TheBackShed.com

Forum Index : Microcontroller and PC projects : PicoMiteVGA: Framework for ray casting using the DDA method

Posted: 03:55pm 08 Feb 2026 Copy link to clipboard	Martin H. Guru

DDA method (Digital Differential Analyser).Much faster than my previous attempts.

' Raycaster 2 in MMBasic, DDA method (Digital Differential Analyser)
mmb4w=0
CLS
If mmb4w Then
MODE -7 :CLS RGB(cyan)
PAGE WRITE 1
Else
MODE 2: CLS RGB(cyan)
FRAMEBUFFER create:FRAMEBUFFER write f
End If
CLS
mapS=64:mapy=24:mapx=24
' --- Labyrinth Definition ---
Dim mapW = 57
Dim mapH = 51
Dim m(mapW, mapH)
Restore MapData1
For y = 0 To mapH-1 :Read k$:k$=k$+"1"
For x=0 To Len(k$):m(x, y)=Val(Mid$(k$,x+1,1)):Next :Next
'For y = 0 To mapH-1 : For x = 0 To mapW-1 : Read m(x, y) : Next x : Next y
' --- Player Setup ---
px = 26.5 : py = 45.5
dx = 1.0 : dy = 0.5
planeX = 0.0 : planeY = 0.66
moveSpeed = 0.2
rotSpeed = 0.1
buffer = 0.2
' --- Grafic Setup ---
resStep = 2
scrW = MM.HRES*.75
scrH = MM.VRES*.75

' Flag to force the first frame
needsRedraw = 1

Do
' Only paint when something has changed
If needsRedraw = 1 Then
' Ceiling and floor
Box 0, 0, scrW, scrH/2, 0, RGB(0,128,255), RGB(0,128,255)
Box 0, scrH/2, scrW, scrH/2, 0, RGB(255,128,0), RGB(255,128,0)
'DDA
For x = 0 To scrW - 1 Step resStep
cameraX = 2 * x / scrW - 1
rayDx = dx + planeX * cameraX
rayDy = dy + planeY * cameraX
mx = Int(px) : my = Int(py)

If rayDx = 0 Then dDx = 1e30 Else dDx = Abs(1 / rayDx)
If rayDy = 0 Then dDy = 1e30 Else dDy = Abs(1 / rayDy)

If rayDx < 0 Then
stepX = -1 : sdX = (px - mx) * dDx
Else
stepX = 1 : sdX = (mx + 1.0 - px) * dDx
End If
If rayDy < 0 Then
stepY = -1 : sdY = (py - my) * dDy
Else
stepY = 1 : sdY = (my + 1.0 - py) * dDy
End If
hit = 0
Do While hit = 0
If sdX < sdY Then
sdX = sdX + dDx : mx = mx + stepX : side = 0
Else
sdY = sdY + dDy : my = my + stepY : side = 1
EndIf
If m(mx, my) > 0 Then hit = 1
Loop
If side = 0 Then pDist = (sdX - dDx) Else pDist = (sdY - dDy)
If pDist < 0.1 Then pDist = 0.1

lH = Int(scrH / pDist)
yS = (scrH / 2) - (lH / 2)
wallCol = RGB(GREEN)
If side = 1 Then wallCol = RGB(0, 128, 0)
Box x, yS, resStep, lH, , wallCol
Next x
If mmb4w Then
PAGE WRITE 0:Blit 0,0,0,0,scrW,scrH,1:PAGE WRITE 1
Else
FRAMEBUFFER write n
Text 290,0,"X="+Str$(Int(px))+" "
Text 290,12,"Y="+Str$(Int(py))+" "
FRAMEBUFFER write f
Blit framebuffer F,N,0,0,0,0,scrW,scrH
End If
needsRedraw = 0 ' Reset Redraw Flag
End If

