Enhancements to breadcrumb trail

trailfragshader.glsl

@@ -1,12 +1,17 @@
-#version 460 core
-// Colors the trail geometry with a solid uniform tint.
+#version 330 core
+// Colors the trail geometry by age: newest samples are red and old samples
+// fade toward brown before they expire from the CPU-side trail window.
 out vec4 FragColor;
 
-in vec3 FragPos;
+in float TrailTimestamp;
 
-uniform vec3 objectcolor;
+uniform float currentTime;
+uniform float maxAge;
+uniform vec3 recentColor;
+uniform vec3 oldColor;
 
 void main()
 {
-    FragColor = vec4(objectcolor, 1.0);
+    float ageRatio = clamp((currentTime - TrailTimestamp) / maxAge, 0.0, 1.0);
+    FragColor = vec4(mix(recentColor, oldColor, ageRatio), 1.0);
 }