From 8147fb1110fd0037610de6701e83ccd29f4d0432 Mon Sep 17 00:00:00 2001 From: Sadeep Madurange Date: Thu, 25 Dec 2025 22:48:14 +0800 Subject: Use the full post instead of the log for Matrix. --- _site/log/matrix-digital-rain/index.html | 151 ++++++++++++++++++++++++++----- 1 file changed, 129 insertions(+), 22 deletions(-) (limited to '_site/log/matrix-digital-rain/index.html') diff --git a/_site/log/matrix-digital-rain/index.html b/_site/log/matrix-digital-rain/index.html index b428f9e..7c8c659 100644 --- a/_site/log/matrix-digital-rain/index.html +++ b/_site/log/matrix-digital-rain/index.html @@ -2,12 +2,12 @@ - Matrix Rain: 2025 refactor + Recreating the Matrix rain with ANSI escape sequences - Matrix Rain: 2025 refactor + Recreating the Matrix rain with ANSI escape sequences @@ -41,34 +41,141 @@
-

MATRIX RAIN: 2025 REFACTOR

+

RECREATING THE MATRIX RAIN WITH ANSI ESCAPE SEQUENCES

21 DECEMBER 2025

-

Unicode support added. ASCII + Katakana working:

+

My 2022 implementation of the Matrix rain had too many loose ends. Unicode +support was inflexible: the character set had to be a single contiguous block +with no way to mix ASCII with something like Katakana; Phosphor decay level was +stored in a dedicated array–still don’t understand why I did that when I had +already used bit-packing for the RGB channels; The algorithm was difficult to +decipher. The 2022 version worked, but that’s not the same thing as correct.

+ +

I began by placing the decay factor in the MSB of the 4-byte RGB value. The PD +value plays a somewhat analogous role to an alpha channel in that both +influence transparency. However, they work very differently. So, I avoided +labelling it A so as not to cause confusion:

+ +
enum {
+    R,  /* Red   */
+    G,  /* Green */
+    B,  /* Blue  */ 
+    PD  /* Phosphor decay level */
+};
+
+typedef union color_tag {
+    uint32_t value;
+    unsigned char color[4];
+} color;
+
+ +

The decision to use union over more portable bit twiddling was made three years +ago, as I recall, for readability. Seeing as all my systems are little-endian, +this is unlikely to cause any trouble. Besides, if union is never to be used, +why is it in the language anyway?

+ +

The blend() function, which emulates the dim afterglow of Phosphor by eroding +the RGB channels towards the background, with minor refactoring, remains as +elegant as it did three years ago:

+ +
#define DECAY_MPLIER  2
+
+static inline void blend(matrix *mat,
+    size_t row, size_t col)
+{
+    unsigned char *color;
+
+    color = mat->rgb[index(mat, row, col)].color;
+    color[R] = color[R] - (color[R] - RGB_BG_RED) / DECAY_MPLIER;
+    color[G] = color[G] - (color[G] - RGB_BG_GRN) / DECAY_MPLIER;
+    color[B] = color[B] - (color[B] - RGB_BG_BLU) / DECAY_MPLIER;
+}
+
+ +

While the memory inefficiency of Phosphor decay was a technical oversight I +hadn’t noticed, the limitation around mixing nonadjacent Unicode blocks was a +nagging concern even three years ago. So, a fix was long overdue.

+ +

In the new version, I introduced an array that enables a user to add as +many Unicode blocks as they want. The insert_code() function picks a block +from it at random, and then picks a character from that block at random:

+ +
#define UNICODE(min, max)  (((uint64_t)max << 32) | min)
+
+static uint64_t glyphs[] = {
+    UNICODE(0x0021, 0x007E), /* ASCII */
+    UNICODE(0xFF65, 0xFF9F), /* Half-width Katakana */
+};
+
+static uint8_t glyphlen = (sizeof glyphs) / (sizeof glyphs[0]);
+
+static inline void insert_code(matrix *mat,
+    size_t row, size_t col) 
+{
+    uint64_t block;
+    uint32_t unicode_min, unicode_max;
+
+    block = glyphs[(rand() % glyphlen)];
+    unicode_min = (uint32_t)block;
+    unicode_max = (uint32_t)(block >> 32);
+
+    mat->code[index(mat, row, col)] = rand()
+        % (unicode_max - unicode_min)
+        + unicode_min;
+}
+
+ +

The Unicode blocks are stored in 8-byte containers: the low four bytes form the +first codepoint and the high four bytes the last. Here, I chose bitwise +operations over unions because, first and foremost, the operations themselves +are trivial and idiomatic, and the UNICODE() macro simplifies the management of +charsets.

+ +

The init_term() function is the arbiter of this zero-dependency software. It +prepares the graphical environment so that I can interact with it via ANSI +escape codes instead of unnecessary layers of abstraction:

+ +
static inline int init_term(const struct winsize *ws) 
+{
+    struct termios ta;
+
+    if (tcgetattr(STDIN_FILENO, &ta) == 0) {
+        ta.c_lflag &= ~ECHO;
+        if (tcsetattr(STDIN_FILENO, TCSANOW, &ta) == 0) {
+            wprintf(L"\x1b[48;2;%d;%d;%dm", 
+                RGB_BG_RED, RGB_BG_GRN, RGB_BG_BLU);
+            wprintf(L"%s", ANSI_FONT_BOLD);
+            wprintf(L"%s", ANSI_CRSR_HIDE);
+            wprintf(L"%s", ANSI_CRSR_RESET);
+            wprintf(L"%s", ANSI_SCRN_CLEAR);
+            setvbuf(stdout, 0, _IOFBF, 0);
+            ioctl(STDOUT_FILENO, TIOCGWINSZ, ws);
+            return 1;
+        }
+    }
+    return 0;
+}
+
+ +

insert_code() seeds the Matrix, blend() creates the old monochrome CRT display +nostalgia, and ANSI control sequences paint the screen. The result is a digital +rain that captures the original Matrix aesthetic with high visual fidelity:

+ +
$ cc -O3 main.c -o matrix
+$ ./matrix
+
-

Algorithm notes: mat.col[] = shuffled column indices, mat.row[] = last row per -column. shuffle() sets working set, main loop draws columns via index i (line -333), swap() rotates set.

+

There was no cause to measure the program’s performance characteristics +precisely; it’s gentle on the CPU. On my ThinkPad T490 running OpenBSD, which +has a resolution of 1920x1080, it uses about 2-3% of the CPU, with occasional +jumps of up to about 8%; the cores remain silent, the fans don’t whir, the rain +falls in quiet.

-

Phosphor decay moved to LSB of RGB union. Should have done this originally.

- -

RGB/PD union stays. Little-endian machine, portability not a concern.

- -

Charset via UNICODE(min, max) macro - packs range into uint64, insert_code() -unpacks and selects random char.

- -

Half-width Katakana (U+FF61-U+FF9F) for column alignment.

- -

Removed license, automake files. Build: cc -O3 main.c -o matrix

- -

Performance: 2% CPU, OpenBSD, T490.

- -

Commit: -03f8d87

+

Files: source.tar.gz

by W. D. Sadeep Madurange

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