From fbc5d7dd1a9192c29daccdf12a7a067037ff2c2a Mon Sep 17 00:00:00 2001
From: Matt Kosarek <matt.kosarek@canonical.com>
Date: Mon, 29 Dec 2025 10:02:38 -0500
Subject: Improve the sun shader with the help of AI

---
 themes/src/shaders/sun_frag.cpp | 40 +++++++++++++++++++++++++++++++++++++++-
 themes/src/shaders/sun_vert.cpp | 27 ++++++++++++++++++---------
 2 files changed, 57 insertions(+), 10 deletions(-)

(limited to 'themes/src/shaders')

diff --git a/themes/src/shaders/sun_frag.cpp b/themes/src/shaders/sun_frag.cpp
index d1ea160..30553e0 100644
--- a/themes/src/shaders/sun_frag.cpp
+++ b/themes/src/shaders/sun_frag.cpp
@@ -1,8 +1,46 @@
 #include "sun_frag.h"
 
 const char* shader_sun_frag = "varying lowp vec4 VertexColor; \n"
+"varying lowp vec2 TexCoord; \n"
+"uniform lowp float time; \n"
+" \n"
+"// Simple noise function for edge distortion \n"
+"lowp float noise(lowp vec2 p) { \n"
+"    return sin(p.x * 10.0 + time) * cos(p.y * 10.0 + time * 0.5) * 0.5 + 0.5; \n"
+"} \n"
 " \n"
 "void main() { \n"
-"    gl_FragColor = VertexColor; \n"
+"    // TexCoord is now normalized: center is (0,0), edges are at distance ~1 \n"
+"    lowp float dist = length(TexCoord); \n"
+" \n"
+"    // Add animated noise to the edge \n"
+"    lowp float angle = atan(TexCoord.y, TexCoord.x); \n"
+"    lowp float wave = sin(angle * 8.0 + time * 2.0) * 0.05 + sin(angle * 4.0 - time * 1.5) * 0.03; \n"
+"    lowp float noiseValue = noise(TexCoord + time * 0.1) * 0.02; \n"
+" \n"
+"    // Create soft edge using smoothstep - ensure fade reaches zero at the actual edge \n"
+"    lowp float innerEdge = 0.2; \n"
+"    lowp float outerEdge = 1.0; \n"
+"    lowp float alpha = 1.0 - smoothstep(innerEdge, outerEdge, dist); \n"
+" \n"
+"    // Apply wave distortion to the edge \n"
+"    alpha *= 1.0 - smoothstep(0.85 + wave + noiseValue * 2.0, 1.0, dist); \n"
+" \n"
+"    // Make edges even more transparent with additional fade \n"
+"    alpha = alpha * alpha * alpha; \n"
+" \n"
+"    // Add slight glow effect at the edge \n"
+"    lowp float glow = smoothstep(0.5, 0.8, dist) * (1.0 - smoothstep(0.8, 1.0, dist)); \n"
+" \n"
+"    // Create orange gradient from center \n"
+"    lowp vec3 orangeColor = vec3(1.0, 0.5, 0.1); \n"
+"    lowp float centerGradient = smoothstep(0.6, 0.0, dist); \n"
+"    lowp vec3 baseColor = mix(VertexColor.rgb, orangeColor, centerGradient * 0.6); \n"
+" \n"
+"    // Mix in the glow with a brighter color \n"
+"    lowp vec3 glowColor = baseColor * 1.3; \n"
+"    lowp vec3 finalColor = mix(baseColor, glowColor, glow * 0.5); \n"
+" \n"
+"    gl_FragColor = vec4(finalColor, VertexColor.a * alpha); \n"
 "} \n"
 " \n";
diff --git a/themes/src/shaders/sun_vert.cpp b/themes/src/shaders/sun_vert.cpp
index ca617c0..bacf3a6 100644
--- a/themes/src/shaders/sun_vert.cpp
+++ b/themes/src/shaders/sun_vert.cpp
@@ -1,16 +1,25 @@
 #include "sun_vert.h"
 
 const char* shader_sun_vert = " \n"
-"attribute vec2 position;  \n"
-"attribute vec4 color;  \n"
-"attribute mat4 vMatrix;  \n"
-"uniform mat4 projection;  \n"
-"uniform mat4 model;  \n"
+"attribute vec2 position; \n"
+"attribute vec4 color; \n"
+"attribute mat4 vMatrix; \n"
+"uniform mat4 projection; \n"
+"uniform mat4 model; \n"
 "varying lowp vec4 VertexColor; \n"
+"varying lowp vec2 TexCoord; \n"
 " \n"
-"void main() {  \n"
-"    vec4 fragmentPosition = projection * model * vMatrix * vec4(position.x, position.y, 0, 1);  \n"
-"    gl_Position = fragmentPosition;  \n"
-"    VertexColor = color;  \n"
+"void main() { \n"
+"    vec4 fragmentPosition = projection * model * vMatrix * vec4(position.x, position.y, 0, 1); \n"
+"    gl_Position = fragmentPosition; \n"
+"    VertexColor = color; \n"
+"    // Normalize the position - the center is at (0,0) and edge vertices are at distance 'radius' \n"
+"    // We want TexCoord to be in the range roughly [-1, 1] at the edges \n"
+"    lowp float maxDist = length(position); \n"
+"    if (maxDist > 0.1) { \n"
+"        TexCoord = position / maxDist; \n"
+"    } else { \n"
+"        TexCoord = vec2(0.0, 0.0); \n"
+"    } \n"
 "} \n"
 " \n";
-- 
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