View a vehicle track on a ground grid

palmering · Post by **palmering** » Tue Dec 04, 2007 10:43 am

Hi,
I want to do a program which plots a vehicle running on the ground with a square grid from driver's point of view. I don't need drawing the vehicle but I would want draw the track as it is traveled.
The grid has to rotate and move freely.
Can anyone help me?

This is a modified version of a moving 3d objet. It may be useful.

Code: Select all

'Shaded 3-D animation with shadows [solid5.bas] for QB4.5/PDS
'By Rich Geldreich 1992
'Modified by Palmering 2007 (sorry Rich!)
'Notes...
'   The PolyFill routine is the major  bottleneck  of  this  program.
'QB's  LINE  command isn't as fast as I would like it to be...  On my
'286-10, the speed isn't that bad (after all, this is all-QB!).  On a
'386 or 486, this thing should fly...  [hopefully]
'   This program is 100% public domain- but  of  course  please  give
'some credit if you use anything from this program.  Thanks!
DEFINT A-Z
DECLARE SUB DrawLine (xs%, ys%, xe%, ye%, EdgeList() AS ANY)
DECLARE SUB DrawObject ()
DECLARE SUB EdgeFill (EdgeList() AS ANY, YLow%, YHigh%, C%)
DECLARE SUB PolyFill (x1%, y1%, x2%, y2%, x3%, y3%, C%)
DECLARE SUB RotatePoints ()
 
CONST True = -1, False = 0
 
TYPE EdgeType              'for fast polygon rasterization
		Low         AS INTEGER
		High        AS INTEGER
END TYPE
TYPE PointType
		XObject     AS INTEGER 'original coordinate
		ZObject     AS INTEGER 'rotated coordinate
		XWorld      AS INTEGER
		ZWorld      AS INTEGER
		XView       AS INTEGER 'rotated & translated coordinate
		YView       AS INTEGER
END TYPE
TYPE PolyType
		P1          AS INTEGER '3 points which make up the polygon (points
		P2          AS INTEGER 'to the point list array)
		P3          AS INTEGER
END TYPE
 
DIM SHARED EdgeList(199) AS EdgeType
DIM SHARED SineTable(359 + 90) AS LONG 'cos(x)=sin(x+90)
DIM SHARED R1, R2, R3, ox, oy, oz
DIM SHARED MaxPoints, MaxPolys, MaxLines
 
DIM SHARED Polys(100) AS PolyType
DIM SHARED Points(100) AS PointType

DIM SHARED s, XLow(1), XHigh(1), YLow(1), YHigh(1)
 
MaxPoints = 7  'Surface
'Points follow...
DATA -100,-100, -100,100, -1,100, -1,-100
DATA 1,-100, 1,100, 100,100, 100,-100
MaxPolys = 3
DATA 3,0,1, 3,1,2, 7,4,5, 7,5,6


FOR a = 0 TO MaxPoints
		READ Points(a).XObject, Points(a).ZObject
NEXT

FOR a = 0 TO MaxPolys
		READ Polys(a).P1, Polys(a).P2, Polys(a).P3
NEXT

'Precalculate the sine table
a = 0

FOR a! = 0 TO (359 + 90) / 57.29 STEP 1 / 57.29
		SineTable(a) = SIN(a!) * 1024: a = a + 1
NEXT
 
PRINT "Strike a key...": DO: LOOP WHILE INKEY$ = ""
 
R1 = 0: R2 = 0: R3 = 330      'three angles of rotation
ox = 0: oy = 0: oz = 300 'object's origin (this program cannot
					'currently handle the object when it goes   
				'behind the viewer!)
s = 1: t = 0
 
SCREEN 7, , 0, 0
OUT &H3C8, 0                'set 16 shades
FOR a = 0 TO 15
	OUT &H3C9, (a * 255) \ 15    'R
	OUT &H3C9, (a * 255) \ 15    'G
	OUT &H3C9, (a * 255) \ 15    'B
	IF a = 7 THEN OUT &H3C7, 16: OUT &H3C8, 16
NEXT

SCREEN 7, , 1, 0
 
YHigh(0) = -32768: ShadowYHigh(0) = -32768
YHigh(1) = -32768: ShadowYHigh(1) = -32768
DO
		'Flip active and work pages so user doesn't see our messy drawing
		SCREEN 7, , s, t: SWAP s, t
 
