' Adapted code from Microsoft Small Basic Example
' smallbasic.com
' smallbasic.com/program/?LZW978
'
' original upload code:- ?BRS931
' new uploda code LZW978
' Raycaster maze
' uses a simple ray casting technique (see lodev.org for tutorial) to draw
' vertical stripes down the graphics window.
' Each stripe is drawn to a size dependent upon the distance of the wall from the viewer.
' "Rays" are cast across a viewing plane in front of the viewer, from left to right.
' the height of the wall stripe depends on the distance of the wall from the viewer.

InitialSetUp:
' set up screen width and height
' values also used to determine the width and height of the "viewing plane"
' "size" is used to determine the width of each vertical line drawn.
' a smaller value makes the walls sharper, but draws slower (there are more lines)
' a larger value makes the walls blockier, but draws more quickly
'w = 511
'h = 384
Mode 4
w = MM.HRes
h = MM.VRes
size = 8
'intensity of light source. The lower the number the further you can see.
intensity = 50
'
' set up the player's start position and direction
' these are the x/y co-ordinates of the world map
' nb absolute values place the player at grid intersections!!
posX = 5.5
posY = 10.5
dirX = 1
dirY = 1
planeX = 0
'
' plane y is the size of the viewing plane in degrees
' (altering this gives different perspective views)
planeY = 0.66
completed = 1
'
' movespeed is how far forward you move each step.
' bigger values create bigger steps, lower values mean smaller (smoother) steps
' rotspeed is how much you rotate left/right when you turn
' a value of 1/3 of rotspeed seems about right
moveSpeed = 0.2
rotSpeed = 0.07

' call the setupmap subroutine to draw the initial map view
setupmap()
main()

Do
Movement

Loop Until KeyDown=27


Sub Movement
keypress = KeyDown
If keypress > 0 Then
'ensures that will not try to draw, when previous frame is still drawing
moveX = dirX * movespeed
moveY = dirY * movespeed
' checks that nothing is in front then moves forward
If keypress = 128 Then
If worldMap(Int(posX + moveX),Int(posy)) = 0 Then
posX = posX + moveX
EndIf
If worldMap(Int(posx),Int(posY + moveY)) = 0 Then
posY = posY + moveY
EndIf
EndIf
' checks that nothing is in behind then moves backwards
If keypress = 129 Then
If worldMap(Int(posX - dirX * moveX,Int(posy)) = 0 Then
posX = posX - moveX
EndIf
If worldMap(Int(posx),Int(posY - moveY)) = 0 Then
posY = posY - moveY
EndIf
EndIf
' rotate the view anticlockwise if turning left
If keypress = 130 Then
oldDirx = dirX
CosrotspeedL = Cos(-1 * rotspeed)
SinrotspeedL = Sin(-1 * rotspeed)
dirX = dirX * CosrotspeedL - dirY * SinrotspeedL
dirY = oldDirX * SinrotspeedL + dirY * CosrotspeedL
oldPlanex = planeX
planeX = planeX * CosrotspeedL - planeY * SinrotspeedL
planeY = oldPlaneX * SinrotspeedL + planeY * CosrotspeedL
'
'
EndIf
' rotate the view clockwise if turning right
If keypress = 131 Then
oldDirx = dirX
CosrotspeedR = Cos(rotspeed)
SinrotspeedR = Sin(rotspeed)
dirX = dirX * CosrotspeedR - dirY * SinrotspeedR
dirY = oldDirX * SinrotspeedR + dirY * CosrotspeedR
oldPlaneX = planeX
planeX = planeX * CosrotspeedR - planeY * SinrotspeedR
planeY = oldPlaneX * SinrotspeedR + planeY * CosrotspeedR
'
'
EndIf
'call main subroutine to draw the new frame/view
main()
EndIf
End Sub


Sub main
completed = 0
For x = 0 To w / size ' calculate ray position and direction
cameraX = (2*x)/(w/size) - 1 ' x-coordinate in camera space
rayPosX = posX
rayPosY = posY
rayDirX = dirX + planeX * cameraX
rayDirY = dirY + planeY * cameraX
'
'which box of the map we're in
mapX = Int(rayPosX)
mapY = Int(rayPosY)

' length of ray from current position to next x or y-side
sideDistX = 0
sideDistY = 0

' length of ray from one x or y-side to next x or y-side
deltaDistX = Sqr(1 + (rayDirY * rayDirY) / (rayDirX * rayDirX))
deltaDistY = Sqr(1 + (rayDirX * rayDirX) / (rayDirY * rayDirY))
perpWallDist = 0

'what direction to step in x or y-direction (either +1 or -1)
stepX = 0
stepY = 0
hit = 0 ' was there a wall hit?
side = 0 ' was a NS or a EW wall hit?

' calculate step and initial sideDist
If rayDirX < 0 Then
stepX = -1
sideDistX = (rayPosX - mapX) * deltaDistX
Else
stepX = 1
sideDistX = (mapX + 1.0 - rayPosX) * deltaDistX
EndIf
If rayDirY < 0 Then
stepY = -1
sideDistY = (rayPosY - mapY) * deltaDistY
Else
stepY = 1
sideDistY = (mapY + 1.0 - rayPosY) * deltaDistY
EndIf

' perform DDA
' trace a "ray" until it hits a wall, and determine if it's an "X" (horizontal) or "Y" (vertical) wall
Do
' jump to next map square, OR in x-direction, OR in y-direction
If sideDistX < sideDistY Then
sideDistX = sideDistX + deltaDistX
mapX = mapx + stepX
side = 0
Else
sideDistY = sideDistY + deltaDistY
mapY = mapy + stepY
side = 1
EndIf

' Check if ray has hit a wall
If worldMap(mapX,mapY) > 0 Then
hit = 1
EndIf
Loop While hit=0

' Calculate distance projected on camera direction.
If side = 0 Then
perpWallDist = Abs((mapX - rayPosX + (1 - stepX) / 2) / rayDirX)
Else
perpWallDist = Abs((mapY - rayPosY + (1 - stepY) / 2) / rayDirY)
EndIf
' Calculate height of line to draw on screen
lineHeight = Int(Abs(h / perpWallDist))+1

'if height if line to be drawn is > than height of graphics window then limit height of line
If lineHeight > h Then
lineHeight = h
EndIf
'
' calculate lowest and highest pixel to fill in current stripe
drawStart = (lineHeight * -1) / 2 + h / 2
If drawStart < 0 Then
drawStart = 0
EndIf
drawEnd = lineHeight / 2 + h / 2
If drawEnd >= h Then
drawEnd = h - 1
EndIf


'draw the pixels of the stripe as a vertical line
'
' if the colour intensity is > 0 then draw the line,
Line (x*size,drawstart)-((x*size)+size,drawend),worldmap(mapx,mapy),bf
Line (x*size,0)-((x*size)+size,drawstart),0,bf
Line (x*size,drawend)-((x*size)+size,h),0,bf
Next
completed = 1
End Sub


Sub setupmap
Dim worldmap(22,22)
mapwidth = 21
mapheight = 21
'define the map in the mapline array as strings
Data 1,5,5,5,5,5,5,1,1,1,1,1,1,1,1,5,5,5,5,5,5
Data 6,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,5
Data 6,0,0,0,0,0,0,0,2,0,0,0,0,0,5,0,0,0,0,5,1
Data 6,0,0,0,0,0,0,0,0,0,0,0,3,0,5,0,0,0,0,5,1
Data 6,0,0,0,0,0,0,0,2,6,0,0,3,0,5,0,2,2,2,0,1
Data 6,0,4,0,2,0,0,0,6,0,0,0,0,0,5,0,0,0,0,0,1
Data 6,0,4,0,3,1,0,0,6,0,1,6,6,0,4,4,4,4,4,4,1
Data 6,0,0,0,0,0,0,0,0,0,1,0,0,0,4,0,0,0,0,0,1
Data 6,0,0,2,3,0,0,0,0,0,1,0,0,0,4,0,0,0,0,0,1
Data 1,0,0,0,0,0,0,0,0,0,0,0,0,0,4,0,0,0,0,0,3
Data 1,0,0,0,0,2,2,0,0,0,2,2,0,0,0,0,0,0,0,0,3
Data 1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3
Data 1,0,0,0,0,2,2,0,0,0,2,2,0,0,0,3,3,3,0,3,3
Data 1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3,3,0,3,1
Data 1,0,3,3,3,3,3,1,1,1,1,1,1,1,1,0,1,1,0,1,1
Data 1,0,0,0,0,0,0,1,1,1,1,0,0,0,0,0,0,0,0,0,2
Data 1,0,0,0,0,0,0,0,1,1,1,0,0,0,0,0,0,0,0,0,2
Data 1,0,0,2,0,0,0,0,0,1,1,0,0,0,0,0,0,0,0,0,2
Data 1,0,0,0,0,0,0,0,0,1,1,6,5,4,3,2,1,1,3,0,2
Data 1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,3
Data 1,1,1,1,1,1,1,1,1,1,1,6,5,4,3,2,1,1,2,2,2

'
' define some parameters that state how big the map is
mapsizex = mapwidth
mapsizey = mapheight
'
'try to read this in and convert it into a two dimensional array
For yloop = 1 To mapheight
For xloop = 1 To mapwidth
Read worldmap(xloop,yloop)
Next
Next
End Sub

If worldMap(Int(posX - dirX * moveX,Int(posy)) = 0 Then

If worldMap(Int(posX - dirX * moveX),Int(posy)) = 0 Then