大画面用に設計する

[SerializeField]
private float minAspectRatio = 4f / 3f;

[SerializeField]
private float maxAspectRatio = 21f / 9f;

private Camera _camera;

private void Awake()
{
    _camera = GetComponent<Camera>();
}

public void MaintainAspectRatio()
{
    int viewWidth = Screen.width;
    int viewHeight = Screen.height;

    // 1. Calculate screen aspect ratio
    float scaleScreen = viewWidth / (float)viewHeight;
    Rect rect = _camera.pixelRect;

    // 2. Scale to the fullest of the lower between width or height
    if (scaleScreen > maxAspectRatio)
    {
        // use height, lock width to max at aspect scale
        rect.width = viewHeight * maxAspectRatio;
        rect.height = viewHeight;
    }
    else if (scaleScreen < minAspectRatio)
    {
        // use width, lock height to min at aspect scale
        rect.width = viewWidth;
        rect.height = viewWidth / minAspectRatio;
    }
    else
    {
        // within allowed aspect ratio range, use full screen
        rect.width = viewWidth;
        rect.height = viewHeight;
    }

    rect.x = Mathf.Floor((viewWidth - rect.width) * 0.5f);
    rect.y = Mathf.Floor((viewHeight - rect.height) * 0.5f);

    Debug.Log("camera view width = " + rect.width +
        " height = " + rect.height +
        " x = " + rect.x +
        " y = " + rect.y);

    // 3. Commit the new size to the camera so that it takes effect
    _camera.pixelRect = rect;
}

/**
 * @brief Calculates a bounded-aspect-ratio gameplay viewport and scissor
 * rectangle and records them directly into a Vulkan command buffer.
 *
 * @note Requires `VK_DYNAMIC_STATE_VIEWPORT` and `VK_DYNAMIC_STATE_SCISSOR` to
 * be enabled on the bound graphics `VkPipeline`.
 *
 * @param command_buffer   Active `VkCommandBuffer` in the recording state.
 * @param window_width     Full physical window or swapchain width in pixels.
 * @param window_height    Full physical window or swapchain height in pixels.
 * @param min_aspect_ratio Minimum allowed aspect ratio (`width / height`).
 * @param max_aspect_ratio Maximum allowed aspect ratio (`width / height`).
 */
void MaintainAspectRatio(VkCommandBuffer command_buffer, uint32_t window_width,
                         uint32_t window_height, float min_aspect_ratio,
                         float max_aspect_ratio) {
  if (command_buffer == VK_NULL_HANDLE || window_width == 0 ||
      window_height == 0 || min_aspect_ratio <= 0.0f ||
      max_aspect_ratio < min_aspect_ratio) {
    return;
  }

  // 1. Calculate screen aspect ratio.
  const float view_width = static_cast<float>(window_width);
  const float view_height = static_cast<float>(window_height);
  const float scale_screen = view_width / view_height;

  // 2. Scale to the fullest of the lower between width or height.
  float rect_width = view_width;
  float rect_height = view_height;
  if (scale_screen > max_aspect_ratio) {
    // Use height, lock width to max at aspect scale (pillarbox).
    rect_width = std::floor(view_height * max_aspect_ratio);
    rect_height = view_height;
  } else if (scale_screen < min_aspect_ratio) {
    // Use width, lock height to min at aspect scale (letterbox).
    rect_width = view_width;
    rect_height = std::floor(view_width / min_aspect_ratio);
  } else {
    // Within allowed aspect ratio range, use full screen.
    rect_width = view_width;
    rect_height = view_height;
  }

  const float rect_x = std::floor((view_width - rect_width) * 0.5f);
  const float rect_y = std::floor((view_height - rect_height) * 0.5f);

  // 3. Commit the new viewport and scissor to the command buffer so that
  // subsequent gameplay draw calls are transformed and clipped to this region.
  const VkViewport viewport = {
      .x = rect_x,
      .y = rect_y,
      .width = rect_width,
      .height = rect_height,
      .minDepth = 0.0f,
      .maxDepth = 1.0f,
  };
  const VkRect2D scissor = {
      .offset =
          {
              .x = static_cast<int32_t>(rect_x),
              .y = static_cast<int32_t>(rect_y),
          },
      .extent =
          {
              .width = static_cast<uint32_t>(rect_width),
              .height = static_cast<uint32_t>(rect_height),
          },
  };

  vkCmdSetViewport(command_buffer, 0, 1, &viewport);
  vkCmdSetScissor(command_buffer, 0, 1, &scissor);
}

