From 389d5b0f606e1e9e75cb68abfba52f21cb97d915 Mon Sep 17 00:00:00 2001
From: Martin Valigursky <mvaligursky@snapchat.com>
Date: Thu, 30 Nov 2023 12:05:16 +0000
Subject: [PATCH] Fringing / Chromatic Aberration added to render pass compose

---
 .../src/examples/graphics/post-processing.mjs | 30 ++++++++++++
 extras/render-passes/render-pass-compose.js   | 47 ++++++++++++++++++-
 2 files changed, 75 insertions(+), 2 deletions(-)

diff --git a/examples/src/examples/graphics/post-processing.mjs b/examples/src/examples/graphics/post-processing.mjs
index e5a55394eac..252f05f6563 100644
--- a/examples/src/examples/graphics/post-processing.mjs
+++ b/examples/src/examples/graphics/post-processing.mjs
@@ -157,6 +157,24 @@ function controls({ observer, ReactPCUI, React, jsx, fragment }) {
                     precision: 2
                 })
             )
+        ),
+        jsx(Panel, { headerText: 'Fringing' },
+            jsx(LabelGroup, { text: 'enabled' },
+                jsx(BooleanInput, {
+                    type: 'toggle',
+                    binding: new BindingTwoWay(),
+                    link: { observer, path: 'data.fringing.enabled' }
+                })
+            ),
+            jsx(LabelGroup, { text: 'intensity' },
+                jsx(SliderInput, {
+                    binding: new BindingTwoWay(),
+                    link: { observer, path: 'data.fringing.intensity' },
+                    min: 0,
+                    max: 100,
+                    precision: 0
+                })
+            )
         )
     );
 }
@@ -520,6 +538,14 @@ async function example({ canvas, deviceType, assetPath, glslangPath, twgslPath,
                     composePass.vignetteIntensity = value;
                 }
             }
+            if (pathArray[1] === 'fringing') {
+                if (pathArray[2] === 'enabled') {
+                    composePass.fringingEnabled = value;
+                }
+                if (pathArray[2] === 'intensity') {
+                    composePass.fringingIntensity = value;
+                }
+            }
         });
 
         data.set('data', {
@@ -546,6 +572,10 @@ async function example({ canvas, deviceType, assetPath, glslangPath, twgslPath,
                 outer: 1.0,
                 curvature: 0.5,
                 intensity: 0.3
+            },
+            fringing: {
+                enabled: false,
+                intensity: 50
             }
         });
 
diff --git a/extras/render-passes/render-pass-compose.js b/extras/render-passes/render-pass-compose.js
index ce2cf3f937d..49695ee80a2 100644
--- a/extras/render-passes/render-pass-compose.js
+++ b/extras/render-passes/render-pass-compose.js
@@ -51,10 +51,31 @@ const fragmentShader = `
 
     #endif
 
+    #ifdef FRINGING
+
+        uniform float fringingIntensity;
+
+        vec3 fringing(vec2 uv, vec3 color) {
+
+            // offset depends on the direction from the center, raised to power to make it stronger away from the center
+            vec2 centerDistance = uv0 - 0.5;
+            vec2 offset = fringingIntensity * pow(centerDistance, vec2(2.0, 2.0));
+
+            color.r = texture2D(sceneTexture, uv0 - offset).r;
+            color.b = texture2D(sceneTexture, uv0 + offset).b;
+            return color;
+        }
+
+    #endif
+
     void main() {
         vec4 scene = texture2D(sceneTexture, uv0);
         vec3 result = scene.rgb;
 
+        #ifdef FRINGING
+            result = fringing(uv0, result);
+        #endif
+
         #ifdef BLOOM
             vec3 bloom = texture2D(bloomTexture, uv0).rgb;
             result += bloom * bloomIntensity;
@@ -105,6 +126,10 @@ class RenderPassCompose extends RenderPassShaderQuad {
 
     vignetteIntensity = 0.3;
 
+    _fringingEnabled = false;
+
+    fringingIntensity = 10;
+
     _key = '';
 
     constructor(graphicsDevice) {
@@ -115,6 +140,7 @@ class RenderPassCompose extends RenderPassShaderQuad {
         this.bloomIntensityId = graphicsDevice.scope.resolve('bloomIntensity');
         this.bcsId = graphicsDevice.scope.resolve('brightnessContrastSaturation');
         this.vignetterParamsId = graphicsDevice.scope.resolve('vignetterParams');
+        this.fringingIntensityId = graphicsDevice.scope.resolve('fringingIntensity');
     }
 
     set bloomTexture(value) {
@@ -150,6 +176,17 @@ class RenderPassCompose extends RenderPassShaderQuad {
         return this._vignetteEnabled;
     }
 
+    set fringingEnabled(value) {
+        if (this._fringingEnabled !== value) {
+            this._fringingEnabled = value;
+            this._shaderDirty = true;
+        }
+    }
+
+    get fringingEnabled() {
+        return this._fringingEnabled;
+    }
+
     set toneMapping(value) {
         if (this._toneMapping !== value) {
             this._toneMapping = value;
@@ -187,7 +224,8 @@ class RenderPassCompose extends RenderPassShaderQuad {
             const key = `${this.toneMapping}` +
                 `-${this.bloomTexture ? 'bloom' : 'nobloom'}` +
                 `-${this.gradingEnabled ? 'grading' : 'nograding'}` +
-                `-${this.vignetteEnabled ? 'vignette' : 'novignette'}`;
+                `-${this.vignetteEnabled ? 'vignette' : 'novignette'}` +
+                `-${this.fringingEnabled ? 'fringing' : 'nofringing'}`;
 
             if (this._key !== key) {
                 this._key = key;
@@ -195,7 +233,8 @@ class RenderPassCompose extends RenderPassShaderQuad {
                 const defines =
                     (this.bloomTexture ? `#define BLOOM\n` : '') +
                     (this.gradingEnabled ? `#define GRADING\n` : '') +
-                    (this.vignetteEnabled ? `#define VIGNETTE\n` : '');
+                    (this.vignetteEnabled ? `#define VIGNETTE\n` : '') +
+                    (this.fringingEnabled ? `#define FRINGING\n` : '');
 
                 const fsChunks =
                 shaderChunks.decodePS +
@@ -224,6 +263,10 @@ class RenderPassCompose extends RenderPassShaderQuad {
             this.vignetterParamsId.setValue([this.vignetteInner, this.vignetteOuter, this.vignetteCurvature, this.vignetteIntensity]);
         }
 
+        if (this._fringingEnabled) {
+            this.fringingIntensityId.setValue(this.fringingIntensity / this.sceneTexture.height);
+        }
+
         super.execute();
     }
 }