workaround for zero-size objects in priority formula

libraries/shared/src/PrioritySortUtil.h

@@ -112,11 +112,19 @@ namespace PrioritySortUtil {
             glm::vec3 position = thing.getPosition();
             glm::vec3 offset = position - _view.getPosition();
             float distance = glm::length(offset) + 0.001f; // add 1mm to avoid divide by zero
-            float radius = thing.getRadius();
+            const float MIN_RADIUS = 0.1f; // WORKAROUND for zero size objects (we still want them to sort by distance)
+            float radius = glm::min(thing.getRadius(), MIN_RADIUS);
+            float cosineAngle = (glm::dot(offset, _view.getDirection()) / distance);
+            float age = (float)(usecTimestampNow() - thing.getTimestamp());
 
-            float priority = _angularWeight * (radius / distance)
-                + _centerWeight * (glm::dot(offset, _view.getDirection()) / distance)
-                + _ageWeight * (float)(usecTimestampNow() - thing.getTimestamp());
+            // we modulatate "age" drift rate by the cosineAngle term to make periphrial objects sort forward
+            // at a reduced rate but we don't want the "age" term to go zero or negative so we clamp it
+            const float MIN_COSINE_ANGLE_FACTOR = 0.1f;
+            float cosineAngleFactor = glm::max(cosineAngle, MIN_COSINE_ANGLE_FACTOR);
+
+            float priority = _angularWeight * glm::max(radius, MIN_RADIUS) / distance
+                + _centerWeight * cosineAngle
+                + _ageWeight * cosineAngleFactor * age;
 
             // decrement priority of things outside keyhole
             if (distance - radius > _view.getCenterRadius()) {