cool-bun-demo/bun.c

#include <math.h>

// Custom
#include <hardware/custom.h>

// WaitBlit()
#include <clib/graphics_protos.h>

// AllocMem(), FreeMem()
#include <clib/exec_protos.h>
#include <exec/memory.h>

#include "screen.h"
#include "bun.h"
#include "system/system.h"

#define COOL_BUN_WIDTH (32)
#define COOL_BUN_WIDTH_BYTES (COOL_BUN_WIDTH / 8)
#define COOL_BUN_HEIGHT (32)
#define COOL_BUN_PLANES (2)
#define COOL_BUN_LAST_ROW (COOL_BUN_HEIGHT - 1)
#define COOL_BUN_LAST_ROW_BYTES (COOL_BUN_LAST_ROW * COOL_BUN_WIDTH_BYTES)

#define COOL_BUN_PLANE_SIZE (COOL_BUN_WIDTH_BYTES * COOL_BUN_HEIGHT)
#define COOL_BUN_MEMORY_SIZE (COOL_BUN_PLANE_SIZE * COOL_BUN_PLANES)

#define BUN_MAX_RANGE (31 + 320)

#define BUN_COUNT (12)
#define BUN_SPEED (1)

#define BUN_HORIZ_DISTANCE_BETWEEN_BUNS ((BUN_MAX_RANGE / 4) - COOL_BUN_WIDTH)
#define BUN_TOTAL_HORIZ_DISTANCE (BUN_HORIZ_DISTANCE_BETWEEN_BUNS + COOL_BUN_WIDTH)
#define BUN_ROW_START (50)
#define BUN_VERT_DISTANCE_BETWEEN_BUNS (30)
#define BUN_TOTAL_VERT_DISTANCE (COOL_BUN_HEIGHT + BUN_VERT_DISTANCE_BETWEEN_BUNS)
#define FRAME_MAX (BUN_TOTAL_HORIZ_DISTANCE / BUN_SPEED)

#define BUN_WAVE_LENGTH (FRAMES_FOR_SCREEN / 2)

// linked as raw bytes in assembler
extern unsigned char chip coolbun[];

#define BLTCON0( \
  minterm, aChan, bChan, cChan, dChan, shift \
) (minterm + (aChan << 11) + (bChan << 10) + (cChan << 9) + (dChan << 8) + (shift << 12))
#define BLTCON1(descending, shift) ((descending << 1) + (shift << 12))

extern struct Custom far custom;

void setupBun(void) {
}

void teardownBun(void) {
}

#define BLITTER_ASCENDING (0)
#define BLITTER_DESCENDING (1)

struct BunClear {
  uint16_t memoryStartOffsetBytes;
  uint16_t widthWords;
  uint16_t heightRows;
  uint8_t direction;
};

#define BUN_OFF_RIGHT_SIDE (0)
#define BUN_OFF_LEFT_SIDE (1)
#define BUN_ANYWHERE (2)

uint8_t *coolbunPlaneStarts[3][2];

void bun_offRightSide(
  int plusXValue,
  int y,
  struct ScreenSetup *screenSetup,
  struct CurrentScreen *currentScreen,
  struct BunClear *bunClear
) {
  uint8_t i, plane = 0;
  uint8_t shift = plusXValue & 15;
  uint8_t wordShift = (plusXValue >> 4);
  uint16_t bltalwm, bltcon0, bltcon1, bltdmod, bltsize;

  bunClear->memoryStartOffsetBytes =  (y * screenSetup->byteWidth) +
    screenSetup->byteWidth - COOL_BUN_WIDTH_BYTES +
    wordShift * 2;
  bunClear->heightRows = COOL_BUN_HEIGHT;
  bunClear->widthWords = 2 - wordShift;
  bunClear->direction = BLITTER_ASCENDING;

  bltalwm = 0x0000;
  for (i = 0; i <= 15 - shift; ++i) {
    bltalwm += (1 << (15 - i));
  }

  bltcon0 = BLTCON0(0xf0, 1, 0, 0, 1, shift);
  bltcon1 = BLTCON1(bunClear->direction, shift);

  bltdmod = screenSetup->byteWidth - COOL_BUN_WIDTH_BYTES +
    wordShift * 2;

  bltsize = bunClear->widthWords + (bunClear->heightRows << 6);

  for (plane = 0; plane < 2; ++plane) {
    custom.bltcon0 = bltcon0;
    custom.bltcon1 = bltcon1;

    custom.bltapt = coolbunPlaneStarts[BUN_OFF_LEFT_SIDE][plane];
    custom.bltdpt = currentScreen->planes[plane] +
      bunClear->memoryStartOffsetBytes;

    custom.bltafwm = 0xffff;
    custom.bltalwm = bltalwm;

    custom.bltamod = wordShift * 2;
    custom.bltdmod = bltdmod;

    custom.bltsize = bltsize;

