; SPDX-FileCopyrightText: 2024-2026 Zayn Otley ; SPDX-License-Identifier: AGPL-3.0-or-later ; See LICENSES/AGPL-3.0-or-later.txt. ; ============================================================================ ; VOODOO MEGA DEMO - Twisting Starfield Tunnel with Rainbow Scrolltext ; IE32 for Intuition Engine - Voodoo 3D (640x480, triangle rasteriser) ; ============================================================================ ; ; === SDK QUICK REFERENCE === ; Target CPU: IE32 (custom 32-bit RISC, unsigned arithmetic only) ; Video chip: 3DFX Voodoo SST-1 (hardware 3D, Z-buffer, triangle rasteriser) ; Audio engine: SID (6502 CPU core + SID synthesiser) ; Assembler: ie32asm (IntuitionEngine native assembler) ; Include file: ie32.inc (Voodoo + SID player MMIO definitions) ; ; === WHAT THIS DEMO DOES === ; 1. TWISTING STARFIELD TUNNEL ; 256 stars distributed in a cylindrical pattern rush toward the camera. ; The tunnel centre oscillates via sine waves (Lissajous-like motion). ; Stars are coloured by depth: white and amber close, cyan and violet ; in the middle distance, blue in the far field. ; ; 2. RAINBOW BITMAP SCROLLTEXT ; Classic 5x7 bitmap font rendered as coloured Voodoo span quads. ; Horizontal scrolling with Y-axis sine-wave wobble. ; Per-character rainbow colour cycling via phase-shifted sine waves. ; ; 3. SID MUSIC PLAYBACK ; "Reggae 2" by Djinn/Fraction (1998) -- authentic 6502 code executed ; on the IntuitionEngine's internal 6502 CPU core, driving the SID ; synthesiser for genuine Commodore 64 sound. ; ; === THESE EFFECTS === ; The starfield tunnel, scrolltext, and chiptune music are the three ; pillars of the demoscene tradition that began on the Commodore 64 and ; Amiga in the mid-1980s. Nearly every demo combined these elements: ; ; - STARFIELD: evolved from 2D dots (1985) to 3D perspective (1988) to ; tunnel effects (1992) to hardware-accelerated geometry (1996+). ; This demo uses the Voodoo to render each star as a depth-scaled ; triangle, a technique that became possible with consumer 3D hardware. ; ; - SCROLLTEXT: the standard way to display credits and greetings. ; A 5x7 bitmap font (448 bytes for 64 characters) was the classic ; "small" format -- readable, memory-efficient, and fast to render. ; The sine-wave wobble and rainbow colouring are signature demoscene ; embellishments. ; ; - SID MUSIC: the MOS 6581 Sound Interface Device in the Commodore 64 ; produced a distinctive sound that defined an entire genre. A .SID ; file contains actual 6502 machine code that drives the chip's ; registers. The IntuitionEngine runs this code on its real 6502 core, ; with SID register writes ($D400-$D41C) remapped to the native ; synthesiser -- authentic playback without cycle-accurate emulation. ; ; === THE UNSIGNED ARITHMETIC CHALLENGE === ; The IE32 CPU has only unsigned 32-bit arithmetic. For 3D graphics where ; coordinates can be negative (left of centre, above centre), we use an ; offset-based technique: add WORLD_OFFSET (600) to all coordinates before ; calculation, keeping everything positive. After perspective projection, ; we subtract the projected offset to recover the true screen position: ; ; screen_x = proj_x - offset_proj + CENTER_X ; ; This works because projection is linear: ; proj(value + offset) = proj(value) + proj(offset) ; ; The sine table also uses an unsigned encoding: values 0-254 where ; 127 represents zero, 254 represents +1, and 0 represents -1. ; ; === MEMORY MAP === ; $0000-$0FFF Stack / reserved ; $1000-$87FF Program code ; $8800-$88FF Runtime variables (angles, star temps, scroll state) ; $10000-$103FF Sine lookup table (256 entries * 4 bytes) ; $20000-$20FFF Star data array (256 stars * 16 bytes) ; $0F0000+ Voodoo / SID player MMIO registers ; ; === BUILD AND RUN === ; sdk/bin/ie32asm sdk/examples/asm/voodoo_mega_demo.asm ; ; (c) 2024-2026 Zayn Otley - AGPL-3.0-or-later ; ============================================================================ .include "ie32.inc" ; ============================================================================ ; Constants ; ============================================================================ ; --- Display --- .equ SCREEN_W 640 .equ SCREEN_H 480 .equ CENTER_X 320 .equ CENTER_Y 240 ; --- Fixed-point --- .equ FP_SHIFT 4 ; 12.4 vertex format (pixel * 16) ; --- Starfield --- .equ NUM_STARS 256 .equ TUNNEL_RADIUS 150 ; Max distance from tunnel centre axis .equ NEAR_PLANE 80 ; Respawn threshold .equ FAR_PLANE 1000 ; Spawn distance .equ FOCAL_LENGTH 200 ; Perspective projection focal length .equ TWIST_AMP 120 ; Tunnel centre oscillation amplitude .equ WORLD_OFFSET 600 ; Keeps all unsigned coords positive .equ PROJ_SCALE_MAX_Z 2304 ; Covers initial and respawned star depth .equ PROJ_SCALE_SHIFT 8 ; Projection scale table fractional bits ; --- Scrolltext --- .equ SCROLL_SPEED 3 ; Pixels per frame .equ CHAR_WIDTH 6 ; 5 content + 1 spacing .equ CHAR_HEIGHT 7 .equ PIXEL_SIZE 4 ; Screen pixels per font pixel .equ TEXT_SHADOW_OFFSET 2 ; Pixel offset for dark readability pass .equ SCROLL_Y_POS 340 ; Base Y position on screen .equ WOBBLE_AMP 50 ; Sine-wave Y amplitude .equ MAX_CHARS 24 ; Max visible characters .equ SCROLL_WRAP 6944 ; 217 message chars * 32 pixels/char ; --- Runtime variables --- .equ frame_counter 0x8800 .equ rand_seed 0x8804 .equ twist_x 0x8808 .equ twist_y 0x880C .equ cur_z 0x8810 .equ offset_proj 0x8814 ; --- Scrolltext variables --- .equ scroll_offset 0x8880 .equ scroll_char_num 0x8884 .equ scroll_char_code 0x8888 .equ scroll_pixel_x 0x888C .equ scroll_pixel_y 0x8890 .equ scroll_screen_x 0x8894 .equ scroll_screen_y 0x8898 .equ scroll_font_ptr 0x889C .equ scroll_font_row 0x88A0 .equ scroll_base_x 0x88A4 .equ scroll_base_y 0x88A8 .equ scroll_msg_len 0x88AC .equ scroll_span_start 0x88B0 .equ scroll_span_width 0x88B4 .equ scroll_shadow_pass 0x88B8 .equ scroll_rect_w 0x88BC .equ proj_scale 0x88C0 ; --- Lookup tables and star data --- .equ sin_table 0x10000 ; 256 entries (unsigned: 0=min, 127=zero, 254=max) .equ proj_scale_table 0x11000 ; (FOCAL_LENGTH << 8) / z lookup table .equ star_array 0x20000 ; 16 bytes per star: angle, radius, z, speed ; --- Embedded SID file size --- .equ sid_data_size 4790 ; ============================================================================ ; Program entry -- initialise Voodoo, sine table, stars, SID music ; ============================================================================ .org 0x1000 start: ; --- Enable Voodoo, set 640x480, configure Z-buffer --- LDA #1 STA @VOODOO_ENABLE LDA #0x02800000 OR A, #0x1E0 STA @VOODOO_VIDEO_DIM ; Depth test (less or equal; the function sits in bits 5-7, hence *32), ; dithering, RGB writes and depth writes. LDA #VOODOO_FBZ_DEPTH_ENABLE|(VOODOO_DEPTH_LESSEQUAL*32)|VOODOO_FBZ_DITHER|VOODOO_FBZ_RGB_WRITE|VOODOO_FBZ_DEPTH_WRITE STA @VOODOO_FBZ_MODE LDA #0 SHL A, #16 OR A, #SCREEN_W STA @VOODOO_CLIP_LEFT_RIGHT LDA #0 SHL A, #16 OR A, #SCREEN_H STA @VOODOO_CLIP_LOW_Y_HIGH LDA #VOODOO_COMBINE_ITERATED STA @VOODOO_FBZCOLOR_PATH ; --- Zero frame counter and scroll offset --- LDA #0 STA @frame_counter STA @scroll_offset LDA #54321 STA @rand_seed ; --- Build the 256-entry sine table at runtime --- JSR build_sin_table ; --- Build reciprocal projection table once instead of dividing per star --- JSR build_proj_scale_table ; --- Scatter 256 stars randomly through the tunnel --- JSR init_stars ; --- Start SID music: "Reggae 2" by Djinn/Fraction (1998) --- ; a demo without music is incomplete. The SID player loads the ; embedded .SID file into the 6502 CPU core, which executes the original ; C64 music player code ~50 times per second to drive the synthesiser. LDA #sid_data