getPaletteIndex()

uint8_t getPaletteIndex	(	uint32_t	millis32,
		int	i,
		int	j,
		uint32_t	y_speed )

Definition at line 113 of file FireMatrix.h.

                                                                           {
    // This function calculates which color to use from our palette for each LED
    
    // Get the scale factor from the UI slider (controls the "size" of the fire)
    uint16_t scale = scaleXY.as<uint16_t>();
    
    // Calculate 3D coordinates for the Perlin noise function:
    uint16_t x = i * scale;                           // X position (horizontal in matrix)
    uint32_t y = j * scale + y_speed;                 // Y position (vertical) + movement offset
    uint16_t z = millis32 / invSpeedZ.as<uint16_t>(); // Z position (time dimension)
    
    // Generate 16-bit Perlin noise value using these coordinates
    // The << 8 shifts values left by 8 bits (multiplies by 256) to use the full 16-bit range
    uint16_t noise16 = inoise16(x << 8, y << 8, z << 8);
    
    // Convert 16-bit noise to 8-bit by taking the high byte (>> 8 shifts right by 8 bits)
    uint8_t noise_val = noise16 >> 8;
    
    // Calculate how much to subtract based on vertical position (j)
    // This creates the fade-out effect from bottom to top
    // abs8() ensures we get a positive value
    // The formula maps j from 0 to HEIGHT-1 to a value from 255 to 0
    int8_t subtraction_factor = abs8(j - (HEIGHT - 1)) * 255 / (HEIGHT - 1);
    
    // Subtract the factor from the noise value (with underflow protection)
    // qsub8 is a "saturating subtraction" - it won't go below 0
    return qsub8(noise_val, subtraction_factor);
}

References HEIGHT, inoise16(), invSpeedZ(), scale, scaleXY(), x, y, y_speed, and z.

Referenced by loop().

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