Help with Qbasic Polygon Texture Mapping.

[aliasNIGMA]

I really need help with texture mapping.

Heres the scenario:

3 co-ordinates for a triangle on the screen. (the screen poly)

3 mapping co-ordinates that pertain to a 100 x 100 2d array.

A texture is stored in the 2d array.


I am trying to get the texture information in the mapped polygon to be transfered to the screen polygon.

My problem is, that this screen polygon can be any orientation as can the mapped one.

(This is an ISOMETRIC simulation)

I have tried to keep the example of the situation simple. Ive spent a good deal of time trying to build this code and came close numerous times.

Is there a piece of code or a library that can do this?
HOW?

Lol thanks for any help you might be able to provide.

 

[qbasicking]

I'm not quite sure what you need
You need to be able to rotate it and skew it, is that right?

 

[aliasNIGMA]

The idea is... im trying to transform the picture that falls within the mapped polygon into a completely different polygon on the screen.

I am using triangular polys, and either triangle can have any orientation.

Ive been working on this for a while but I always get something wrong.

Here is a rough code ive been working with:

DECLARE SUB mvconvert (xsratio#, ysratio#, trianglenum!)
DECLARE SUB texload (file$)
DECLARE SUB pal ()
DECLARE SUB drawTRIANGLE (trianglenum!)
DECLARE SUB getSLOPES (trianglenum!)

DIM SHARED texturedim 'texture array dimension

DIM SHARED texture(a, a) AS INTEGER 'texture array

DIM SHARED vx(100) 'vertice arrays
DIM SHARED vy(100)
DIM SHARED vz(100)

DIM SHARED mx(100) AS INTEGER 'mapped vertice arrays
DIM SHARED my(100) AS INTEGER
DIM SHARED mz(100) AS INTEGER

DIM SHARED t1(100) AS INTEGER 'triangle point index arrays
DIM SHARED t2(100) AS INTEGER
DIM SHARED t3(100) AS INTEGER

DIM SHARED rslopeAB AS DOUBLE 'real side slopes
DIM SHARED rslopeAC AS DOUBLE
DIM SHARED rslopeBC AS DOUBLE

DIM SHARED mslopeAB AS DOUBLE 'mapped side slopes
DIM SHARED mslopeAC AS DOUBLE
DIM SHARED mslopeBC AS DOUBLE

DIM SHARED rdistAB AS DOUBLE 'vertical distance between points
DIM SHARED rdistBC AS DOUBLE
DIM SHARED rdistAC AS DOUBLE
DIM SHARED rdistDC AS DOUBLE

DIM SHARED mdistAB AS DOUBLE 'vertical distance between points
DIM SHARED mdistBC AS DOUBLE
DIM SHARED mdistAC AS DOUBLE
DIM SHARED MdistDC AS DOUBLE
DIM SHARED mipcolor

DIM SHARED root$

SCREEN 13
root$ = "d:\docume~1\aliasn~1\mydocu~1\myfile~1\qb\game\"
CALL pal
CALL texload("2.2d&quot

'**************** Temp test values
t1(0) = 0
t2(0) = 1
t3(0) = 2

vx(0) = 50
vy(0) = 50

vx(1) = 100
vy(1) = 50

vx(2) = 75
vy(2) = 95

mx(0) = 20
my(0) = 20

mx(1) = 80
my(1) = 20

mx(2) = 50
my(2) = 80



DO
f$ = INKEY$
'LINE (vx(0), vy(0))-(vx(1), vy(1))
'LINE (vx(2), vy(2))-(vx(1), vy(1))
'LINE (vx(0), vy(0))-(vx(2), vy(2))

'LINE (150 + mx(0), my(0))-(150 + mx(1), my(1))
'LINE (150 + mx(2), my(2))-(150 + mx(1), my(1))
'LINE (150 + mx(0), my(0))-(150 + mx(2), my(2))

CALL getSLOPES(0)

LOCATE 1, 1
PRINT "AB", rslopeAB
PRINT "BC", rslopeBC
PRINT "AC", rslopeAC


CALL drawTRIANGLE(0)


IF RIGHT$(f$, 1) = "H" THEN vy(2) = vy(2) - 5
IF RIGHT$(f$, 1) = "P" THEN vy(2) = vy(2) + 5
IF RIGHT$(f$, 1) = "K" THEN vx(2) = vx(2) - 5
IF RIGHT$(f$, 1) = "M" THEN vx(2) = vx(2) + 5

