carrera3d.bas

' ------------- Carrera 3D ---------------
' ----------- by DMSC - 2015 -------------
'
' Modified to run under FastBasic - 2017

' Reserve memory for graphics and set 160x96 mode
' dlist = display lists pointer.
'         150 bytes per display list, total of 11*6 = 66 display lists,
'         but can't cross 1k boundary => 11KBytes, 44 pages
' gbase = graphic data pointer
'         40 bytes per line, total of 48*4*2 = 384 lines => 15KBytes, 60 pages
dim memory(27647) byte

' display list must be aligned to 1024 bytes:
dlist = (adr(memory)+1023)/1024 * 1024
gbase = dlist + $2C00

' Sets graphics mode, 160x96, 4 colors.
graphics 7
pmgraphics 1

' Sets the start of the image to 255, (full color 3),
' we then use a "move" to copy to all the line.
img = dpeek(88)

' Make display-lists and graphics data
' Size of display list
dlsize = 156
' Loop over all Y values
for y=1 to 48
  r = y+14
  zpos = 19200/r - 300
  p = r/8
  n = (r+p+3)/2
  z = 2*r+p
  ' Loop over the 4 possible X values
  for x=0 to 3
    ' Clean the screen
    mset img, 80, 255
    ' Draws the road with color 1 borders
    color 1
    plot x,1
    drawto p+x,1
    color 0
    drawto z+x-1,1
    color 1
    drawto z+p+x,1
    move img+n, gbase + x * 80, 80
    ' Draw the road with color 2 borders
    color 2
    plot x,1
    drawto p+x,1
    plot z+x,1
    drawto z+p+x,1
    move img+n, gbase + 40 + x * 80, 80
  next x
  ' Now, calculate the shifted track position for each curve value and set
  ' the value in each of the display lists.
  d = dlist + 3 * y
  for curvature=-5 to 5
    ' Calculate the X position
    x = 81 - y * 189/100
    x = ( x*x*curvature/729 + 80 -r -p )
    ' Get the graphics address to print this position
    tmp = gbase + 40 - n + x&3 * 80
    tmp = tmp - x/4
    ' Calculate each of the 6 frames (with shifted Z value)
    for z=zpos to zpos+100 step 17
      poke d,77
      dpoke d+1, tmp + (z/50)&1 * 40
      d = d + dlsize
    next z
    d = d+88
  next curvature
  ' Advance the pointer to the graphics data
  gbase=gbase+320
  ' Fixes crossing over 4KB - this depends on the initial address!!
  if gbase&4095 > $EFF
    gbase = gbase+256
  endif
next y

' Adds display list first and last bytes to all DLs
d = dlist
for curvature=0 to 10
  for z=0 to 5
    ' First, 3 * 8 blank lines
    dpoke d, $7070
    poke d+2, $70
    d = d + dlsize
    ' At end, 8 blank lines, one text window line
    dpoke d-9, $4270
    dpoke d-7, dpeek(660)
    ' Jump to start
    poke d-5, $41
    dpoke d-4, d - dlsize
  next z
  d = d + 88
next curvature

' Clears PM data
mset pmadr(0), 1024, 0

' Our car bitmap data for the PM 0 and 1
data pm1() byte = $18,$18,$18,$3C,$3C,$24,$24,$3C,$00,$18,$18,$3C,$7E,$7E,$00,$FF,$00,$7E,$7E
data pm0() byte = $24,$24,$24,$3C,$3C,$00,$7E,$18,$DB,$C3,$C3,$C3,$FF,$FF,$FF,$C3,$C3,$C3,$C3

' Move to PM
move adr(pm1), pmadr(1)+97, 19
move adr(pm0), pmadr(0)+99, 19

' P/M over playfield and P0+P1 / P2+P3 blends
poke 623,33

' Set color registers
poke 712, 8
dpoke 704, $4482

poke 710, $D2
dpoke 708, $EE52
dpoke 706, $8640

' P0 quad width, P1 double width
dpoke $d008, 259

' P2 shows distance traveled, set a basic shape
dpoke pmadr(2)+131, 511

' Enable ANTIC P/M DMA
poke 559, 58

' Start of game loop
spos = 3000
do

  '# Current "drag"
  drag = 0

  '# Position in track
  trackPos = 0
  '# Current speed
  speed = 0
  '# Track "low" position
  trackLow = 0
  '# Location of "curve" DL ( 1024 * (c+5) )
  curvature = 5
  '# End of current track segment
  segend = 99
  '# Position of car
  x = 1920

  ' Main game loop, starts from "spos".
  ' On first run has a value bigger than the end,
  ' so the race goes straight to the end screen.
  for z=spos to 3000
    ' Waits for VBLANK, read collision register
    pause
    tmp = peek($d004)

    ' Clear collision register
    poke $d01e, 0

    ' Set PM0 and PM1 x coordinates
    pmhpos 0, x/16 - 8
    pmhpos 1, x/16

    ' Sets DL (for next frame)
    dpoke 560, dlist + curvature * 1024 + dlsize * (trackPos mod 6)

    ' Advance track position
    trackLow = trackLow + speed
    trackPos = trackPos + trackLow / 112
    trackLow = trackLow mod 112

    ' "motor" sound. Note the values of frequency=k*31-1 produce pure tones,
    ' but we don't have enough space to filter out.
    sound 0, 255 - speed, 6, 8
    ' Process collisions with the outside of the track
    if tmp
      ' Decreases the speed by 5%
      speed = speed * 19 / 20
    else
      ' Increases the speed, max speed is 2 if button is not pressed, 1 if pressed.
      ' Scaled by 112
      speed = ( 211 + 112 * STRIG(0) + speed * 99 ) / 100
    endif
    ' Read joystick
    tmp = STICK(0)
    ' Updates X position, adds joystick and "drag" times "speed"
    ' As drag is scaled by 50/9, speed by 112, and c by 16, we need to
    ' divide by (50*112)/(9*16) = 38.88 ~ 39
    x = x + (tmp&4) * 4 - (tmp&8) * 2 - drag*speed/39
    ' Test if current track segment is over
    if trackPos > segend
      ' Yes, generate a new segment
      ' (first, set text position to 0)
      poke 657, 0

      ' New random direction
      curvature = rand(11)
      ' Drag is from -0.9 to 0.9 (scaled by 50/9)
      drag = curvature - 5
      ' New random length, from 10 to 110.
      segend=segend+rand(100)+10
      ' Shows the current time and position
      print "T:"; z, "D:"; trackPos,
    endif

    ' Sets the Player 2 position to current track position
    pmhpos 2, 48 + trackPos / 32
  next z

  ' End of game, shows score, turns of sound and waits for keystroke
  print "LAST:"; trackPos,
  sound
  get tmp

  ' Next race starts at time 0 (a full race)
  spos=0
loop