easeInSine16()

u16 fl::easeInSine16

(

u16

i

)

16-bit sine ease-in function Takes an input value 0-65535 and returns an eased value 0-65535

Definition at line 265 of file ease.cpp.

                        {
    // ease-in sine: 1 - cos(t * π/2)
    // Handle boundary conditions explicitly
    if (i == 0)
        return 0;
    // Remove the hard-coded boundary for 65535 and let math handle it
        
    // For 16-bit: use cos32 for efficiency and accuracy
    // Map i from [0,65535] to [0,4194304] in cos32 space (zero to quarter wave)
    // Formula: 1 - cos(t * π/2) where t goes from 0 to 1
    // sin32/cos32 quarter cycle is 16777216/4 = 4194304
    u32 angle = ((fl::u64)i * 4194304ULL) / 65535ULL;
    i32 cos_result = fl::cos32(angle);
 
    // Convert cos32 output and apply easing formula: 1 - cos(t * π/2)
    // cos32 output range is [-2147418112, 2147418112]
    // At t=0: cos(0) = 2147418112, result should be 0
    // At t=1: cos(π/2) = 0, result should be 65535
    
    const fl::i64 MAX_COS32 = 2147418112LL;
    
    // Calculate: (MAX_COS32 - cos_result) and scale to [0, 65535]
    fl::i64 adjusted = MAX_COS32 - (fl::i64)cos_result;
    
    // Scale from [0, 2147418112] to [0, 65535]
    fl::u64 result = (fl::u64)adjusted * 65535ULL + (MAX_COS32 >> 1); // Add half for rounding
    u16 final_result = (u16)(result / (fl::u64)MAX_COS32);
    
    return final_result;
}

References cos32().

Referenced by ease16(), and ease16().

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