Increase the resolution for Capture_Depth_Point_Cloud

### Checklist

- [X] I have searched for [similar issues](https://github.com/isl-org/Open3D/issues).
- [X] For Python issues, I have tested with the [latest development wheel](https://www.open3d.org/docs/latest/getting_started.html#development-version-pip).
- [X] I have checked the [release documentation](https://www.open3d.org/docs/release/) and the [latest documentation](https://www.open3d.org/docs/latest/) (for `main` branch).

### My Question

Hello,

I am trying to convert mesh (.stl) object to point cloud.

```
extrinsic = np.array(T_wc)
camera_params = o3d.camera.PinholeCameraParameters()
camera_params.intrinsic = params.intrinsic
camera_params.extrinsic = extrinsic

# Apply the updated camera parameters to the visualizer
ctr.convert_from_pinhole_camera_parameters(camera_params,True)
vis.poll_events()
vis.update_renderer()

# Capture the point cloud from the camera's perspective
vis.capture_depth_point_cloud(pcd_temp_path,True,False)
```
This is the result I am getting
The point cloud is very sparse, I would like to get a more dense point cloud.

For reasons I cannot mention, I cannot use the [Ray_casting](https://www.open3d.org/docs/latest/tutorial/geometry/ray_casting.html) function from open3d.

What is the way to improve the density of my point cloud using `capture_depth_point_cloud` or any other post processing methods?