I've implimented some (but not quite all) of the fixes. The code has been shrunk, some if thens have been ditched and a slight clipping bug fixed, also interpolation bug at the bottom of the triangle has been mended.
Thanks to Jim and Stonemonkey, here's the source with example. Feel free to use it;
' Brand New Assembly Language Flatshaded Triangle Renderer
' Coded by Shockwave / DBF / S!P 2006 Use freely but credit Plz!
' Thanks to Stonemonkey and Jim Shaw for help with this technique.
'
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
OPTION STATIC
OPTION EXPLICIT
CONST XRES = 800
CONST YRES = 600
CONST HALFX = XRES/2
CONST HALFY = YRES/2
DIM SHARED BUFFER ( XRES * YRES ) AS UINTEGER
DIM SHARED AS DOUBLE OLDTIME,GADD
DIM SHARED AS UINTEGER TICKS,NEWTIME
'#define PTC_WIN
#Include Once "tinyptc.bi"
DECLARE SUB DELTA()
DECLARE SUB FLAT_TRIANGLE( BYVAL X1 AS INTEGER , BYVAL Y1 AS INTEGER, BYVAL X2 AS INTEGER , BYVAL Y2 AS INTEGER , BYVAL X3 AS INTEGER, BYVAL Y3 AS INTEGER , BYVAL TC AS INTEGER)
'-------------------------------------------------------------------------
' Open Screen.
'-------------------------------------------------------------------------
If( ptc_open( "TRIANGLE ROUTINE WITH ASSEMBLY LANGUAGE RASTERISING BY SHOCKWAVE^S!P^DBF", XRES, YRES ) = 0 ) Then
End -1
End If
OLDTIME = TIMER
DO
GADD=GADD+.002
DELTA()
FLAT_TRIANGLE(HALFX+500*SIN(GADD),HALFY+400*COS(GADD),HALFX+150*SIN(GADD*2),HALFY+200*COS(GADD*3),HALFX+300*SIN(GADD/2),HALFY+100*COS(GADD*5),&H88FF55)
GADD=GADD+10
FLAT_TRIANGLE(HALFX+500*SIN(GADD),HALFY+400*COS(GADD),HALFX+150*SIN(GADD*2),HALFY+200*COS(GADD*3),HALFX+300*SIN(GADD/2),HALFY+100*COS(GADD*5),&HFF88F55)
GADD=GADD-10
PTC_UPDATE@BUFFER(0)
ERASE BUFFER
TICKS=TICKS+1
LOOP UNTIL INKEY$ = CHR$(27)
SUB FLAT_TRIANGLE(BYVAL X1 AS INTEGER , BYVAL Y1 AS INTEGER, BYVAL X2 AS INTEGER , BYVAL Y2 AS INTEGER , BYVAL X3 AS INTEGER, BYVAL Y3 AS INTEGER , BYVAL TC AS INTEGER)
'-------------------------------------------------------------------------
' FLAT TRIANGLE RENDERER WITH ASSEMBLY LANGUAGE RASTERISING BY SHOCKWAVE ^ DBF ^ S!P 2006.
'-------------------------------------------------------------------------
'-------------------------------------------------------------------------
' WE NEED TO SORT THESE POINTS INTO ORDER FROM TOP TO BOTTOM, AN EXCHANGE SORT IS OK.
' AS WE ONLY HAVE GOT 3 POINTS TO ARRANGE.
'-------------------------------------------------------------------------
DIM AS INTEGER TEMPX,TEMPY,LO,LI
DIM AS INTEGER PX(3)
DIM AS INTEGER PY(3)
DIM TFLAG AS INTEGER
dim pp as uinteger PTR
DIM AS INTEGER IL1,IL2,SLICE
TFLAG=0
PX(1)= X1
PX(2)= X2
PX(3)= X3
PY(1)= Y1
PY(2)= Y2
PY(3)= Y3
FOR LO = 1 TO 2
FOR LI =1 TO 2
IF PY(LI+1) <= PY(LI) THEN
TEMPX = PX(LI) : TEMPY = PY(LI)
PX(LI) = PX(LI+1)
PY(LI) = PY(LI+1)
PX(LI+1) = TEMPX
PY(LI+1) = TEMPY
END IF
NEXT LI
NEXT LO
DIM AS DOUBLE XP1,XP2:' SCREEN POSITIONS.
