TEXTURE MAPPING (Walls only)

TEXTURE MAPPING (Walls only)

I have been testing and trying to do
texture mapping and I finaly found out
the basics and got it to work. So I
have first written down the matimatical
basics and then a easy to understand
basic code. Hope you find it useful
And if you do then please write me
a note and dont forget to give me some
credit in your production…
First you got your picture in memory,
wich I describe like this:

[code lang=”delphi”]
Xm
+——–+
| |
| | Ym
| |
+——–+
[/code]

And this picture shall be putted out
in this polygone:
[code lang=”delphi”]
X1,Y1
+—___ x2,y2
| —+
| |
| |
| ___—+
+— X3,Y3
X4,Y4

[/code]
Now you only got to do this procedure
every pixel in the polygone:

PLOT X, Y, POINT(Xp, Yp)

Well what is Xp and Yp then?
Well you only got to use theese two
formulas:

[code lang=”delphi”]
Xm*(X-X1)
Xp = ————
X2 -x1

(Y2-Y1)*(X-X1)
Ym*(y-ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ)
X2 -x1
Yp = ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
X*(Y3-Y2-Y4+Y1)
Y4-Y2+ÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄÄ
X2 -x1

[/code]
As a little hint I could say that you
better do this in assembler and that
yoy draw the polygone in columns not
by lines. And make some kind of
delta values and just add in the inner
loops.

Well I maybe shall help you started
with a little test in Basic. You maybe
dont recognise the formula but if you
dont then you better dont try to code
any Texture mapping at all!!!

[code lang=”basic”]FOR X = x1 TO X2
Xp = (Xm * (X – x1)) / (X2 – x1)
Ys = Y1 + ((y2 – Y1) / (X2 – x1) * (X – x1))
Ye = Y4 + ((Y3 – Y4) / (X2 – x1) * (X – x1))
FOR Y = Ys TO Ye
Yp = (Ym * (Y – Y1)) / (Ye – Ys)
PLOT X, Y, POINT(Xp, Yp)
NEXT Y
NEXT X
[/code]
Some more hints is to make the original
picture in a length and width of 32, 64
128 or something equaly easy to ROL
instead of MULU.

Then I in my own code (On ST) got one
seperate precalculated code for every
colour to plot, and one extra for
transparent picture. (Windows) And
the transparent cod is one line long
and includes a RTS so guess what P-time
that one takes!?!

Well thats it, good luck from
PeyloW of T.O.Y.S.

Greetz goes to:
TaM, Thanx for all but coding
Me, Say helo to Josefin.
AIO (Pseudo), Thanx for all muzix.
Hydrogen, Hey there.
Eagle, Havent seen you for a long…
OB, I look forward to SUB STAION.
MF, Min sladd tack !!!
And to all others…

My address if you need it ?!?

PeyloW of T.O.Y.S.
Greby
59042 Horn
Sweden

And phone #:
0494-30404
(I love a long chat but only 18-21)

See ya…

[tags]Delphi, Graphic[/tags]