; SPDX-FileCopyrightText: 2024-2026 Zayn Otley ; SPDX-License-Identifier: AGPL-3.0-or-later ; See LICENSES/AGPL-3.0-or-later.txt. ; ============================================================================ ; ROTATING CUBE + COPPER RAINBOW - 3D WIREFRAME WITH RASTER BAR BACKGROUND ; M68020 assembly for Intuition Engine - VGA 320x200, copper coprocessor ; ============================================================================ ; ; === SDK QUICK REFERENCE === ; Assembler: vasmm68k_mot -Fbin -m68020 -devpac -o rotating_cube_copper_68k.ie68 rotating_cube_copper_68k.asm ; Video mode: VGA Mode 13h (320x200, 256 colours, linear framebuffer) ; Audio: SID music via embedded 6502 CPU core ; Copper: 100-line animated rainbow gradient behind the scene ; CPU: Motorola 68020 (32-bit, big-endian) ; Include: ie68.inc (hardware register and macro definitions) ; ; === WHAT THIS DEMO DOES === ; Combines four classic demoscene effects into a single production: ; 1. A wireframe 3D cube rotating in real time on X and Y axes ; 2. A circular scrolltext orbiting the screen centre like a clock face ; 3. Animated rainbow raster bars using the copper coprocessor ; 4. SID music ("Edge of Disgrace" by Goto80) via the 6502 core ; ; === 3D WIREFRAME RENDERING === ; Real-time 3D wireframe rendering was one of the most impressive feats of ; early computer graphics. Elite (1984) on the BBC Micro rendered an entire ; 3D universe with just a 2 MHz 6502. The technique uses: ; ; - Pre-computed sine/cosine lookup tables (avoiding slow trig functions) ; - Fixed-point arithmetic (8.8 format) for fractional precision without FPU ; - 3x3 rotation matrices decomposed into sequential Y-axis then X-axis turns ; - Perspective projection: screen_x = (x * focal_length) / z + centre_x ; - Line drawing via Bresenham's algorithm (integer arithmetic only) ; ; === COPPER RASTER BARS === ; On the Amiga (1985), the "copper" coprocessor could change hardware ; registers synchronised to the electron beam position. This enabled ; effects impossible with normal VGA hardware -- changing the background ; colour on every scanline to create smooth gradients and "raster bars." ; ; The Intuition Engine emulates this capability. Our copper program runs ; in parallel with the CPU, issuing WAIT/MOVE commands that modify palette ; entry #1 at specific scanlines. Since the screen is filled with colour ; index 1, different scanlines display different colours -- creating the ; animated rainbow tube effect. ; ; The colour calculation uses phase-shifted sine waves for RGB components ; (red = sin(hue), green = sin(hue + 120 degrees), blue = sin(hue + 240 degrees)), ; modulated by a brightness sine wave that creates the illusion of a 3D ; tube surface. ; ; === M68K-SPECIFIC NOTES === ; - The IE VideoChip must be enabled (VIDEO_CTRL=1) for the copper to work, ; even when using VGA for display -- a common gotcha ; - The copper list is built dynamically and updated each frame ; - Copper list memory layout: line 0 has no WAIT (36 bytes), subsequent ; lines include WAIT + SETBASE overhead (44 bytes each) ; - The screen is filled with colour index 1 (not 0!) so the copper's ; palette changes are visible ; ; === ARCHITECTURE OVERVIEW === ; ; M68020 (main CPU) Copper (runs in parallel) ; +--------------------+ +------------------------+ ; | Init VGA + copper | | | ; | Start SID music | | For each scanline: | ; | | | WAIT for beam pos | ; | Main loop: | | SETBASE VGA_DAC | ; | Wait vsync | | MOVE palette idx 1 | ; | Clear to idx 1 | | MOVE R, G, B values | ; | Draw scroller | | | ; | Rotate + project | | (restarted each vsync) | ; | Draw cube edges | +------------------------+ ; | Update copper | ; +--------------------+ 6502 (audio coprocessor) ; +------------------------+ ; | Execute SID player | ; | Write SID regs -> synth| ; +------------------------+ ; ; === MEMORY MAP === ; $001000 Code entry point (PROGRAM_START) ; $FF0000 Stack top (STACK_TOP, grows downward) ; VGA_VRAM Linear framebuffer (64000 bytes) ; copper_list Dynamic copper program (~4800 bytes) ; sid_data Embedded .SID file (6502 code + music data) ; ; === BUILD AND RUN === ; vasmm68k_mot -Fbin -m68020 -devpac -o rotating_cube_copper_68k.ie68 \ ; sdk/examples/asm/rotating_cube_copper_68k.asm ; ; (c) 2024-2026 Zayn Otley - AGPL-3.0-or-later ; ============================================================================ include "ie68.inc" org PROGRAM_START ; ---------------------------------------------------------------------------- ; Screen geometry -- Mode 13h constants ; ---------------------------------------------------------------------------- SCR_W equ 320 SCR_H equ 200 CENTER_X equ 160 CENTER_Y equ 100 FRAME_BYTES equ SCR_W*SCR_H FRAME_LONGS equ FRAME_BYTES/4 PRESENT_BLOCKS equ FRAME_BYTES/32 ; ---------------------------------------------------------------------------- ; 3D cube parameters ; ---------------------------------------------------------------------------- NUM_VERTICES equ 8 NUM_EDGES equ 12 CUBE_SIZE equ 40 ; Smaller cube to leave room for scroller DISTANCE equ 256 ; Perspective focal length ; ---------------------------------------------------------------------------- ; Fixed-point format (8.8) ; ---------------------------------------------------------------------------- FP_SHIFT equ 8 FP_ONE equ 256 ; ---------------------------------------------------------------------------- ; Circular scroller parameters ; Characters orbit around screen centre like numbers on a clock face. ; Polar coordinates (angle + radius) are converted to Cartesian (x, y). ; ---------------------------------------------------------------------------- SCROLL_RADIUS equ 75 ; Distance from centre to text SCROLL_CENTER_X equ 160 SCROLL_CENTER_Y equ 100 NUM_VISIBLE equ 12 ; Characters visible at once CHAR_SPACING equ 21 ; Angular spacing (256/12 ~ 21) DRAW_CHAR_SIZE equ 8 ; 8x8 pixel font SCROLL_SPEED equ 1 ; Rotation speed per frame ; ---------------------------------------------------------------------------- ; Copper raster bar configuration ; 100 colour changes x 2 scanlines each = 200 lines (full screen coverage) ; ---------------------------------------------------------------------------- NUM_COPPER_LINES equ 100 LINES_PER_CHANGE equ 2 ; ============================================================================ ; ENTRY POINT - HARDWARE INITIALISATION ; ============================================================================ start: move.l #STACK_TOP,sp ; --- Enable IE VideoChip (required for copper coprocessor) --- ; The copper is part of the IE video system, not the VGA. ; Without this, copper instructions silently do nothing. move.l #1,VIDEO_CTRL ; --- Configure VGA --- move.b #VGA_MODE_13H,VGA_MODE move.b #VGA_CTRL_ENABLE,VGA_CTRL bsr clear_back_buffer bsr present_frame ; --- Build and activate copper program --- bsr build_copper_list move.l #copper_list,COPPER_PTR move.l #1,COPPER_CTRL ; --- Start SID music --- move.l #sid_data,SID_PLAY_PTR move.l #sid_data_end-sid_data,SID_PLAY_LEN start_sid_loop ; --- Initialise animation state --- clr.l angle_x clr.l angle_y clr.l scroll_angle clr.l scroll_char_offset clr.l raster_phase ; ============================================================================ ; MAIN LOOP - ONE ITERATION PER FRAME ; ============================================================================ ; Order matters: render the whole frame in RAM first, then copy the completed ; image into Mode 13h VRAM during vblank. This keeps the demo in Mode 13h ; without showing half-cleared or half-drawn visible VRAM. ; ---------------------------------------------------------------------------- main_loop: ; --- Clear back buffer to colour index 1 --- ; index 1: The copper modifies palette entry 1 per scanline. ; Pixels with index 1 show the copper's current colour, creating ; the rainbow gradient. Index 0 would not be affected. bsr clear_back_buffer ; --- Draw circular scroller (behind cube) --- bsr draw_circular_scroll ; --- 3D cube rendering pipeline --- bsr calc_rotation bsr transform_vertices bsr draw_edges ; --- Advance cube rotation --- addq.l #2,angle_x addq.l #3,angle_y andi.l #$FF,angle_x andi.l #$FF,angle_y ; --- Advance scroller rotation --- move.l scroll_angle,d0 addq.l #SCROLL_SPEED,d0 andi.l #$FF,d0 move.l d0,scroll_angle ; --- Advance copper colour animation --- ; The phase offset makes colours scroll vertically through the bars move.l raster_phase,d0 addq.l #3,d0 andi.l #$FF,d0 move.l d0,raster_phase bsr update_copper_colors ; --- VSync synchronisation (two-stage wait) --- .wait_not_vb: move.b VGA_STATUS,d0 andi.b #VGA_STATUS_VSYNC,d0 bne.s .wait_not_vb .wait_vb: move.b VGA_STATUS,d0 andi.b #VGA_STATUS_VSYNC,d0 beq.s .wait_vb ; --- Present the completed RAM frame to visible Mode 13h VRAM --- bsr present_frame bra main_loop ; ============================================================================ ; CLEAR BACK BUFFER TO COLOUR INDEX 1 ; ============================================================================ ; The visible Mode 13h aperture is only written by present_frame. All drawing ; happens in normal RAM so scanout cannot catch partially rendered objects. ; ---------------------------------------------------------------------------- clear_back_buffer: movem.l d0-d1/a0,-(sp) lea back_buffer,a0 move.w #FRAME_LONGS-1,d0 move.l #$01010101,d1 .clear_loop: move.l d1,(a0)+ dbf d0,.clear_loop movem.l (sp)+,d0-d1/a0 rts ; ============================================================================ ; PRESENT BACK BUFFER TO VISIBLE MODE 13H VRAM ; ============================================================================ ; Mode 13h exposes a 64KB VGA aperture, so the back buffer lives in normal RAM. ; Copying byte-by-byte matches the VGA byte-addressed Chain-4 write path. ; ---------------------------------------------------------------------------- present_frame: movem.l d0-d1/a0-a1,-(sp) lea back_buffer,a0 lea VGA_VRAM,a1 move.w #PRESENT_BLOCKS-1,d0 .copy_loop: rept 32 move.b (a0)+,d1 move.b d1,(a1)+ endr dbf d0,.copy_loop movem.l (sp)+,d0-d1/a0-a1 rts ; ============================================================================ ; DRAW CIRCULAR SCROLLER ; ============================================================================ ; Characters orbit the screen centre using polar-to-Cartesian conversion: ; x = centre_x + radius * cos(angle) ; y = centre_y + radius * sin(angle) ; Each of the 12 visible characters is offset by CHAR_SPACING (21 angle units) ; from its neighbour, evenly distributing them around the circle. ; ---------------------------------------------------------------------------- draw_circular_scroll: movem.l d0-d7/a0-a4,-(sp) moveq #0,d7 ; Visible character index (0..11) .char_loop: ; --- Calculate angular position for this character --- move.l scroll_angle,d0 move.l d7,d1 mulu.w #CHAR_SPACING,d1 add.l d1,d0 andi.l #$FF,d0 ; Wrap to full circle ; --- Look up sin and cos from table --- lea sin_table,a0 move.l d0,d1 add.w d1,d1 ; *2 for word access move.w (a0,d1.w),d2 ; sin(angle) move.l d0,d1 addi.l #64,d1 ; cos = sin(angle + 64) andi.l #$FF,d1 add.w d1,d1 move.w (a0,d1.w),d3 ; cos(angle) ; --- Convert polar to Cartesian --- move.w d3,d4 ext.l d4 muls.w #SCROLL_RADIUS,d4 asr.l #FP_SHIFT,d4 addi.l #SCROLL_CENTER_X,d4 subi.l #DRAW_CHAR_SIZE/2,d4 ; Centre character on point move.w d2,d5 ext.l d5 muls.w #SCROLL_RADIUS,d5 asr.l #FP_SHIFT,d5 addi.l #SCROLL_CENTER_Y,d5 subi.l #DRAW_CHAR_SIZE/2,d5 ; --- Get character from message (with wrapping) --- move.l scroll_char_offset,d6 add.l d7,d6 lea scroll_message,a1 lea scroll_msg_end,a2 move.l a2,d0 sub.l a1,d0 subq.l #1,d0 ; Message length (excluding null) .wrap_check: cmp.l d0,d6 blt.s .no_wrap sub.l d0,d6 bra.s .wrap_check .no_wrap: move.b (a1,d6.l),d6 andi.l #$7F,d6 ; Mask to 7-bit ASCII ; --- Draw the character --- bsr draw_scroll_char ; --- Next visible character --- addq.l #1,d7 cmpi.l #NUM_VISIBLE,d7 blt .char_loop ; --- Advance message offset periodically --- ; Every 32 angle steps, shift the message by one character move.l scroll_angle,d0 andi.l #$1F,d0 bne.s .no_advance lea scroll_message,a1 lea scroll_msg_end,a2 move.l a2,d0 sub.l a1,d0 subq.l #1,d0 move.l scroll_char_offset,d1 addq.l #1,d1 cmp.l d0,d1 blt.s .no_wrap_offset moveq #0,d1 .no_wrap_offset: move.l d1,scroll_char_offset .no_advance: movem.l (sp)+,d0-d7/a0-a4 rts ; ============================================================================ ; DRAW SCROLL CHARACTER (8x8 BITMAP FONT) ; ============================================================================ ; Input: d4=x, d5=y, d6=ASCII code ; Renders a single character from the bitmap font with animated colour ; based on scroll_angle and pixel position. ; ---------------------------------------------------------------------------- draw_scroll_char: movem.l d0-d7/a0-a2,-(sp) ; --- Bounds check --- tst.l d4 bmi .char_done cmpi.l #SCR_W-8,d4 bgt .char_done tst.l d5 bmi .char_done cmpi.l #SCR_H-8,d5 bgt .char_done ; --- Look up character in font --- lea simple_font,a0 subi.l #32,d6 ; ASCII space = font index 0 bmi .char_done cmpi.l #95,d6 ; Font covers ASCII 32-126 bge .char_done lsl.l #3,d6 ; *8 bytes per character add.l d6,a0 ; --- Calculate back-buffer destination --- lea back_buffer,a1 move.l d5,d0 mulu.w #SCR_W,d0 add.l d4,d0 add.l d0,a1 ; --- Render 8 rows of 8 pixels --- moveq #7,d7 .row_loop: move.b (a0)+,d0 ; Row bitmap (8 pixels as bits) moveq #7,d3 .col_loop: btst d3,d0 ; Test pixel bit beq.s .skip_pixel ; Animated colour based on position and time move.l scroll_angle,d1 add.l d7,d1 add.l d3,d1 andi.l #$3F,d1 addi.l #64,d1 ; Use palette entries 64-127 move.b d1,(a1) .skip_pixel: addq.l #1,a1 dbf d3,.col_loop ; Advance to next back-buffer row (320 - 8 pixels already advanced) lea SCR_W-8(a1),a1 dbf d7,.row_loop .char_done: movem.l (sp)+,d0-d7/a0-a2 rts ; ============================================================================ ; CALCULATE ROTATION MATRIX COMPONENTS ; ============================================================================ ; Pre-computes sin/cos for both rotation angles from the lookup table. ; ---------------------------------------------------------------------------- calc_rotation: movem.l d0-d1/a0,-(sp) lea sin_table,a0 move.l angle_x,d0 andi.l #$FF,d0 add.w d0,d0 move.w (a0,d0.w),sin_x move.l angle_x,d0 addi.l #64,d0 andi.l #$FF,d0 add.w d0,d0 move.w (a0,d0.w),cos_x move.l angle_y,d0 andi.l #$FF,d0 add.w d0,d0 move.w (a0,d0.w),sin_y move.l angle_y,d0 addi.l #64,d0 andi.l #$FF,d0 add.w d0,d0 move.w (a0,d0.w),cos_y movem.l (sp)+,d0-d1/a0 rts ; ============================================================================ ; TRANSFORM AND PROJECT ALL VERTICES ; ============================================================================ ; Applies Y-rotation, X-rotation, then perspective projection to each vertex. ; See rotating_cube_68k.asm for detailed mathematical commentary on the ; rotation matrix decomposition and fixed-point arithmetic. ; ---------------------------------------------------------------------------- transform_vertices: movem.l d0-d7/a0-a2,-(sp) lea cube_vertices,a0 lea projected_x,a1 lea projected_y,a2 moveq #NUM_VERTICES-1,d7 .vertex_loop: move.w (a0)+,d0 ; x move.w (a0)+,d1 ; y move.w (a0)+,d2 ; z ext.l d0 ext.l d1 ext.l d2 ; --- Y-axis rotation --- move.l d0,d3 move.l d2,d4 move.w cos_y,d5 ext.l d5 muls.w d5,d3 move.w sin_y,d5 ext.l d5 muls.w d5,d4 sub.l d4,d3 asr.l #FP_SHIFT,d3 move.l d0,d4 move.l d2,d6 move.w sin_y,d5 ext.l d5 muls.w d5,d4 move.w cos_y,d5 ext.l d5 muls.w d5,d6 add.l d4,d6 asr.l #FP_SHIFT,d6 move.l d3,d0 move.l d6,d2 ; --- X-axis rotation --- move.l d1,d3 move.l d2,d4 move.w cos_x,d5 ext.l d5 muls.w d5,d3 move.w sin_x,d5 ext.l d5 muls.w d5,d4 sub.l d4,d3 asr.l #FP_SHIFT,d3 move.l d1,d4 move.l d2,d6 move.w sin_x,d5 ext.l d5 muls.w d5,d4 move.w cos_x,d5 ext.l d5 muls.w d5,d6 add.l d4,d6 asr.l #FP_SHIFT,d6 move.l d3,d1 move.l d6,d2 ; --- Perspective projection --- add.l #DISTANCE,d2 beq.s .skip_div bmi.s .skip_div move.l d0,d3 muls.w #DISTANCE,d3 divs.w d2,d3 ext.l d3 add.l #CENTER_X,d3 move.w d3,(a1)+ move.l d1,d3 muls.w #DISTANCE,d3 divs.w d2,d3 ext.l d3 add.l #CENTER_Y,d3 move.w d3,(a2)+ dbf d7,.vertex_loop bra.s .done .skip_div: move.w #-1000,(a1)+ move.w #-1000,(a2)+ dbf d7,.vertex_loop .done: movem.l (sp)+,d0-d7/a0-a2 rts ; ============================================================================ ; DRAW ALL EDGES ; ============================================================================ draw_edges: movem.l d0-d7/a0-a2,-(sp) lea