio1,good1_vy+yv*ratio1,good1_vz+zv*ratio1)

	;
	; Calculate & add second new vert...
	;

	; Find Y distance from good vert 2 to clipping plane.
	clip_y_dist# = good2_vy-plane_y

	; Vector to bad vert from good vert 2.
	xv# = bad_vx-good2_vx
	yv# = bad_vy-good2_vy
	zv# = bad_vz-good2_vz
	
	y_dist# = good2_vy-bad_vy
	side# = 1.0/y_dist
	ratio2# = clip_y_dist*side
	new2_v = AddVertex(dest_surf,good2_vx+xv*ratio2,good2_vy+yv*ratio2,good2_vz+zv*ratio2)
	
	; Make the 2 clipped triangles, wound in the specified way.
	Select wind_order
	Case WIND_012
		AddTriangle(dest_surf,new1_v,good1_v,good2_v)
		AddTriangle(dest_surf,good2_v,new2_v,new1_v)
	Case WIND_102
		AddTriangle(dest_surf,good1_v,new1_v,good2_v)
		AddTriangle(dest_surf,good2_v,new1_v,new2_v)
	Case WIND_201
		AddTriangle(dest_surf,good1_v,good2_v,new1_v)
		AddTriangle(dest_surf,good2_v,new2_v,new1_v)
	End Select

	;
	; Update the requested settings for the 2 new verts...
	;
	
	If vert_info And CLIP_NORMALS
		; Retrieve original triangle's normals.
		bad_nx#   = VertexNX(source_surf,bad_v)
		bad_ny#   = VertexNY(source_surf,bad_v)
		bad_nz#   = VertexNZ(source_surf,bad_v)
		good1_nx# = VertexNX(source_surf,good1_v)
		good1_ny# = VertexNY(source_surf,good1_v)
		good1_nz# = VertexNZ(source_surf,good1_v)
		good2_nx# = VertexNX(source_surf,good2_v)
		good2_ny# = VertexNY(source_surf,good2_v)
		good2_nz# = VertexNZ(source_surf,good2_v)
	
		; Calculate & set normals for the 2 new verts.
		nx# = good1_nx + (bad_nx-good1_nx) * ratio1
		ny# = good1_ny + (bad_ny-good1_ny) * ratio1
		nz# = good1_nz + (bad_nz-good1_nz) * ratio1
		nl# = Sqr(nx*nx + ny*ny + nz*nz)
		VertexNormal dest_surf,new1_v,nx/nl,ny/nl,nz/nl
		nx# = good2_nx + (bad_nx-good2_nx) * ratio2
		ny# = good2_ny + (bad_ny-good2_ny) * ratio2
		nz# = good2_nz + (bad_nz-good2_nz) * ratio2
		nl# = Sqr(nx*nx + ny*ny + nz*nz)
		VertexNormal dest_surf,new2_v,nx/nl,ny/nl,nz/nl
	EndIf

	If vert_info And CLIP_UV_SET0
		; Retrieve original triangle's set 0 UVs.
		bad_tu#   = VertexU(source_surf,bad_v,0)
		bad_tv#   = VertexV(source_surf,bad_v,0)
		good1_tu# = VertexU(source_surf,good1_v,0)
		good1_tv# = VertexV(source_surf,good1_v,0)
		good2_tu# = VertexU(source_surf,good2_v,0)
		good2_tv# = VertexV(source_surf,good2_v,0)
	
		; Calculate & set set 0 UVs for the 2 new verts.
		u# = good1_tu + (bad_tu-good1_tu) * ratio1
		v# = good1_tv + (bad_tv-good1_tv) * ratio1
		VertexTexCoords dest_surf,new1_v, u,v,0, 0
		u# = good2_tu + (bad_tu-good2_tu) * ratio2
		v# = good2_tv + (bad_tv-good2_tv) * ratio2
		VertexTexCoords dest_surf,new2_v, u,v,0, 0
	EndIf

