From 0902b5b835d417904acbeb2e649ced31654e66c9 Mon Sep 17 00:00:00 2001
From: Valerie <sleeplessval@gmail.com>
Date: Fri, 3 May 2024 23:58:07 -0400
Subject: [PATCH] created signal effect with NTSC emulation

---
 shaders/lang/en_US.lang    |  4 ++++
 shaders/module/signal.frag | 31 +++++++++++++++++++++++++++++++
 shaders/shaders.properties |  2 +-
 shaders/var/scanline.glsl  |  6 +++---
 shaders/var/signal.glsl    |  4 ++++
 5 files changed, 43 insertions(+), 4 deletions(-)
 create mode 100644 shaders/module/signal.frag
 create mode 100644 shaders/var/signal.glsl

diff --git a/shaders/lang/en_US.lang b/shaders/lang/en_US.lang
index 5afec9b..2b4dfae 100644
--- a/shaders/lang/en_US.lang
+++ b/shaders/lang/en_US.lang
@@ -52,6 +52,10 @@ suffix.valBits=-bit
 
 screen.SCREEN=Screen
 
+option.signal=Signal
+value.signal.0=RGB (Off)
+value.signal.1=NTSC
+
 option.interlacing=Interlacing
 
 option.scanline=Scanlines
diff --git a/shaders/module/signal.frag b/shaders/module/signal.frag
new file mode 100644
index 0000000..4c69ef5
--- /dev/null
+++ b/shaders/module/signal.frag
@@ -0,0 +1,31 @@
+
+#include "/var/signal.glsl"
+
+#define signal 0 // [0 1]
+
+vec3 ntsc(vec3 color) {
+	//	convert to YIQ
+	float y = dot(color, vec3(0.299, 0.587, 0.114));
+	float i = dot(color, vec3(0.596, -.274, -.322));
+	float q = dot(color, vec3(0.211, -.523, 0.312));
+
+	//	faux ntsc signal
+	float carrier = 6.283 * 3.570 * gl_FragCoord.x;
+	float phase = sin(carrier) * i + cos(carrier) * q;
+	float quad = cos(carrier) * i - sin(carrier) * q;
+
+	//	decode faux signal
+	i = quad * cos(carrier);
+	q = phase * sin(carrier);
+
+	//	convert back to RGB
+	vec3 yiqColor = vec3(y, i, q);
+
+	vec3 outColor = vec3(0);
+	outColor.r = dot(yiqColor, vec3(1, 0.956, 0.619));
+	outColor.g = dot(yiqColor, vec3(1, -.272, -.674));
+	outColor.b = dot(yiqColor, vec3(1, -1.106, 1.703));
+
+	return outColor;
+}
+
diff --git a/shaders/shaders.properties b/shaders/shaders.properties
index eef852d..a18aeb7 100644
--- a/shaders/shaders.properties
+++ b/shaders/shaders.properties
@@ -20,7 +20,7 @@ screen.COLOR.columns=3
 screen.COLOR=colorMode dithering <empty> colorDepth <empty> monoPalette hueBits satBits valBits
 
 #	screen effects
-screen.SCREEN=interlacing scanline aberration
+screen.SCREEN=signal <empty> interlacing scanline aberration
 
 #	console effects
 screen.CONSOLE.columns=1
diff --git a/shaders/var/scanline.glsl b/shaders/var/scanline.glsl
index 9861367..4d87a7c 100644
--- a/shaders/var/scanline.glsl
+++ b/shaders/var/scanline.glsl
@@ -1,5 +1,5 @@
 
-#define SCANLINE_SOFT 1
-#define SCANLINE_HARD 2
-#define SCANLINE_STRETCH 3
+#define SCANLINE_SOFT		1
+#define SCANLINE_HARD		2
+#define SCANLINE_STRETCH	3
 
diff --git a/shaders/var/signal.glsl b/shaders/var/signal.glsl
new file mode 100644
index 0000000..866ec50
--- /dev/null
+++ b/shaders/var/signal.glsl
@@ -0,0 +1,4 @@
+
+#define SIGNAL_RGB		0
+#define SIGNAL_NTSC		1
+