Ensure that particles are processed at least once before being used

servers/rendering/renderer_rd/storage_rd/particles_storage.cpp

@@ -1415,6 +1415,7 @@ void ParticlesStorage::update_particles() {
 		}
 
 		bool zero_time_scale = Engine::get_singleton()->get_time_scale() <= 0.0;
+		bool updated = false;
 
 		if (particles->clear && particles->pre_process_time > 0.0) {
 			double frame_time;
@@ -1429,6 +1430,7 @@ void ParticlesStorage::update_particles() {
 			while (todo >= 0) {
 				_particles_process(particles, frame_time);
 				todo -= frame_time;
+				updated = true;
 			}
 		}
 
@@ -1450,9 +1452,10 @@ void ParticlesStorage::update_particles() {
 			}
 			double todo = particles->frame_remainder + delta;
 
-			while (todo >= frame_time) {
+			while (todo >= frame_time || (particles->clear && !updated)) {
 				_particles_process(particles, frame_time);
 				todo -= decr;
+				updated = true;
 			}
 
 			particles->frame_remainder = todo;
@@ -1460,14 +1463,16 @@ void ParticlesStorage::update_particles() {
 		} else {
 			if (zero_time_scale) {
 				_particles_process(particles, 0.0);
+				updated = true;
 			} else {
 				_particles_process(particles, RendererCompositorRD::singleton->get_frame_delta_time());
+				updated = true;
 			}
 		}
 
 		//copy particles to instance buffer
 
-		if (particles->draw_order != RS::PARTICLES_DRAW_ORDER_VIEW_DEPTH && particles->transform_align != RS::PARTICLES_TRANSFORM_ALIGN_Z_BILLBOARD && particles->transform_align != RS::PARTICLES_TRANSFORM_ALIGN_Z_BILLBOARD_Y_TO_VELOCITY) {
+		if (updated && particles->draw_order != RS::PARTICLES_DRAW_ORDER_VIEW_DEPTH && particles->transform_align != RS::PARTICLES_TRANSFORM_ALIGN_Z_BILLBOARD && particles->transform_align != RS::PARTICLES_TRANSFORM_ALIGN_Z_BILLBOARD_Y_TO_VELOCITY) {
 			//does not need view dependent operation, do copy here
 			ParticlesShader::CopyPushConstant copy_push_constant;
 

servers/rendering/renderer_rd/storage_rd/particles_storage.h

@@ -485,9 +485,9 @@ public:
 	_FORCE_INLINE_ RID particles_get_instance_buffer_uniform_set(RID p_particles, RID p_shader, uint32_t p_set) {
 		Particles *particles = particles_owner.get_or_null(p_particles);
 		ERR_FAIL_COND_V(!particles, RID());
-		if (particles->particles_transforms_buffer_uniform_set.is_null()) {
+		if (particles->particles_transforms_buffer_uniform_set.is_null() || !RD::get_singleton()->uniform_set_is_valid(particles->particles_transforms_buffer_uniform_set)) {
 			_particles_update_buffers(particles);
-
+			update_particles();
 			Vector<RD::Uniform> uniforms;
 
 			{