From 270b39b2eb44247cff75ddd216a8e67f8f264991 Mon Sep 17 00:00:00 2001 From: XScorpion2 Date: Sun, 19 May 2019 11:19:46 -0500 Subject: Spirals, Pinwheels, and Documentation....Oh My! RGB Matrix Effects (#5877) * Spirals, Pinwheels, and Documentation....Oh My! * Spiral effect band thickness adjustments * Fixing animation spin directions --- lib/lib8tion/trig8.h | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) (limited to 'lib') diff --git a/lib/lib8tion/trig8.h b/lib/lib8tion/trig8.h index 6ef3ce625f..cfba6373fb 100644 --- a/lib/lib8tion/trig8.h +++ b/lib/lib8tion/trig8.h @@ -255,5 +255,30 @@ LIB8STATIC uint8_t cos8( uint8_t theta) return sin8( theta + 64); } +/// Fast 16-bit approximation of atan2(x). +/// @returns atan2, value between 0 and 255 +LIB8STATIC uint8_t atan2_8(int16_t dy, int16_t dx) +{ + if (dy == 0) + { + if (dx >= 0) + return 0; + else + return 128; + } + + int16_t abs_y = dy > 0 ? dy : -dy; + int8_t a; + + if (dx >= 0) + a = 32 - (32 * (dx - abs_y) / (dx + abs_y)); + else + a = 96 - (32 * (dx + abs_y) / (abs_y - dx)); + + if (dy < 0) + return -a; // negate if in quad III or IV + return a; +} + ///@} #endif -- cgit v1.2.3