Fix particle jitter when scene tree is paused.

drivers/gles3/storage/particles_storage.cpp

@@ -513,7 +513,7 @@ void ParticlesStorage::_particles_process(Particles *p_particles, double p_delta
 	GLES3::TextureStorage *texture_storage = GLES3::TextureStorage::get_singleton();
 	GLES3::MaterialStorage *material_storage = GLES3::MaterialStorage::get_singleton();
 
-	double new_phase = Math::fmod(p_particles->phase + (p_delta / p_particles->lifetime) * p_particles->speed_scale, 1.0);
+	double new_phase = Math::fmod(p_particles->phase + (p_delta / p_particles->lifetime), 1.0);
 
 	//update current frame
 	ParticlesFrameParams frame_params;
@@ -534,7 +534,7 @@ void ParticlesStorage::_particles_process(Particles *p_particles, double p_delta
 	p_particles->phase = new_phase;
 
 	frame_params.time = RSG::rasterizer->get_total_time();
-	frame_params.delta = p_delta * p_particles->speed_scale;
+	frame_params.delta = p_delta;
 	frame_params.random_seed = p_particles->random_seed;
 	frame_params.explosiveness = p_particles->explosiveness;
 	frame_params.randomness = p_particles->randomness;
@@ -1097,8 +1097,6 @@ void ParticlesStorage::update_particles() {
 			fixed_fps = particles->fixed_fps;
 		}
 
-		bool zero_time_scale = Engine::get_singleton()->get_time_scale() <= 0.0;
-
 		if (particles->clear && particles->pre_process_time > 0.0) {
 			double frame_time;
 			if (fixed_fps > 0) {
@@ -1115,37 +1113,27 @@ void ParticlesStorage::update_particles() {
 			}
 		}
 
+		double time_scale = MAX(particles->speed_scale, 0.0);
+
 		if (fixed_fps > 0) {
-			double frame_time;
-			double decr;
-			if (zero_time_scale) {
-				frame_time = 0.0;
-				decr = 1.0 / fixed_fps;
-			} else {
-				frame_time = 1.0 / fixed_fps;
-				decr = frame_time;
-			}
+			double frame_time = 1.0 / fixed_fps;
 			double delta = RSG::rasterizer->get_frame_delta_time();
 			if (delta > 0.1) { //avoid recursive stalls if fps goes below 10
 				delta = 0.1;
 			} else if (delta <= 0.0) { //unlikely but..
 				delta = 0.001;
 			}
-			double todo = particles->frame_remainder + delta;
+			double todo = particles->frame_remainder + delta * time_scale;
 
 			while (todo >= frame_time) {
 				_particles_process(particles, frame_time);
-				todo -= decr;
+				todo -= frame_time;
 			}
 
 			particles->frame_remainder = todo;
 
 		} else {
-			if (zero_time_scale) {
-				_particles_process(particles, 0.0);
-			} else {
-				_particles_process(particles, RSG::rasterizer->get_frame_delta_time());
-			}
+			_particles_process(particles, RSG::rasterizer->get_frame_delta_time() * time_scale);
 		}
 
 		if (particles->request_process_time > 0.0) {

scene/resources/particle_process_material.cpp

@@ -1034,7 +1034,7 @@ void ParticleProcessMaterial::_update_shader() {
 			code += "	{\n";
 		}
 		code += "		float vel_mag = length(VELOCITY);\n";
-		code += "		float vel_infl = clamp(dynamic_params.turb_influence * turbulence_influence, 0.0, 1.0);\n";
+		code += "		float vel_infl = clamp(dynamic_params.turb_influence * turbulence_influence, 0.0, 1.0) * (DELTA <= 0.0 ? 0.0 : 1.0);\n";
 		code += "		VELOCITY = mix(VELOCITY, normalize(noise_direction) * vel_mag * (1.0 + (1.0 - vel_infl) * 0.2), vel_infl);\n";
 		code += "		vel_mag = length(controlled_displacement);\n";
 		code += "		controlled_displacement = mix(controlled_displacement, normalize(noise_direction) * vel_mag * (1.0 + (1.0 - vel_infl) * 0.2), vel_infl);\n";

servers/rendering/renderer_rd/storage_rd/particles_storage.cpp

@@ -814,7 +814,7 @@ void ParticlesStorage::_particles_process(Particles *p_particles, double p_delta
 		p_particles->particles_material_uniform_set = RD::get_singleton()->uniform_set_create(uniforms, particles_shader.default_shader_rd, 1);
 	}
 
