diff --git a/app-proto/inversive-display/src/inversive.frag b/app-proto/inversive-display/src/inversive.frag
index 5620210..da2f415 100644
--- a/app-proto/inversive-display/src/inversive.frag
+++ b/app-proto/inversive-display/src/inversive.frag
@@ -141,11 +141,11 @@ void main() {
     int frag_cnt = 0;
     for (int i = 0; i < sphere_cnt; ++i) {
         vec2 hit_depths = sphere_cast(sphere_list[i], dir);
-        if (!isnan(hit_depths[0])) {
+        if (hit_depths[0] > 0.) {
             frags[frag_cnt] = sphere_shading(sphere_list[i], hit_depths[0] * dir, color_list[i], i);
             ++frag_cnt;
         }
-        if (!isnan(hit_depths[1])) {
+        if (hit_depths[1] > 0.) {
             frags[frag_cnt] = sphere_shading(sphere_list[i], hit_depths[1] * dir, color_list[i], i);
             ++frag_cnt;
         }