3 files changed, 21 insertions, 0 deletions
diff --git a/source/blender/render/extern/include/RE_pipeline.h b/source/blender/render/extern/include/RE_pipeline.h
index 984b1a8e651..ecdd1774221 100644
--- a/source/blender/render/extern/include/RE_pipeline.h
+++ b/source/blender/render/extern/include/RE_pipeline.h
@@ -170,6 +170,8 @@ void RE_FreeRender (struct Render *re);
 void RE_FreeAllRender (void);
 /* only call on file load */
 void RE_FreeAllRenderResults(void);
+/* for external render engines that can keep persistent data */
+void RE_FreePersistentData(void);
 
 /* get results and statistics */
 void RE_FreeRenderResult(struct RenderResult *rr);
diff --git a/source/blender/render/intern/source/external_engine.c b/source/blender/render/intern/source/external_engine.c
index 736cb5de7c3..d771cf2253d 100644
--- a/source/blender/render/intern/source/external_engine.c
+++ b/source/blender/render/intern/source/external_engine.c
@@ -382,6 +382,11 @@ int RE_engine_render(Render *re, int do_all)
 	if (type->render)
 		type->render(engine, re->scene);
 
+	if(!(re->r.mode & R_PERSISTENT_DATA)) {
+		RE_engine_free(re->engine);
+		re->engine = NULL;
+	}
+
 	if (re->result->do_exr_tile) {
 		BLI_rw_mutex_lock(&re->resultmutex, THREAD_LOCK_WRITE);
 		render_result_exr_file_end(re);
diff --git a/source/blender/render/intern/source/pipeline.c b/source/blender/render/intern/source/pipeline.c
index 369818d37d5..3797430952c 100644
--- a/source/blender/render/intern/source/pipeline.c
+++ b/source/blender/render/intern/source/pipeline.c
@@ -244,6 +244,7 @@ Render *RE_GetRender(const char *name)
 	return re;
 }
 
+
 /* if you want to know exactly what has been done */
 RenderResult *RE_AcquireResultRead(Render *re)
 {
@@ -424,6 +425,19 @@ void RE_FreeAllRenderResults(void)
 	}
 }
 
+void RE_FreePersistentData()
+{
+	Render *re;
+
+	/* render engines can be kept around for quick re-render, this clears all */
+	for (re = RenderGlobal.renderlist.first; re; re = re->next) {
+		if (re->engine) {
+			RE_engine_free(re);
+			re->engine = NULL;
+		}
+	}
+}
+
 /* ********* initialize state ******** */