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Orange
2026-04-23 19:23:13 +03:00
parent 2eccb4023f
commit 42a8a5a763
1 changed files with 17 additions and 11 deletions
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28
source/engines/source_engine/formulas.cpp
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@@ -38,24 +38,30 @@ 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;
// Source (inherited from Quake) stores FOV as horizontal FOV at a 4:3
// reference aspect. Convert to vertical FOV first, then use the
// standard vfov-based projection against the caller's actual aspect.
// 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 tan_half_vfov = std::tan(half_hfov_4_3) / k_source_reference_aspect;
const float fov_half_tan = std::tan(angles::degrees_to_radians(field_of_view) / 2.f) * k_multiply_factor;
const float x_axis = 1.f / (aspect_ratio * tan_half_vfov);
const float y_axis = 1.f / tan_half_vfov;
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},
{x_axis, 0, 0, 0},
{0, y_axis, 0, 0},
{0, 0, far / (far - near), -(near * far) / (far - near)},
{0, 0, 1, 0},
};
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},
{x_axis, 0, 0, 0},
{0, y_axis, 0, 0},
{0, 0, (far + near) / (far - near), -(2.f * far * near) / (far - near)},
{0, 0, 1, 0},
};
std::unreachable();
}