9 files changed, 35 insertions, 23 deletions
diff --git a/intern/cycles/blender/addon/engine.py b/intern/cycles/blender/addon/engine.py
index 910ac4a373e..88526212d31 100644
--- a/intern/cycles/blender/addon/engine.py
+++ b/intern/cycles/blender/addon/engine.py
@@ -60,9 +60,8 @@ def init():
 
     path = os.path.dirname(__file__)
     user_path = os.path.dirname(os.path.abspath(bpy.utils.user_resource('CONFIG', path='')))
-    temp_path = bpy.app.tempdir
 
-    _cycles.init(path, user_path, temp_path, bpy.app.background)
+    _cycles.init(path, user_path, bpy.app.background)
     _parse_command_line()
 
 
diff --git a/intern/cycles/blender/python.cpp b/intern/cycles/blender/python.cpp
index f509d5c2eeb..f3279ff03a3 100644
--- a/intern/cycles/blender/python.cpp
+++ b/intern/cycles/blender/python.cpp
@@ -138,20 +138,18 @@ static const char *PyC_UnicodeAsByte(PyObject *py_str, PyObject **coerce)
 
 static PyObject *init_func(PyObject * /*self*/, PyObject *args)
 {
-  PyObject *path, *user_path, *temp_path;
+  PyObject *path, *user_path;
   int headless;
 
-  if (!PyArg_ParseTuple(args, "OOOi", &path, &user_path, &temp_path, &headless)) {
+  if (!PyArg_ParseTuple(args, "OOi", &path, &user_path, &headless)) {
     return nullptr;
   }
 
-  PyObject *path_coerce = nullptr, *user_path_coerce = nullptr, *temp_path_coerce = nullptr;
+  PyObject *path_coerce = nullptr, *user_path_coerce = nullptr;
   path_init(PyC_UnicodeAsByte(path, &path_coerce),
-            PyC_UnicodeAsByte(user_path, &user_path_coerce),
-            PyC_UnicodeAsByte(temp_path, &temp_path_coerce));
+            PyC_UnicodeAsByte(user_path, &user_path_coerce));
   Py_XDECREF(path_coerce);
   Py_XDECREF(user_path_coerce);
-  Py_XDECREF(temp_path_coerce);
 
   BlenderSession::headless = headless;
 
diff --git a/intern/cycles/blender/sync.cpp b/intern/cycles/blender/sync.cpp
index 56137374d8e..588e057b9ad 100644
--- a/intern/cycles/blender/sync.cpp
+++ b/intern/cycles/blender/sync.cpp
@@ -832,6 +832,14 @@ SessionParams BlenderSync::get_session_params(BL::RenderEngine &b_engine,
   SessionParams params;
   PointerRNA cscene = RNA_pointer_get(&b_scene.ptr, "cycles");
 
+  if (background && !b_engine.is_preview()) {
+    /* Viewport and preview renders do not require temp directory and do request session
+     * parameters more often than the background render.
+     * Optimize RNA-C++ usage and memory allocation a bit by saving string access which we know is
+     * not needed for viewport render. */
+    params.temp_dir = b_engine.temporary_directory();
+  }
+
   /* feature set */
   params.experimental = (get_enum(cscene, "feature_set") != 0);
 
diff --git a/intern/cycles/session/session.cpp b/intern/cycles/session/session.cpp
index a839303debc..2c50a9a6d7f 100644
--- a/intern/cycles/session/session.cpp
+++ b/intern/cycles/session/session.cpp
@@ -426,6 +426,11 @@ void Session::do_delayed_reset()
   buffer_params_.update_passes(scene->passes);
   tile_manager_.update(buffer_params_, scene);
 
+  /* Update temp directory on reset.
+   * This potentially allows to finish the existing rendering with a previously configure temporary
+   * direcotry in the host software and switch to a new temp directory when new render starts. */
+  tile_manager_.set_temp_dir(params.temp_dir);
+
   /* Progress. */
   progress.reset_sample();
   progress.set_total_pixel_samples(static_cast<uint64_t>(buffer_params_.width) *
diff --git a/intern/cycles/session/session.h b/intern/cycles/session/session.h
index 3f73593f008..adfd1346600 100644
--- a/intern/cycles/session/session.h
+++ b/intern/cycles/session/session.h
@@ -69,6 +69,9 @@ class SessionParams {
 
   ShadingSystem shadingsystem;
 