-	double new_phase = Math::fmod((double)p_particles->phase + (p_delta / p_particles->lifetime) * p_particles->speed_scale, 1.0);
+	double new_phase = Math::fmod((double)p_particles->phase + (p_delta / p_particles->lifetime), 1.0);
 
 	//move back history (if there is any)
 	for (uint32_t i = p_particles->frame_history.size() - 1; i > 0; i--) {
@@ -839,7 +839,7 @@ void ParticlesStorage::_particles_process(Particles *p_particles, double p_delta
 	p_particles->phase = new_phase;
 
 	frame_params.time = RendererCompositorRD::get_singleton()->get_total_time();
-	frame_params.delta = p_delta * p_particles->speed_scale;
+	frame_params.delta = p_delta;
 	frame_params.random_seed = p_particles->random_seed;
 	frame_params.explosiveness = p_particles->explosiveness;
 	frame_params.randomness = p_particles->randomness;
@@ -1158,6 +1158,10 @@ void ParticlesStorage::_particles_process(Particles *p_particles, double p_delta
 		//fill the trail params
 		for (uint32_t i = 0; i < p_particles->trail_params.size(); i++) {
 			uint32_t src_idx = i * p_particles->frame_history.size() / p_particles->trail_params.size();
+			if (p_particles->speed_scale <= 0.0) {
+				// Stop trails.
+				src_idx = 0;
+			}
 			p_particles->trail_params[i] = p_particles->frame_history[src_idx];
 		}
 	} else {
@@ -1529,7 +1533,6 @@ void ParticlesStorage::update_particles() {
 			}
 		}
 
-		bool zero_time_scale = Engine::get_singleton()->get_time_scale() <= 0.0;
 		double todo = particles->request_process_time;
 		if (particles->clear) {
 			todo += particles->pre_process_time;
@@ -1554,37 +1557,26 @@ void ParticlesStorage::update_particles() {
 			particles->speed_scale = tmp_scale;
 		}
 
+		double time_scale = MAX(particles->speed_scale, 0.0);
+
 		if (fixed_fps > 0) {
-			double frame_time;
-			double decr;
-			if (zero_time_scale) {
-				frame_time = 0.0;
-				decr = 1.0 / fixed_fps;
-			} else {
-				frame_time = 1.0 / fixed_fps;
-				decr = frame_time;
-			}
+			double frame_time = 1.0 / fixed_fps;
 			double delta = RendererCompositorRD::get_singleton()->get_frame_delta_time();
 			if (delta > 0.1) { //avoid recursive stalls if fps goes below 10
 				delta = 0.1;
 			} else if (delta <= 0.0) { //unlikely but..
 				delta = 0.001;
 			}
-			todo = particles->frame_remainder + delta;
+			todo = particles->frame_remainder + delta * time_scale;
 
 			while (todo >= frame_time || particles->clear) {
 				_particles_process(particles, frame_time);
-				todo -= decr;
+				todo -= frame_time;
 			}
 
 			particles->frame_remainder = todo;
-
 		} else {
-			if (zero_time_scale) {
-				_particles_process(particles, 0.0);
-			} else {
-				_particles_process(particles, RendererCompositorRD::get_singleton()->get_frame_delta_time());
-			}
+			_particles_process(particles, RendererCompositorRD::get_singleton()->get_frame_delta_time() * time_scale);
 		}
 
 		// Ensure that memory is initialized (the code above should ensure that _particles_process is always called at least once upon clearing).