`omath::source_engine::MeshTrait` — mesh transformation trait for Source Engine

Header: omath/engines/source_engine/traits/mesh_trait.hpp Namespace: omath::source_engine Purpose: provide Source Engine-specific rotation matrix computation for omath::primitives::Mesh

Summary

MeshTrait is a trait class that provides the rotation_matrix function for transforming meshes in Source Engine's coordinate system. It serves as a template parameter to omath::primitives::Mesh, enabling engine-specific rotation behavior.

Coordinate System

Source Engine uses: * Up axis: +Z * Forward axis: +Y * Right axis: +X * Handedness: Right-handed * Rotation order: Pitch (X) → Yaw (Z) → Roll (Y)

API

namespace omath::source_engine {

class MeshTrait final {
public:
    [[nodiscard]]
    static Mat4X4 rotation_matrix(const ViewAngles& rotation);
};

} // namespace omath::source_engine

Method: `rotation_matrix`

static Mat4X4 rotation_matrix(const ViewAngles& rotation);

Computes a 4×4 rotation matrix from Source Engine-style Euler angles.

Parameters: * rotation — ViewAngles containing pitch, yaw, and roll angles

Returns: 4×4 rotation matrix suitable for mesh transformation

Implementation: Delegates to source_engine::rotation_matrix(rotation) defined in formulas.hpp.

Usage

With Mesh

using namespace omath::source_engine;

// Create mesh (MeshTrait is used automatically)
Mesh my_mesh(vertices, indices);

// Set rotation using ViewAngles
ViewAngles angles;
angles.pitch = PitchAngle::from_degrees(30.0f);
angles.yaw = YawAngle::from_degrees(45.0f);
angles.roll = RollAngle::from_degrees(0.0f);

my_mesh.set_rotation(angles);

// The rotation matrix is computed using MeshTrait::rotation_matrix
auto matrix = my_mesh.get_to_world_matrix();

Direct Usage

using namespace omath::source_engine;

ViewAngles angles;
angles.pitch = PitchAngle::from_degrees(45.0f);
angles.yaw = YawAngle::from_degrees(90.0f);
angles.roll = RollAngle::from_degrees(0.0f);

Mat4X4 rot_matrix = MeshTrait::rotation_matrix(angles);

// Use the matrix directly
Vector3<float> local_point{1, 0, 0};
auto rotated = rot_matrix * mat_column_from_vector(local_point);

Rotation Conventions

The rotation matrix is built following Source Engine's conventions:

Pitch (rotation around X-axis / right axis)
Positive pitch looks upward (+Z direction)
Range: typically [-89°, 89°]
Yaw (rotation around Z-axis / up axis)
Positive yaw rotates counterclockwise when viewed from above
Range: [-180°, 180°]
Roll (rotation around Y-axis / forward axis)
Positive roll tilts right
Range: [-180°, 180°]

Composition: The matrices are combined in the order Pitch × Yaw × Roll, producing a rotation that: * First applies roll around the forward axis * Then applies yaw around the up axis * Finally applies pitch around the right axis

This matches Source Engine's internal rotation order.

The trait delegates to the formula defined in formulas.hpp:

[[nodiscard]]
Mat4X4 rotation_matrix(const ViewAngles& angles) noexcept;

See Formulas Documentation for details on the rotation matrix computation.

Type Alias

The Source Engine mesh type is pre-defined:

namespace omath::source_engine {
    using Mesh = primitives::Mesh<Mat4X4, ViewAngles, MeshTrait, float>;
}

Use this alias to ensure correct trait usage:

using namespace omath::source_engine;

// Correct: uses Source Engine trait
Mesh my_mesh(vbo, vao);

// Avoid: manually specifying template parameters
primitives::Mesh<Mat4X4, ViewAngles, MeshTrait, float> verbose_mesh(vbo, vao);

Notes

Angle ranges: Ensure angles are within valid ranges (pitch: [-89°, 89°], yaw/roll: [-180°, 180°])
Performance: Matrix computation is O(1) with ~64 floating-point operations
Caching: The mesh caches the transformation matrix; recomputed only when rotation changes
Compatibility: Works with all Source Engine games (CS:GO, TF2, Portal, Half-Life 2, etc.)

omath::source_engine::MeshTrait — mesh transformation trait for Source Engine