Source: math8.h

math8¶

Integer trig, beat timing, saturating arithmetic and a fast generator.

Functions¶

Return	Name	Description
`constexpr uint8_t`	`sin8` `constexpr`
`constexpr uint8_t`	`cos8` `constexpr`
`constexpr uint8_t`	`triwave8` `constexpr`	A triangle wave, the textbook fold of a ramp and a sharper alternative to the sine.
`constexpr uint8_t`	`atan2_8` `constexpr`
`constexpr uint8_t`	`dist8` `constexpr`
`constexpr uint8_t`	`qadd8` `constexpr`	Add or subtract clamping at the ends, so a bright pixel plus more stays bright.
`constexpr uint8_t`	`qsub8` `constexpr`
`constexpr uint8_t`	`nscale8` `constexpr`	Scale a byte by a fraction, under the name an LED developer already reaches for.
`constexpr uint8_t`	`map8` `constexpr`	Rescale a byte onto a range, the input's top reaching the range's top exactly.
`constexpr uint8_t`	`beat8` `constexpr`
`constexpr uint8_t`	`beatsin8` `constexpr`	A sine oscillating between two bounds at a given rate, with a timebase and a fixed offset.
`constexpr uint16_t`	`beatsin16` `constexpr`

sin8¶

constexpr

constexpr constexpr uint8_t sin8(uint8_t i)

cos8¶

constexpr

constexpr constexpr uint8_t cos8(uint8_t i)

triwave8¶

constexpr

constexpr constexpr uint8_t triwave8(uint8_t i)

A triangle wave, the textbook fold of a ramp and a sharper alternative to the sine.

atan2_8¶

constexpr

constexpr constexpr uint8_t atan2_8(int16_t y, int16_t x)

dist8¶

constexpr

constexpr constexpr uint8_t dist8(int16_t dx, int16_t dy)

qadd8¶

constexpr

constexpr constexpr uint8_t qadd8(uint8_t a, uint8_t b)

Add or subtract clamping at the ends, so a bright pixel plus more stays bright.

qsub8¶

constexpr

constexpr constexpr uint8_t qsub8(uint8_t a, uint8_t b)

nscale8¶

constexpr

constexpr constexpr uint8_t nscale8(uint8_t val, uint8_t scale)

Scale a byte by a fraction, under the name an LED developer already reaches for.

map8¶

constexpr

constexpr constexpr uint8_t map8(uint8_t in, uint8_t rangeStart, uint8_t rangeEnd)

Rescale a byte onto a range, the input's top reaching the range's top exactly.

beat8¶

constexpr

constexpr constexpr uint8_t beat8(uint8_t bpm, uint32_t ms, uint32_t timebase = 0)

beatsin8¶

constexpr

constexpr constexpr uint8_t beatsin8(uint8_t bpm, uint32_t ms, uint8_t low = 0, uint8_t high = 255, uint32_t timebase = 0, uint8_t phase = 0)

A sine oscillating between two bounds at a given rate, with a timebase and a fixed offset.

beatsin16¶

constexpr

constexpr constexpr uint16_t beatsin16(uint8_t bpm, uint32_t ms, uint16_t low = 0, uint16_t high = 65535, uint32_t timebase = 0, uint8_t phase = 0)

Variables¶

Return	Name	Description
`constexpr uint8_t`	`sin8_lut` `constexpr`	The sine table over a 256-step circle, from which the cosine is a quarter turn.

sin8_lut¶

constexpr

constexpr uint8_t sin8_lut = {
    128,131,134,137,140,144,147,150,153,156,159,162,165,168,171,174,
    177,179,182,185,188,191,193,196,199,201,204,206,209,211,213,216,
    218,220,222,224,226,228,230,232,234,235,237,239,240,241,243,244,
    245,246,248,249,250,250,251,252,253,253,254,254,254,255,255,255,
    255,255,255,255,254,254,254,253,253,252,251,250,250,249,248,246,
    245,244,243,241,240,239,237,235,234,232,230,228,226,224,222,220,
    218,216,213,211,209,206,204,201,199,196,193,191,188,185,182,179,
    177,174,171,168,165,162,159,156,153,150,147,144,140,137,134,131,
    128,125,122,119,116,112,109,106,103,100,97,94,91,88,85,82,
    79,77,74,71,68,65,63,60,57,55,52,50,47,45,43,40,
    38,36,34,32,30,28,26,24,22,21,19,17,16,15,13,12,
    11,10,8,7,6,6,5,4,3,3,2,2,2,1,1,1,
    1,1,1,1,2,2,2,3,3,4,5,6,6,7,8,10,
    11,12,13,15,16,17,19,21,22,24,26,28,30,32,34,36,
    38,40,43,45,47,50,52,55,57,60,63,65,68,71,74,77,
    79,82,85,88,91,94,97,100,103,106,109,112,116,119,122,125
}

The sine table over a 256-step circle, from which the cosine is a quarter turn.

Random8¶

class Random8

src/core/util/math8.h:121

A small seedable generator, cheap on the hot path and reproducible per effect.

Public Methods¶

constexpr inline explicit constexpr Random8(uint32_t seed = 0x1234ABCDu)

constexpr inline constexpr void seed(uint32_t s) : Seed the sequence, so a run is reproducible.

constexpr inline constexpr uint8_t next8() : The next byte in the sequence.

constexpr inline constexpr uint16_t next16() : The next two bytes.

constexpr inline constexpr uint8_t below(uint8_t bound) : The next value below a bound, or between two.

constexpr inline constexpr uint8_t below(uint8_t min, uint8_t max) : The next value below a bound, or between two.

More info¶

This is the recognizable surface an embedded or LED developer already knows, under the same names, written fresh against our own architecture. Prior art is FastLED's lib8tion by Mark Kriegsman: we carry the ideas, the names and the textbook algorithms, and the code is ours.

It is all integer and table-backed where that pays, with no float and no heap, so it is safe in the render loop. The time-dependent helpers take the current time as a parameter rather than reading a clock, which keeps the time source at the domain edge instead of buried in core. A timebase shifts the phase origin, so an effect wanting its oscillation to start at a chosen moment passes that moment.

Why the range map divides rather than shifts¶

The input's top must reach the range's top exactly. An earlier form scaled by a power of two, which made the top unreachable and collapsed a one-step span: a bar height of one could never be reached. Dividing by the full byte range fixes it, and the span is held wide so the widest case cannot wrap.