STA @SID_PLAY_PTR LDA #sid_data_size STA @SID_PLAY_LEN LDA #0x05 ; Start (bit 0) + Loop (bit 2) STA @SID_PLAY_CTRL ; ============================================================================ ; Main loop -- one iteration per frame (~60 FPS) ; ============================================================================ main_loop: ; --- Clear framebuffer to near-black with blue tint --- LDA #0xFF040410 STA @VOODOO_COLOR0 LDA #0 STA @VOODOO_FAST_FILL_CMD JSR draw_background ; --- Calculate tunnel twist (X axis) --- ; different frequencies: if both axes used the same sine, the tunnel ; would move in a circle. Different rates create a Lissajous figure. LDA @frame_counter AND A, #255 JSR get_sin MUL A, #TWIST_AMP SHR A, #6 SUB A, #238 STA @twist_x ; --- Calculate tunnel twist (Y axis, different frequency + phase) --- LDA @frame_counter MUL A, #3 SHR A, #1 ADD A, #64 ; 90-degree phase offset AND A, #255 JSR get_sin MUL A, #TWIST_AMP SHR A, #6 SUB A, #238 STA @twist_y ; --- Process all 256 stars --- LDY #0 star_loop: ; Calculate star array address: base + index * 16 LDA Y SHL A, #4 LDX #star_array ADD X, A ; Load star data into working variables LDA [X] STA @0x8820 ; angle PUSH X ADD X, #4 LDA [X] STA @0x8824 ; radius ADD X, #4 LDA [X] STA @0x8828 ; z ADD X, #4 LDA [X] STA @0x882C ; speed POP X ; --- Move star toward the camera --- LDA @0x8828 SUB A, @0x882C STA @0x8828 ; --- Respawn if star has passed the near plane --- LDA @0x8828 SUB A, #NEAR_PLANE JGT A, no_respawn JSR random AND A, #255 STA @0x8820 ; new angle JSR random AND A, #255 MUL A, #TUNNEL_RADIUS SHR A, #8 ADD A, #15 STA @0x8824 ; new radius JSR random AND A, #511 ADD A, #FAR_PLANE STA @0x8828 ; new z JSR random AND A, #7 ADD A, #2 STA @0x882C ; new speed (2-9) no_respawn: ; --- Write updated star data back --- LDA @0x8820 STA [X] ADD X, #4 LDA @0x8824 STA [X] ADD X, #4 LDA @0x8828 STA [X] ADD X, #4 LDA @0x882C STA [X] ; === 3D to 2D projection === ; the offset technique: cos/sin values are 0-254 (127 = zero). ; Multiplying by radius gives an unsigned result that cannot represent ; negative coordinates. Adding WORLD_OFFSET keeps everything positive ; through division; we subtract the projected offset afterwards. ; Cosine = sin(angle + 64) LDA @0x8820 ADD A, #64 AND A, #255 JSR get_sin STA @0x8830 ; cos_val LDA @0x8820 JSR get_sin STA @0x8834 ; sin_val ; local_x = cos * radius / 64 + WORLD_OFFSET LDA @0x8830 MUL A, @0x8824 SHR A, #6 ADD A, #WORLD_OFFSET STA @0x8838 ; local_y = sin * radius / 64 + WORLD_OFFSET LDA @0x8834 MUL A, @0x8824 SHR A, #6 ADD A, #WORLD_OFFSET STA @0x883C ; Apply twist offset LDA @0x8838 ADD A, @twist_x ADD A, #128 STA @0x8838 LDA @0x883C ADD A, @twist_y ADD A, #128 STA @0x883C ; Validate Z (skip if too close for safe division) LDA @0x8828 STA @cur_z LDB #10 SUB B, A JGT B, skip_star ; Perspective projection: proj = world * scale >> 8 ; Scale table removes three divides from the per-star hot path. LDA @cur_z SHL A, #2 LDX #proj_scale_table ADD X, A LDA [X] STA @proj_scale LDA @0x8838 MUL A, @proj_scale SHR A, #PROJ_SCALE_SHIFT STA @0x8848 ; proj_x LDA @0x883C MUL A, @proj_scale SHR A, #PROJ_SCALE_SHIFT STA @0x884C ; proj_y ; Subtract projected offset to recover true screen position LDA #127 MUL A, @0x8824 SHR A, #6 ADD A, #WORLD_OFFSET ADD A, #128 MUL A, @proj_scale SHR A, #PROJ_SCALE_SHIFT STA @offset_proj LDA @0x8848 SUB A, @offset_proj ADD A, #CENTER_X STA @0x8850 ; screen_x LDA @0x884C SUB A, @offset_proj ADD A, #CENTER_Y STA @0x8854 ; screen_y ; --- Screen bounds check (sign-bit trick for unsigned "negative") --- LDA @0x8850 AND A, #0x80000000 JNZ A, skip_star LDA @0x8850 SUB A, #SCREEN_W AND A, #0x80000000 JZ A, skip_star LDA @0x8854 AND A, #0x80000000 JNZ A, skip_star LDA @0x8854 SUB A, #SCREEN_H AND A, #0x80000000 JZ A, skip_star ; --- Depth-based size and colour (atmospheric perspective) --- ; Close stars burn white and amber; distant stars fall through cyan, ; violet, and blue. The ramp is branch-based to avoid extra table loads. LDA @cur_z SUB A, #150 JLT A, depth_white LDA @cur_z SUB A, #240 JLT A, depth_amber LDA @cur_z SUB A, #380 JLT A, depth_cyan LDA @cur_z SUB A, #620 JLT A, depth_violet LDA @cur_z SUB A, #900 JLT A, depth_blue ; Very far: dim blue. LDA #10 STA @0x8858 LDA #0x0300 STA @VOODOO_START_R LDA #0x0500 STA @VOODOO_START_G LDA #0x0A00 STA @VOODOO_START_B JMP color_ok depth_blue: LDA #16 STA @0x8858 LDA #0x0400 STA @VOODOO_START_R LDA #0x0800 STA @VOODOO_START_G LDA #0x1000 STA @VOODOO_START_B JMP color_ok depth_violet: LDA #24 STA @0x8858 LDA #0x0C00 STA @VOODOO_START_R LDA #0x0500 STA @VOODOO_START_G LDA #0x1000 STA @VOODOO_START_B JMP color_ok depth_cyan: LDA #32 STA @0x8858 LDA #0x0800 STA @VOODOO_START_R LDA #0x1000 STA @VOODOO_START_G STA @VOODOO_START_B JMP color_ok depth_amber: LDA #48 STA @0x8858 LDA #0x1000 STA @VOODOO_START_R LDA #0x0B00 STA @VOODOO_START_G LDA #0x0400 STA @VOODOO_START_B JMP color_ok depth_white: LDA #64 STA @0x8858 LDA #0x1000 STA @VOODOO_START_R STA @VOODOO_START_G STA @VOODOO_START_B color_ok: LDA #0x1000 STA @VOODOO_START_A LDA #0x8000 STA @VOODOO_START_Z ; --- Convert to 12.4 fixed-point --- LDA @0x8850 SHL A, #4 STA @0x8850 LDA @0x8854 SHL A, #4 STA @0x8854 ; --- Draw star as upward-pointing triangle --- ; A (top) ; / \ ; B---C (bottom) ; Vertex A (top centre) LDA @0x8850 STA @VOODOO_VERTEX_AX LDA @0x8854 SUB A, @0x8858 STA @VOODOO_VERTEX_AY ; Vertex B (bottom left) LDA @0x8850 SUB A, @0x8858 STA @VOODOO_VERTEX_BX LDA @0x8854 ADD A, @0x8858 STA @VOODOO_VERTEX_BY ; Vertex C (bottom right) LDA @0x8850 ADD A, @0x8858 STA @VOODOO_VERTEX_CX LDA @0x8854 ADD A, @0x8858 STA @VOODOO_VERTEX_CY LDA #0 STA @VOODOO_TRIANGLE_CMD skip_star: ADD Y, #1 LDB #NUM_STARS SUB B, Y JNZ B, star_loop ; --- Draw scrolltext --- JSR draw_scrolltext ; --- Swap buffers --- LDA #VOODOO_SWAP_VSYNC STA @VOODOO_SWAP_BUFFER_CMD ; --- Advance animation --- LDA @frame_counter ADD A, #1 STA @frame_counter LDA @scroll_offset ADD A, #SCROLL_SPEED LDB A SUB B, #SCROLL_WRAP JLT B, scroll_advance_store LDA B scroll_advance_store: STA @scroll_offset JMP main_loop ; ============================================================================ ; Subroutines ; ============================================================================ ; ---------------------------------------------------------------------------- ; draw_background -- two Gouraud shaded triangles for a cheap deep-space wash ; ---------------------------------------------------------------------------- draw_background: LDA #0 STA @VOODOO_COLOR_SELECT LDA #0x0200 STA @VOODOO_START_R LDA #0x0200 STA @VOODOO_START_G LDA #0x0800 STA @VOODOO_START_B LDA #0x1000 STA @VOODOO_START_A LDA #0xF000 STA @VOODOO_START_Z LDA #1 STA @VOODOO_COLOR_SELECT LDA #0x0800 STA @VOODOO_START_R LDA #0x0200 STA @VOODOO_START_G LDA #0x1000 STA @VOODOO_START_B LDA #0x1000 STA @VOODOO_START_A LDA #0xF000 STA @VOODOO_START_Z LDA #2 STA @VOODOO_COLOR_SELECT LDA #0x0000 STA @VOODOO_START_R LDA #0x0800 STA @VOODOO_START_G LDA #0x1000 STA @VOODOO_START_B LDA #0x1000 STA @VOODOO_START_A LDA #0xF000 STA @VOODOO_START_Z LDA #0 STA @VOODOO_VERTEX_AX STA @VOODOO_VERTEX_AY LDA #10240 ; 640 << 4 STA @VOODOO_VERTEX_BX LDA #0 STA @VOODOO_VERTEX_BY LDA #0 STA @VOODOO_VERTEX_CX LDA #7680 ; 480 << 4 STA @VOODOO_VERTEX_CY LDA #0 STA @VOODOO_TRIANGLE_CMD LDA #0 STA @VOODOO_COLOR_SELECT LDA #0x0800 STA @VOODOO_START_R LDA #0x0200 STA @VOODOO_START_G LDA #0x1000 STA @VOODOO_START_B LDA #0x1000 STA @VOODOO_START_A LDA #0xF000 STA @VOODOO_START_Z LDA #1 STA @VOODOO_COLOR_SELECT LDA #0x0200 STA @VOODOO_START_R LDA #0x0000 STA @VOODOO_START_G LDA #0x0800 STA @VOODOO_START_B LDA #0x1000 STA @VOODOO_START_A