sinbad/src/appGameIslands.c

#include "islands.h"
#include "engineCamera.h"
#include "enginePhysics.h"
#include "engineRectangle.h"
#include "engineVector.h"
#include <math.h>
#include <raylib.h>
#include <raymath.h>

// How far an island can drift from the camera before it's considered "left
// behind" and gets regenerated fresh outside the current view, the same
// recycling idea used for enemies/birds so the world stays populated as the
// player explores.
#define ISLAND_RECYCLE_DISTANCE 800.0f
#define ISLAND_MIN_SPAWN_DISTANCE 80
#define ISLAND_MAX_SPAWN_DISTANCE 600
// Concentric elevation bands, each a fraction of the coastline radius at
// that angle — same idea as a real elevation-banded map (shore/lowland/
// highland rings), just three tiers instead of five since this renders at
// pixel-art scale, not map scale.
#define ISLAND_GRASS_SCALE 0.72f
#define ISLAND_HILL_SCALE 0.35f
// Native resolution the shape is painted at. Higher than the 16x16 ship/bird
// sprites — islands are the biggest thing on screen now, and matching their
// texel density would make each "pixel" a huge, coarse block; this keeps
// the pixel-art look while the individual pixels stay small relative to the
// island's size.
#define ISLAND_IMAGE_SIZE 128

// A coastline is two overlapping cosine lobes (a broad one for bays/
// peninsulas, a finer one for coastal roughness) plus light jitter, instead
// of a single jittered circle — the same kind of shape irregularity a real
// procedural terrain generator uses, just far cheaper.
static void GenerateCoastline(float shoreRadiusPx[ISLAND_SHAPE_POINTS], float baseRadius) {
  float amp1 = (float)GetRandomValue(15, 30) / 100.0f;
  float freq1 = (float)GetRandomValue(2, 3);
  float phase1 = (float)GetRandomValue(0, 628) / 100.0f;
  float amp2 = (float)GetRandomValue(5, 15) / 100.0f;
  float freq2 = (float)GetRandomValue(5, 8);
  float phase2 = (float)GetRandomValue(0, 628) / 100.0f;

  for (int i = 0; i < ISLAND_SHAPE_POINTS; i++) {
    float angle = (2.0f * PI * (float)i) / (float)ISLAND_SHAPE_POINTS;
    float shapeFactor = 1.0f
        + amp1 * cosf(freq1 * angle + phase1)
        + amp2 * cosf(freq2 * angle + phase2);
    if (shapeFactor < 0.5f) shapeFactor = 0.5f;

    float jitter = (float)GetRandomValue(90, 110) / 100.0f;
    shoreRadiusPx[i] = baseRadius * shapeFactor * jitter;
  }

  // Average each radius with its neighbours a couple of times so the
  // outline reads as an irregular but rounded coastline instead of a spiky
  // star.
  for (int pass = 0; pass < 2; pass++) {
    float smoothed[ISLAND_SHAPE_POINTS];
    for (int i = 0; i < ISLAND_SHAPE_POINTS; i++) {
      int prev = (i - 1 + ISLAND_SHAPE_POINTS) % ISLAND_SHAPE_POINTS;
      int next = (i + 1) % ISLAND_SHAPE_POINTS;
      smoothed[i] = (shoreRadiusPx[prev] + shoreRadiusPx[i] + shoreRadiusPx[next]) / 3.0f;
    }
    for (int i = 0; i < ISLAND_SHAPE_POINTS; i++) shoreRadiusPx[i] = smoothed[i];
  }
}

static float SampleRadius(const float shoreRadiusPx[ISLAND_SHAPE_POINTS], float angle) {
  float t = angle / (2.0f * PI) * ISLAND_SHAPE_POINTS;
  int i0 = ((int)t) % ISLAND_SHAPE_POINTS;
  int i1 = (i0 + 1) % ISLAND_SHAPE_POINTS;
  float frac = t - (int)t;
  return shoreRadiusPx[i0] * (1.0f - frac) + shoreRadiusPx[i1] * frac;
}

static Texture2D GenerateIslandTexture(const float shoreRadiusPx[ISLAND_SHAPE_POINTS],
                                       Color shoreColor, Color grassColor, Color hillColor) {
  Image image = GenImageColor(ISLAND_IMAGE_SIZE, ISLAND_IMAGE_SIZE, BLANK);
  float center = ISLAND_IMAGE_SIZE / 2.0f;

  for (int y = 0; y < ISLAND_IMAGE_SIZE; y++) {
    for (int x = 0; x < ISLAND_IMAGE_SIZE; x++) {
      float dx = (x + 0.5f) - center;
      float dy = (y + 0.5f) - center;
      float dist = sqrtf(dx * dx + dy * dy);

      float angle = atan2f(dy, dx);
      if (angle < 0.0f) angle += 2.0f * PI;

      float shoreRadius = SampleRadius(shoreRadiusPx, angle);

      if (dist <= shoreRadius * ISLAND_HILL_SCALE) {
        ImageDrawPixel(&image, x, y, hillColor);
      } else if (dist <= shoreRadius * ISLAND_GRASS_SCALE) {
        ImageDrawPixel(&image, x, y, grassColor);
      } else if (dist <= shoreRadius) {
        ImageDrawPixel(&image, x, y, shoreColor);
      }
    }
  }