		'Wait for vertical retrace to reduce flicker
		WAIT &H3DA, 8
 
		'Erase the old image from the screen
		IF YHigh(s) <> -32768 THEN
			IF YHigh(s) < 100 THEN
				LINE (XLow(s), YLow(s))-(XHigh(s), YHigh(s)), 0, BF
			ELSEIF YLow(s) < 100 THEN
				LINE (XLow(s), YLow(s))-(XHigh(s), 99), 0, BF
				LINE (XLow(s), 100)-(XHigh(s), YHigh(s)), 0, BF
			ELSE
				LINE (XLow(s), YLow(s))-(XHigh(s), YHigh(s)), 0, BF
			END IF
		END IF
		RotatePoints
 
		XLow(s) = 32767: XHigh(s) = -32768
		YLow(s) = 32767: YHigh(s) = -32768
		DrawObject
 
		R1 = (R1 + D1) MOD 360: IF R1 < 0 THEN R1 = R1 + 360
		R2 = (R2 + D2) MOD 360: IF R2 < 0 THEN R2 = R2 + 360
		R3 = (R3 + D3) MOD 360: IF R3 < 0 THEN R3 = R3 + 360
		oz = oz + dz: ox = ox + dx: oy = oy + dy
		IF oz < 300 THEN            'determina limite acercamiento zoom
			oz = 300: dz = 0
		ELSEIF oz > 8000 THEN       'determina limite alejamiento zoom
			oz = 8000: dz = 0
		END IF
		IF ox <4000> 4000 THEN
			ox = 4000: dx = 0
		END IF
		a$ = INKEY$
		SELECT CASE a$
		CASE "4"
	D1 = D1 - 1
		CASE "6"
	D1 = D1 + 1
		CASE "8"
	D2 = D2 - 1
		CASE "2"
	D2 = D2 + 1
		CASE "5"
	D1 = 0: D2 = 0: D3 = 0
		CASE "0"
	R1 = 0: R2 = 0: R3 = 0
	D1 = 0: D2 = 0: D3 = 0
	oz = 500: ox = 0: oy = 0
	dx = 0: dz = 0: dy = 0
		CASE "+"
	D3 = D3 + 1
		CASE "-"
	D3 = D3 - 1
		CASE "/"
	dy = dy + 1
		CASE "*"
	dy = dy - 1
CASE CHR$(27)
	END
		CASE CHR$(0) + CHR$(72)
	dz = dz + 5
		CASE CHR$(0) + CHR$(80)
	dz = dz - 5
		CASE CHR$(0) + CHR$(77)
	dx = dx + 5
		CASE CHR$(0) + CHR$(75)
	dx = dx - 5
		END SELECT
LOOP

'Enters a line into the edge list. For each scan line, the line's
'X coordinate is found. Notice the lack of floating point math in this
'subroutine.
SUB DrawLine (xs, ys, xe, ye, EdgeList() AS EdgeType)
 
		IF ys > ye THEN SWAP xs, xe: SWAP ys, ye
 
		IF ye <0> 199 THEN EXIT SUB

		IF ys < 0 THEN
	xs = xs + ((xe - xs) * -ys) \ (ye - ys)
	ys = 0

		END IF
 
		xd = xe - xs
		yd = ye - ys
 
		IF yd <0> 199 THEN ye = 199
 
		xdirect = SGN(xd) + xi
 
		FOR Y = ys TO ye
	IF xs <EdgeList> EdgeList(Y).High THEN EdgeList(Y).High = xs
 
	xr = xr + xrs
	IF xr > 0 THEN
			xr = xr - yd
			xs = xs + xdirect
	ELSE
			xs = xs + xi
	END IF
		NEXT
 
END SUB

SUB DrawObject
 
'Plot the polygons.
FOR a = 0 TO MaxPolys
	P1 = Polys(a).P1: P2 = Polys(a).P2: P3 = Polys(a).P3
	PolyFill (Points(P1).XView), (Points(P1).YView), (Points(P2).XView), (Points(P2).YView), (Points(P3).XView), (Points(P3).YView), 15 '(Polys(a).Intensity)
NEXT

END SUB

SUB EdgeFill (EdgeList() AS EdgeType, YLow, YHigh, C)
		FOR a = YLow TO YHigh
	LINE (EdgeList(a).Low, a)-(EdgeList(a).High, a), C
		NEXT
END SUB

'Draws a polygon to the screen. Simply finds the start and stop X
'coordinates for each scan line within the polygon and uses the
'LINE command for filling.
SUB PolyFill (x1, y1, x2, y2, x3, y3, C) 'for QB 4.5 guys
 