LDA #0xF000 STA @VOODOO_START_Z LDA #2 STA @VOODOO_COLOR_SELECT LDA #0x0000 STA @VOODOO_START_R LDA #0x0800 STA @VOODOO_START_G LDA #0x1000 STA @VOODOO_START_B LDA #0x1000 STA @VOODOO_START_A LDA #0xF000 STA @VOODOO_START_Z LDA #10240 STA @VOODOO_VERTEX_AX LDA #0 STA @VOODOO_VERTEX_AY LDA #10240 STA @VOODOO_VERTEX_BX LDA #7680 STA @VOODOO_VERTEX_BY LDA #0 STA @VOODOO_VERTEX_CX LDA #7680 STA @VOODOO_VERTEX_CY LDA #0 STA @VOODOO_TRIANGLE_CMD RTS ; ---------------------------------------------------------------------------- ; get_sin -- look up unsigned sine value from table ; Input: A = angle (0-255) ; Output: A = sine value (0-254, where 127 = zero) ; ---------------------------------------------------------------------------- get_sin: AND A, #255 MUL A, #4 LDX #sin_table ADD X, A LDA [X] RTS ; ---------------------------------------------------------------------------- ; random -- linear congruential generator (Numerical Recipes constants) ; Output: A = pseudo-random 32-bit value ; ---------------------------------------------------------------------------- random: LDA @rand_seed MUL A, #1664525 ADD A, #1013904223 STA @rand_seed RTS ; ============================================================================ ; draw_scrolltext -- render bitmap font text with rainbow colours and wobble ; ============================================================================ ; ; quads instead of pixels: each "on" pixel in the 5x7 font is drawn as ; a 4x4 screen-pixel quad (two Voodoo triangles). This makes the text large ; enough to read at 640x480 while keeping the charming bitmap aesthetic. ; ; The rainbow colour uses phase-shifted sine waves for R, G, B: ; Red = sin(angle + 0 degrees) ; Green = sin(angle + 120 degrees) ; Blue = sin(angle + 240 degrees) draw_scrolltext: PUSH Y LDA #1 STA @scroll_shadow_pass JSR draw_scrolltext_pass LDA #0 STA @scroll_shadow_pass JSR draw_scrolltext_pass POP Y RTS draw_scrolltext_pass: PUSH Y ; Fixed alpha for all scrolltext. LDA #0x1000 STA @VOODOO_START_A LDA @scroll_shadow_pass JZ A, scroll_z_front LDA #0x2400 JMP scroll_z_store scroll_z_front: LDA #0x2000 scroll_z_store: STA @VOODOO_START_Z ; Calculate first visible character index. LDA @scroll_offset SHR A, #5 STA @scroll_char_num LDY #0 scroll_char_loop: LDA Y SUB A, #MAX_CHARS JGE A, scroll_text_done ; Modulo wraparound for looping message (217 characters). LDA @scroll_char_num ADD A, Y scroll_mod: SUB A, #217 JGE A, scroll_mod ADD A, #217 ; Fetch ASCII character from message. LDX #scroll_message ADD X, A LDA [X] AND A, #0xFF STA @scroll_char_code JZ A, scroll_text_done ; --- Character X position --- LDA Y MUL A, #24 STA @scroll_base_x LDB @scroll_offset AND B, #31 LDA @scroll_base_x SUB A, B STA @scroll_base_x ; --- Character Y position (with sine-wave wobble) --- LDA @scroll_base_x ADD A, @frame_counter SHR A, #3 AND A, #255 JSR get_sin MUL A, #WOBBLE_AMP SHR A, #7 ADD A, #SCROLL_Y_POS SUB A, #20 STA @scroll_base_y ; --- Font data pointer --- LDA @scroll_char_code SUB A, #32 STA @scroll_font_ptr ; Bounds check (ASCII 32-95 only). LDA @scroll_font_ptr AND A, #0x80000000 JNZ A, scroll_next_chr LDA @scroll_font_ptr SUB A, #64 AND A, #0x80000000 JZ A, scroll_next_chr LDA @scroll_font_ptr MUL A, #7 STA @scroll_font_ptr LDA #font_data ADD A, @scroll_font_ptr STA @scroll_font_ptr ; --- Shadow or rainbow colour --- LDA @scroll_shadow_pass JZ A, scroll_colour_rainbow LDA #0x0100 STA @VOODOO_START_R STA @VOODOO_START_G LDA #0x0180 STA @VOODOO_START_B JMP scroll_colour_done scroll_colour_rainbow: ; Red (phase 0 degrees). LDA Y SHL A, #5 ADD A, @frame_counter SHL A, #2 AND A, #255 JSR get_sin SHR A, #4 SHL A, #8 ADD A, #0x0400 STA @VOODOO_START_R ; Green (phase 120 degrees = 85). LDA Y SHL A, #5 ADD A, @frame_counter SHL A, #2 ADD A, #85 AND A, #255 JSR get_sin SHR A, #4 SHL