' Wait for button (does not block, but checks efficiently)
k$ = UCase$(Inkey$)
If k$ <> "" Then
' Enable redraw when a movement key is pressed
If Instr("WASD", k$) > 0 Then needsRedraw = 1
Select Case k$
Case "W"
If m(Int(px + dx * buffer), Int(py)) = 0 Then px = px + dx * moveSpeed
If m(Int(px), Int(py + dy * buffer)) = 0 Then py = py + dy * moveSpeed
Case "S"
If m(Int(px - dx * buffer), Int(py)) = 0 Then px = px - dx * moveSpeed
If m(Int(px), Int(py - dy * buffer)) = 0 Then py = py - dy * moveSpeed
Case "D"
oldDx = dx : dx = dx * Cos(rotSpeed) - dy * Sin(rotSpeed)
dy = oldDx * Sin(rotSpeed) + dy * Cos(rotSpeed)
oldPx = planeX : planeX = planeX * Cos(rotSpeed) - planeY * Sin(rotSpeed)
planeY = oldPx * Sin(rotSpeed) + planeY * Cos(rotSpeed)
Case "A"
oldDx = dx : dx = dx * Cos(-rotSpeed) - dy * Sin(-rotSpeed)
dy = oldDx * Sin(-rotSpeed) + dy * Cos(-rotSpeed)
oldPx = planeX : planeX = planeX * Cos(-rotSpeed) - planeY * Sin(-rotSpeed)
planeY = oldPx * Sin(-rotSpeed) + planeY * Cos(-rotSpeed)
End Select
End If
Loop Until k$ = Chr$(27)
If mmb4w Then PAGE WRITE 0
MapData1: '
Data "11111111111111111111111111111111111111111111111111111111"
Data "11111111111111111111111110000000000111111111111111111111"
Data "11111000011111111010111110000000000111111111111111111111"
Data "11111000011111100000000000000000000100111111111111111111"
Data "11111000011111100000000010000000000100111111111111111111"
Data "11111011111111110011111110000000000111111111111111111111"
Data "11111000000000110011111110000000000111111111111111111111"
Data "11111000000001110010111111111001111111111111111111111111"
Data "11111000000000000000111111111001111111111111111111111111"
Data "11111000000000000000111111111001111111111111111111111111"
Data "10000000000001000000111111111001111111111111111111111111"
Data "11111000000001111111111111111001111111111111111111111111"
Data "10000011111101111111111111111001111111111111111111111111"
Data "10011111001111111111111100000000011111111111111111111111"
Data "10111111001111111111111100111001111111111111111111111111"
Data "10011111001111111111111100111001111111111111111111111111"
Data "10000001001111111111111100111001111111111111111111111111"
Data "10000011001111111111111111111001111111111111111111111111"
Data "10010101111011111111111111111001010100111111101111110111"
Data "10011000000001111111111101110000111011111111101000000011"
Data "10010000000001111111111100000000000010010001001000000000"
Data "10011000000001111111111000000000000001111111101000000011"
Data "10001000000000111111111000000000000000000000001000000000"
Data "10001000000001111111111000000000000000000000000000000001"
Data "10001000000001111111111000000000000001000000001000000000"
Data "10011000000001111111111000000000000000111001111000000001"
Data "10011000000001111111111111010000101111110000101000000011"
Data "10011111011011111111111111111101110100110001001011110101"
Data "10001111001111111111111111111000111111111000100110010001"
Data "10011111001111111111111111110000111111110001001000100100"
Data "10010001001111111111111111111000111111111000111111111111"
Data "10000001001111111111111111110001111111110001001000010111"
Data "10011111001111101111111111111001111111111000000000000111"
Data "10001010001111011110101111110001011111110000000000001111"
Data "10000000000000000000011111111000111111111011001010110111"
Data "10000000000000000000000111110000111111111111111111111111"
Data "10000000000000010000011111110001111111111111111111111111"
Data "11101110111101111111111111111000111111111111111111111111"
Data "11111111110010000111111111101101111011111111111111111111"
Data "11111111110000011111111100000000000011111111111111111111"
Data "11111111111011111111111100001001000001111111111111111111"
Data "11111111111001111111111000000000000011111111111111111111"
Data "11111111111001111111111111111001111111111111111111111111"
Data "11111111111111111111111100001001000011111111111111111111"
Data "11111111111111111111111100000000000001111111111111111111"
Data "11111111111111111111111100001001000011111111111111111111"
Data "11111111111111111111111111111001111111111111111111111111"
Data "11111111111111111111111100000000000011111111111111111111"
Data "11111111111111111111111100000000000011111111111111111111"
Data "11111111111111111111111100101010001011111111111111111111"
Data "11111111111111111111111111111111111111111111111111111111"

