getPaletteIndex()

uint8_t getPaletteIndex	(	uint32_t	millis32,
		int	width,
		int	max_width,
		int	height,
		int	max_height,
		uint32_t	y_speed )

Definition at line 112 of file FireCylinder.h.

                                          {
    // This function calculates which color to use from our palette for each LED
    
    // Get the scale factor from the UI slider
    uint16_t scale = scaleXY.as<uint16_t>();
    
    // Convert width position to an angle (0-255 represents 0-360 degrees)
    // This maps our flat coordinate to a position on a cylinder
    float xf = (float)width / (float)max_width;  // Normalized position (0.0 to 1.0)
    uint8_t x = (uint8_t)(xf * 255);            // Convert to 0-255 range for trig functions
    
    // Calculate the sine and cosine of this angle to get 3D coordinates on the cylinder
    uint32_t cosx = cos8(x);  // cos8 returns a value 0-255 representing cosine
    uint32_t sinx = sin8(x);  // sin8 returns a value 0-255 representing sine
    
    // Apply scaling to the sine/cosine values
    // This controls how "wide" the noise pattern is around the cylinder
    float trig_scale = scale * scaleX.value();
    cosx *= trig_scale;
    sinx *= trig_scale;
    
    // Calculate Y coordinate (vertical position) with speed offset for movement
    uint32_t y = height * scale + y_speed;
    
    // Calculate Z coordinate (time dimension) - controls how the pattern changes over time
    uint16_t z = millis32 / invSpeedZ.as<uint16_t>();
    FL_UNUSED(z);  // Suppress unused variable warning
 
    // Generate 16-bit Perlin noise using our 4D coordinates (x,y,z,t)
    // The << 8 shifts values left by 8 bits (multiplies by 256) to use the full 16-bit range
    // The last parameter (0) could be replaced with another time variable for more variation
    uint16_t noise16 = inoise16(cosx << 8, sinx << 8, y << 8, 0);
    
    // Convert 16-bit noise to 8-bit by taking the high byte
    uint8_t noise_val = noise16 >> 8;
    
    // Calculate how much to subtract based on vertical position (height)
    // This creates the fade-out effect from bottom to top
    // The formula maps height from 0 to max_height-1 to a value from 255 to 0
    int8_t subtraction_factor = abs8(height - (max_height - 1)) * 255 /
                                (max_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 FL_UNUSED, inoise16(), invSpeedZ(), scale, scaleX(), scaleXY(), x, y, y_speed, and z.

Referenced by loop().

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