Скачать 2D-BumpMapping Tutorial

01.03.1998
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2d-bumpmapping is one of the simplest and at least I think
it looks very nice. In this tutorial you will learn to make
a simple bumpmapper for your demo,game or whatever. I will
write the code in pascal, but it shouldn't be too hard to
translate it to C++ or so.

What is bumpmapping?
For those of you nerds who doesn't know what bumpmapping is
I can tell you it's a cool effect that make the surface of
something look bumpy. Look at the example file.


The first thing we have to have is a environmentmap. That
is the lightsource it self. It looks pretty much like a
phong light, if you have seen one. The environmentmap
is a 256*256 array or bytes.

environmentmap=Array[0..255,0..255]of byte;

Now if you use TP 7.0 like me, you have to be a litte sad.
Cause TP can't handle arrays that big. It's one byte too big.
So this is the one I use:
environmentmap=Array[0..255,0..254]of byte;

Procedure CreateEnvironmentMap;
var i,j:integer; nX,nY,nZ:real; (float)
begin
for i := 0 to 255 do
 for j := 0 to 254 do begin
   nX:=(i-128)/128;
   nY:=(j-128)/128;
   nZ:=1-sqrt(nX*nX+nY*nY);      (*get the unit vector*)
   if nz<0 then nZ:=0;
   environmentmap[i,j]:=Round(nZ*256);
  end;
end;

Now, that was very difficult, was it. It won't get any harder either.

You will have to have some kind of array that is the surface to be
bumpmapped. I use a virtual screen for mine. Dark color in the
surface are high and bright colors are low.

Then, for every pixel you draw you check the pixels closest neighbours.

  nx:=bumpmap[x-1,y]-bumpmap[x+1,y];
  ny:=bumpmap[x,y-1]-bumpmap[x,y+1];

Then the distance from the pixel to the centre of the light

  lx:=x-lightx; (*Where lightx and lighty is the position of the*)
  ly:=y-lighty; (*light i.e 160,100*)

Then decrement the nx and ny values with lx and ly.
After that, increment nx and ny with 128;

Check that it's in the range
  if (nx<0) or (nx>255) then nx:=0;
  if (ny<0) or (ny>255) then ny:=0;
The draw the pixel
  putpixel(i,j,environmentmap[nx,ny]);

That it, pretty simple, isn't it. Now, why is this effect useful.
Well, you can do some really cool demoeffect, like a combined plasma
and bumpmapper. A maybe you the effect in games.
How about a C&C clone with bumpmapped ground.
Would, look a lot more realistic.
Bumpmapping is also used in 3d-games. The only one i've seen yet is
the faboulos game: MechWarrior 2: Mercheneries. The ground in some
levels is bumpmapped, very nice. BTW, the code contained in the
package wont compile without my units, so it's only for your viewing
pleasure.