[SerializeField]
private Camera _camera;

[SerializeField]
private float _referenceWidth = 1920f;

[SerializeField]
private float _referenceHeight = 1080f;

[SerializeField]
private float _referenceVerticalFov = 60f;

public float ReferenceAspectRatio => _referenceWidth / Mathf.Max(0.0001f, _referenceHeight);

private void Awake()
{
    if (_camera == null)
    {
        _camera = GetComponent<Camera>();
    }
}

// Built-in Render Pipeline callback. In URP, subscribe to
// RenderPipelineManager.beginCameraRendering or call UpdateFov() on resize.
private void OnPreCull()
{
    UpdateFov();
}

public void UpdateFov()
{
    if (_camera == null || _camera.orthographic)
    {
        return;
    }

    float referenceAspect = ReferenceAspectRatio;
    float currentAspect = _camera.aspect;
    if (currentAspect <= 0.0001f)
    {
        return;
    }

    float targetVerticalFov;

    if (currentAspect >= referenceAspect)
    {
        // Viewport is wider than (or equal to) the reference safe area
        targetVerticalFov = _referenceVerticalFov;
    }
    else
    {
        // Viewport is skinnier than the reference safe area
        float referenceHorizontalFov = Camera.VerticalToHorizontalFieldOfView(_referenceVerticalFov, referenceAspect);
        targetVerticalFov = Camera.HorizontalToVerticalFieldOfView(referenceHorizontalFov, currentAspect);
        targetVerticalFov = Mathf.Clamp(targetVerticalFov, 1f, 179f);
    }

    if (!Mathf.Approximately(_camera.fieldOfView, targetVerticalFov))
    {
        _camera.fieldOfView = targetVerticalFov;
    }
}

/**
 * @brief Calculates an aspect-aware Vulkan perspective projection matrix using
 * GLM that keeps a reference safe area (e.g., 1920x1080) visible across
 * aspect ratios.
 *
 * @note Uses `glm::perspectiveZO` for Vulkan's `[0, 1]` depth range and
 * inverts `projection[1][1]` for Vulkan's top-left (`+Y` down) clip space.
 *
 * @param viewport_width         Active gameplay viewport width in pixels.
 * @param viewport_height        Active gameplay viewport height in pixels.
 * @param reference_width        Authored safe-area reference width in pixels.
 * @param reference_height       Authored safe-area reference height in pixels.
 * @param reference_vertical_fov Authored vertical FOV in degrees (e.g., 60.0f).
 * @param near_plane             Near clipping plane distance (`zNear > 0.0f`).
 * @param far_plane              Far clipping plane distance (`zFar > zNear`).
 * @return Aspect-aware `glm::mat4` perspective projection matrix for Vulkan.
 */
glm::mat4 CalculateAspectAwareProjectionMatrix(
    float viewport_width, float viewport_height, float reference_width = 1920.0f,
    float reference_height = 1080.0f, float reference_vertical_fov = 60.0f,
    float near_plane = 0.1f, float far_plane = 100.0f) {
  if (viewport_width <= 0.0001f || viewport_height <= 0.0001f) {
    return glm::mat4(1.0f);
  }

  // 1. Compare the active viewport aspect ratio against the reference safe
  // area.
  const float reference_aspect =
      reference_width / std::max(0.0001f, reference_height);
  const float current_aspect = viewport_width / viewport_height;

  float target_vertical_fov_rad = glm::radians(reference_vertical_fov);

  if (current_aspect >= reference_aspect) {
    // Viewport is wider than (or equal to) the reference safe area (Hor+).
    target_vertical_fov_rad = glm::radians(reference_vertical_fov);
  } else {
    // Viewport is skinnier than the reference safe area (Vert+):
    // Convert reference vertical FOV -> reference horizontal FOV -> new
    // vertical FOV at current_aspect so the safe area is never cropped.
    const float tan_half_horiz =
        std::tan(target_vertical_fov_rad * 0.5f) * reference_aspect;
    target_vertical_fov_rad = 2.0f * std::atan(tan_half_horiz / current_aspect);
    target_vertical_fov_rad = std::clamp(
        target_vertical_fov_rad, glm::radians(1.0f), glm::radians(179.0f));
  }

  // 2. Build the Vulkan [0, 1] depth perspective matrix and flip +Y clip space.
  glm::mat4 projection = glm::perspectiveZO(
      target_vertical_fov_rad, current_aspect, near_plane, far_plane);
  projection[1][1] *= -1.0f;
  return projection;
}