starfield.h

/*
 * Copyright © 2026 Synthstrom Audible Limited
 *
 * This file is part of The Synthstrom Audible Deluge Firmware.
 *
 * The Synthstrom Audible Deluge Firmware is free software: you can redistribute it and/or modify it under the
 * terms of the GNU General Public License as published by the Free Software Foundation,
 * either version 3 of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
 * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 * See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with this program.
 * If not, see <https://www.gnu.org/licenses/>.
 */
 
#pragma once
 
#include <array>
#include <cstddef>
#include <cstdint>
 
namespace deluge::hid::display {

class Starfield {
public:

    static constexpr size_t kNumStars = 60;
    static constexpr float kMaxDepth = 32.0f;
    static constexpr float kZStep = 0.4f;
    static constexpr float kFov = 3.14159265358979323846f;
    static constexpr float kCentreX = 64.0f;
    static constexpr float kCentreY = 26.0f;
    static constexpr float kNearThreshold = kMaxDepth * 0.4f;
    static constexpr float kMinDepth = 0.01f;


    struct Projected {
        int32_t x;    
        int32_t y;    
        int32_t size; 
    };

    Starfield() { scatter(); }

    void scatter();

    void advance();

    [[nodiscard]] Projected project(size_t i) const;

    [[nodiscard]] float depthOf(size_t i) const { return stars_[i].z; }
 
private:
    struct Star {
        float x; 
        float y; 
        float z; 
    };

    uint32_t nextRandom();

    float nextRandomFloat();

    void respawn(Star& star, float z);
 
    std::array<Star, kNumStars> stars_{};
    uint32_t rngState_{0xCAFE5678};
};
 
} // namespace deluge::hid::display