    WaitBlit();
  }
}

void bun_offLeftSide(
  int minusXValue,
  int y,
  struct ScreenSetup *screenSetup,
  struct CurrentScreen *currentScreen,
  struct BunClear *bunClear
) {
  unsigned char plane;
  uint8_t shift = minusXValue & 15;
  uint8_t wordShift = (minusXValue >> 4);
  uint8_t i;
  uint16_t bltalwm, bltcon0, bltcon1, bltdmod, bltsize;

  // y can't be 0 otherwise we will corrupt memory for now
  if (y == 0) return;

  bunClear->memoryStartOffsetBytes = (screenSetup->byteWidth * (y + COOL_BUN_LAST_ROW)) +
    2 - wordShift * 2;
  bunClear->heightRows = COOL_BUN_HEIGHT;
  bunClear->widthWords = 2 - wordShift;
  bunClear->direction = BLITTER_DESCENDING;

  bltalwm = 0x0000;
  for (i = 0; i <= 15 - shift; ++i) {
    bltalwm += (1 << i);
  }

  bltcon0 = BLTCON0(0xf0, 1, 0, 0, 1, shift);
  bltcon1 = BLTCON1(bunClear->direction, shift);
  bltdmod = screenSetup->byteWidth - 4 + wordShift * 2;

  bltsize = bunClear->widthWords + (bunClear->heightRows << 6);

  for (plane = 0; plane < 2; ++plane) {
    // shift left, so descending
    custom.bltcon0 = bltcon0;
    custom.bltcon1 = bltcon1;

    // a has bun data
    custom.bltapt = coolbunPlaneStarts[BUN_OFF_RIGHT_SIDE][plane];

    // d is the part on screen
    custom.bltdpt = currentScreen->planes[plane] + bunClear->memoryStartOffsetBytes;

    custom.bltafwm = 0xffff;
    custom.bltalwm = bltalwm;

    custom.bltamod = wordShift * 2;
    custom.bltdmod = bltdmod;

    custom.bltsize = bltsize;

    WaitBlit();
  }
}

void bun_anywhere(
  int x,
  int y,
  struct ScreenSetup *screenSetup,
  struct CurrentScreen *currentScreen,
  struct BunClear *bunClear
) {
  uint8_t plane;
  uint8_t shift = x & 15;
  uint8_t needsExtraWord = shift != 0;
  uint16_t bltcon0, bltcon1, bltalwm, bltamod, bltdmod, bltsize;

  bunClear->memoryStartOffsetBytes = WORD_ALIGNED_BYTE_POSITION(screenSetup->width, x, y);

  bunClear->heightRows = COOL_BUN_HEIGHT;
  bunClear->widthWords = 2 + needsExtraWord;
  bunClear->direction = BLITTER_ASCENDING;

  // buns will never interfere with a background so they don't need a mask
  bltcon0 = BLTCON0(0xf0, 1, 0, 0, 1, shift);
  bltcon1 = BLTCON1(bunClear->direction, shift);

  if (needsExtraWord) {
    bltalwm = 0x0000;
  } else {
    bltalwm = 0xffff;
  }

  bltamod = -(needsExtraWord * 2);
  bltdmod = screenSetup->byteWidth - COOL_BUN_WIDTH_BYTES - (needsExtraWord * 2);
  bltsize = bunClear->widthWords + (bunClear->heightRows << 6);

  for (plane = 0; plane < 2; ++plane) {
    custom.bltcon0 = bltcon0;
    custom.bltcon1 = bltcon1;

    custom.bltapt = coolbunPlaneStarts[BUN_ANYWHERE][plane];
    custom.bltdpt = currentScreen->planes[plane] +
      bunClear->memoryStartOffsetBytes;

    custom.bltafwm = 0xffff;
    custom.bltalwm = bltalwm;

    custom.bltamod = bltamod;
    custom.bltdmod = bltdmod;
    custom.bltsize = bltsize;

    WaitBlit();
  }
}

void renderBun(
  int x,
  int y,
  struct ScreenSetup *screenSetup,
  struct CurrentScreen *currentScreen,
  struct BunClear *bunClear
) {
  /**
    * Conditions that will cause the program to crash if met. If your bun
    * isn't rendering, it's due to here.
    *
    * TODO: Handle top/bottom off-screen as well.
    */
  if (x < -31) return;
  if (x > screenSetup->width + 31) return;
  if (y < 1) return;
  if (y > screenSetup->height - COOL_BUN_HEIGHT - 1) return;

  if (x < 0) {
    bun_offLeftSide(
      -x,
      y,
      screenSetup,
      currentScreen,
      bunClear
    );
  } else if (x > screenSetup->width - COOL_BUN_WIDTH) {
    bun_offRightSide(
      x - (screenSetup->width - COOL_BUN_WIDTH),
      y,
      screenSetup,
      currentScreen,
      bunClear
    );
  } else {
    bun_anywhere(
      x,
      y,
      screenSetup,
      currentScreen,
      bunClear
    );
  }
}

