From 61f05282053c9f7a17b2d409f19c02dfeee2b790 Mon Sep 17 00:00:00 2001
From: minjaesong <alswo9628@gmail.com>
Date: Fri, 15 Sep 2023 15:51:37 +0900
Subject: [PATCH] more 'correct' dithering shader code

---
 src/net/torvald/terrarum/TerrarumPostProcessor.kt | 7 +++++++
 src/shaders/postproc_dither.frag                  | 7 ++++---
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/src/net/torvald/terrarum/TerrarumPostProcessor.kt b/src/net/torvald/terrarum/TerrarumPostProcessor.kt
index 6bdc63a29..51eeb8ddb 100644
--- a/src/net/torvald/terrarum/TerrarumPostProcessor.kt
+++ b/src/net/torvald/terrarum/TerrarumPostProcessor.kt
@@ -51,6 +51,10 @@ object TerrarumPostProcessor : Disposable {
 
     private val recommendRatio = 1.5f
 
+    /*private val testfill = Texture("./assets/test_fill.tga").also {
+        it.setFilter(Texture.TextureFilter.Linear, Texture.TextureFilter.Linear)
+    }*/
+
     private val shaderQuant = mapOf(
             8 to 255f,
             10 to 1023f,
@@ -77,6 +81,7 @@ object TerrarumPostProcessor : Disposable {
         shaderPostNoDither.dispose()
         if (::lutTex.isInitialized) lutTex.tryDispose()
         if (::outFBO.isInitialized) outFBO.dispose()
+//        testfill.dispose()
     }
 
     private var deltatBenchStr = "ΔF: Gathering data"
@@ -239,6 +244,7 @@ object TerrarumPostProcessor : Disposable {
 
         App.getCurrentDitherTex().bind(1)
         fbo.colorBufferTexture.bind(0)
+//        testfill.bind(0)
 
         shader.bind()
         shader.setUniformMatrix("u_projTrans", projMat)
@@ -246,6 +252,7 @@ object TerrarumPostProcessor : Disposable {
         shader.setUniformi("rnd", rng.nextInt(8192), rng.nextInt(8192))
         shader.setUniformi("u_pattern", 1)
         shader.setUniformf("quant", shaderQuant[App.getConfigInt("displaycolourdepth")] ?: 255f)
+//        shader.setUniformf("quant", 1f)
         shader.setUniformMatrix4fv("swizzler", swizzler, rng.nextInt(24), 16*4)
         App.fullscreenQuad.render(shader, GL20.GL_TRIANGLE_FAN)
 
diff --git a/src/shaders/postproc_dither.frag b/src/shaders/postproc_dither.frag
index 9f593c65c..e520dd139 100644
--- a/src/shaders/postproc_dither.frag
+++ b/src/shaders/postproc_dither.frag
@@ -37,7 +37,8 @@ vec4 invQuant = vec4(1.0 / quant);
 out vec4 fragColor;
 
 const vec2 boolean = vec2(0.0, 1.0);
-
+const vec4 halfPulldown = vec4(0.5 / 255.0); // 255.0 comes from the dithering pattern, not the quantiser
+const vec4 halfPullUp = vec4(255.0 / 254.5); // 255.0 comes from the dithering pattern, not the quantiser
 const vec2 patternsize = vec2(1.0/512.0, 1.0/512.0);
 
 
@@ -46,8 +47,8 @@ vec4 nearestColour(vec4 inColor) {
 }
 
 vec4 getDitherredDot(vec4 inColor) {
-    vec4 bayerThreshold = swizzler * vec4(texture(u_pattern, (gl_FragCoord.xy + rnd) * patternsize));
-    return nearestColour(fma(bayerThreshold, invQuant, inColor));
+    vec4 bayerThreshold = swizzler * vec4(texture(u_pattern, (gl_FragCoord.xy + rnd) * patternsize) - halfPulldown);
+    return nearestColour(fma(bayerThreshold, invQuant, inColor * halfPullUp));
 }
 
 void main(void) {