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Some really rough/hacky code that remaps 6 32x32 LED panels to a 96x96 size triangle (3 panels on bottom row, 2 on middle row, and 1 panel on top row).

The order of wiring is specific and unusual, in order to support smaller IDC cable lengths. The IDC ribbon starts with the PI at the bottom right panel, snakes along to the left, then up to the left panel of the second row, snaking right and up to the top row.

The two panels in the middle row are placed upside-down.

Use --led-chain=6 when running.

Tested with Adafruit HAT (PWM mod) and 6 Adafruit 5mm pitch 32x32 LED matrix panels. https://github.com/hzeller/rpi-rgb-led-matrix/

main.cc

bool remapPixels (int& x, int& y) {
  int width = LED_PIXELS_WIDTH;
  int height = LED_PIXELS_HEIGHT;

  // now we remap this pixel to the new space
  int nx = x;
  int ny = y;

  // find out which row we are on
  int row;
  if (y >= 0 && y < 32) row = 0;
  else if (y >= 32 && y < 64) row = 1;
  else if (y >= 64 && y < 96) row = 2;
  else return false;

  if (row == 0) {
    // outside of top row bounds
    if (x < 32 || x >= 64) return false;
    // center top row of pixels
    nx -= 32;
  } else if (row == 1) {
    // outside of middle row bounds
    if (x < 16 || x >= 80) return false;
    // remap the Y value to the single row format
    ny -= 32;

    if (x >= 16 && x < 48) {
      // middle row, left panel...
      // third panel in the chain
      
      // remove border
      nx -= 16;
      // now offset & flip horizontally to correct position
      nx = 64 + (32 - nx - 1);
    } else {
      // don't need to do anything here,
      // srcX = (48..80) - border = 32..64
      // dstX = 32..64

      // remove border
      nx -= 16;
      // remove first panel
      nx -= 32;
      // offset and flip
      nx = 32 + (32 - nx - 1);
    }

    // flip the Y value
    ny = 32 - ny - 1;
  } else {
    // outside of bounds
    if (x < 0 || x >= 96) return false;

    // remap Y value to single row
    ny -= 64;
    // move to last 3 panels
    nx += (3 * 32);
  }

  // apply remap
  x = nx;
  y = ny;
  return true;
}

// ... in Run() ...
// ...
  int width = 96;
  int height = 96;

  for (int i = 0; i < width * height; i++) {
    int x = i % width;
    int y = i / width;
    int nx = x;
    int ny = y;
    if (remapPixels(nx, ny)) {
      // do some operations on the original pixel coordinate
      // to get a new RGB value
      int r, g, b;
      pixelShader(x, y, width, height, r, g, b);

      // set this pixel color at the new pixel coordinate
      canvas()->SetPixel(nx, ny, r, g, b);
    }
  }
// ...