From e37b18336a63213ba0fbffcbdc9dcd2a4b941398 Mon Sep 17 00:00:00 2001
From: Olivier Prat <olivier@zvork.fr>
Date: Wed, 25 Apr 2018 12:08:08 +0200
Subject: [PATCH] Improved anti-aliasing on text

---
 libraries/render-utils/src/sdf_text3D.slf | 31 +++++++++++++++--------
 1 file changed, 21 insertions(+), 10 deletions(-)

diff --git a/libraries/render-utils/src/sdf_text3D.slf b/libraries/render-utils/src/sdf_text3D.slf
index 2742341628..08e50ee8c5 100644
--- a/libraries/render-utils/src/sdf_text3D.slf
+++ b/libraries/render-utils/src/sdf_text3D.slf
@@ -20,14 +20,15 @@ uniform vec4 Color;
 in vec3 _normalWS;
 in vec2 _texCoord0;
 
-const float gamma = 2.2;
-const float smoothing = 32.0;
+#define TAA_TEXTURE_LOD_BIAS    -3.0
+
 const float interiorCutoff = 0.8;
 const float outlineExpansion = 0.2;
+const float taaBias = pow(2.0, TAA_TEXTURE_LOD_BIAS);
 
-void main() {
+float evalSDF(vec2 texCoord) {
     // retrieve signed distance
-    float sdf = texture(Font, _texCoord0).g;
+    float sdf = textureLod(Font, texCoord, TAA_TEXTURE_LOD_BIAS).g;
     if (Outline) {
         if (sdf > interiorCutoff) {
             sdf = 1.0 - sdf;
@@ -35,12 +36,22 @@ void main() {
             sdf += outlineExpansion;
         }
     }
-    // perform adaptive anti-aliasing of the edges
-    // The larger we're rendering, the less anti-aliasing we need
-    float s = smoothing * length(fwidth(_texCoord0));
-    float w = clamp(s, 0.0, 0.5);
-    float a = smoothstep(0.5 - w, 0.5 + w, sdf);
-    
+    // Rely on TAA for anti-aliasing
+    return step(0.5, sdf);
+}
+
+void main() {
+    vec2 dxTexCoord = dFdx(_texCoord0) * 0.5 * taaBias;
+    vec2 dyTexCoord = dFdy(_texCoord0) * 0.5 * taaBias;
+
+	// Perform 4x supersampling for anisotropic filtering
+    float a;
+	a = evalSDF(_texCoord0);
+	a += evalSDF(_texCoord0+dxTexCoord);
+	a += evalSDF(_texCoord0+dyTexCoord);
+	a += evalSDF(_texCoord0+dxTexCoord+dyTexCoord);
+    a *= 0.25;
+
     // discard if invisible
     if (a < 0.01) {
         discard;