From d30422800302d024499d5f895b2fbf598fe21a5a Mon Sep 17 00:00:00 2001
From: Juan Linietsky <reduzio@gmail.com>
Date: Mon, 19 Nov 2018 20:34:29 -0300
Subject: [PATCH] Do not draw particles if they are not processing at all,
 fixes #19507

---
 drivers/dummy/rasterizer_dummy.h           |  2 ++
 drivers/gles2/rasterizer_storage_gles2.cpp |  4 ++++
 drivers/gles2/rasterizer_storage_gles2.h   |  2 ++
 drivers/gles3/rasterizer_storage_gles3.cpp |  7 +++++++
 drivers/gles3/rasterizer_storage_gles3.h   |  2 ++
 servers/visual/rasterizer.h                |  2 ++
 servers/visual/visual_server_scene.cpp     | 11 ++++++++---
 7 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/drivers/dummy/rasterizer_dummy.h b/drivers/dummy/rasterizer_dummy.h
index bd3a36feefb..7c095e37989 100644
--- a/drivers/dummy/rasterizer_dummy.h
+++ b/drivers/dummy/rasterizer_dummy.h
@@ -681,6 +681,8 @@ public:
 	int particles_get_draw_passes(RID p_particles) const { return 0; }
 	RID particles_get_draw_pass_mesh(RID p_particles, int p_pass) const { return RID(); }
 
+	virtual bool particles_is_inactive(RID p_particles) const { return false; }
+
 	/* RENDER TARGET */
 
 	RID render_target_create() { return RID(); }
diff --git a/drivers/gles2/rasterizer_storage_gles2.cpp b/drivers/gles2/rasterizer_storage_gles2.cpp
index d646500a236..3beb8eac33e 100644
--- a/drivers/gles2/rasterizer_storage_gles2.cpp
+++ b/drivers/gles2/rasterizer_storage_gles2.cpp
@@ -3842,6 +3842,10 @@ RID RasterizerStorageGLES2::particles_get_draw_pass_mesh(RID p_particles, int p_
 void RasterizerStorageGLES2::update_particles() {
 }
 
+bool RasterizerStorageGLES2::particles_is_inactive(RID p_particles) const {
+	return true;
+}
+
 ////////
 
 void RasterizerStorageGLES2::instance_add_skeleton(RID p_skeleton, RasterizerScene::InstanceBase *p_instance) {
diff --git a/drivers/gles2/rasterizer_storage_gles2.h b/drivers/gles2/rasterizer_storage_gles2.h
index 59f911e880a..5bdc65a0b5d 100644
--- a/drivers/gles2/rasterizer_storage_gles2.h
+++ b/drivers/gles2/rasterizer_storage_gles2.h
@@ -1090,6 +1090,8 @@ public:
 	virtual int particles_get_draw_passes(RID p_particles) const;
 	virtual RID particles_get_draw_pass_mesh(RID p_particles, int p_pass) const;
 
+	virtual bool particles_is_inactive(RID p_particles) const;
+
 	/* INSTANCE */
 
 	virtual void instance_add_skeleton(RID p_skeleton, RasterizerScene::InstanceBase *p_instance);
diff --git a/drivers/gles3/rasterizer_storage_gles3.cpp b/drivers/gles3/rasterizer_storage_gles3.cpp
index 65543956faf..9e0d36f5c80 100644
--- a/drivers/gles3/rasterizer_storage_gles3.cpp
+++ b/drivers/gles3/rasterizer_storage_gles3.cpp
@@ -6455,6 +6455,13 @@ void RasterizerStorageGLES3::update_particles() {
 	glDisable(GL_RASTERIZER_DISCARD);
 }
 
+bool RasterizerStorageGLES3::particles_is_inactive(RID p_particles) const {
+
+	const Particles *particles = particles_owner.getornull(p_particles);
+	ERR_FAIL_COND_V(!particles, false);
+	return !particles->emitting && particles->inactive;
+}
+
 ////////
 
 void RasterizerStorageGLES3::instance_add_skeleton(RID p_skeleton, RasterizerScene::InstanceBase *p_instance) {
diff --git a/drivers/gles3/rasterizer_storage_gles3.h b/drivers/gles3/rasterizer_storage_gles3.h
index 8c843e4d967..398ffdeb823 100644
--- a/drivers/gles3/rasterizer_storage_gles3.h
+++ b/drivers/gles3/rasterizer_storage_gles3.h
@@ -1261,6 +1261,8 @@ public:
 	virtual int particles_get_draw_passes(RID p_particles) const;
 	virtual RID particles_get_draw_pass_mesh(RID p_particles, int p_pass) const;
 
+	virtual bool particles_is_inactive(RID p_particles) const;
+
 	/* INSTANCE */
 
 	virtual void instance_add_skeleton(RID p_skeleton, RasterizerScene::InstanceBase *p_instance);
diff --git a/servers/visual/rasterizer.h b/servers/visual/rasterizer.h
index f9beeb226c4..4329203ccb1 100644
--- a/servers/visual/rasterizer.h
+++ b/servers/visual/rasterizer.h
@@ -518,6 +518,8 @@ public:
 	virtual void particles_set_fractional_delta(RID p_particles, bool p_enable) = 0;
 	virtual void particles_restart(RID p_particles) = 0;
 
+	virtual bool particles_is_inactive(RID p_particles) const = 0;
+
 	virtual void particles_set_draw_order(RID p_particles, VS::ParticlesDrawOrder p_order) = 0;
 
 	virtual void particles_set_draw_passes(RID p_particles, int p_count) = 0;
diff --git a/servers/visual/visual_server_scene.cpp b/servers/visual/visual_server_scene.cpp
index 13de92f2261..1deca7bc66c 100644
--- a/servers/visual/visual_server_scene.cpp
+++ b/servers/visual/visual_server_scene.cpp
@@ -1912,9 +1912,14 @@ void VisualServerScene::_prepare_scene(const Transform p_cam_transform, const Ca
 
 			if (ins->base_type == VS::INSTANCE_PARTICLES) {
 				//particles visible? process them
-				VSG::storage->particles_request_process(ins->base);
-				//particles visible? request redraw
-				VisualServerRaster::redraw_request();
+				if (VSG::storage->particles_is_inactive(ins->base)) {
+					//but if nothing is going on, don't do it.
+					keep = false;
+				} else {
+					VSG::storage->particles_request_process(ins->base);
+					//particles visible? request redraw
+					VisualServerRaster::redraw_request();
+				}
 			}
 
 			if (geom->lighting_dirty) {