esp32-sk6812/include/fasttrigon.h

/*!
 * \file
 * 
 * This file contains function prototypes for very fast lookup-table based
 * trigonometric functions.
 * 
 * The functions take an argument that is dependent on the lookup-table size
 * (LUT_SIZE). LUT_SIZE corresponds to 2π. Values outside the range
 * [0..LUT_SIZE] are supported and interpreted normally, so just replace 2π
 * with LUT_SIZE and you're done.
 */

#pragma once

#include <cstdint>

#define FASTTRIGON_8BIT(x) ((x) >> (fasttrigon::PRECISION_BITS - 8))

namespace fasttrigon {
    static const uint32_t LUT_SIZE = 2048;
    static const uint32_t PRECISION_BITS = 11;
    static const  int32_t SCALE = 1023;
    static const uint32_t UNIT_SHIFT = PRECISION_BITS-1;

    /*!
    * \returns 127 * sin(2π * arg / LUT_SIZE)
    */
    int32_t fastsin(int32_t arg);

    /*!
    * \returns 127 * cos(2π * arg / LUT_SIZE)
    */
    int32_t fastcos(int32_t arg);

    /*!
    * \returns 127 * tan(2π * arg / LUT_SIZE)
    */
    int32_t fasttan(int32_t arg);
}