	If vert_info And CLIP_UV_SET1
		; Retrieve original triangle's set 1 UVs.
		bad_tu#   = VertexU(source_surf,bad_v,1)
		bad_tv#   = VertexV(source_surf,bad_v,1)
		good1_tu# = VertexU(source_surf,good1_v,1)
		good1_tv# = VertexV(source_surf,good1_v,1)
		good2_tu# = VertexU(source_surf,good2_v,1)
		good2_tv# = VertexV(source_surf,good2_v,1)
	
		; Calculate & set set 1 UVs for the 2 new verts.
		u# = good1_tu + (bad_tu-good1_tu) * ratio1
		v# = good1_tv + (bad_tv-good1_tv) * ratio1
		VertexTexCoords dest_surf,new1_v, u,v,0, 1
		u# = good2_tu + (bad_tu-good2_tu) * ratio2
		v# = good2_tv + (bad_tv-good2_tv) * ratio2
		VertexTexCoords dest_surf,new2_v, u,v,0, 1
	EndIf

	If vert_info And CLIP_RGBA
		; Retrieve original triangle's vert colors.
		bad_r#   = VertexRed(source_surf,bad_v)
		bad_g#   = VertexGreen(source_surf,bad_v)
		bad_b#   = VertexBlue(source_surf,bad_v)
		good1_r# = VertexRed(source_surf,good1_v)
		good1_g# = VertexGreen(source_surf,good1_v)
		good1_b# = VertexBlue(source_surf,good1_v)
		good2_r# = VertexRed(source_surf,good2_v)
		good2_g# = VertexGreen(source_surf,good2_v)
		good2_b# = VertexBlue(source_surf,good2_v)
	
		; Retrieve original triangle's vert alpha.
		bad_a# = VertexAlpha(source_surf,bad_v)
		good1_a# = VertexAlpha(source_surf,good1_v)
		good2_a# = VertexAlpha(source_surf,good2_v)
	
		; Calculate & set color and alpha for the 2 new verts.
		r# = good1_r + (bad_r-good1_r) * ratio1
		g# = good1_g + (bad_g-good1_g) * ratio1
		b# = good1_b + (bad_b-good1_b) * ratio1
		a# = good1_a + (bad_a-good1_a) * ratio1
		VertexColor dest_surf,new1_v,r,g,b,a
		r# = good2_r + (bad_r-good2_r) * ratio2
		g# = good2_g + (bad_g-good2_g) * ratio2
		b# = good2_b + (bad_b-good2_b) * ratio2
		a# = good2_a + (bad_a-good2_a) * ratio2
		VertexColor dest_surf,new2_v,r,g,b,a
	EndIf

End Function


;
; Creates various meshes to demonstrate clipping on.
;
Function create_meshes()

	Dim mesh.infoT(4)
	
	; Textured sphere.
	mesh(0) = New infoT
	mesh(0)\mesh = CreateSphere(16)
	mesh(0)\FX = 16
	mesh(0)\vert_info = CLIP_NORMALS+CLIP_UV_SET0
	ScaleMesh mesh(0)\mesh,1.2,1.2,1.2
	EntityTexture mesh(0)\mesh,tex
	HideEntity mesh(0)\mesh
		
	; Vertex colored cone.
	mesh(1) = New infoT
	mesh(1)\mesh = CreateCone(32,1)
	mesh(1)\FX = 2+16
	mesh(1)\vert_info = CLIP_NORMALS+CLIP_RGBA
	UpdateNormals mesh(1)\mesh
	For s=1 To 2
		surf = GetSurface(mesh(1)\mesh,s)
		For v=0 To CountVertices(surf)-1
			VertexColor surf,v,Rand(0,255),Rand(0,255),Rand(0,255)
		Next
	Next
	HideEntity mesh(1)\mesh
	
	; Plain cylinder.
	mesh(2) = New infoT
	mesh(2)\mesh = CreateCylinder(32,1)
	mesh(2)\FX = 16
	mesh(2)\vert_info = CLIP_NORMALS
	HideEntity mesh(2)\mesh
	
	; Textured, vertex colored cube.
	mesh(3) = New infoT
	mesh(3)\mesh = CreateCube()
	mesh(3)\FX = 2+16
	mesh(3)\vert_info = CLIP_NORMALS+CLIP_UV_SET0+CLIP_RGBA
	surf = GetSurface(mesh(3)\mesh,1)
	For v=0 To CountVertices(surf)-1
		VertexColor surf,v,Rand(0,255),Rand(0,255),Rand(0,255)
	Next
	EntityTexture mesh(3)\mesh,tex
	HideEntity mesh(3)\mesh

