Render Engines: fix crash when changing render engine during rendering

Crash would have been happen when changing render ending at the same time
rendering happens. It could be final Cycles render or even preview LUX render.

1 files changed, 17 insertions, 7 deletions

diff --git a/source/blender/render/intern/source/external_engine.c b/source/blender/render/intern/source/external_engine.c
index 8bdb805ada2..9053bc84bbc 100644
--- a/source/blender/render/intern/source/external_engine.c
+++ b/source/blender/render/intern/source/external_engine.c
@@ -316,6 +316,7 @@ int RE_engine_render(Render *re, int do_all)
 {
 	RenderEngineType *type = RE_engines_find(re->r.engine);
 	RenderEngine *engine;
+	int persistent_data = re->r.mode & R_PERSISTENT_DATA;
 
 	/* verify if we can render */
 	if (!type->render)
@@ -349,11 +350,17 @@ int RE_engine_render(Render *re, int do_all)
 	re->i.totface = re->i.totvert = re->i.totstrand = re->i.totlamp = re->i.tothalo = 0;
 
 	/* render */
-	if (!re->engine)
-		re->engine = RE_engine_create(type);
-
 	engine = re->engine;
 
+	if (!engine) {
+		engine = RE_engine_create(type);
+
+		if (persistent_data)
+			re->engine = engine;
+	}
+
+	engine->flag |= RE_ENGINE_RENDERING;
+
 	/* TODO: actually link to a parent which shouldn't happen */
 	engine->re = re;
 
@@ -382,8 +389,13 @@ 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);
+	engine->tile_x = 0;
+	engine->tile_y = 0;
+	engine->flag &= ~RE_ENGINE_RENDERING;
+
+	/* re->engine becomes zero if user changed active render engine during render */
+	if (!persistent_data || !re->engine) {
+		RE_engine_free(engine);
 		re->engine = NULL;
 	}
 
@@ -393,8 +405,6 @@ int RE_engine_render(Render *re, int do_all)
 		BLI_rw_mutex_unlock(&re->resultmutex);
 	}
 
-	engine->tile_x = 0;
-	engine->tile_y = 0;
 	freeparts(re);
 
 	render_result_free_list(&engine->fullresult, engine->fullresult.first);