[Question] Noise Present in Synthetic Depth Image Compared to Real Depth Image

[Deok-min]

I encountered an issue when generating synthetic depth images using the below code in this repository.

DepthImage* ProjectiveSemanticIntegrator::get_synthetic_depth_image(
    const Camera& camera, const Transform& T_L_C, const TsdfLayer& tsdf_layer) {
  
  // Metric truncation distance for this layer
  const float truncation_distance_m =
      truncation_distance_vox_ * tsdf_layer.voxel_size();

  // Get preallocated space for the synthetic depth image
  const SphereTracer::SubsampledImageSize image_size =
      sphere_tracer_.getSubsampledImageSize(
          camera, sphere_tracing_ray_subsampling_factor_);
  DepthImage* synthetic_depth_image = synthetic_depth_images_.get(
      image_size.rows, image_size.cols, MemoryType::kDevice);

  // Create a synthetic depth image
  timing::Timer sphere_trace_timer("semantic/integrate/sphere_trace");
  sphere_tracer_.renderImageOnGPU(
      camera, T_L_C, tsdf_layer, truncation_distance_m, synthetic_depth_image,
      MemoryType::kDevice, sphere_tracing_ray_subsampling_factor_);
  sphere_trace_timer.Stop();

  return synthetic_depth_image;
}

Unlike the real depth image, the synthetic depth image contains noticeable noise. I have included two images for comparison below, one showing the real depth image (without noise) and the other showing the synthesized depth image (with noise).
The real depth pointcloud looks like,

And the synthesized depth looks like,

The synthetic depth image seems to include voxels in locations that should not logically exist based on the scene’s structure and the real depth image.
Could you give me advice for what could be causing this issue and potential solutions to address it?

Thank you for reading.