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Orange 95c0873b8c Documents view angle struct and related API

Adds documentation for the `omath::ViewAngles` struct,
clarifying its purpose, common usage patterns,
and the definition of the types of pitch, yaw and roll.

Also, adds short explanations of how to use ViewAngles and what tradeoffs exist
between using raw float types and strongly typed Angle<> types.

2025-11-01 09:12:04 +03:00

2.4 KiB

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`omath::projection::Error` — Error codes for world/screen projection

Header: omath/projection/error_codes.hpp Namespace: omath::projection Type: enum class Error : uint16_t

These error codes are returned by camera/projection helpers (e.g., Camera::world_to_screen, Camera::screen_to_world) wrapped in std::expected<..., Error>. Use them to distinguish clipping/visibility problems from matrix/math failures.

Enum values

enum class Error : uint16_t {
  WORLD_POSITION_IS_OUT_OF_SCREEN_BOUNDS,
  INV_VIEW_PROJ_MAT_DET_EQ_ZERO,
};

WORLD_POSITION_IS_OUT_OF_SCREEN_BOUNDS The input point cannot produce a valid on-screen coordinate:
- Clip-space w == 0 (point at/infinite or behind camera plane), or
- After projection, any NDC component is outside [-1, 1].
INV_VIEW_PROJ_MAT_DET_EQ_ZERO The View × Projection matrix is not invertible (determinant ≈ 0). Unprojection (screen_to_world / view_port_to_screen) requires an invertible matrix.

Typical usage

using omath::projection::Error;

auto pix = cam.world_to_screen(point);
if (!pix) {
  switch (pix.error()) {
    case Error::WORLD_POSITION_IS_OUT_OF_SCREEN_BOUNDS:
      // Cull label/marker; point is off-screen or behind camera.
      break;
    case Error::INV_VIEW_PROJ_MAT_DET_EQ_ZERO:
      // Investigate camera/projection setup; near/far/FOV or trait bug.
      break;
  }
}

// Unproject a screen pixel (top-left origin) at depth 1.0
if (auto world = cam.screen_to_world({sx, sy, 1.0f})) {
  // use *world
} else if (world.error() == Error::INV_VIEW_PROJ_MAT_DET_EQ_ZERO) {
  // handle singular VP matrix
}

When you might see these errors

Out-of-bounds
- The world point lies outside the camera frustum.
- The point is behind the camera (clip w <= 0).
- Extremely large coordinates cause overflow and fail NDC bounds.
Non-invertible VP
- Degenerate projection settings (e.g., near == far, zero FOV).
- Trait builds P or V incorrectly (wrong handedness/order).
- Numerical issues from nearly singular configurations.

Recommendations

Validate camera setup: near > 0, far > near, sensible FOV (e.g., 30°–120°).
For UI markers: treat WORLD_POSITION_IS_OUT_OF_SCREEN_BOUNDS as a simple cull signal.
Log INV_VIEW_PROJ_MAT_DET_EQ_ZERO — it usually indicates a configuration or math bug worth fixing rather than hiding.

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omath::projection::Error — Error codes for world/screen projection