message: Debugging: write input buffers to disk on '@'-key
diff: #include "common/sg/common/FrameBuffer.h"
  #include "common/sg/visitor/GatherNodesByName.h"
  #include "common/sg/visitor/GatherNodesByPosition.h"
  +#include "common/sg/common/FrameBuffer.h"
  #include "sg_imgui/ospray_sg_ui.h"
  @@ -351,6 +352,14 @@ namespace ospray {
  case '!':
  saveScreenshot = true;
  break;
  + case '@': {
  + auto fb = scenegraph->child("frameBuffer").nodeAs<sg::FrameBuffer>();
  + auto fbSize = fb->size();
  + utility::writePFM("denoiser_normal.pfm", fbSize.x, fbSize.y, (vec3f*)fb->map(OSP_FB_NORMAL));
  + utility::writePFM("denoiser_albedo.pfm", fbSize.x, fbSize.y, (vec3f*)fb->map(OSP_FB_ALBEDO));
  + utility::writePFM("denoiser_color.pfm", fbSize.x, fbSize.y, (vec4f*)fb->map(OSP_FB_COLOR));
  + }
  + break;
  case 'X':
  if (viewPort.up == vec3f(1,0,0) || viewPort.up == vec3f(-1.f,0,0)) {
  viewPort.up = - viewPort.up;
  