+  /* Session-specific temporary directory to store in-progress EXR files in. */
+  string temp_dir;
+
   SessionParams()
   {
     headless = false;
diff --git a/intern/cycles/session/tile.cpp b/intern/cycles/session/tile.cpp
index afd1f334120..ab1b3b8ec36 100644
--- a/intern/cycles/session/tile.cpp
+++ b/intern/cycles/session/tile.cpp
@@ -23,6 +23,7 @@
 #include "scene/film.h"
 #include "scene/integrator.h"
 #include "scene/scene.h"
+#include "session/session.h"
 #include "util/algorithm.h"
 #include "util/foreach.h"
 #include "util/log.h"
@@ -394,6 +395,11 @@ void TileManager::update(const BufferParams &params, const Scene *scene)
   }
 }
 
+void TileManager::set_temp_dir(const string &temp_dir)
+{
+  temp_dir_ = temp_dir;
+}
+
 bool TileManager::done()
 {
   return tile_state_.next_tile_index == tile_state_.num_tiles;
@@ -452,7 +458,8 @@ const int2 TileManager::get_size() const
 
 bool TileManager::open_tile_output()
 {
-  write_state_.filename = path_temp_get("cycles-tile-buffer-" + tile_file_unique_part_ + "-" +
+  write_state_.filename = path_join(temp_dir_,
+                                    "cycles-tile-buffer-" + tile_file_unique_part_ + "-" +
                                         to_string(write_state_.tile_file_index) + ".exr");
 
   write_state_.tile_out = ImageOutput::create(write_state_.filename);
diff --git a/intern/cycles/session/tile.h b/intern/cycles/session/tile.h
index 7c8f7570d3e..80a5db543cd 100644
--- a/intern/cycles/session/tile.h
+++ b/intern/cycles/session/tile.h
@@ -71,6 +71,8 @@ class TileManager {
    * Will store all parameters needed for buffers access outside of the scene graph. */
   void update(const BufferParams &params, const Scene *scene);
 
+  void set_temp_dir(const string &temp_dir);
+
   inline int get_num_tiles() const
   {
     return tile_state_.num_tiles;
@@ -136,6 +138,8 @@ class TileManager {
   bool open_tile_output();
   bool close_tile_output();
 
+  string temp_dir_;
+
   /* Part of an on-disk tile file name which avoids conflicts between several Cycles instances or
    * several sessions. */
   string tile_file_unique_part_;
diff --git a/intern/cycles/util/path.cpp b/intern/cycles/util/path.cpp
index e27c929fba9..4efdeeae7f0 100644
--- a/intern/cycles/util/path.cpp
+++ b/intern/cycles/util/path.cpp
@@ -66,7 +66,6 @@ typedef struct stat path_stat_t;
 
 static string cached_path = "";
 static string cached_user_path = "";
-static string cached_temp_path = "";
 static string cached_xdg_cache_path = "";
 
 namespace {
@@ -336,11 +335,10 @@ static string path_xdg_cache_get()
 }
 #endif
 
-void path_init(const string &path, const string &user_path, const string &temp_path)
+void path_init(const string &path, const string &user_path)
 {
   cached_path = path;
   cached_user_path = user_path;
-  cached_temp_path = temp_path;
 
 #ifdef _MSC_VER
   // workaround for https://svn.boost.org/trac/boost/ticket/6320
@@ -384,15 +382,6 @@ string path_cache_get(const string &sub)
 #endif
 }
 
-string path_temp_get(const string &sub)
-{
-  if (cached_temp_path == "") {
-    cached_temp_path = Filesystem::temp_directory_path();
-  }
-
-  return path_join(cached_temp_path, sub);
-}
-
 #if defined(__linux__) || defined(__APPLE__)
 string path_xdg_home_get(const string &sub = "");
 #endif
diff --git a/intern/cycles/util/path.h b/intern/cycles/util/path.h
index 7ec5ed60d7f..98c3302eae2 100644
--- a/intern/cycles/util/path.h
+++ b/intern/cycles/util/path.h
@@ -32,10 +32,9 @@
 CCL_NAMESPACE_BEGIN
 
 /* program paths */
-void path_init(const string &path = "", const string &user_path = "", const string &tmp_path = "");
+void path_init(const string &path = "", const string &user_path = "");
 string path_get(const string &sub = "");
 string path_user_get(const string &sub = "");
-string path_temp_get(const string &sub = "");
 string path_cache_get(const string &sub = "");
 
 /* path string manipulation */