3D Advanced Product Generation

The 3D Advanced module enables the user to create 3D Textured Mesh and True Ortho products from HxMap’s Product Generation Perspective. The following guide provides a quick start to installation and use of the module.

System Requirements

3D Advanced module requires GPU for certain compute tasks of the meshing pipeline. Other than the GPU, machine requirements are the same as described in System Requirements.

GPU Requirement for 3D Advanced

Manufacturer: NVIDIA
Model: Must support NVIDIA CUDA Runtime at CUDA compute capability level 6.0 or higher
See https://developer.nvidia.com/cuda-gpus for a lookup of capability level of various NVIDIA GPUs

Installation

3D Advanced module is packaged in four additional installer executables Place the installers in the same directory as the HxMap Full Installer, and run the Full Installer. 3D Advanced installers will be automatically detected and included in the installation. It is not possible to run 3D Advanced module installation separate from HxMap Full Installer. Distributed installation can be achieved following the instructions in Distributed HxMap deployment. Nodes should be configured to advertise their GPU as described in GPU Resource .

Workflow

The reconstruction process to generate 3D textured mesh and true ortho depends on accurate geometry and radiometry to achieve good results. The required workflow for 3D Advanced Product Generation is:

Triangulate Images
Match Lidar
Run Blockwide Radiometry
Run Product Generation
QC and Edit Products

When the 3D Advanced module is installed, a new Product Type will be available, ‘MESH’. This Product Type will automatically create both the 3D textured mesh in Cesium 3D Tiles format and the true ortho in GeoTIFF format. Set the Radiometry template for the MESH Product to Frame Sense Full in order to take advantage of the Blockwide Radiometry result.

In the Product Generation wizard Project Specification page for MESH Product Type, there are two key settings.

Setting

Description

AOI

An AOI should be given for each product generation run. It will be used as the limit for the 3D reconstruction process and should have full coverage in all image views and lidar for proper reconstruction and texturing results.

Target Dilution

The mesh texture quality and run time depend on density of input images. Target Dilution parameter may be used to reduce planned image density to an optimal value for mesh generation. Image density is quantified by the flight plan value Tau calculated in MissionPro and is a function of forward and side overlap together with image area.

Recommended Tau values for 3D Advanced with nadir + obliques in different landscapes are:

Hybrid mesh: rural and suburban area 25 - 32, city with high rise buildings 55
Image only mesh: rural and suburban area 32, city with high rise building not recommended

Plan with the recommended Tau value in MissionPro for the most economical flight plan to support 3D Advanced product generation. In case a higher Tau value is needed to support other product specifications in the project, use Target Dilution to reduce the image input for the MESH product type. The list below shows the dilution strategies available, choose the dilution strategy will reduce Tau closest to the recommended value without going below it.

1:1 All Images (no Tau reduction)
1:2 Obliques only - all nadirs and obliques from every other take are used, (Tau reduced by ~43%)
1:2 - every other take is used, Tau reduced by 50%
1:3 - every third take is used, Tau reduced by 66%
1:4 every 4th take is used, Tau reduced by 75%

For 3D Advanced with nadir images only, a Tau value of 25 is recommended for all landscapes, generally no dilution is necessary. Note that vertical facades may not be optimally textured with nadir views.

Quality Control

The 3D Editor perspective is used to QC and edit the generated mesh. During the QC process, the user collects volumes which should be added to or substracted from the mesh geometry. Once the volumes have been collected, an update job can be run to update the mesh geometry and textures, and recreate the true orthos.

QC Step	Example	Notes
Create a new 3D Editor project with the HxMap Block used to generate the mesh		Create a new 3D Model File for the edit project. Coordinate Reference System for the 3D Editor project should be the same which is used for the MESH product generation.
Load the generated 3D Tiles as an overlay in the 3D Editor
Collect mesh edit volumes		Use 3D Editor’s ‘Collect Object’ feature to digitize the mesh edit volumes Collected objects can be either addition volumes or subtraction volumes Place subtraction volumes on the 3D Model Layer #9999 Addition volumes can be assigned on any other Layer Use subtraction volumes to remove false features that were created in the mesh Use addition volumes to repair objects which are poorly reconstructed, like glass facades or irregular structures.
Run the mesh fix		Load the MESH job result in Product Generation perspective Select the job result Menu Tools → Edit Mesh… Select the TDC file which contains the edit volumes The Edit Mesh job result will be added to the parent job definition which is edited.

Notes for 3D Advanced in HxMap 4.6

Coordinate Reference Systems which are supported for 3D Advanced Product Generation
- EPSG systems
- Ellipsoidal systems