Model Targets Supported Objects & CAD Model Best Practices

Supported Object Types

The Vuforia Model Targets Feature provides robust recognition and tracking for supported objects and use cases.

The types of supported objects range from toys to full-sized vehicles, to cultural landmarks and to medical, manufacturing and industrial equipment.

To get the best tracking experience, we highlight the best practices and properties of physical objects that are supported by Vuforia's Model Target technology. Good and bad examples are shown to demonstrate the specific quality differences. These images are exemplary and only act as an indication. You may verify if your specific use-case comply with these recommendations

Due to limitations of the technology, using Model Targets for articulated objects and mostly transparent objects is currently not supported.

Moving objects

Model Target tracking works best if the object is static and does not move after having been detected. Then the user can move around the object without losing tracking of the object. If your target is moving, make sure to use the Default Tracking Optimization setting

Sufficient Geometric Detail - Complex Enough Model

Geometric complexity is key to distinguish an object from other shapes in the environment. Simple shapes such as cubes, spheres, or very elongated simple shapes may be easily confused with other objects in the user’s setting.

Therefore, base your experience on products or objects that have enough sharp edges, dents, bulges, etc.

It is recommended to avoid symmetric objects as the Vuforia Engine tracking technology won’t be able to tell its sides apart. Additionally, repeated parts and patterns, such as identical extrusions on a surface, can further cause confusion for detection and tracking.

 

Non-flexible and Rigid

While the Model Target tracker can tolerate some deviation between physical and digital model, expect that objects that articulate and/or flex may fail to be detected or tracked effectively.
As a best practice, remove parts from the CAD model that are not always present on the physical object (e.g. one variant of a product has some small attachment that is not present in another) or parts that are known to move.
This however only works if most of the object is rigid. Objects that mostly consist of articulated or flexible parts are not supported.

 

Matching CAD-model

Physical objects should have the exact same shape and size as their CAD model used for target generation. It is important to have a strong overlap for the robustness of the experience.
While wrongly scaled objects might be detected, tracking performance will be sub-par if metric scales don't correspond between the physical and the digital object.
Because of that, make sure that your model target is set to the correct size of the physical object in meters as accurately as possible.

For practical reasons - since sometimes CAD models simply don't represent the physical objects on a 1:1 - the tracking technology can tolerate up to 10% of deviation between the real object and Model Target as a compromise. See Best Practices for Scaling Model Targets for more information.

 

Colored or Patterned Surface 

Objects with colored or patterned surfaces typically work better. Objects in a single uniform color are difficult to robustly track, though they can be reliably detected. Some variation in surface appearance is required to distinguish the object from the background and other objects. For this reason, a pure white object on a pure white background or pure black objects on very dark backgrounds may not work well.
Similarly, objects that are mainly black, transparent, or highly reflective may also affect detection and tracking since they do not provide sufficient surface details.
Sometimes 3D printed objects made from a single-color material are also difficult to track.

NOTE: The color of the physical model does not necessarily have to exactly follow the color in the CAD model used for target generation. For example, Model Target databases may be used to detect and track color variations of the same product.

Texturing

It can be helpful to include textures for your model if these provide visual fidelity and resembles the appearance of the physical object. The textures can be surface patterns, labels, prints, or flat elements - such as gauge-backplates. Also, photorealistic textures from 3D scans can improve Model Target tracking performance and recognition accuracy on Advanced Model targets. The MTG will provide a warning if it detects missing textures on a model that consists  of a single mesh.

Textures and accurate color details help Vuforia Engine extracting the necessary information from the geometry and improves detection and tracking; though, the final detection and tracking performance depend on many run-time factors such as lighting intensity and color. if your model contains realistic texture and colors, select the Realistic Appearance in the Coloring tab in the MTG.

3D scans with textures

To get the best out of textures and colors for 3D scanned models, avoid scans with hard shadows that are not seen on the physical object during tracking. Scan objects in a well and evenly lit environment without direct sunlight or strongly colored light sources.

See the Guide to Create Model Targets from 3D Scans and Images for more information.

Use Non-Realistic in the cases where the textures or color of your model do not match the real object; e.g., when the model parts areartificially colored in the CAD software or using the Automatic Coloring of Model Targets in the MTG, or if there are differently textured variants of the object (e.g. a toy that comes with different painting, but have the same shape for each variant).

Supported texture formats

The currently supported texture formats are JPG, PNG, and PGM in either 32-bit, 24-bit, and 8-bit. Have this in mind when importing models to the MTG, as using other file formats for your CAD-model texture may result in import errors.

 

CAD Model Best Practices

As a general rule, the CAD model used as input for the Model Target Generator should

  • have a maximum of 400,000 polygons or triangles: and
  • contain a maximum of 20 parts: and 
  • contain a maximum of 5 textures: and
  • use a right-hand coordinate system.

These recommendations have been compiled based on common problems encountered with CAD models. Note that due to the large variety of CAD software available, with numerous possible generation pipelines, it's difficult to provide solutions that work in all cases.

In cases where the imported CAD model is complex and exceed the above specifications, the MTG has an option to simplify the model through the Complexity tab. See How to Create Model Targets - simplification for more information.

The following advice is by necessity somewhat generic, and specific models may have still particular issues. Feel free to get in touch via the forums if the Model Target Generator isn't working properly for your particular model.

Large Holes

Models sometimes tend to have cracks in their polygonal representation. This typically results from wrong tessellation, simplification, or combination mismatches. Try to avoid these as such holes create unnecessary, false details on the object that create computational overhead and potentially lead to false detections.

Tip: Modern CAD software packages can verify the models for holes and cracks prior to 3D printing, such a tool can be helpful to verify your model before working with Vuforia.

 

Missing Parts

During the conversion pipeline, some parts of a model might be corrupted, have wrong (transparent) material properties, or simply be missing in an assembly filter. Visually compare the loaded CAD model in the Model Target Generator to contain all your desired parts, visually matching with the physical object to be augmented.

NOTE: As explained above, in case parts are known to be non-rigid (moving) it is recommended to remove them from the model.

 

Incorrect Normals

Normals facing the wrong direction - away from the physical surface normal - might cause mesh elements not to render leading to various side-effects. Additional edges, visible inside objects of a complex model, screen-door effects on surfaces, etc. can create a wrong visual representation of the CAD model and result in low detection and tracking performance. Incorrect normals can also yield apparently missing parts, see above section. Visually verify the integrity of normal distribution, some packages provide tools to conform normals.