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Merge pull request #185 from orange-cpp/feature/unreal-engine-projection-fix

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Feature/unreal engine projection fix
This commit is contained in:
Orange++
2026-04-23 22:46:10 +03:00
committed by GitHub
parent 3eb9daf10b e62e8672b3
commit 35bb1bc3c0
5 changed files with 89 additions and 26 deletions
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2
include/omath/engines/unreal_engine/camera.hpp
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@@ -9,5 +9,5 @@
namespace omath::unreal_engine
{
using Camera = projection::Camera<Mat4X4, ViewAngles, CameraTrait, NDCDepthRange::ZERO_TO_ONE, {.inverted_right = true}>;
using Camera = projection::Camera<Mat4X4, ViewAngles, CameraTrait, NDCDepthRange::ZERO_TO_ONE>;
} // namespace omath::unreal_engine

53
include/omath/linear_algebra/mat.hpp
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@@ -707,6 +707,59 @@ namespace omath
else
std::unreachable();
}
// Horizontal-FOV variants — use these when the engine reports FOV as
// horizontal (UE's FMinimalViewInfo::FOV, Quake-family fov_x, etc.).
// X and Y scales derived as: X = 1 / tan(hfov/2), Y = aspect / tan(hfov/2).
template<class Type = float, MatStoreType St = MatStoreType::ROW_MAJOR,
NDCDepthRange DepthRange = NDCDepthRange::NEGATIVE_ONE_TO_ONE>
[[nodiscard]]
Mat<4, 4, Type, St> mat_perspective_left_handed_horizontal_fov(const float horizontal_fov,
const float aspect_ratio, const float near,
const float far) noexcept
{
const float inv_tan_half_hfov = 1.f / std::tan(angles::degrees_to_radians(horizontal_fov) / 2.f);
const float x_axis = inv_tan_half_hfov;
const float y_axis = inv_tan_half_hfov * aspect_ratio;
if constexpr (DepthRange == NDCDepthRange::ZERO_TO_ONE)
return {{x_axis, 0.f, 0.f, 0.f},
{0.f, y_axis, 0.f, 0.f},
{0.f, 0.f, far / (far - near), -(near * far) / (far - near)},
{0.f, 0.f, 1.f, 0.f}};
else if constexpr (DepthRange == NDCDepthRange::NEGATIVE_ONE_TO_ONE)
return {{x_axis, 0.f, 0.f, 0.f},
{0.f, y_axis, 0.f, 0.f},
{0.f, 0.f, (far + near) / (far - near), -(2.f * near * far) / (far - near)},
{0.f, 0.f, 1.f, 0.f}};
else
std::unreachable();
}
template<class Type = float, MatStoreType St = MatStoreType::ROW_MAJOR,
NDCDepthRange DepthRange = NDCDepthRange::NEGATIVE_ONE_TO_ONE>
[[nodiscard]]
Mat<4, 4, Type, St> mat_perspective_right_handed_horizontal_fov(const float horizontal_fov,
const float aspect_ratio, const float near,
const float far) noexcept
{
const float inv_tan_half_hfov = 1.f / std::tan(angles::degrees_to_radians(horizontal_fov) / 2.f);
const float x_axis = inv_tan_half_hfov;
const float y_axis = inv_tan_half_hfov * aspect_ratio;
if constexpr (DepthRange == NDCDepthRange::ZERO_TO_ONE)
return {{x_axis, 0.f, 0.f, 0.f},
{0.f, y_axis, 0.f, 0.f},
{0.f, 0.f, -far / (far - near), -(near * far) / (far - near)},
{0.f, 0.f, -1.f, 0.f}};
else if constexpr (DepthRange == NDCDepthRange::NEGATIVE_ONE_TO_ONE)
return {{x_axis, 0.f, 0.f, 0.f},
{0.f, y_axis, 0.f, 0.f},
{0.f, 0.f, -(far + near) / (far - near), -(2.f * near * far) / (far - near)},
{0.f, 0.f, -1.f, 0.f}};
else
std::unreachable();
}
template<class Type = float, MatStoreType St = MatStoreType::ROW_MAJOR,
NDCDepthRange DepthRange = NDCDepthRange::NEGATIVE_ONE_TO_ONE>
[[nodiscard]]