A, #8 ADD A, #0x0400 STA @VOODOO_START_G ; Blue (phase 240 degrees = 170). LDA Y SHL A, #5 ADD A, @frame_counter SHL A, #2 ADD A, #170 AND A, #255 JSR get_sin SHR A, #4 SHL A, #8 ADD A, #0x0400 STA @VOODOO_START_B scroll_colour_done: ; --- Render 5x7 character bitmap as horizontal spans --- PUSH Y LDY #0 ; Row counter scroll_row_loop: LDA Y SUB A, #7 JGE A, scroll_row_done ; Load font row byte. LDA @scroll_font_ptr LDX A ADD X, Y LDA [X] AND A, #0xFF STA @scroll_font_row LDX #0 ; Column counter scroll_span_scan: LDA X SUB A, #5 JGE A, scroll_row_done_spans ; Test current font bit using a small mask table. LDA X PUSH X LDX #font_mask_table ADD X, A LDA [X] AND A, #0xFF POP X LDB @scroll_font_row AND B, A JZ B, scroll_span_skip_pixel LDA X STA @scroll_span_start LDA #0 STA @scroll_span_width scroll_span_grow: LDA X SUB A, #5 JGE A, scroll_span_draw LDA X PUSH X LDX #font_mask_table ADD X, A LDA [X] AND A, #0xFF POP X LDB @scroll_font_row AND B, A JZ B, scroll_span_draw ADD X, #1 LDA @scroll_span_width ADD A, #1 STA @scroll_span_width JMP scroll_span_grow scroll_span_draw: ; Screen position for this span. LDA @scroll_span_start MUL A, #PIXEL_SIZE ADD A, @scroll_base_x STA @scroll_screen_x PUSH Y LDA Y MUL A, #PIXEL_SIZE ADD A, @scroll_base_y STA @scroll_screen_y POP Y LDA @scroll_span_width MUL A, #PIXEL_SIZE STA @scroll_rect_w LDA @scroll_shadow_pass JZ A, scroll_no_shadow_offset LDA @scroll_screen_x ADD A, #TEXT_SHADOW_OFFSET STA @scroll_screen_x LDA @scroll_screen_y ADD A, #TEXT_SHADOW_OFFSET STA @scroll_screen_y scroll_no_shadow_offset: JSR draw_scroll_rect JMP scroll_span_scan scroll_span_skip_pixel: ADD X, #1 JMP scroll_span_scan scroll_row_done_spans: ADD Y, #1 JMP scroll_row_loop scroll_row_done: POP Y scroll_next_chr: ADD Y, #1 JMP scroll_char_loop scroll_text_done: POP Y RTS draw_scroll_rect: ; Bounds check. Voodoo clipping handles the right and bottom edges. LDA @scroll_screen_x AND A, #0x80000000 JNZ A, scroll_rect_done LDA @scroll_screen_x SUB A, #SCREEN_W JGE A, scroll_rect_done LDA @scroll_screen_y AND A, #0x80000000 JNZ A, scroll_rect_done LDA @scroll_screen_y SUB A, #SCREEN_H JGE A, scroll_rect_done ; Convert position and width to 12.4 fixed-point. LDA @scroll_screen_x SHL A, #4 STA @scroll_screen_x LDA @scroll_screen_y SHL A, #4 STA @scroll_screen_y LDA @scroll_rect_w SHL A, #4 STA @scroll_rect_w ; Triangle 1: top-left, top-right, bottom-left. LDA @scroll_screen_x STA @VOODOO_VERTEX_AX LDA @scroll_screen_y STA @VOODOO_VERTEX_AY LDA @scroll_screen_x ADD A, @scroll_rect_w STA @VOODOO_VERTEX_BX LDA @scroll_screen_y STA @VOODOO_VERTEX_BY LDA @scroll_screen_x STA @VOODOO_VERTEX_CX LDA @scroll_screen_y ADD A, #64 STA @VOODOO_VERTEX_CY LDA #0 STA @VOODOO_TRIANGLE_CMD ; Triangle 2: top-right, bottom-right, bottom-left. LDA @scroll_screen_x ADD A, @scroll_rect_w STA @VOODOO_VERTEX_AX LDA @scroll_screen_y STA @VOODOO_VERTEX_AY LDA @scroll_screen_x ADD A, @scroll_rect_w STA @VOODOO_VERTEX_BX LDA @scroll_screen_y ADD A, #64 STA @VOODOO_VERTEX_BY LDA @scroll_screen_x STA @VOODOO_VERTEX_CX LDA @scroll_screen_y ADD A, #64 STA @VOODOO_VERTEX_CY LDA #0 STA @VOODOO_TRIANGLE_CMD scroll_rect_done: RTS ; ============================================================================ ; build_sin_table -- generate 256-entry unsigned sine table using quarter-wave ; ============================================================================ ; quarter-wave: a full sine has mirror symmetry. We store only one ; quarter (64 values in quarter_sin) and derive the other three quadrants ; at runtime, saving ROM space and demonstrating the technique. build_sin_table: LDY #0 LDX #sin_table sin_loop: ; Determine quadrant (bits 7-6) LDA Y SHR A, #6 STA @0x8870 ; Index within quadrant (bits 5-0) LDA Y AND A, #63 ; Mirror index for odd quadrants (1, 3) LDB @0x8870 AND B, #1 JZ B, no_mirror LDB #63 SUB B, A LDA B no_mirror: ; Look up quarter-sine value PUSH X LDX #quarter_sin ADD X, A LDA [X] AND A, #0xFF POP X ; Quadrants 2-3 are the negative half: value = 127 - quarter_sin ; Quadrants 0-1 are the positive half: value = quarter_sin + 127 LDB @0x8870 AND B, #2 JZ B, sin_pos LDB #127 SUB B, A LDA B JMP store_sin sin_pos: ADD A, #127 store_sin: STA [X] ADD X, #4 ADD Y, #1 LDB #256 SUB B, Y JNZ B, sin_loop RTS ; ============================================================================ ; build_proj_scale_table -- generate reciprocal projection scale values ; ============================================================================ ; Each entry is (FOCAL_LENGTH << 8) / z. Building this once is much cheaper ; than dividing three times for every visible star on every frame. build_proj_scale_table: LDY #0 LDX #proj_scale_table proj_scale_loop: LDA Y JZ A, proj_scale_zero LDA #FOCAL_LENGTH SHL A, #PROJ_SCALE_SHIFT DIV A, Y JMP proj_scale_store proj_scale_zero: LDA #0 proj_scale_store: STA [X] ADD X, #4 ADD Y, #1 LDB #PROJ_SCALE_MAX_Z ADD B, #1 SUB B, Y JNZ B, proj_scale_loop RTS ; ============================================================================ ; init_stars -- scatter 256 stars randomly through the tunnel volume ; ============================================================================ init_stars: LDY #0 LDX #star_array init_loop: JSR random AND A, #255 STA [X] ; angle ADD X, #4 JSR random AND A, #255 MUL A, #TUNNEL_RADIUS SHR A, #8 ADD A, #15 STA [X] ; radius ADD X, #4 JSR random AND A, #2047 ADD A, #NEAR_PLANE STA [X] ; z (wider initial spread) ADD X, #4 JSR random AND A, #7 ADD A, #2 STA [X] ; speed (2-9) ADD X, #4 ADD Y, #1 LDB #NUM_STARS SUB B, Y JNZ B, init_loop RTS ; ============================================================================ ; Data section ; ============================================================================ ; ---------------------------------------------------------------------------- ; Quarter-sine table (64 entries, 0-127) ; Full table is built at runtime by build_sin_table using symmetry. ; ---------------------------------------------------------------------------- quarter_sin: .byte 0, 3, 6, 10, 13, 16, 19, 22 .byte 25, 28, 31, 34, 37, 40, 43, 46 .byte 49, 51, 54, 57, 60, 62, 65, 68 .byte 70, 73, 75, 78, 80, 82, 85, 87 .byte 89, 91, 94, 96, 98, 100, 102, 103 .byte 105, 107, 108, 110, 112, 113, 114, 116 .byte 117, 118, 119, 120, 121, 122, 123, 124 .byte 124, 125, 125, 126, 126, 127, 127, 127 ; ---------------------------------------------------------------------------- ; Scroll message (217 characters, loops continuously) ; ---------------------------------------------------------------------------- scroll_message: .ascii " INTUITION ENGINE 3DFX VOODOO TWISTING STARFIELD TUNNEL CODE: IE32 RISC ASM BY INTUITION MUSIC: REGGAE 2 BY DJINN (6502 + SID) GREETINGS TO ALL DEMOSCENERS... VISIT INTUITIONSUBSYNTH.COM " .byte 0 ; ---------------------------------------------------------------------------- ; Font bit masks for columns 0-4. ; ---------------------------------------------------------------------------- font_mask_table: .byte 0x10, 0x08, 0x04, 0x02, 0x01 ; ---------------------------------------------------------------------------- ; 5x7 bitmap font data (ASCII 32-95, 64 characters, 448 bytes) ; Each character is 7 bytes (one per row), bits 4-0 = columns left to right. ; ---------------------------------------------------------------------------- font_data: ; Space (32) .byte 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 ; ! (33) .byte 0x04, 0x04, 0x04, 0x04, 0x00, 0x04, 0x00 ; " (34) .byte 0x0A, 0x0A, 0x00, 0x00, 0x00, 0x00, 0x00 ; # (35) .byte 0x0A, 0x1F, 0x0A, 0x0A, 0x1F, 0x0A, 0x00 ; $ (36) .byte 0x04, 0x0F, 0x14, 0x0E, 0x05, 0x1E, 0x04 ; % (37) .byte 0x18, 0x19, 0x02, 