IF NOT f$ = "" THEN
CLS
LOCATE 10, 10
PRINT mslopeAC
PRINT mslopeAB
PRINT mslopeBC





END IF

LOOP


SUB drawTRIANGLE (trianglenum)

'point of origin is point number one. ix iy are relative to this point.
'
'yside = y value on the side of the triangle
'xside = x value on the side of the triangle
'
'yside2 = y value on the side of the triangle relative to point 2
'xside2 = x value on the side of the triangle relative to point 2
'
'
'rdistAB
'rdistBC

DIM xside AS DOUBLE
DIM xside2 AS DOUBLE
DIM yside AS DOUBLE
DIM yside2 AS DOUBLE
DIM rxpnt AS DOUBLE
DIM rypnt AS DOUBLE
DIM xsratio AS DOUBLE 'transfered variables to map variable converter.
DIM ysratio AS DOUBLE




ix = vx(t1(trianglenum)) 'sets relative points to starting origin.
iy = vy(t1(trianglenum))

'IF rdistAC = 0 THEN rdistAC = .1

IF NOT rdistDC = 0 THEN 'if statements that prevent triangle from being drawn

FOR yside = 0 TO rdistAC STEP rdistAC / rdistDC * .5

xside = yside / rdistAC
xside = yside / rslopeAC
xside2 = vx(t2(trianglenum)) - vx(t1(trianglenum)) + (rdistBC * (yside / -rdistAC) / rslopeBC) 'xside.... other side of triangle relative to origin
yside2 = vy(t2(trianglenum)) - vy(t1(trianglenum)) + (rdistBC * (yside / -rdistAC)) 'yside.... other side of triangle relative to origin


FOR rxpnt = xside TO xside2 STEP .5 '**************mirror trouble here
rypnt = ABS(rxpnt - xside) * rslopeAB
'*** get mapping variables ready

IF NOT (xside2 - xside) = 0 THEN

PSET (vx(t1(0)) + rxpnt, vx(t1(0)) + yside), 31
xsratio = rxpnt / ABS(xside2 - xside)
ysratio = yside / (rdistAC)

END IF


CALL mvconvert(ABS(xsratio), ABS(ysratio), trianglenum)

'PSET (rxpnt + ix, rypnt + yside + iy), 31' mipcolor


NEXT rxpnt

PSET (ix + xside2, iy + yside2), 4
PSET (ix + xside, iy + yside), 4

'SLEEP
NEXT yside


END IF



END SUB


SUB getSLOPES (trianglenum)

IF NOT (vx(t2(trianglenum)) - vx(t1(trianglenum))) = 0 THEN
rslopeAB = (vy(t2(trianglenum)) - vy(t1(trianglenum))) / (vx(t2(trianglenum)) - vx(t1(trianglenum)))
ELSE
rslopeAB = 32000
END IF


IF NOT (vx(t2(trianglenum)) - vx(t3(trianglenum))) = 0 THEN
rslopeBC = (vy(t2(trianglenum)) - vy(t3(trianglenum))) / (vx(t2(trianglenum)) - vx(t3(trianglenum)))
ELSE
rslopeBC = 32000
END IF

IF NOT (vx(t3(trianglenum)) - vx(t1(trianglenum))) = 0 THEN
rslopeAC = (vy(t3(trianglenum)) - vy(t1(trianglenum))) / (vx(t3(trianglenum)) - vx(t1(trianglenum)))
ELSE
rslopeAC = 32000
END IF

IF rslopeAB = 0 THEN rslopeAB = .000001
IF rslopeBC = 0 THEN rslopeBC = .000001
IF rslopeAC = 0 THEN rslopeAC = .000001



mslopeAB = (my(t2(trianglenum)) - my(t1(trianglenum))) / (mx(t2(trianglenum)) - mx(t1(trianglenum)))
mslopeBC = (my(t3(trianglenum)) - my(t2(trianglenum))) / (mx(t3(trianglenum)) - mx(t2(trianglenum)))
mslopeAC = (my(t3(trianglenum)) - my(t1(trianglenum))) / (mx(t3(trianglenum)) - mx(t1(trianglenum)))

rdistAB = (vy(t2(trianglenum)) - vy(t1(trianglenum)))
rdistBC = (vy(t2(trianglenum)) - vy(t3(trianglenum)))
rdistAC = (vy(t3(trianglenum)) - vy(t1(trianglenum)))

mdistAB = (my(t2(trianglenum)) - my(t1(trianglenum)))
mdistBC = (my(t2(trianglenum)) - my(t3(trianglenum)))
mdistAC = (my(t3(trianglenum)) - my(t1(trianglenum)))

