fix 0 particle/s

src/scene/particles.cpp

@@ -121,6 +121,7 @@ void Scene_Particles::step(const PT::BVH<PT::Object>& scene, float dt) {
 
     float cos = std::cos(Radians(opt.angle) / 2.0f);
 
+    if(opt.pps > 0.0f) {
         double cooldown = 1.0 / opt.pps;
         while(particle_cooldown <= 0.0f) {
 
@@ -143,6 +144,8 @@ void Scene_Particles::step(const PT::BVH<PT::Object>& scene, float dt) {
         }
 
         particle_cooldown -= dt;
+    }
+
     particles = std::move(next);
 }