31
source/engines/source_engine/formulas.cpp
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@@ -38,25 +38,24 @@ namespace omath::source_engine
Mat4X4 calc_perspective_projection_matrix(const float field_of_view, const float aspect_ratio, const float near,
const float far, const NDCDepthRange ndc_depth_range) noexcept
{
// NOTE: Need magic number to fix fov calculation, since source inherit Quake proj matrix calculation
constexpr auto k_multiply_factor = 0.75f;
const float fov_half_tan = std::tan(angles::degrees_to_radians(field_of_view) / 2.f) * k_multiply_factor;
// Source (inherited from Quake) stores FOV as horizontal FOV at a 4:3
// reference aspect. Convert to true vertical FOV, then delegate to the
// standard vertical-FOV left-handed builder with the caller's actual
// aspect ratio.
// vfov = 2 · atan( tan(hfov_4:3 / 2) / (4/3) )
constexpr float k_source_reference_aspect = 4.f / 3.f;
const float half_hfov_4_3 = angles::degrees_to_radians(field_of_view) / 2.f;
const float vfov_deg = angles::radians_to_degrees(
2.f * std::atan(std::tan(half_hfov_4_3) / k_source_reference_aspect));
if (ndc_depth_range == NDCDepthRange::ZERO_TO_ONE)
return {
{1.f / (aspect_ratio * fov_half_tan), 0, 0, 0},
{0, 1.f / (fov_half_tan), 0, 0},
{0, 0, far / (far - near), -(near * far) / (far - near)},
{0, 0, 1, 0},
};
return mat_perspective_left_handed<
float, MatStoreType::ROW_MAJOR, NDCDepthRange::ZERO_TO_ONE>(
vfov_deg, aspect_ratio, near, far);
if (ndc_depth_range == NDCDepthRange::NEGATIVE_ONE_TO_ONE)
return {
{1.f / (aspect_ratio * fov_half_tan), 0, 0, 0},
{0, 1.f / (fov_half_tan), 0, 0},
{0, 0, (far + near) / (far - near), -(2.f * far * near) / (far - near)},
{0, 0, 1, 0},
};
return mat_perspective_left_handed<
float, MatStoreType::ROW_MAJOR, NDCDepthRange::NEGATIVE_ONE_TO_ONE>(
vfov_deg, aspect_ratio, near, far);
std::unreachable();
}
} // namespace omath::source_engine

27
source/engines/unreal_engine/formulas.cpp
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@@ -2,7 +2,6 @@
// Created by Vlad on 3/22/2025.
//
#include "omath/engines/unreal_engine/formulas.hpp"
namespace omath::unreal_engine
{
Vector3<float> forward_vector(const ViewAngles& angles) noexcept
@@ -25,22 +24,34 @@ namespace omath::unreal_engine
}
Mat4X4 calc_view_matrix(const ViewAngles& angles, const Vector3<float>& cam_origin) noexcept
{
return mat_camera_view<float, MatStoreType::ROW_MAJOR>(forward_vector(angles), -right_vector(angles),
return mat_camera_view<float, MatStoreType::ROW_MAJOR>(forward_vector(angles), right_vector(angles),
up_vector(angles), cam_origin);
}
Mat4X4 rotation_matrix(const ViewAngles& angles) noexcept
{
return mat_rotation_axis_x<float, MatStoreType::ROW_MAJOR>(angles.roll)
* mat_rotation_axis_z<float, MatStoreType::ROW_MAJOR>(angles.yaw)
* mat_rotation_axis_y<float, MatStoreType::ROW_MAJOR>(-angles.pitch);
// UE FRotator is intrinsic Z-Y-X (Yaw → Pitch → Roll applied in local
// frame), which for column-vector composition is Rz·Ry·Rx.
// Pitch and roll axes in omath spin opposite to UE's convention, so
// both carry a sign flip.
return mat_rotation_axis_z<float, MatStoreType::ROW_MAJOR>(angles.yaw)
* mat_rotation_axis_y<float, MatStoreType::ROW_MAJOR>(-angles.pitch)
* mat_rotation_axis_x<float, MatStoreType::ROW_MAJOR>(-angles.roll);
}
Mat4X4 calc_perspective_projection_matrix(const float field_of_view, const float aspect_ratio, const float near,
const float far, const NDCDepthRange ndc_depth_range) noexcept
{
// UE stores horizontal FOV in FMinimalViewInfo — use the left-handed
// horizontal-FOV builder directly.
if (ndc_depth_range == NDCDepthRange::ZERO_TO_ONE)
return mat_perspective_left_handed<float, MatStoreType::ROW_MAJOR, NDCDepthRange::ZERO_TO_ONE>(
return mat_perspective_left_handed_horizontal_fov<
float, MatStoreType::ROW_MAJOR, NDCDepthRange::ZERO_TO_ONE>(
field_of_view, aspect_ratio, near, far);
return mat_perspective_left_handed(field_of_view, aspect_ratio, near, far);
if (ndc_depth_range == NDCDepthRange::NEGATIVE_ONE_TO_ONE)
return mat_perspective_left_handed_horizontal_fov<
float, MatStoreType::ROW_MAJOR, NDCDepthRange::NEGATIVE_ONE_TO_ONE>(
field_of_view, aspect_ratio, near, far);
std::unreachable();
}
} // namespace omath::unreal_engine

2
tests/engines/unit_test_unreal_engine.cpp
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@@ -44,7 +44,7 @@ TEST(unit_test_unreal_engine, ForwardVectorRotationRoll)
{
omath::unreal_engine::ViewAngles angles;
angles.roll = omath::unreal_engine::RollAngle::from_degrees(-90.f);
angles.roll = omath::unreal_engine::RollAngle::from_degrees(90.f);
const auto forward = omath::unreal_engine::up_vector(angles);
EXPECT_NEAR(forward.x, omath::unreal_engine::k_abs_right.x, 0.00001f);