  Texture2D texture = LoadTextureFromImage(image);
  UnloadImage(image);
  SetTextureFilter(texture, TEXTURE_FILTER_POINT);
  return texture;
}

static void GenerateIsland(Island *island, Vector2 position) {
  if (island->sprite.texture.id != 0) {
    UnloadTexture(island->sprite.texture);
  }

  island->position = position;

  float worldDiameter = (float)GetRandomValue(220, 380);

  float basePixelRadius = (float)GetRandomValue(30, 44);
  float shoreRadiusPx[ISLAND_SHAPE_POINTS];
  GenerateCoastline(shoreRadiusPx, basePixelRadius);

  // The collision radius has to track the coastline's actual average
  // extent, not a fraction of the destRec/canvas size — the canvas has a
  // fair amount of open water margin around the shore (needed so the
  // harmonic wobble and jitter don't clip off-canvas), so anything based on
  // worldDiameter directly ends up much bigger than the visible island,
  // making the ship "bump" into open water well before the shore.
  float avgRadiusPx = 0.0f;
  for (int i = 0; i < ISLAND_SHAPE_POINTS; i++) avgRadiusPx += shoreRadiusPx[i];
  avgRadiusPx /= ISLAND_SHAPE_POINTS;
  float pixelToWorld = worldDiameter / (float)ISLAND_IMAGE_SIZE;
  // Slightly over the average so the collision circle covers the coastline
  // at most angles instead of sitting exactly on it — the shape bulges out
  // past the average at peninsulas, and a ship visually overlapping the
  // shore reads worse than the collision boundary having a little slack.
  island->radius = avgRadiusPx * pixelToWorld * 1.05f;

  // Slight per-island tint variation so a cluster of islands doesn't look
  // like the same stamp copy-pasted around.
  Color shoreColor = (Color){
      (unsigned char)Clamp(233 + GetRandomValue(-10, 10), 0, 255),
      (unsigned char)Clamp(220 + GetRandomValue(-10, 10), 0, 255),
      (unsigned char)Clamp(178 + GetRandomValue(-10, 10), 0, 255),
      255};
  Color grassColor = (Color){
      (unsigned char)Clamp(80 + GetRandomValue(-15, 15), 0, 255),
      (unsigned char)Clamp(168 + GetRandomValue(-15, 15), 0, 255),
      (unsigned char)Clamp(84 + GetRandomValue(-15, 15), 0, 255),
      255};
  Color hillColor = (Color){
      (unsigned char)Clamp(52 + GetRandomValue(-12, 12), 0, 255),
      (unsigned char)Clamp(120 + GetRandomValue(-12, 15), 0, 255),
      (unsigned char)Clamp(64 + GetRandomValue(-12, 12), 0, 255),
      255};

  Texture2D texture = GenerateIslandTexture(shoreRadiusPx, shoreColor, grassColor, hillColor);

  island->sprite = (Sprite){
      .texture = texture,
      .frameSize = {ISLAND_IMAGE_SIZE, ISLAND_IMAGE_SIZE},
      .sourceRec = {0.0f, 0.0f, ISLAND_IMAGE_SIZE, ISLAND_IMAGE_SIZE},
      .destRec = {position.x, position.y, worldDiameter, worldDiameter},
      .origin = {worldDiameter / 2.0f, worldDiameter / 2.0f},
      .rotation = 0.0f,
      .color = WHITE};
}

Islands CreateIslands(Camera2D *camera) {
  Islands islands = {.count = MAX_ISLANDS};
  Rectangle cameraRec = GetCameraRectangle(camera);

  for (int i = 0; i < islands.count; i++) {
    GenerateIsland(&islands.island[i],
                   GetPositionOutsideRectangle(cameraRec, ISLAND_MIN_SPAWN_DISTANCE, ISLAND_MAX_SPAWN_DISTANCE));
  }

  return islands;
}

void UpdateIslands(Islands *islands, Camera2D *camera) {
  Rectangle cameraRec = GetCameraRectangle(camera);

  for (int i = 0; i < islands->count; i++) {
    if (GetDistanceBetweenTwoVectors(islands->island[i].position, camera->target) > ISLAND_RECYCLE_DISTANCE) {
      GenerateIsland(&islands->island[i],
                     GetPositionOutsideRectangle(cameraRec, ISLAND_MIN_SPAWN_DISTANCE, ISLAND_MAX_SPAWN_DISTANCE));
    }
  }
}

void RenderIslands(Islands *islands) {
  for (int i = 0; i < islands->count; i++) {
    RenderSprite(&islands->island[i].sprite);
  }
}

void UnloadIslands(Islands *islands) {
  for (int i = 0; i < islands->count; i++) {
    UnloadTexture(islands->island[i].sprite.texture);
  }
}