		'find lowest and high X & Y coordinates
		IF y1 < y2 THEN YLow = y1 ELSE YLow = y2
		IF y3 <YLow> y2 THEN YHigh = y1 ELSE YHigh = y2
		IF y3 > YHigh THEN YHigh = y3
 
		IF x1 < x2 THEN XLow = x1 ELSE XLow = x2
		IF x3 <XLow> x2 THEN XHigh = x1 ELSE XHigh = x2
		IF x3 > XHigh THEN XHigh = x3
 
		IF YLow <0> 199 THEN YHigh = 199
 
		IF XLow <XLow> XHigh(s) THEN XHigh(s) = XHigh
 
		IF YLow <YLow> YHigh(s) THEN YHigh(s) = YHigh
 

		'check for polygons which cannot be visible
		IF YHigh <0> 199 OR XLow > 319 OR XHigh <0> 300 THEN STOP
 
	Points(a).XWorld = x2
	Points(a).ZWorld = z3
NEXT

EXIT SUB
 
Rotate3D:
		x1 = (xo * c1& - zo * s1&) \ 1024 'yaw
		z1 = (xo * s1& + zo * c1&) \ 1024
 
		z3 = (z1 * c3& - yo * s3&) \ 1024 + oz 'pitch
		y2 = (z1 * s3& + yo * c3&) \ 1024
 
		x2 = (x1 * c2& + y2 * s2&) \ 1024 + ox 'roll
		y3 = (y2 * c2& - x1 * s2&) \ 1024 + oy
 
RETURN
END SUB

Thanks a lot

Codemss · Post by **Codemss** » Tue Dec 04, 2007 12:55 pm

Well, I don't that anybody from this site will give you the code, but let me give you a little advice. First: do you know ANYTHING about 3d?
No -> Get a tutorial(look on the tutorials section of Petes site).
Yes -> Read on.

First, try to code it yourself. If you don't know where to start, describe what you want to archieve, and then ask how to do that. Still nobody will give you an engine or something, but I'm sure you will be helped.
If you know where to start, start coding until you run into a problem. Describe your problem here and ask for help.

I'd be happy to help you, but I won't write a complete engine for you. Cya!

palmering · Post by **palmering** » Tue Dec 04, 2007 1:39 pm

Codemss wrote:Well, I don't that anybody from this site will give you the code, but let me give you a little advice. First: do you know ANYTHING about 3d?
No -> Get a tutorial(look on the tutorials section of Petes site).
Yes -> Read on.

First, try to code it yourself. If you don't know where to start, describe what you want to archieve, and then ask how to do that. Still nobody will give you an engine or something, but I'm sure you will be helped.
If you know where to start, start coding until you run into a problem. Describe your problem here and ask for help.

I'd be happy to help you, but I won't write a complete engine for you. Cya!

Ok, you're right. I don't need a complete engine at all. I've read a lot of tutorials and at last I found the above-mentioned code which is similar to what I want to do. I understood it. The diference is that this code just draws some polygons and shows them. You can rotate, zoom in/out and move with keys. Instead, I want to draw an infinite surface with a grid in perspective and it moving around.
Perhaps someone did something similar.

Post by **burger2227** » Tue Dec 04, 2007 2:18 pm

A 286? Wow, you need something a little faster. Try it on a friends machine and good luck. My old lady tossed mine out when she tossed me out. Unfortunately, I did not end up in the same garbage bin!

I had a ton of good DOS games on that sucker!

Ted

Codemss · Post by **Codemss** » Tue Dec 04, 2007 3:12 pm

Ow sorry. I thought you meant to built that code out to an engine or something. Thought you was a noob haha.

I think you can just take a polyfiller from somewhere (or make your own if you can, else you can try to learn it, I believe it ain't that hard).

Then you have to sort the polygons on z-center (average of 3 points). Then draw them using the z-center (so that the fartherst polygons are drawed the first, and possibly overdrawed by polygons that are closer).
Just draw all polygons like that, maybe you have to clip it(maybe it is smart to make 2 subs, normalpoly, that you call when all the points where the poly consists from are on the screen, and clippoly that you call when the poly needs to be clipped. if none of the points of the poly is on the screen, then you may still need to display it).

You might want to learn about Gauraud, lambert and (fake) phong shading, maybe about environment mapping.
You can find tut's on the tutorials section on petesqbsite. I like the series of Relsoft, but there are plenty of others also.
Greets,

Codemss