Cycles: Use lower progressive update timeout for preview rendering

This ways previews are refreshing with the same ratio as job was expecting
this to happen, giving more instant feedback on the changes.

intern/cycles/blender/blender_sync.cpp

@@ -554,6 +554,13 @@ SessionParams BlenderSync::get_session_params(BL::RenderEngine b_engine,
 		                               b_engine.support_display_space_shader(b_scene);
 	}
 
+	if(b_engine.is_preview()) {
+		/* For preview rendering we're using same timeout as
+		 * blender's job update.
+		 */
+		params.progressive_update_timeout = 0.1;
+	}
+
 	return params;
 }
 

intern/cycles/render/session.cpp

@@ -889,7 +889,7 @@ bool Session::update_progressive_refine(bool cancel)
 
 	double current_time = time_dt();
 
-	if (current_time - last_update_time < 1.0) {
+	if (current_time - last_update_time < params.progressive_update_timeout) {
 		/* if last sample was processed, we need to write buffers anyway  */
 		if (!write)
 			return false;

intern/cycles/render/session.h

@@ -59,6 +59,7 @@ public:
 	double cancel_timeout;
 	double reset_timeout;
 	double text_timeout;
+	double progressive_update_timeout;
 
 	ShadingSystem shadingsystem;
 
@@ -80,6 +81,7 @@ public:
 		cancel_timeout = 0.1;
 		reset_timeout = 0.1;
 		text_timeout = 1.0;
+		progressive_update_timeout = 1.0;
 
 		shadingsystem = SHADINGSYSTEM_SVM;
 		tile_order = TILE_CENTER;
@@ -101,6 +103,7 @@ public:
 		&& cancel_timeout == params.cancel_timeout
 		&& reset_timeout == params.reset_timeout
 		&& text_timeout == params.text_timeout
+		&& progressive_update_timeout == params.progressive_update_timeout
 		&& tile_order == params.tile_order
 		&& shadingsystem == params.shadingsystem); }