IF rdistAB = 0 THEN rdistAB = .000001
IF rdistBC = 0 THEN rdistBC = .000001
IF rdistAC = 0 THEN rdistAC = .000001



dy = (((vy(t2(trianglenum)) - vy(t1(trianglenum))) / 2)) + vy(t1(trianglenum))
dx = (((vx(t2(trianglenum)) - vx(t1(trianglenum))) / 2)) + vx(t1(trianglenum))

rdistDC = SQR((vy(t3(trianglenum)) - dy) ^ 2 + (vx(t3(trianglenum)) - dx) ^ 2)

'rslopeDC = (vy(t3(trianglenum)) - dy) / (vx(t3(trianglenum)) - dx)



PSET (dx, dy), 5

END SUB

SUB mvconvert (xsratio#, ysratio#, trianglenum)

DIM myside AS DOUBLE
DIM mxside AS DOUBLE

'origin is mapped point 1

myside = ysratio# * mdistAC
mxside = myside / mslopeAC

mxside2 = mx(t2(trianglenum)) - mx(t1(trianglenum)) + (mdistBC * (myside / -mdistAC) / mslopeBC) 'xside.... other side of triangle relative to origin
myside2 = -(my(t2(trianglenum)) - my(t1(trianglenum)) + (mdistBC * (myside / mdistAC)))'yside.... other side of triangle relative to origin



mxpt = ABS(mxside2 - mxside) * xsratio# '+ mxside
mypt = ABS(mxpt - mxside) * mslopeAB


'mipcolor = texture(mxpt + mxside + mx(t1(trianglenum)), mypt + my(t1(trianglenum)))

'LOCATE 10, 20
'PRINT mslopeAC
'PRINT myside
'PRINT myside'mx(t1(trianglenum))
'SLEEP

'COLOR RND * 100
'PSET (220 + mxpt, 120 + myside)' + mypt)
PSET (200 + mxpt + mx(t1(trianglenum)), 100 + mypt + myside + my(t1(trianglenum)))
'LINE (200, 100)-(200 + mx(t3(0)), 100 + my(t3(0))), 4


END SUB

SUB pal
CLOSE #1
OPEN root$ + "qb.pal" FOR INPUT AS #1

INPUT #1, a$
INPUT #1, a$
INPUT #1, a$

FOR i = 0 TO 255

INPUT #1, r, g, B

intmod = 0
IF choice = 2 THEN intmod = 60

red = (r \ 4) - intmod
green = (g \ 4) - intmod
blue = (B \ 4) - intmod

IF blue <= 0 THEN blue = 0
IF green <= 0 THEN green = 0
IF red <= 0 THEN red = 0

IF blue >= 63 THEN blue = 63
IF green >= 63 THEN green = 63
IF red >= 63 THEN red = 63

man = 65536 * blue + 256 * green + red

PALETTE i, man

NEXT i
CLOSE #1


END SUB

SUB texload (file$)
zoom = 1
peffect = 0

'file$ = &quot;0&quot;

IF file$ = &quot;&quot; THEN GOSUB picdisplayend
'file$ = file$ + &quot;.2d&quot;

file$ = root$ + file$


OPEN file$ FOR INPUT AS #1

rec = 1
INPUT #1, texboundx
INPUT #1, texboundy
REDIM texture(texboundx, texboundy) AS INTEGER

header = 3


FOR ii = 0 TO texboundy - 1
FOR i = 0 TO texboundx - 1

rec = (i + (ii * texboundy)) + header

INPUT #1, texture(i, ii)
PSET (i + 200, 100 + ii), texture(i, ii)

NEXT i
NEXT ii

CLOSE #1


picdisplayend:
REDIM picarray(0, 0) AS INTEGER

END SUB