perlin_i16_optimized.h

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#pragma once
 
// 2D Perlin noise i16-optimized implementation
// Extracted from animartrix_detail.hpp
//
// i16-optimized Perlin: Uses i16 for lerp/grad hot path (2x faster multiplies)
// Coordinates stay as i32 (s16x16) externally but convert to i16 for interpolation
 
#include "fl/math/fixed_point/s16x16.h"
#include "fl/stl/compiler_control.h"
 
namespace fl {
 
struct perlin_i16_optimized {
    static constexpr int HP_BITS = 16;
    static constexpr fl::i32 HP_ONE = static_cast<fl::i32>(1) << HP_BITS;
 
    // Build fade LUT - still i32 for API compatibility
    static void init_fade_lut(fl::i32 *table);
 
    // Public API: accepts s16x16 raw values
    static fl::s16x16 pnoise2d(fl::s16x16 fx, fl::s16x16 fy,
                                      const fl::i32 *fade_lut,
                                      const fl::u8 *perm);
 
    // Hot path: uses i16 arithmetic for lerp/grad after extracting fractional part
    static fl::i32 pnoise2d_raw(fl::i32 fx_raw, fl::i32 fy_raw,
                                        const fl::i32 *fade_lut,
                                        const fl::u8 *perm);
 
  private:
    static constexpr int FP_BITS = fl::s16x16::FRAC_BITS;
    static constexpr fl::i32 FP_ONE = static_cast<fl::i32>(1) << FP_BITS;
    // For i16 coordinates: use full 16-bit value (no room for 1.0 in i16)
    // Coordinates are fractional parts only (0-65535), HP_ONE stays as i32
    static constexpr fl::i32 HP_ONE_I16 = HP_ONE;
 
    // Extract fractional part as i16 (range 0-65535)
    static FASTLED_FORCE_INLINE void floor_frac_i16(fl::i32 fp16, int &ifloor, fl::i16 &frac16);
 
    // Fade optimized for i16 input (coordinates), returns i32 (can be 0-65536)
    static FASTLED_FORCE_INLINE fl::i32 fade(fl::i16 t, const fl::i32 *table);
 
    // Standard lerp (i32), but benefits from smaller grad results
    static FASTLED_FORCE_INLINE fl::i32 lerp(fl::i32 t, fl::i32 a, fl::i32 b);
 
    // i16 grad: Takes i16 coordinates (faster than i32), returns i32
    static FASTLED_FORCE_INLINE fl::i32 grad_i16(int hash, fl::i16 x, fl::i16 y);
};
 
}  // namespace fl