Fix T93727: Tiled render error in Cycles after changing temp directory

Consider temporary directory to be variant part of session configuration
which gets communicated to the tile manager on render reset.

This allows to be able to render with one temp directory, change the
directory, render again and have proper render result even with enabled
persistent data.

For the ease of access to the temp directory expose it via the render
engine API (engine.temp_directory).

Differential Revision: https://developer.blender.org/D13790

3 files changed, 13 insertions, 8 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);