SideFX Houdini users get help in processing image series for point cloud generation and reverse engineering to take Houdini’s pipeline for game developers to a new level. In this case, we are talking about photogrammetry integrated into Houdini on the basis of Capturing Reality. We are also pleased to announce that the Capturing Reality plug-in for Houdini is in open beta. The plug-in maps a handful of stages from the main Capturing Reality software as Houdini nodes, so users don’t have to perform constant import and export functions between the two packages. Combined with the optimised tools in Houdini, this results in a significant production boost for game content developers.
In media productions, the use of photogrammetry is growing as software solutions become more affordable and professional technical equipment has become more accessible. Time is always a driving factor in media productions. Studios are turning to photogrammetry to create digital sets faster. This is an area that already offers a range of solutions for processing image series. Well-known examples include Agisoft’s Photoscan, 3D Zephyr, Recap and Capturing Reality. The latter solution enjoys a special status in the community, as its accuracy and, above all, processing speed are said to leave its competitors out in the symbolic rain. Reason enough to take a closer look at the symbiosis between the VFX giant and the photogrammetry giant.
Fast to the target
The number of nodes of the capturing reality plug-in is manageable and can be counted on one hand during the test period. The starting point is within an empty geometry node. Using the node called RC Register Images, users can import an image series into Houdini that is optimised for the photogrammetry workflow of Capturing Reality. Once the image series has been added, users can use the RC Align Images node to initiate the analysis of the image pairs and placement of the cameras in 3D space. As a result of the operation, the object in the image series is displayed as a point cloud with colour values. Even with an image series that was taken under strict conditions, it can happen that far more points are present during generation than is sensible and the scene resembles a fine spray mist. The area to be processed must be narrowed down. To do this, it is sufficient to delete the points that are not required and draw a bounding box around the required points. How the process takes place is up to the user and usually does not take long. There is no RC node for this, but it is not necessary as Houdini provides numerous ready-made tools for this.
To obtain a 3D object from the point cloud, another Capturing Reality Node called RC Create Model is used. Two inputs must be used for a correct display, ideally starting with the second input to prevent unnecessary computing operations that could lead to a crash if cancelled – provided Auto Update is set. The first input is the direct output of the RC Align Images node. All points resulting from the calculation of the image series are fed in here. The second input requires the bounding box information, which should display or mark out the selected points for reconstruction.
After a processing time, which can vary depending on the resolution and length of the image series, the 3D object is visible in the scene graph, but must still be correctly placed in the Origin by the user. The colouring of the object at this point appears plausible, but is based on the vertex colours, which were taken from the point cloud and interpolated. This is relatively easy to recognise by looking at the number of areas.
There are now two basic methods for proceeding. The first leads back to the RC Create Model Node. An RC Texture Model Node must be added to the node – the fifth RC Node in the bundle. There is a field in the settings that makes it possible to derive a lower-resolution model from the scan model with just a few settings. In addition to specifying an output path, the settings options for the function also allow the user to specify the resolution of the textures to be created based on a power of two or to select from the options. There is also a slider that asks the user to specify the percentage by which the algorithm should reduce the object.
Once the settings have been made, the object can be created at the touch of a button. As this is an automatic process, the topology of the grid may not correspond to the desired standard for some objects. It is therefore also a good idea to prepare the object in Houdini. SideFX offers special tools for game content developers.
The sample data sets from SideFX are relatively simple, so a reality capture test was carried out in Houdini using an image set from 3D-Scanstore. In addition to 3D models, image sets can now also be purchased for your own mesh generation: 3dscanstore.com
Fine tuning and function
When you get right down to it, users receive two nodes that can be used to create 3D objects from image series. As the old saying goes, the devil is in the detail and the settings may need to be adjusted for accuracy when processing the different image pairs. The accuracy of the reconstruction can be checked when using the node called RC Extract Cameras. If image series were created using a cage or a fixed camera rig, the position of the different cameras in the room can be displayed using RC Extract Cameras. Any deviations can thus be counteracted in a targeted manner.
Up to this point, we have talked about the workflow rather than the plug-in itself. Firstly, the plug-in must be downloaded and installed. SideFX has added a separate subpage on the official homepage with download links for Houdini version 16.5 and 17 as well as sample files. When the RC Align Images node is inserted and the display flag is set, the plugin asks for an active Capturing Reality licence. If no licence is available, the query window allows you to select a specific licence model. Regardless of which one is selected, a Capturing Reality account is always important, as Capturing Reality will ask for a licence the first time it is used. Users who do not yet have a licence are asked to select a licence model at this point.
Potential users must be aware that the Houdini plug-in is free of charge within the beta. However, a purchased capturing reality licence must be acquired via the user’s own account. The demo and Steam versions are not compatible. However, the costs for Capturing Reality are manageable and reasonable in terms of functionality and user-friendliness. In addition, the Capturing Reality community is active and is constantly growing. If a problem is identified in the community in order to find a solution, new users can look forward to help.
Costs: For individual users and indie studios, we recommend the promo programme for 99 euros for three months of use. Updates are included, a maximum of 2500 images per object can be imported and an internet connection is required to export the data. For a fair price, users in the entertainment industry get a photogrammetry turbo.
Links
Houdini Capturing Reality Plug-in, documentation and sample files
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