hg_stereographic_unprojection.hpp

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// Copyright 2023, Collabora, Ltd.
// SPDX-License-Identifier: BSL-1.0
/*!
 * @file
 * @brief Stereographic unprojection
 * @author Moshi Turner <moses@collabora.com>
 * @ingroup tracking
 */
 
#pragma once
#include "math/m_eigen_interop.hpp"
 
static inline Eigen::Vector3f
stereographic_unprojection(float sg_x, float sg_y)
{
        float X = sg_x;
        float Y = sg_y;
 
        float denom = (1 + X * X + Y * Y);
 
        float x = (2 * X) / denom;
        float y = (2 * Y) / denom;
        float z = (-1 + X * X + Y * Y) / denom;
 
        // forward is -z
        return {x, y, z};
        // return {x / -z, y / -z};
}