edge_list,a0 moveq #NUM_EDGES-1,d7 .edge_loop: move.b (a0)+,d0 move.b (a0)+,d1 ext.w d0 ext.w d1 lea projected_x,a1 lea projected_y,a2 move.w d0,d2 add.w d2,d2 move.w (a1,d2.w),d3 move.w (a2,d2.w),d4 move.w d1,d2 add.w d2,d2 move.w (a1,d2.w),d5 move.w (a2,d2.w),d6 ; Edge colour varies by index move.l d7,d2 andi.l #7,d2 add.l #40,d2 lsl.l #4,d2 addi.l #15,d2 andi.l #$FF,d2 bsr draw_line dbf d7,.edge_loop movem.l (sp)+,d0-d7/a0-a2 rts ; ============================================================================ ; DRAW LINE - BRESENHAM'S ALGORITHM ; ============================================================================ ; Input: d3=x1, d4=y1, d5=x2, d6=y2, d2=colour ; Uses fast-reject visibility test plus per-pixel bounds checking. ; ---------------------------------------------------------------------------- draw_line: movem.l d0-d7/a0,-(sp) cmpi.w #0,d3 blt.s .check_x2 cmpi.w #SCR_W,d3 bge.s .check_x2 cmpi.w #0,d4 blt.s .check_x2 cmpi.w #SCR_H,d4 bge.s .check_x2 bra.s .start_line .check_x2: cmpi.w #0,d5 blt .line_done cmpi.w #SCR_W,d5 bge .line_done cmpi.w #0,d6 blt .line_done cmpi.w #SCR_H,d6 bge .line_done .start_line: move.w d5,d0 sub.w d3,d0 move.w d6,d1 sub.w d4,d1 moveq #1,d7 tst.w d0 bge.s .dx_pos neg.w d0 moveq #-1,d7 .dx_pos: move.w d7,-(sp) moveq #1,d7 tst.w d1 bge.s .dy_pos neg.w d1 moveq #-1,d7 .dy_pos: move.w d7,-(sp) cmp.w d1,d0 bge.s .x_major move.w d1,d7 lsr.w #1,d7 .y_loop: bsr plot_pixel cmp.w d6,d4 beq.s .line_done_pop add.w (sp),d4 sub.w d0,d7 bge.s .y_loop add.w d1,d7 add.w 2(sp),d3 bra.s .y_loop .x_major: move.w d0,d7 lsr.w #1,d7 .x_loop: bsr plot_pixel cmp.w d5,d3 beq.s .line_done_pop add.w 2(sp),d3 sub.w d1,d7 bge.s .x_loop add.w d0,d7 add.w (sp),d4 bra.s .x_loop .line_done_pop: addq.l #4,sp .line_done: movem.l (sp)+,d0-d7/a0 rts ; ============================================================================ ; PLOT PIXEL WITH BOUNDS CHECKING ; ============================================================================ ; Input: d3=x, d4=y, d2=colour ; ---------------------------------------------------------------------------- plot_pixel: tst.w d3 bmi.s .skip cmpi.w #SCR_W,d3 bge.s .skip tst.w d4 bmi.s .skip cmpi.w #SCR_H,d4 bge.s .skip movem.l d0-d1/a0,-(sp) lea back_buffer,a0 move.w d4,d0 mulu #SCR_W,d0 add.w d3,d0 move.b d2,(a0,d0.l) movem.l (sp)+,d0-d1/a0 .skip: rts ; ============================================================================ ; BUILD COPPER LIST ; ============================================================================ ; Creates the copper program that executes during each frame. For each ; of 100 scanlines, the copper WAITs for the beam to reach that position, ; then writes new R/G/B values into palette entry 1. The actual colour ; values are placeholders here -- update_copper_colors fills them in each ; frame for smooth animation. ; ; Copper instructions used: ; SETBASE - Select target device (VIDEO for WAIT, VGA_DAC for palette) ; WAIT - Pause until beam reaches specified scanline ; MOVE - Write a value to the selected device's register ; END - Stop execution (restarted automatically at next vsync) ; ---------------------------------------------------------------------------- build_copper_list: movem.l d0-d7/a0,-(sp) lea copper_list,a0 moveq #0,d7 .build_loop: move.l d7,d0 mulu.w #LINES_PER_CHANGE,d0 cmpi.l #SCR_H,d0 bge.s .build_end ; First line needs no WAIT (starts at top of screen) tst.l d7 beq.s .no_wait ; WAIT for beam to reach this scanline move.l #COP_SETBASE_VIDEO,(a0)+ lsl.l #8,d0 lsl.l #4,d0 ; scanline * 4096 move.l d0,(a0)+ .no_wait: ; Write palette entry 1 with new R/G/B move.l #COP_SETBASE_VGA_DAC,(a0)+ move.l #COP_MOVE_VGA_WINDEX,(a0)+ move.l #1,(a0)+ ; Palette index 1 move.l #COP_MOVE_VGA_DATA,(a0)+ move.l #0,(a0)+ ; R (placeholder) move.l #COP_MOVE_VGA_DATA,(a0)+ move.l #0,(a0)+ ; G (placeholder) move.l #COP_MOVE_VGA_DATA,(a0)+ move.l #0,(a0)+ ; B (placeholder) addq.l #1,d7 cmpi.l #NUM_COPPER_LINES,d7 blt.s .build_loop .build_end: move.l #COP_END,(a0)+ movem.l (sp)+,d0-d7/a0 rts ; ============================================================================ ; UPDATE COPPER COLOURS ; ============================================================================ ; Modifies the R/G/B values in the copper list each frame to animate ; the rainbow gradient. The effect creates the illusion of a 3D "tube" ; surface using: ; ; BRIGHTNESS: A sine wave modulated by scanline position, creating bright ; centres and dark edges for each band ; HUE: Determined by colour group + animation phase, scrolling ; colours through the rainbow over time ; RGB: Phase-shifted sine waves approximate HSV-to-RGB conversion: ; Red = sin(hue), Green = sin(hue + 120 deg), Blue = sin(hue + 240 deg) ; ; Memory layout of copper list: ; Line 0: 36 bytes (no WAIT instruction) ; Line 1+: 44 bytes each (includes WAIT + SETBASE overhead) ; R value offset within a line's palette block: varies by line index ; ---------------------------------------------------------------------------- update_copper_colors: movem.l d0-d7/a0-a2,-(sp) lea copper_list,a0 lea sin_table,a1 move.l raster_phase,d6 moveq #0,d7 .update_loop: ; --- Calculate pointer to this line's R value --- tst.l d7 bne.s .not_line0 ; Line 0: R at offset 16 (no WAIT) lea 16(a0),a2 bra.s .calc_color .not_line0: ; Lines 1+: offset = 36 + (line-1)*44 + 24 move.l d7,d0 subq.l #1,d0 mulu.w #44,d0 addi.l #36+24,d0 lea (a0,d0.l),a2 .calc_color: ; --- Colour group (bands of similar colour) --- move.l d7,d0 lsr.l #2,d0 ; line / 4 ; --- Brightness (tube effect via sine wave) --- move.l d7,d1 lsl.l #4,d1 ; Convert the line index to a 16-byte record offset. add.l d6,d1 ; Add animation phase andi.l #$FF,d1 move.l d1,d2 add.w d2,d2 ; *2 for word access move.w (a1,d2.w),d3 ; sin value (-256..+256) bpl.s .bright_pos neg.w d3 ; Absolute value for brightness .bright_pos: ; --- Hue (colour group + animation phase) --- move.l d0,d4 lsl.l #3,d4 ; *8 for hue spread add.l d6,d4 ; Add animation phase andi.l #$FF,d4 ; --- Red: sin(hue) * brightness --- move.l d4,d1 add.w d1,d1 move.w (a1,d1.w),d2 bpl.s .r_pos moveq #0,d2 bra.s .r_scale .r_pos: mulu.w d3,d2 lsr.l #8,d2 lsr.l #2,d2 ; Scale to 0-63 (VGA DAC range) .r_scale: andi.l #$3F,d2 move.l d2,(a2) ; --- Green: sin(hue + 120 deg) * brightness --- ; 120 deg ~ 85 in 256-unit system move.l d4,d1 addi.l #85,d1 andi.l #$FF,d1 add.w d1,d1 move.w (a1,d1.w),d2 bpl.s .g_pos moveq #0,d2 bra.s .g_scale .g_pos: mulu.w d3,d2 lsr.l #8,d2 lsr.l #2,d2 .g_scale: andi.l #$3F,d2 move.l d2,8(a2) ; --- Blue: sin(hue + 240 deg) * brightness --- ; 240 deg ~ 170 in 256-unit system move.l d4,d1 addi.l #170,d1 andi.l #$FF,d1 add.w d1,d1 move.w (a1,d1.w),d2 bpl.s .b_pos moveq #0,d2 bra.s .b_scale .b_pos: mulu.w d3,d2 lsr.l #8,d2 lsr.l #2,d2 .b_scale: andi.l #$3F,d2 move.l d2,16(a2) addq.l #1,d7 cmpi.l #NUM_COPPER_LINES,d7 blt .update_loop movem.l (sp)+,d0-d7/a0-a2 rts ; ============================================================================ ; DATA SECTION ; ============================================================================ even ; --- Animation state variables --- angle_x: dc.l 0 ; Cube X rotation (0-255) angle_y: dc.l 0 ; Cube Y rotation (0-255) sin_x: dc.w 0 ; Cached sin(angle_x) cos_x: dc.w 0 ; Cached cos(angle_x) sin_y: dc.w 0 ; Cached sin(angle_y) cos_y: dc.w 0 ; Cached cos(angle_y) scroll_angle: dc.l 0 ; Scroller orbit position (0-255) scroll_char_offset: dc.l 0 ; Current message character offset raster_phase: dc.l 0 ; Copper colour animation phase (0-255) ; --- Mode 13h RAM back buffer --- ; Visible VGA VRAM is updated only by present_frame. even back_buffer: ds.b FRAME_BYTES ; --- Copper list buffer --- ; Reserved space for the dynamically-built copper program. ; Maximum: 36 + 99*44 + 4 = ~4400 bytes, rounded up to 4800. even copper_list: ds.l 1200 ; --- Cube vertices (x, y, z as signed 16-bit words) --- ; Centred at origin, half-width = CUBE_SIZE. ; ; 7--------6 ; /| /| ; / | / | ; 4--------5 | ; | 3-----|--2 ; | / | / ; |/ |/ ; 0--------1 ; cube_vertices: dc.w -CUBE_SIZE, -CUBE_SIZE, -CUBE_SIZE ; 0: front-bottom-left dc.w CUBE_SIZE, -CUBE_SIZE, -CUBE_SIZE ; 1: front-bottom-right dc.w CUBE_SIZE, CUBE_SIZE, -CUBE_SIZE ; 2: front-top-right dc.w -CUBE_SIZE, CUBE_SIZE, -CUBE_SIZE ; 3: front-top-left dc.w -CUBE_SIZE, -CUBE_SIZE, CUBE_SIZE ; 4: back-bottom-left dc.w CUBE_SIZE, -CUBE_SIZE, CUBE_SIZE ; 5: back-bottom-right dc.w CUBE_SIZE, CUBE_SIZE, CUBE_SIZE ; 6: back-top-right dc.w -CUBE_SIZE, CUBE_SIZE, CUBE_SIZE ; 7: back-top-left ; --- Edge list (pairs of vertex indices) --- edge_list: ; Front face dc.b 0, 1 dc.b 1, 2 dc.b 2, 3 dc.b 3, 0 ; Back face dc.b 4, 5 dc.b 5, 6 dc.b 6, 7 dc.b 7, 4 ; Connecting edges dc.b 0, 4 dc.b 1, 5 dc.b 2, 6 dc.b 3, 7 even ; --- Projected 2D coordinates (filled at runtime) --- projected_x: ds.w NUM_VERTICES projected_y: ds.w NUM_VERTICES ; --- Sine table (256 entries, 8.8 fixed-point) --- ; Values: -256 to +256 representing -1.0 to +1.0 ; cos(a) = sin(a + 64), where 64 = 90 degrees in 256-unit system sin_table: ; Quadrant 1: 0 to 90 degrees dc.w 0, 6, 12, 18, 25, 31, 37, 43 dc.w 49, 56, 62, 68, 74, 80, 86, 92 dc.w 97, 103, 109, 115, 120, 126, 131, 136 dc.w 142, 147, 152, 157, 162, 167, 171, 176 dc.w 181, 185, 189, 193, 197, 201, 205, 209 dc.w 212, 216, 219, 222, 225, 228, 231, 234 dc.w 236, 238, 241, 243, 245, 247, 248, 250 dc.w 251, 252, 253, 254, 255, 255, 256, 256 ; Quadrant 2: 90 to 180 degrees dc.w 256, 256, 256, 255, 255, 254, 253, 252 dc.w 251, 250, 248, 247, 245, 243, 241, 238 dc.w 236, 234, 231, 228, 225, 222, 219, 216 dc.w 212, 209, 205, 201, 197, 193, 189, 185 dc.w 181, 176, 171, 167, 162, 157, 152, 147 dc.w 142, 136, 131, 126, 120, 115, 109, 103 dc.w 97, 92, 86, 80, 74, 68, 62, 56 dc.w 49, 43, 37, 31, 25, 18, 12, 6 ; Quadrant 3: 180 to 270 degrees dc.w 0, -6, -12, -18, -25, -31, -37, -43 dc.w -49, -56, -62, -68, -74, -80, -86, -92 dc.w -97, -103, -109, -115, -120, -126, -131, -136 dc.w -142, -147, -152, -157, -162, -167, -171, -176 dc.w -181, -185, -189, -193, -197, -201, -205, -209 dc.w -212, -216, -219, -222, -225, -228, -231, -234 dc.w -236, -238, -241, -243, -245, -247, -248, -250 dc.w -251, -252, -253, -254, -255, -255, -256, -256 ; Quadrant 4: 270 to 360 degrees dc.w -256, -256, -256, -255, -255, -254, -253, -252 dc.w -251, -250, -248, -247, -245, -243, -241, -238 dc.w -236, -234, -231, -228, -225, -222, -219, -216 dc.w -212, -209, -205, -201, -197, -193, -189, -185 dc.w -181, -176, -171, -167, -162, -157, -152, -147 dc.w -142, -136, -131, -126, -120, -115, -109, -103 dc.w -97, -92, -86, -80, -74, -68, -62, -56 dc.w -49, -43, -37, -31, -25, -18, -12, -6 ; ============================================================================ ; BITMAP FONT (8x8 PIXELS, ASCII 32-126) ; ============================================================================ ; Each character is 8 bytes. Each byte is one row of 8 pixels, where bit 7 ; (MSB) is the leftmost pixel and bit 0 is the rightmost. ; Font address = simple_font + (ASCII - 32) * 8 ; ---------------------------------------------------------------------------- even simple_font: ; Space (32) dc.b $00,$00,$00,$00,$00,$00,$00,$00 ; ! (33) dc.b $18,$18,$18,$18,$18,$00,$18,$00 ; " (34) dc.b $6C,$6C,$6C,$00,$00,$00,$00,$00 ; # (35) dc.b $6C,$6C,$FE,$6C,$FE,$6C,$6C,$00 ; $ (36) dc.b $18,$3E,$60,$3C,$06,$7C,$18,$00 ; % (37) dc.b $00,$C6,$CC,$18,$30,$66,$C6,$00 ; & (38) dc.b $38,$6C,$38,$76,$DC,$CC,$76,$00 ; ' (39) dc.b $18,$18,$30,$00,$00,$00,$00,$00 ; ( (40) dc.b $0C,$18,$30,$30,$30,$18,$0C,$00 ; ) (41) dc.b $30,$18,$0C,$0C,$0C,$18,$30,$00 ; * (42) dc.b $00,$66,$3C,$FF,$3C,$66,$00,$00 ; + (43) dc.b $00,$18,$18,$7E,$18,$18,$00,$00 ; , (44) dc.b $00,$00,$00,$00,$00,$18,$18,$30 ; - (45) dc.b $00,$00,$00,$7E,$00,$00,$00,$00 ; . (46) dc.b $00,$00,$00,$00,$00,$18,$18,$00 ; / (47) dc.b $06,$0C,$18,$30,$60,$C0,$80,$00 ; 0 (48) dc.b $7C,$C6,$CE,$DE,$F6,$E6,$7C,$00 ; 1 (49) dc.b $18,$38,$18,$18,$18,$18,$7E,$00 ; 2 (50) dc.b $7C,$C6,$06,$1C,$30,$66,$FE,$00 ; 3 (51) dc.b $7C,$C6,$06,$3C,$06,$C6,$7C,$00 ; 4 (52) dc.b $1C,$3C,$6C,$CC,$FE,$0C,$1E,$00 ; 5 (53) dc.b $FE,$C0,$FC,$06,$06,$C6,$7C,$00 ; 6 (54) dc.b $38,$60,$C0,$FC,$C6,$C6,$7C,$00 ; 7 (55) dc.b $FE,$C6,$0C,$18,$30,$30,$30,$00 ; 8 (56) dc.b $7C,$C6,$C6,$7C,$C6,$C6,$7C,$00 ; 9 (57) dc.b $7C,$C6,$C6,$7E,$06,$0C,$78,$00 ; : (58) dc.b $00,$18,$18,$00,$00,$18,$18,$00 ; ; (59) dc.b $00,$18,$18,$00,$00,$18,$18,$30 ; < (60) dc.b $0C,$18,$30,$60,$30,$18,$0C,$00 ; = (61) dc.b $00,$00,$7E,$00,$00,$7E,$00,$00 ; > (62) dc.b $30,$18,$0C,$06,$0C,$18,$30,$00 ; ? (63) dc.b $7C,$C6,$0C,$18,$18,$00,$18,$00 ; @ (64) dc.b $7C,$C6,$DE,$DE,$DE,$C0,$78,$00 ; A (65) dc.b $38,$6C,$C6,$FE,$C6,$C6,$C6,$00 ; B (66) dc.b $FC,$66,$66,$7C,$66,$66,$FC,$00 ; C (67) dc.b $3C,$66,$C0,$C0,$C0,$66,$3C,$00 ; D (68) dc.b $F8,$6C,$66,$66,$66,$6C,$F8,$00 ; E (69) dc.b $FE,$62,$68,$78,$68,$62,$FE,$00 ; F (70) dc.b $FE,$62,$68,$78,$68,$60,$F0,$00 ; G (71) dc.b $3C,$66,$C0,$C0,$CE,$66,$3A,$00 ; H (72) dc.b $C6,$C6,$C6,$FE,$C6,$C6,$C6,$00 ; I (73) dc.b $3C,$18,$18,$18,$18,$18,$3C,$00 ; J (74) dc.b $1E,$0C,$0C,$0C,$CC,$CC,$78,$00 ; K (75) dc.b $E6,$66,$6C,$78,$6C,$66,$E6,$00 ; L (76) dc.b $F0,$60,$60,$60,$62,$66,$FE,$00 ; M (77) dc.b $C6,$EE,$FE,$FE,$D6,$C6,$C6,$00 ; N (78) dc.b $C6,$E6,$F6,$DE,$CE,$C6,$C6,$00 ; O (79) dc.b $7C,$C6,$C6,$C6,$C6,$C6,$7C,$00 ; P (80) dc.b $FC,$66,$66,$7C,$60,$60,$F0,$00 ; Q (81) dc.b $7C,$C6,$C6,$C6,$D6,$DE,$7C,$06 ; R (82) dc.b $FC,$66,$66,$7C,$6C,$66,$E6,$00 ; S (83) dc.b $7C,$C6,$60,$38,$0C,$C6,$7C,$00 ; T (84) dc.b $7E,$5A,$18,$18,$18,$18,$3C,$00 ; U (85) dc.b $C6,$C6,$C6,$C6,$C6,$C6,$7C,$00 ; V (86) dc.b $C6,$C6,$C6,$C6,$6C,$38,$10,$00 ; W (87) dc.b $C6,$C6,$D6,$FE,$FE,$EE,$C6,$00 ; X (88) dc.b $C6,$C6,$6C,$38,$6C,$C6,$C6,$00 ; Y (89) dc.b $66,$66,$66,$3C,$18,$18,$3C,$00 ; Z (90) dc.b $FE,$C6,$8C,$18,$32,$66,$FE,$00 ; [ (91) dc.b $3C,$30,$30,$30,$30,$30,$3C,$00 ; \ (92) dc.b $C0,$60,$30,$18,$0C,$06,$02,$00 ; ] (93) dc.b $3C,$0C,$0C,$0C,$0C,$0C,$3C,$00 ; ^ (94) dc.b $10,$38,$6C,$C6,$00,$00,$00,$00 ; _ (95) dc.b $00,$00,$00,$00,$00,$00,$00,$FE ; ` (96) dc.b $30,$18,$0C,$00,$00,$00,$00,$00 ; a (97) dc.b $00,$00,$78,$0C,$7C,$CC,$76,$00 ; b (98) dc.b $E0,$60,$7C,$66,$66,$66,$DC,$00 ; c (99) dc.b $00,$00,$7C,$C6,$C0,$C6,$7C,$00 ; d (100) dc.b $1C,$0C,$7C,$CC,$CC,$CC,$76,$00 ; e (101) dc.b $00,$00,$7C,$C6,$FE,$C0,$7C,$00 ; f (102) dc.b $38,$6C,$60,$F8,$60,$60,$F0,$00 ; g (103) dc.b $00,$00,$76,$CC,$CC,$7C,$0C,$F8 ; h (104) dc.b $E0,$60,$6C,$76,$66,$66,$E6,$00 ; i (105) dc.b $18,$00,$38,$18,$18,$18,$3C,$00 ; j (106) dc.b $06,$00,$0E,$06,$06,$66,$66,$3C ; k (107) dc.b $E0,$60,$66,$6C,$78,$6C,$E6,$00 ; l (108) dc.b $38,$18,$18,$18,$18,$18,$3C,$00 ; m (109) dc.b $00,$00,$EC,$FE,$D6,$D6,$C6,$00 ; n (110) dc.b $00,$00,$DC,$66,$66,$66,$66,$00 ; o (111) dc.b $00,$00,$7C,$C6,$C6,$C6,$7C,$00 ; p (112) dc.b $00,$00,$DC,$66,$66,$7C,$60,$F0 ; q (113) dc.b $00,$00,$76,$CC,$CC,$7C,$0C,$1E ; r (114) dc.b $00,$00,$DC,$76,$60,$60,$F0,$00 ; s (115) dc.b $00,$00,$7E,$C0,$7C,$06,$FC,$00 ; t (116) dc.b $30,$30,$FC,$30,$30,$34,$18,$00 ; u (117) dc.b $00,$00,$CC,$CC,$CC,$CC,$76,$00 ; v (118) dc.b $00,$00,$C6,$C6,$C6,$6C,$38,$00 ; w (119) dc.b $00,$00,$C6,$D6,$D6,$FE,$6C,$00 ; x (120) dc.b $00,$00,$C6,$6C,$38,$6C,$C6,$00 ; y (121) dc.b $00,$00,$C6,$C6,$C6,$7E,$06,$FC ; z (122) dc.b $00,$00,$FE,$8C,$18,$32,$FE,$00 ; { (123) dc.b $0E,$18,$18,$70,$18,$18,$0E,$00 ; | (124) dc.b $18,$18,$18,$18,$18,$18,$18,$00 ; } (125) dc.b $70,$18,$18,$0E,$18,$18,$70,$00 ; ~ (126) dc.b $76,$DC,$00,$00,$00,$00,$00,$00 even ; --- Scroll message --- scroll_message: dc.b " INTUITION ENGINE ... COPPER RASTER BARS - IMPOSSIBLE ON REAL VGA! ... " dc.b "THE COPPER CHANGES PALETTE ENTRIES MID-FRAME FOR THIS RAINBOW EFFECT ... " dc.b "68020 CODE FOR VGA MODE13H 3D CUBE AND 360 DEGREE SCROLLER... " dc.b "6502 CODE FOR EDGE OF DISGRACE BY BOOZE DESIGN FOR SID REMAPPED TO NATIVE SYNTH ... " dc.b "GREETS TO ALL DEMOSCENERS ... " dc.b " " scroll_msg_end: dc.b 0 even ; ============================================================================ ; SID MUSIC DATA ; ============================================================================ ; The .SID file contains actual 6502 machine code -- the original C64 ; music player. The Intuition Engine's 6502 core executes it and intercepts ; SID register writes ($D400-$D418), remapping them to the native synth. ; "Edge of Disgrace" by Booze Design, music by Goto80. ; ---------------------------------------------------------------------------- sid_data: incbin "../assets/music/Edge_of_Disgrace.sid" sid_data_end: end