From cce018f62015c126d643aa85248ecb5af2953e54 Mon Sep 17 00:00:00 2001
From: Valerie <sleeplessval@gmail.com>
Date: Sat, 20 Apr 2024 20:47:00 -0400
Subject: [PATCH] initial implementation of interlace effect

---
 shaders/composite.fsh         | 17 +++++++++++++++--
 shaders/lang/en_US.lang       |  1 +
 shaders/module/interlace.frag | 10 ++++++++++
 shaders/shaders.properties    |  2 +-
 4 files changed, 27 insertions(+), 3 deletions(-)
 create mode 100644 shaders/module/interlace.frag

diff --git a/shaders/composite.fsh b/shaders/composite.fsh
index 881cce2..c5e4a7f 100644
--- a/shaders/composite.fsh
+++ b/shaders/composite.fsh
@@ -14,12 +14,12 @@ float renderRes = pixelSize;
 #define rgbSteps 4 // the number of rgb values to use [2 4 8 16 32 64]
 
 uniform sampler2D gcolor;
-uniform sampler2D colortex1;
 uniform float viewWidth, viewHeight;
 
 varying vec2 texcoord;
 
 #include "/module/dof.frag"
+#include "/module/interlace.frag"
 
 // All components are in the range [0…1], including hue.
 vec3 rgb2hsv(vec3 c)
@@ -151,6 +151,19 @@ void main() {
             final = vec3(lightnessStep(color.r, rgbSteps), lightnessStep(color.g, rgbSteps), lightnessStep(color.b, rgbSteps)).rgb;
         #endif
     #endif
-    gl_FragData[0] = vec4(vec3(final), 1.0); //gcolor
+
+	#ifdef interlacing
+		/* DRAWBUFFERS:01 */
+		//	pull previous buffer
+		vec3 prev = texture2D(colortex1, texcoord).rgb;
+		//	interlace alternates between odd and even lines on world time
+		if(mod(int(gl_FragCoord.y / pixelSize), 2) == mod(worldTime, 2))
+			gl_FragData[0] = vec4(prev, 1);
+		else
+			gl_FragData[0] = vec4(final, 1);
+		gl_FragData[1] = vec4(final, 1);
+	#else
+		gl_FragData[0] = vec4(final, 1.0);
+	#endif
 }
 
diff --git a/shaders/lang/en_US.lang b/shaders/lang/en_US.lang
index 52eef69..afaad72 100644
--- a/shaders/lang/en_US.lang
+++ b/shaders/lang/en_US.lang
@@ -24,6 +24,7 @@ option.satSteps=Saturation Depth
 option.valSteps=Value Depth
 
 screen.SCREEN=Screen
+option.interlacing=Interlacing
 option.aberration=Chromatic Aberration
 
 screen.CONSOLE=Consoles
diff --git a/shaders/module/interlace.frag b/shaders/module/interlace.frag
new file mode 100644
index 0000000..5f7e8b0
--- /dev/null
+++ b/shaders/module/interlace.frag
@@ -0,0 +1,10 @@
+
+//#define interlacing
+
+#ifdef interlacing
+	uniform sampler2D colortex1;
+	const bool colortex1Clear = false;
+
+	uniform int worldTime;
+#endif
+
diff --git a/shaders/shaders.properties b/shaders/shaders.properties
index cf3fb46..610c98a 100644
--- a/shaders/shaders.properties
+++ b/shaders/shaders.properties
@@ -17,7 +17,7 @@ screen.COLOR.columns=3
 screen.COLOR=colorMode dithering <empty> rgbSteps <empty> <empty> hueSteps satSteps valSteps
 
 #	screen effects
-screen.SCREEN=aberration
+screen.SCREEN=interlacing aberration
 
 #	console effects
 screen.CONSOLE.columns=1