#define MAX_SINE_WAVE_CHANGE (20)

int bunAngleAdjustments[BUN_COUNT];

void calculateBunPositions(
  uint16_t frame,
  short int bunPositions[BUN_COUNT][2],
  struct ScreenSetup *screenSetup
) {
  int x, y, row, column, current;
  float angle, startAngle;

  frame %= FRAMES_FOR_SCREEN;

  startAngle = (float)(frame % BUN_WAVE_LENGTH) * 360 / BUN_WAVE_LENGTH;

  for (current = 0; current < BUN_COUNT; ++current) {
    row = current / 4;
    column = current % 4;
    angle = startAngle + bunAngleAdjustments[current];

    x = column * BUN_TOTAL_HORIZ_DISTANCE + ((float)frame * BUN_MAX_RANGE / FRAMES_FOR_SCREEN);
    if (row == 1) {
      x += BUN_TOTAL_HORIZ_DISTANCE / 2;
    }
    x %= BUN_MAX_RANGE;
    x -= 31;

    angle = angle * PI / 180;

    y = BUN_ROW_START +
      row * BUN_TOTAL_VERT_DISTANCE +
      sin(angle) * MAX_SINE_WAVE_CHANGE;

    bunPositions[current][0] = x;
    bunPositions[current][1] = y;
  }
}

short int allBunPositionsByFrame[FRAMES_FOR_SCREEN][BUN_COUNT][2];

void calculateAllBunPositions(
  struct ScreenSetup *screenSetup
) {
  int frame;

  for (frame = 0; frame < FRAMES_FOR_SCREEN; ++frame) {
    calculateBunPositions(
      frame,
      allBunPositionsByFrame[frame],
      screenSetup
    );
  }
}

void buildBunAngleAdjustments() {
  int current, angleAdjustment;
  for (current = 0; current < BUN_COUNT; ++current) {
    angleAdjustment = 0;
    if (current % 2 == 1) angleAdjustment += 180;
    if (current / 4 == 1) angleAdjustment += 90;

    bunAngleAdjustments[current] = angleAdjustment;
  }
}

void precalculeBunRenderInfo(void) {
  int plane;

  for (plane = 0; plane < 2; ++plane) {
    coolbunPlaneStarts[BUN_OFF_LEFT_SIDE][plane] = coolbun + plane * COOL_BUN_PLANE_SIZE;
    coolbunPlaneStarts[BUN_ANYWHERE][plane] = coolbun + plane * COOL_BUN_PLANE_SIZE;
    coolbunPlaneStarts[BUN_OFF_RIGHT_SIDE][plane] = coolbun + 2 +
      COOL_BUN_LAST_ROW_BYTES +
      plane * COOL_BUN_PLANE_SIZE;
  }
}

void setupBunRenderer(
  struct BunRenderer *bunRenderer,
  struct ScreenSetup *screenSetup,
  struct CurrentScreen *currentScreen) {
  bunRenderer->screenSetup = screenSetup;
  bunRenderer->currentScreen = currentScreen;

  setupBun();
  buildBunAngleAdjustments();
  calculateAllBunPositions(screenSetup);
  precalculeBunRenderInfo();
}

int hasBunClear[2] = {0,0};
struct BunClear bunClearForScreen[2][BUN_COUNT];

void clearCurrentBuns(
  struct BunRenderer *bunRenderer
) {
  int bun, plane;
  struct BunClear *currentBunClear;
  uint16_t bltcon0, bltcon1, bltdmod, bltsize;

  if (!hasBunClear[bunRenderer->currentScreen->currentBuffer]) return;

  bltcon0 = 0xc0 + (1 << 8);

  for (bun = 0; bun < BUN_COUNT; ++bun) {
    currentBunClear = &bunClearForScreen[bunRenderer->currentScreen->currentBuffer][bun];

    bltcon1 = BLTCON1(currentBunClear->direction, 0);
    bltdmod = bunRenderer->screenSetup->byteWidth - (currentBunClear->widthWords * 2);
    bltsize = currentBunClear->widthWords + (currentBunClear->heightRows << 6);

    for (plane = 0; plane < 2; ++plane) {
      custom.bltcon0 = bltcon0;
      custom.bltcon1 = bltcon1;
      custom.bltadat = 0x0000;
      custom.bltafwm = 0xffff;
      custom.bltalwm = 0xffff;
      custom.bltdpt = bunRenderer->currentScreen->planes[plane] +
        currentBunClear->memoryStartOffsetBytes;
      custom.bltdmod = bltdmod;
      custom.bltsize = bltsize;

      WaitBlit();
    }
  }
}

void renderBunFrame(
  int frame,
  struct BunRenderer *bunRenderer
) {
  int bun;

  frame %= FRAMES_FOR_SCREEN;

  for (bun = 0; bun < BUN_COUNT; ++bun) {
    renderBun(
      allBunPositionsByFrame[frame][bun][0],
      allBunPositionsByFrame[frame][bun][1],
      bunRenderer->screenSetup,
      bunRenderer->currentScreen,
      &bunClearForScreen[bunRenderer->currentScreen->currentBuffer][bun]
    );
  }

  hasBunClear[bunRenderer->currentScreen->currentBuffer] = 1;
}

void teardownBunRenderer() {
  teardownBun();
}