Add Pixel Rain RGB Matrix effect (#14155)

* Add Pixel animation header file

* Add Pixel animation to documentation

* Add Pixel animation to core include file

* Remove unintended spaces

* Remove seeding of PRNG

* Increase frequency of lit keys

Co-authored-by: filterpaper <filterpaper@localhost>

3 files changed, 47 insertions, 0 deletions

diff --git a/docs/feature_rgb_matrix.md b/docs/feature_rgb_matrix.md
index cad7c50f18..6370c637a2 100644
--- a/docs/feature_rgb_matrix.md
+++ b/docs/feature_rgb_matrix.md
@@ -454,6 +454,7 @@ enum rgb_matrix_effects {
     RGB_MATRIX_HUE_PENDULUM,        // Hue shifts up a slight ammount in a wave to the right, then back to the left
     RGB_MATRIX_HUE_WAVE,            // Hue shifts up a slight ammount and then back down in a wave to the right
     RGB_MATRIX_FRACTAL,             // Single hue fractal filled keys pulsing horizontally out to edges
+    RGB_MATRIX_PIXEL_RAIN,          // Randomly light keys with random hues
 #if define(RGB_MATRIX_FRAMEBUFFER_EFFECTS)
     RGB_MATRIX_TYPING_HEATMAP,      // How hot is your WPM!
     RGB_MATRIX_DIGITAL_RAIN,        // That famous computer simulation
@@ -508,6 +509,7 @@ You can disable a single effect by defining `DISABLE_[EFFECT_NAME]` in your `con
 |`#define DISABLE_RGB_MATRIX_HUE_PENDULUM`              |Disables `RGB_MATRIX_HUE_PENDULUM`             |
 |`#define DISABLE_RGB_MATRIX_HUE_WAVE`                  |Disables `RGB_MATRIX_HUE_WAVE`                 |
 |`#define DISABLE_RGB_MATRIX_FRACTAL`                   |Disables `RGB_MATRIX_FRACTAL`                  |
+|`#define DISABLE_RGB_MATRIX_PIXEL_RAIN `               |Disables `RGB_MATRIX_PIXEL_RAIN `              |
 |`#define DISABLE_RGB_MATRIX_TYPING_HEATMAP`            |Disables `RGB_MATRIX_TYPING_HEATMAP`           |
 |`#define DISABLE_RGB_MATRIX_DIGITAL_RAIN`              |Disables `RGB_MATRIX_DIGITAL_RAIN`             |
 |`#define DISABLE_RGB_MATRIX_SOLID_REACTIVE_SIMPLE`     |Disables `RGB_MATRIX_SOLID_REACTIVE_SIMPLE`    |
diff --git a/quantum/rgb_matrix/animations/pixel_rain_anim.h b/quantum/rgb_matrix/animations/pixel_rain_anim.h
new file mode 100644
index 0000000000..0209d33033
--- /dev/null
+++ b/quantum/rgb_matrix/animations/pixel_rain_anim.h
@@ -0,0 +1,44 @@
+/* Copyright (C) 2021 @filterpaper
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifdef ENABLE_RGB_MATRIX_PIXEL_RAIN
+RGB_MATRIX_EFFECT(PIXEL_RAIN)
+#   ifdef RGB_MATRIX_CUSTOM_EFFECT_IMPLS
+
+static bool PIXEL_RAIN(effect_params_t* params) {
+    static uint32_t wait_timer = 0;
+    if (wait_timer > g_rgb_timer) { return false; }
+
+    inline uint32_t interval(void) { return 500 / scale16by8(qadd8(rgb_matrix_config.speed, 16), 16); }
+
+    bool rain_pixel(uint8_t i, effect_params_t* params, bool off) {
+        if (!HAS_ANY_FLAGS(g_led_config.flags[i], params->flags)) { return true; }
+        if (off) {
+            rgb_matrix_set_color(i, 0,0,0);
+        } else {
+            HSV hsv = {random8(), qadd8(random8() >> 1, 127), rgb_matrix_config.hsv.v};
+            RGB rgb = rgb_matrix_hsv_to_rgb(hsv);
+            rgb_matrix_set_color(i, rgb.r, rgb.g, rgb.b);
+        }
+        wait_timer = g_rgb_timer + interval();
+        return false;
+    }
+
+    return rain_pixel(mod8(random8(), DRIVER_LED_TOTAL), params, random8() & 2);
+}
+
+#   endif // RGB_MATRIX_CUSTOM_EFFECT_IMPLS
+#endif    // ENABLE_RGB_MATRIX_PIXEL_RAIN
diff --git a/quantum/rgb_matrix/animations/rgb_matrix_effects.inc b/quantum/rgb_matrix/animations/rgb_matrix_effects.inc
index 33d2b42286..8ecf4367ff 100644
--- a/quantum/rgb_matrix/animations/rgb_matrix_effects.inc
+++ b/quantum/rgb_matrix/animations/rgb_matrix_effects.inc
@@ -27,6 +27,7 @@
 #include "hue_pendulum_anim.h"
 #include "hue_wave_anim.h"
 #include "fractal_anim.h"
+#include "pixel_rain_anim.h"
 #include "typing_heatmap_anim.h"
 #include "digital_rain_anim.h"
 #include "solid_reactive_simple_anim.h"