DIM AS DOUBLE XI1,XI2:' INTERPOLATIONS.
'***
'*** REGULAR TRIANGLE (Y1<Y2 Y2<Y3)
'***
IF PY(1)<PY(2) AND PY(2)<PY(3) or (PY(2) = PY(3)) THEN
TFLAG=1
XP1 = PX(1)
XP2 = PX(1)
XI1 = (PX(1)-PX(2)) / (PY(2) - PY(1))
XI2 = (PX(1)-PX(3)) / (PY(3) - PY(1))
FOR LO = PY(1) TO PY(2)-1
IF LO>=0 AND LO<YRES THEN
IF XP1<=XP2 THEN
IL1=XP1
IL2=XP2
ELSE
IL1=XP2
IL2=XP1
END IF
IF IL2>XRES THEN IL2=XRES
IF IL1<0 THEN IL1=0
SLICE = IL2-IL1
IF SLICE>0 THEN
PP = @BUFFER(IL1+(LO*XRES))
asm
mov eax,dword ptr[TC]
mov ecx, [slice]
mov edi, [PP]
rep stosd
end asm
END IF
END IF
XP1=XP1-XI1
XP2=XP2-XI2
NEXT
XI1 = (PX(2)-PX(3)) / (PY(3) - PY(2))
XP1 = PX(2)
FOR LO = PY(2) TO PY(3)
IF LO>=0 AND LO<YRES THEN
IF XP1<=XP2 THEN
IL1=XP1
IL2=XP2
ELSE
IL1=XP2
IL2=XP1
END IF
IF IL2>XRES THEN IL2=XRES
IF IL1<0 THEN IL1=0
SLICE = IL2-IL1
IF SLICE>0 THEN
PP = @BUFFER(IL1+(LO*XRES))
asm
mov eax,dword ptr[TC]
mov ecx, [slice]
mov edi, [PP]
rep stosd
end asm
END IF
END IF
XP1=XP1-XI1
XP2=XP2-XI2
NEXT
END IF
'***
'*** FLAT TOPPED TRIANGLE Y1=Y2
'***
IF TFLAG=0 AND PY(1) = PY(2) THEN
TFLAG=1
XP1 = PX(1)
XP2 = PX(2)
XI1 = (PX(1)-PX(3)) / (PY(3) - PY(1))
XI2 = (PX(2)-PX(3)) / (PY(3) - PY(2))
FOR LO = PY(1) TO PY(3)
IF LO>=0 AND LO<YRES THEN
IF XP1<=XP2 THEN
IL1=XP1
IL2=XP2
ELSE
IL1=XP2
IL2=XP1
END IF
IF IL2>XRES THEN IL2=XRES
IF IL1<0 THEN IL1=0
SLICE = IL2-IL1
IF SLICE>0 THEN
PP = @BUFFER(IL1+(LO*XRES))
asm
mov eax,dword ptr[TC]
mov ecx, [slice]
mov edi, [PP]
rep stosd
end asm
END IF
END IF
XP1=XP1-XI1
XP2=XP2-XI2
NEXT
END IF
END SUB
'-------------------------------------------------------------------------
' TIMER MANAGEMENT;
'-------------------------------------------------------------------------
SUB DELTA()
DIM Z AS UINTEGER
IF TIMER-OLDTIME>=1 THEN
NEWTIME = TICKS
OLDTIME = TIMER
PRINT "FPS:"+STR$(NEWTIME)
TICKS =0
END IF
END SUB