	; Textured bars.
	bar = CreateCylinder(16,1)
	ScaleMesh bar,.2,1.5,.2
	mesh(4) = New infoT
	mesh(4)\mesh = CreateMesh()
	AddMesh bar,mesh(4)\mesh
	PositionMesh bar,.5,0,0
	RotateMesh bar,20,0,0
	AddMesh bar,mesh(4)\mesh
	PositionMesh bar,-1,0,0
	RotateMesh bar,20,0,0
	AddMesh bar,mesh(4)\mesh
	mesh(4)\FX = 16
	mesh(4)\vert_info = CLIP_NORMALS+CLIP_UV_SET0
	HideEntity mesh(4)\mesh
	FreeEntity bar
	EntityTexture mesh(4)\mesh,tex
	EntityColor mesh(4)\mesh,200,0,150
	EntityShininess mesh(4)\mesh,1

End Function


;
; Displays info.
;
Function show_info()
	
	If fps_timeout
		frame_count = frame_count + 1

		If MilliSecs() > fps_timeout Then
			fps_timeout = MilliSecs() + 1000 
			fps = frame_count 
			frame_count = 0
		
			If fps < slowest_fps Or slowest_fps = 0 Then slowest_fps = fps
		EndIf 
		
		If frame_time > slowest_frame Then slowest_frame = frame_time
		
		Color 255,255,255
		Text 10,10, "Press to toggle:"
		Text 10,25, "1 - This text"
		Text 10,40, "2 - Clipping plane"
		Text 10,55, "3 - Clipping plane rotation"
		Text 10,70, "4 - Mesh rotation"
		Text 10,85, "5 - Backface culling"
		Text 10,100,"6 - Wireframe"
		Text 10,115,"7 - Slow motion"
		Text 10,130,"8 - Frame lock"
		Text 10,160,"Press SPACE to change mesh"
		Color 255,255,0
		Text 10,190,"Millisecs: " + frame_time
		Text 10,205,"  Slowest: " + slowest_frame
		Color 0,255,255
		Text 10,220,"      FPS: " + fps
		Text 10,235,"    Worst: " + slowest_fps
	Else
		; First call initialization.
		fps_timeout = MilliSecs() + 1000 
	EndIf
	
End Function

Comments

HNPhan
(Posted 22 years ago)
niiice effect!! like the homeworld hyperspace clip fx

BlitzSupport
(Posted 22 years ago)
Whoa, nice one -- very quick!

churchaxe
(Posted 22 years ago)
cooool!

big10p
(Posted 22 years ago)
Thanks all! :)

I haven't seen Homeworld but I think this could be used for all kinds of effects. I first saw this effect in Soul Reaver on the Dreamcast: when you killed an enemy, a diagonal, invisible plane would gradually erase it's body. I always wondered how it was done.

Tracer
(Posted 22 years ago)
Highly awesome!

Tracer

Cygnus
(Posted 22 years ago)
Excelent stuff :D excelent! woo! woo! woo! :D

Gillissie
(Posted 22 years ago)
Very cool. I'm surprised at how fast it runs.

Bot Builder
(Posted 22 years ago)
Wow. Sweet routine. their must be somthing cool to use this for....... :D

Picklesworth
(Posted 22 years ago)
I've been looking for this one so I can have a running example of my jumpgate concept. Thanks a lot!

puki
(Posted 22 years ago)
Yep this is extremely good - very good demo - the only clipping stuff I have noted with regard to Blitz3D surface/vertex stuff.

Braincell
(Posted 22 years ago)
WHOA!!!!!

If you could make another mesh instead of the plane, then we would all have an awesome supa-fast shadow system.

Braincell
(Posted 22 years ago)
<SNIP>

(ouch seems blitzbasic.com is reacting a bit slow so i posted a few times...)

Braincell
(Posted 22 years ago)
<SNIP>

Braincell
(Posted 22 years ago)
<SNIP>

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