Fix the skybox visual artifact bug #10

assets/shaders/skybox.frag

@@ -9,15 +9,19 @@ uniform sampler2D equirect;
 const vec2 inv_atan = vec2(0.15915494309, 0.31830988618);
 
 vec2 sample_spherical_map(vec3 v) {
-    vec2 uv = vec2(atan(v.z, v.x), asin(v.y));
+    vec2 uv = vec2(atan(v.z, v.x), asin(clamp(v.y, -1.0, 1.0)));
     uv *= inv_atan;
     uv += 0.5;
+    uv.x = fract(uv.x);
     return uv;
 }
 
 void main() {
     vec2 uv = sample_spherical_map(normalize(direction));
     uv.y = 1.0 - uv.y;
+    vec2 size = vec2(textureSize(equirect, 0));
+    float epsY = 0.5 / max(size.y, 1.0);
+    uv.y = clamp(uv.y, epsY, 1.0 - epsY);
     vec3 color = texture(equirect, uv).rgb;
     frag_color = vec4(color, 1.0);
 }