This is just a basic framework. Feel free to change and expand it.
Cheers
Martin

Posted: 05:10pm 08 Feb 2026 Copy link to clipboard	LeoNicolas Guru

Nice job Martin

For anyone that wants to know more about DDA and ray casting

https://www.youtube.com/watch?v=NbSee-XM7WA

Posted: 05:25pm 08 Feb 2026 Copy link to clipboard	Martin H. Guru

I forgot to mention,
the keys are ‘AD WS’ and ESC to quit.

Posted: 01:28am 09 Feb 2026 Copy link to clipboard	Peter63 Senior Member

Hello Martin

I tried it on PicoMiteHDMIUSB V6.02.00RC6 and it works perfectly.

/Peter63

Posted: 06:47am 09 Feb 2026 Copy link to clipboard	Martin H. Guru

Peter63 said Hello Martin

I tried it on PicoMiteHDMIUSB V6.02.00RC6 and it works perfectly.

/Peter63

Hi Peter,
Thanks for the feedback. I also tried it on Pico2 with HDMI (Try MODE 3). It should also run on CMM2 and MMBasic for Windows if you set mmb4w=1 at the start of the Programm.

Cheers
Martin
Edited 2026-02-09 16:49 by Martin H.

Posted: 07:51am 09 Feb 2026 Copy link to clipboard	Volhout Guru

Hi Martin,

Works nice (RP2040 VGA), but requires quite a lot of math. So it is somewhat slow.
Maybe a lot better on 2350.

Now I look at what you are planning to do, could you not make use of the 3D DRAW commands in MMBasic. I am not sure the 3D DRAW routines Peter implemented can handle the whole map, but they certainly could handle the visible part of the map (they also can rotate a multiface football).
If you place your camera inside the football (inside your maze) this could work ?

Regards,

Volhout

EDIT: Martin, I tried to speed things up by changing "resStep" from 2 to 5, but that corrupts the drawing. Change line 78 into adding "wallCol" as fill color.
Edited 2026-02-09 18:42 by Volhout

Posted: 08:46am 09 Feb 2026 Copy link to clipboard	Martin H. Guru

Volhout said Hi Martin,

Works nice (RP2040 VGA), but requires quite a lot of math. So it is somewhat slow.
Maybe a lot better on 2350.

Now I look at what you are planning to do, could you not make use of the 3D DRAW commands in MMBasic. I am not sure the 3D DRAW routines Peter implemented can handle the whole map, but they certainly could handle the visible part of the map (they also can rotate a multiface football).
If you place your camera inside the football (inside your maze) this could work ?

Regards,

Volhout

Volhout,
You can speed it up by increasing resStep = 2 to resStep = 4 and changing the box command before NEXT X to ‘Box x, yS, resStep, lH, , wallCol, wallCol’.
This halves the number of calculations required, but also the x resolution.

It could be, of course, possible to use the 3D DRAW routines, but this is a completely different approach to ray casting. To do this, the field of view would have to be vectorised and converted into 3D models. This is certainly possible, but I'm not sure if it would be faster in the end.
The initial aim here was to limit the raycast calculations to simple/fast calculations(certainly still room for improvement). I have no experience with the 3D DRAW routines, but I am open to being convinced.
Cheers
Martin
Edited 2026-02-09 19:02 by Martin H.

Posted: 10:48am 09 Feb 2026 Copy link to clipboard	thwill Guru

A screenshot for those who are interested, but not enough to crank up the 'Mite:

Generated by MMB4L running under WSL2 on Windows whilst simulating a PicoMite

.