0x04, 0x08, 0x13, 0x03 ; & (38) .byte 0x08, 0x14, 0x14, 0x08, 0x15, 0x12, 0x0D ; ' (39) .byte 0x04, 0x04, 0x00, 0x00, 0x00, 0x00, 0x00 ; ( (40) .byte 0x02, 0x04, 0x08, 0x08, 0x08, 0x04, 0x02 ; ) (41) .byte 0x08, 0x04, 0x02, 0x02, 0x02, 0x04, 0x08 ; * (42) .byte 0x00, 0x04, 0x15, 0x0E, 0x15, 0x04, 0x00 ; + (43) .byte 0x00, 0x04, 0x04, 0x1F, 0x04, 0x04, 0x00 ; , (44) .byte 0x00, 0x00, 0x00, 0x00, 0x04, 0x04, 0x08 ; - (45) .byte 0x00, 0x00, 0x00, 0x1F, 0x00, 0x00, 0x00 ; . (46) .byte 0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x00 ; / (47) .byte 0x01, 0x02, 0x02, 0x04, 0x08, 0x08, 0x10 ; 0 (48) .byte 0x0E, 0x11, 0x13, 0x15, 0x19, 0x11, 0x0E ; 1 (49) .byte 0x04, 0x0C, 0x04, 0x04, 0x04, 0x04, 0x0E ; 2 (50) .byte 0x0E, 0x11, 0x01, 0x06, 0x08, 0x10, 0x1F ; 3 (51) .byte 0x0E, 0x11, 0x01, 0x06, 0x01, 0x11, 0x0E ; 4 (52) .byte 0x02, 0x06, 0x0A, 0x12, 0x1F, 0x02, 0x02 ; 5 (53) .byte 0x1F, 0x10, 0x1E, 0x01, 0x01, 0x11, 0x0E ; 6 (54) .byte 0x06, 0x08, 0x10, 0x1E, 0x11, 0x11, 0x0E ; 7 (55) .byte 0x1F, 0x01, 0x02, 0x04, 0x08, 0x08, 0x08 ; 8 (56) .byte 0x0E, 0x11, 0x11, 0x0E, 0x11, 0x11, 0x0E ; 9 (57) .byte 0x0E, 0x11, 0x11, 0x0F, 0x01, 0x02, 0x0C ; : (58) .byte 0x00, 0x00, 0x04, 0x00, 0x04, 0x00, 0x00 ; ; (59) .byte 0x00, 0x00, 0x04, 0x00, 0x04, 0x04, 0x08 ; < (60) .byte 0x02, 0x04, 0x08, 0x10, 0x08, 0x04, 0x02 ; = (61) .byte 0x00, 0x00, 0x1F, 0x00, 0x1F, 0x00, 0x00 ; > (62) .byte 0x08, 0x04, 0x02, 0x01, 0x02, 0x04, 0x08 ; ? (63) .byte 0x0E, 0x11, 0x01, 0x02, 0x04, 0x00, 0x04 ; @ (64) .byte 0x0E, 0x11, 0x17, 0x15, 0x17, 0x10, 0x0E ; A (65) .byte 0x0E, 0x11, 0x11, 0x1F, 0x11, 0x11, 0x11 ; B (66) .byte 0x1E, 0x11, 0x11, 0x1E, 0x11, 0x11, 0x1E ; C (67) .byte 0x0E, 0x11, 0x10, 0x10, 0x10, 0x11, 0x0E ; D (68) .byte 0x1E, 0x11, 0x11, 0x11, 0x11, 0x11, 0x1E ; E (69) .byte 0x1F, 0x10, 0x10, 0x1E, 0x10, 0x10, 0x1F ; F (70) .byte 0x1F, 0x10, 0x10, 0x1E, 0x10, 0x10, 0x10 ; G (71) .byte 0x0E, 0x11, 0x10, 0x17, 0x11, 0x11, 0x0E ; H (72) .byte 0x11, 0x11, 0x11, 0x1F, 0x11, 0x11, 0x11 ; I (73) .byte 0x0E, 0x04, 0x04, 0x04, 0x04, 0x04, 0x0E ; J (74) .byte 0x01, 0x01, 0x01, 0x01, 0x11, 0x11, 0x0E ; K (75) .byte 0x11, 0x12, 0x14, 0x18, 0x14, 0x12, 0x11 ; L (76) .byte 0x10, 0x10, 0x10, 0x10, 0x10, 0x10, 0x1F ; M (77) .byte 0x11, 0x1B, 0x15, 0x15, 0x11, 0x11, 0x11 ; N (78) .byte 0x11, 0x19, 0x15, 0x13, 0x11, 0x11, 0x11 ; O (79) .byte 0x0E, 0x11, 0x11, 0x11, 0x11, 0x11, 0x0E ; P (80) .byte 0x1E, 0x11, 0x11, 0x1E, 0x10, 0x10, 0x10 ; Q (81) .byte 0x0E, 0x11, 0x11, 0x11, 0x15, 0x12, 0x0D ; R (82) .byte 0x1E, 0x11, 0x11, 0x1E, 0x14, 0x12, 0x11 ; S (83) .byte 0x0E, 0x11, 0x10, 0x0E, 0x01, 0x11, 0x0E ; T (84) .byte 0x1F, 0x04, 0x04, 0x04, 0x04, 0x04, 0x04 ; U (85) .byte 0x11, 0x11, 0x11, 0x11, 0x11, 0x11, 0x0E ; V (86) .byte 0x11, 0x11, 0x11, 0x11, 0x0A, 0x0A, 0x04 ; W (87) .byte 0x11, 0x11, 0x11, 0x15, 0x15, 0x1B, 0x11 ; X (88) .byte 0x11, 0x11, 0x0A, 0x04, 0x0A, 0x11, 0x11 ; Y (89) .byte 0x11, 0x11, 0x0A, 0x04, 0x04, 0x04, 0x04 ; Z (90) .byte 0x1F, 0x01, 0x02, 0x04, 0x08, 0x10, 0x1F ; [ (91) .byte 0x0E, 0x08, 0x08, 0x08, 0x08, 0x08, 0x0E ; \ (92) .byte 0x10, 0x08, 0x08, 0x04, 0x02, 0x02, 0x01 ; ] (93) .byte 0x0E, 0x02, 0x02, 0x02, 0x02, 0x02, 0x0E ; ^ (94) .byte 0x04, 0x0A, 0x11, 0x00, 0x00, 0x00, 0x00 ; _ (95) .byte 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x1F ; ============================================================================ ; SID music data -- "Reggae 2" by Kamil Degorski (Djinn) / Fraction (1998) ; ============================================================================ ; embedded: the .SID file contains both the 6502 player code and the ; pattern data. The IntuitionEngine's 6502 core executes this code directly, ; with SID register writes ($D400-$D41C) remapped to the native synthesiser. sid_data: .incbin "../assets/music/Reggae_2.sid" sid_data_end: