SL-15918 - supplementary fix to prevent screen flickr during captures

indra/newview/llviewerwindow.cpp

@@ -5198,13 +5198,30 @@ BOOL LLViewerWindow::simpleSnapshot(LLImageRaw* raw, S32 image_width, S32 image_
         }
     }
 
-    const U32 subfield = 0;
-    const bool do_rebuild = true;
-    const F32 zoom = 1.0;
-    const bool for_snapshot = TRUE;
-
+    // we render the scene more than once since this helps
+    // greatly with the objects not being drawn in the 
+    // snapshot when they are drawn in the scene. This is 
+    // evident when you set this value via the debug setting
+    // called 360CaptureNumRenderPasses to 1. The theory is
+    // that the missing objects are caused by the sUseOcclusion
+    // property in pipeline but that the use in pipeline.cpp
+    // lags by a frame or two so rendering more than once
+    // appears to help a lot.
     for (int i = 0; i < num_render_passes; ++i)
     {
+        // turning this flag off here prohibits the screen swap
+        // to present the new page to the viewer - this stops
+        // the black flash in between captures when the number
+        // of render passes is more than 1. We need to also
+        // set it here because code in LLViewerDisplay resets
+        // it to TRUE each time.
+        gDisplaySwapBuffers = FALSE;
+
+        // actually render the scene
+        const U32 subfield = 0;
+        const bool do_rebuild = true;
+        const F32 zoom = 1.0;
+        const bool for_snapshot = TRUE;
         display(do_rebuild, zoom, subfield, for_snapshot);
     }