Best wishes,

Tom
Edited 2026-02-09 20:49 by thwill

Posted: 03:53pm 09 Feb 2026 Copy link to clipboard	Martin H. Guru

thwill said
Generated by MMB4L running under WSL2 on Windows whilst simulating a PicoMite

.

Best wishes,

Tom

Yes, that sounds reasonable.

Posted: 04:38pm 09 Feb 2026 Copy link to clipboard	matherp Guru

How about this ? - -worth including in the RP2350 firmware?

Manual:

Raycaster_User_Manual.pdf

Example code:

Quote ' ============================================================
' Raycaster Demo for PicoMite MMBasic (RP2350)
' Continuous auto-play loop with animated sliding door
' Demonstrates: RAY MOVE, RAY TURN, RAY CELL, RAY CAST,
' RAY SPRITE, RAY MINIMAP, RAY DOOR
' Press ESC at any time to quit
' ============================================================
Option EXPLICIT
MODE 2
CLS

' ---- Map dimensions ----
Const MAP_W = 57
Const MAP_H = 51
Const FOV = 66

' ---- Start position ----
Const START_X = 25.5
Const START_Y = 23.5
Const START_A = 0

' ---- Variables ----
Dim INTEGER x%, y%, i%, cx%, cy%, door_x%, door_y%, door_wall%
Dim k$
Dim FLOAT moveSpeed, rotSpeed

moveSpeed = 0.2
rotSpeed = 5.625 ' exactly 90 degrees per 16 steps

' ---- Door animation state ----
Dim FLOAT door_offset!, door_target!, door_step!
Dim INTEGER door_animating%
door_step! = 0.1 ' offset change per frame (10 frames to fully open/close)

' ---- Read map data into 1D array ----
Dim INTEGER world%(MAP_W * MAP_H - 1)
Restore MapData1
For y% = 0 To MAP_H - 1
Read k$
k$ = k$ + "1"
For x% = 0 To MAP_W - 1
world%(y% * MAP_W + x%) = Val(Mid$(k$, x% + 1, 1))
Next x%
Next y%

' Vary wall types
For y% = 0 To MAP_H - 1
For x% = 0 To MAP_W - 1
If world%(y% * MAP_W + x%) > 0 Then
world%(y% * MAP_W + x%) = ((x% + y%) Mod 1) + 5
EndIf
Next x%
Next y%

' ---- Set up framebuffer & raycaster ----
FRAMEBUFFER CREATE
FRAMEBUFFER WRITE F
Ray MAP MAP_W, MAP_H, world%()
Ray COLOUR 12, 3, 8, 1, 1, 3

' ---- Load 4bpp RGB121 sprite images via SPRITE LOADARRAY ----
Const C_BLK = &h000000 ' index 0 - transparent
Const C_RED = &hFF0000 ' index 8
Const C_GRN = &h00FF00 ' index 6
Const C_BLU = &h0000FF ' index 1
Const C_YEL = &hFFFF00 ' index 14
Const C_CYN = &h00FFFF ' index 7
Const C_MAG = &hFF00FF ' index 9
Const C_WHT = &hFFFFFF ' index 15

Sprite SET TRANSPARENT 0 ' index 0 (black) is transparent
Dim INTEGER spr%(63) ' reusable 8x8 pixel array

Sprite loadpng 1,"char.png",-2,1
Sprite LOADpng 2, "char2.png",-2,1
Sprite LOADpng 3, "char3.png",-2,1
Sprite LOADpng 4, "char4.png",-2,1

' Sprite 5: White ring on black background
For i% = 0 To 63: spr%(i%) = C_BLK: Next i%
For i% = 2 To 5: spr%(0 * 8 + i%) = C_WHT: spr%(7 * 8 + i%) = C_WHT: Next i%
For i% = 2 To 5: spr%(i% * 8 + 0) = C_WHT: spr%(i% * 8 + 7) = C_WHT: Next i%
spr%(1 * 8 + 1) = C_WHT: spr%(1 * 8 + 6) = C_WHT
spr%(6 * 8 + 1) = C_WHT: spr%(6 * 8 + 6) = C_WHT
Sprite LOADARRAY 5, 8, 8, spr%()

