Graphics 1024,768,32,2
SetBuffer BackBuffer()


Type TVertex	
	;coordinates
	Field x#,y#,z#	
	; projected coordinates
	Field xp#, yp#, zp#, wp#	
	; viewport coordinates
	Field xw#, yw#
End Type


Type TTriAngle
	Field v1.TVertex
	Field v2.TVertex
	Field v3.TVertex
End Type

; Viewport
Global viewWidth# = 1024
Global viewHeight# = 768

Global centerX# = viewWidth*0.5
Global centerY# = viewHeight*0.5

; clipping planes
Global near# = -1
Global far#  = -10

Global width# = 1
Global height#	=viewHeight/viewWidth

; Create 3 triangles
Local tri.TTriAngle = New TTriAngle
tri\v1 = New TVertex:tri\v2 = New TVertex:tri\v3 = New TVertex
	
tri\v1\x = -0.1	:tri\v1\y = -0.2	:tri\v1\z = -2
tri\v2\x = -0.1	:tri\v2\y = 0.2	:tri\v2\z = -2
tri\v3\x = -0.3	:tri\v3\y = 0	:tri\v3\z = -2

tri.TTriAngle = New TTriAngle
tri\v1 = New TVertex:tri\v2 = New TVertex:tri\v3 = New TVertex

tri\v1\x = -0.1	:tri\v1\y = -0.2	:tri\v1\z = -4
tri\v2\x = -0.1	:tri\v2\y = 0.2	:tri\v2\z = -4
tri\v3\x = -0.3	:tri\v3\y = 0	:tri\v3\z = -4

tri.TTriAngle = New TTriAngle

tri\v1 = New TVertex: tri\v2 = New TVertex: tri\v3 = New TVertex
tri\v1\x = -0.1	:tri\v1\y = -0.2	:tri\v1\z = -7
tri\v2\x = -0.1	:tri\v2\y = 0.2	:tri\v2\z = -7
tri\v3\x = -0.3	:tri\v3\y = 0	:tri\v3\z = -7

Repeat	
	For tri.TTriAngle = Each TTriAngle
		;calculate projection
		Projection(tri\v1)
		Projection(tri\v2)
		Projection(tri\v3)
		
		; check if triangle is within clipping planes
		If (tri\v1\z <  near ) And (tri\v1\z >  far ) Then
			If (tri\v2\z <  near ) And (tri\v2\z >  far ) Then
				If (tri\v3\z <  near ) And (tri\v3\z >  far ) Then
		
		
					; Draw triangle wireframe
					Line tri\v1\xw, tri\v1\yw, tri\v2\xw, tri\v2\yw
					Line tri\v2\xw, tri\v2\yw, tri\v3\xw, tri\v3\yw
					Line tri\v3\xw, tri\v3\yw, tri\v1\xw, tri\v1\yw
		
					Text tri\v1\xw, tri\v1\yw, "1"
					Text tri\v2\xw, tri\v2\yw, "2"
					Text tri\v3\xw, tri\v3\yw, "3"
				EndIf
			EndIf
		EndIf
	Next
	
	
	; some little movement to see clipping behaviour
	tri = Last TTriAngle
	tri\v1\z = -5.5+Cos(a)*5.0
	tri\v2\z = -5.5+Cos(a)*5.0
	tri\v3\z = -5.5+Cos(a)*5.0
	a=a+3
	
	
	; key left/right
	If KeyDown(205) Then near=near+.1
	If KeyDown(203) Then near=near-.1
	
	; key up/down
	If KeyDown(200) Then far=far+.1
	If KeyDown(208) Then far=far-.1
	
	Text 0,0, "near clipping plane: "+near
	Text 0,15, "far clipping plane: "+far
	Flip
	Cls
Until KeyHit(1)

Function Projection(vec.TVertex)
	
	; newVector = Projection Matrix * oldVector
	vec\xp = 2*near/width 	* 	vec\x + 0				*	vec\y + 0						*	vec\z + 0*1
	vec\yp = 0				*	vec\x + 2*near/height	*	vec\y + 0						*	vec\z + 0*1
	vec\zp# = 0				*	vec\x + 0				*	vec\y + (far+near)/(near-far)	*	vec\z + -1*1
	vec\wp = 0				*	vec\x + 0				*	vec\y + (2*far*near)/(near-far)	*	vec\z + 0*1
	
	; normalize
	vec\xp = vec\xp/vec\wp
	vec\yp = vec\yp/vec\wp
	
	; calculate viewport coordinates
	vec\xw# = centerX+vec\xp*viewWidth
	vec\yw# = centerY+vec\yp*viewHeight
End Function

Global matrixzahl = 99
Dim matrix#(3,3,matrixzahl)
;0-3 Zellen
;0-3 Spalten

Global vektorzahl = 99
Dim vektor#(3,vektorzahl)
;0-3 Elemente

Function VektorErstellen( vnum, x#,y#,z#,w# )
	vektor(0,vnum) = x
	vektor(1,vnum) = y
	vektor(2,vnum) = z
	vektor(3,vnum) = w
End Function


Function VektorMulMatrix( ausgabevnum, vnum, mnum )
	vektor(0,ausgabevnum) = vektor(0,vnum)*matrix(0,mnum)
	;hier nur angedeutet
End Function