main.c File Reference

DSP-1 pseudo-3D: a cube tumbling in 3D, rotated by the coprocessor. More...

#include <snes.h>
#include <snes/dsp1.h>

Functions
int	main (void)

Variables
static const s16	cube [8][3]
static const u8	dot_pal [4] = { 0x00, 0x00, 0xFF, 0x7F }
static const u8	dot_tile [32]

Detailed Description

DSP-1 pseudo-3D: a cube tumbling in 3D, rotated by the coprocessor.

Each frame the DSP-1 builds a rotation matrix (dsp1Attitude) and transforms the cube's 8 corners through it (dsp1Objective). The corners are drawn as 8 sprites at their orthographically-projected positions, so the cube visibly tumbles in 3D — all the 3D math runs on the NEC uPD77C25, not the 65816.

SNES Concepts

• DSP-1 coprocessor command interface (matrix + vector transform)
• Fixed-point 3D rotation offloaded from the CPU
• Orthographic projection (x',y' straight to screen)

What to Observe

• A cube of 8 dots rotating smoothly about two axes

Modules Used

console, dma, sprite, dsp1

Warning

Needs the DSP-1 firmware in luna (dsp1b.rom) — see the README.

See also

snes/dsp1.h, .claude/notes/tech/dsp1_reference.md

Function Documentation

main()

int main

(

void

)

Variable Documentation

cube

const s16 cube[8][3]

static

Initial value:

                      = {
    {-80,-80,-80}, { 80,-80,-80}, { 80, 80,-80}, {-80, 80,-80},
    {-80,-80, 80}, { 80,-80, 80}, { 80, 80, 80}, {-80, 80, 80},
}

The cube's 8 corners in model space (DSP-1 integer coordinates).

dot_pal

const u8 dot_pal[4] = { 0x00, 0x00, 0xFF, 0x7F }

static

Two colours: index 0 transparent, index 1 white ($7FFF).

dot_tile

const u8 dot_tile[32]

static

Initial value:

                         = {
    0xFF,0x00, 0xFF,0x00, 0xFF,0x00, 0xFF,0x00,
    0xFF,0x00, 0xFF,0x00, 0xFF,0x00, 0xFF,0x00,
    0,0,0,0,0,0,0,0, 0,0,0,0,0,0,0,0
}

8x8 4bpp tile, colour index 1 everywhere. In the SNES 4bpp layout planes 0/1 interleave per row, so plane 0 all-set is the ODD bytes 0,2,…,14.