' ---- Place billboard sprites in the open area ----
' RAY SPRITE id, spritenum, x!, y!
Ray SPRITE 0, 1, 32.5, 23.5 ' Red cross, ahead east
Ray SPRITE 1, 2, 32.5, 24.5 ' Yellow diamond, southeast
Ray SPRITE 2, 3, 26.5, 24.5 ' Green stripes, southwest
Ray SPRITE 3, 4, 26.5, 23.5 ' Checkerboard, behind west
Ray SPRITE 4, 5, 29.5, 22.5 ' White ring, just north

' ---- Pre-programmed input sequence (round trip) ----
Dim seq$
seq$ = "P5W22P3O1P10W15P5D16W5P5W5D16W30D16W5P5W5P5D16W15P3C1P10A16W5P5D32W5D16W22D16D16P5"

Dim INTEGER curpos%, reps%, r%
Dim cmd$

' ============================================================
' MAIN LOOP - runs continuously until ESC
' ============================================================
Do
' ---- Reset camera to start position ----
Ray CAMERA START_X, START_Y, START_A, FOV

' ---- Rebuild door wall (north-south at x=30, y=19..24) ----
Ray CELL 30, 19, 3
Ray CELL 30, 20, 3
Ray CELL 30, 21, 3
Ray CELL 30, 22, 3
Ray CELL 30, 23, 31 ' door (wall type >= 16 = brown/yellow)
Ray CELL 30, 24, 3

' ---- Reset door animation state ----
door_offset! = 0.0
door_target! = 0.0
door_animating% = 0
door_x% = 30: door_y% = 23: door_wall% = 31
Ray DOOR CLEAR

' ---- Execute the sequence ----
curpos% = 1
Do While curpos% <= Len(seq$)
cmd$ = Mid$(seq$, curpos%, 1)
curpos% = curpos% + 1

' Read repeat count
reps% = 0
Do While curpos% <= Len(seq$)
k$ = Mid$(seq$, curpos%, 1)
If k$ >= "0" And k$ <= "9" Then
reps% = reps% * 10 + Val(k$)
curpos% = curpos% + 1
Else
Exit Do
EndIf
Loop
If reps% = 0 Then reps% = 1

' Execute reps% times
For r% = 1 To reps%
k$ = Inkey$
If k$ = Chr$(27) Then GoTo Done

Select Case cmd$
Case "W": Ray MOVE moveSpeed
Case "S": Ray MOVE -moveSpeed
Case "A": Ray TURN -rotSpeed
Case "D": Ray TURN rotSpeed
Case "O"
' Start door open animation
door_target! = 1.0
door_animating% = 1
Ray DOOR door_x%, door_y%, door_offset!
Case "C"
' Start door close animation
door_target! = 0.0
door_animating% = 1
Case "P"
' Pause = render only, no movement
End Select

' ---- Update door animation every frame ----
If door_animating% Then
Pause 50
If door_target! > door_offset! Then
door_offset! = door_offset! + door_step!
If door_offset! >= door_target! Then
door_offset! = door_target!
door_animating% = 0
EndIf
ElseIf door_target! < door_offset! Then
door_offset! = door_offset! - door_step!
If door_offset! <= door_target! Then
door_offset! = door_target!
door_animating% = 0
If door_offset! <= 0.0 Then
Ray DOOR CLOSE door_x%, door_y%
EndIf
EndIf
Else
door_animating% = 0
EndIf
If door_offset! > 0.0 Then
Ray DOOR door_x%, door_y%, door_offset!
EndIf
EndIf

' ---- Render frame ----
Ray RENDER
Ray MINIMAP 2, 2, 48
Line MM.HRES\2 - 4, MM.VRES\2, MM.HRES\2 + 4, MM.VRES\2,, RGB(WHITE)
Line MM.HRES\2, MM.VRES\2 - 4, MM.HRES\2, MM.VRES\2 + 4,, RGB(WHITE)
FRAMEBUFFER COPY F, N
Pause 30
Next r%
Loop

' Brief pause before restarting the loop
Pause 500
Loop

Done:
Ray CLOSE
FRAMEBUFFER CLOSE
CLS
Print "Raycaster demo ended."
End

MapData1:
Data "11111111111111111111111111111111111111111111111111111111"
Data "11111111111111111111111110000000000111111111111111111111"
Data "11111000011111111010111110000000000111111111111111111111"
Data "11111000011111100000000000000000000100111111111111111111"
Data "11111000011111100000000010000000000100111111111111111111"
Data "11111011111111110011111110000000000111111111111111111111"
Data "11111000000000110011111110000000000111111111111111111111"
Data "11111000000001110010111111111001111111111111111111111111"
Data "11111000000000000000111111111001111111111111111111111111"
Data "11111000000000000000111111111001111111111111111111111111"
Data "10000000000001000000111111111001111111111111111111111111"
Data "11111000000001111111111111111001111111111111111111111111"
Data "10000011111101111111111111111001111111111111111111111111"
Data "10011111001111111111111100000000011111111111111111111111"
Data "10111111001111111111111100111001111111111111111111111111"
Data "10011111001111111111111100111001111111111111111111111111"
Data "10000001001111111111111100111001111111111111111111111111"
Data "10000011001111111111111111111001111111111111111111111111"
Data "10010101111011111111111111111001010100111111101111110111"
Data "10011000000001111111111101110000111011111111101000000011"
Data "10010000000001111111111100000000000010010001001000000000"
Data "10011000000001111111111000000000000001111111101000000011"
Data "10001000000000111111111000000000000000000000001000000000"
Data "10001000000001111111111000000000000000000000000000000001"
Data "10001000000001111111111000000000000001000000001000000000"
Data "10011000000001111111111000000000000000111001111000000001"
Data "10011000000001111111111111010000101111110000101000000011"
Data "10011111011011111111111111111101110100110001001011110101"
Data "10001111001111111111111111111000111111111000100110010001"
Data "10011111001111111111111111110000111111110001001000100100"
Data "10010001001111111111111111111000111111111000111111111111"
Data "10000001001111111111111111110001111111110001001000010111"
Data "10011111001111101111111111111001111111111000000000000111"
Data "10001010001111011110101111110001011111110000000000001111"
Data "10000000000000000000011111111000111111111011001010110111"
Data "10000000000000000000000111110000111111111111111111111111"
Data "10000000000000010000011111110001111111111111111111111111"
Data "11101110111101111111111111111000111111111111111111111111"
Data "11111111110010000111111111101101111011111111111111111111"
Data "11111111110000011111111100000000000011111111111111111111"
Data "11111111111011111111111100001001000001111111111111111111"
Data "11111111111001111111111000000000000011111111111111111111"
Data "11111111111001111111111111111001111111111111111111111111"
Data "11111111111111111111111100001001000011111111111111111111"
Data "11111111111111111111111100000000000001111111111111111111"
Data "11111111111111111111111100001001000011111111111111111111"
Data "11111111111111111111111111111001111111111111111111111111"
Data "11111111111111111111111100000000000011111111111111111111"
Data "11111111111111111111111100000000000011111111111111111111"
Data "11111111111111111111111100101010001011111111111111111111"
Data "11111111111111111111111111111111111111111111111111111111"

Posted: 05:13pm 09 Feb 2026 Copy link to clipboard	thwill Guru

Hi Peter,

It's technically impressive, but in my view it's unnecessary "bloat", a piece of functionality that perhaps one person might used to write a Wolfenstein knock-off.

IMO it would be better not to include it and let that one person "show their chops" and get the achievement of doing it in MMBasic alone (might not be possible on the PicoMite) or writing some CSUBs.

YMMV,

Tom
Edited 2026-02-10 03:27 by thwill

To reply to this topic, you need to log in.