2 replies to this topic

[R3sistance]

does anybody know how to program qbasic 3d objects so they appear where they should and use rotation on an object. i can't do most of this i checked qbasic 3d enchanced but they don't explain it clearly enough. . Edited by - R3sistance on October 5, 2001 7:08:29 AM

[Dracoliche]

Well, if you're using qbasic to display 3D graphics, my advice is: get one of those library thingies, like DirectQB. This site has a few 3D demos, IIRC: http://www.neozones.cjb.net/. All the ones that run at an appreciable speed use a library of some sort. As for the maths involved, I can't help much there sorry
3D graphics in qbasic are a pain in the bum and don't work very well to boot.

Edited by - Dracoliche on October 5, 2001 9:31:47 AM

[TerranFury]

The best way to do serious graphics in QB, short of using an external library, is to fill one of those PUT arrays yourself using POKE, and then PUT it on the screen. This is the only way you can do pixel plotting with any kind of speed short of using ASM. I think you'll end up using MODE 13 (known as 13h to C++ and ASM programmers)

Here's an example that will fill the screen with "static":

'$DYNAMIC

DEFINT A-Z



SCREEN 13

'320 x 200



CLS



'Make grayscale pallette (0 = black; 255 = white)



DIM v AS INTEGER

FOR v = 0 TO 255

OUT &H3C8, v                   'color index

OUT &H3C9, INT(v * (63 / 255)) 'r

OUT &H3C9, INT(v * (63 / 255)) 'g

OUT &H3C9, INT(v * (63 / 255)) 'b

NEXT v



'Note: ArraySize = ((ScreenWidth * ScreenHeight) + 4) * (BPP / 16) = 32002

DIM pixels(32002) AS INTEGER    'Create array



DIM memloc AS LONG

memloc = VARSEG(pixels(0))      'Get memory location of array



' Write header.

' 1st 2 words = width * 8

' 2nd 2 words = height * 1

' Note: word = 2 bytes = 16 bits = 1 Integer Variable

pixels(0) = 320 * 8

pixels(1) = 200



DEF SEG = memloc              'Gain direct access to array memory



    offset = 4

    FOR y = 0 TO 199

        FOR x = 0 TO 319

            POKE offset, INT(RND * 256) 'Put random value at x, y

            offset = offset + 1

        NEXT x

    NEXT y



DEF SEG



PUT (0, 0), pixels, PSET



  

There may be errors in this code; but I'm sure that it'll get you headed along the right track. The people at qbasic.com should be able to help you.

Once you can do fast pixel-plotting using the aforementioned technique (PSET is SLOOOOOOW) then you'll just have to do the same old 3d projection and tranformation stuff everyone else does.

That is:
screen_x = vertex.x / vertex.z
screen_y = vertex.y / vertex.z

You can find a simple tutorial at http://www.qbasicnews.com/files/Tutorials/tutor8.txt. It isn't the greatest in the world, but it's a start.

Hope that helps.

Edited by - TerranFury on October 8, 2001 3:32:07 PM