In augmented reality (AR) and mixed reality (MR), scaling refers to how virtual objects are sized and positioned in relation to the real-world environment. Proper scaling is essential for creating a believable and immersive experience where virtual objects appear to coexist naturally within the user’s physical space. When scaling is incorrect, virtual objects may appear either too large or too small compared to real-world elements, which can significantly detract from the experience.
What is Incorrect Scaling?
Incorrect scaling of virtual objects refers to the mismatch between the size of virtual content and its perceived size in the real world. This can occur for several reasons and can have a variety of negative impacts on the user experience.
For example, if a user places a virtual chair in an AR environment, but the chair is too large compared to the real-world furniture, it will appear out of place. Similarly, if the virtual object is too small, it may not be visible or may seem to disappear into the background.
Symptoms of Incorrect Scaling
- Virtual objects appear too large or too small relative to real-world objects.
- Disorienting interactions: Users may experience difficulty interacting with virtual objects if the scale doesn’t match their expectations.
- Lack of spatial coherence: Virtual content seems to be floating unnaturally or doesn’t align with the real-world environment.
- Poor occlusion behavior: Virtual objects may not interact with real-world surfaces in a realistic way.
- Inaccurate object placement: Objects may appear to be “misplaced” in the environment due to incorrect scaling.
Common Causes of Incorrect Scaling
1. Faulty Depth Sensing
AR/MR systems often rely on depth sensors (e.g., LiDAR or Time-of-Flight sensors) to measure the environment’s dimensions and place virtual objects in the correct spatial locations. If these sensors are not calibrated properly or provide inaccurate data, it can lead to errors in the size and positioning of virtual objects.
- Fix: Ensure accurate calibration of depth sensors and consider real-time sensor feedback to maintain correct scale.
2. Inaccurate World Coordinate Systems
Scaling issues can arise if the virtual object’s position is not accurately aligned with the world coordinate system. If the object’s scale is applied incorrectly within the AR/MR space, it may not align with the real-world objects it is intended to interact with.
- Fix: Improve the coordinate system alignment and world space transformations to ensure consistent scaling of virtual objects in relation to real-world surfaces.
3. User-Specific Calibration Issues
Some MR/AR headsets or applications require users to calibrate the system, which includes setting a scale reference (e.g., their height or arm length). If the user fails to calibrate correctly or the system is unable to detect user-specific measurements, it can lead to incorrect scaling.
- Fix: Guide users through proper calibration processes, including automatic calibration based on real-time body detection or adjustments via user input.
4. Lack of Accurate Environmental Scanning
If the system fails to scan the environment thoroughly, it may misinterpret the size or distance of objects, which results in improper scaling of virtual content.
- Fix: Encourage users to scan the environment thoroughly before placing virtual objects. Use algorithms that improve the system’s ability to detect real-world scale during environment scanning.
5. Incorrect Model Scaling
Sometimes, the virtual objects themselves may be designed with incorrect scaling in mind. This may be due to differences in how models are created, imported, or scaled within the application, which results in the object appearing out of proportion.
- Fix: Ensure that virtual objects are created and scaled according to real-world measurements during the model creation process. Use tools to adjust scale within the application based on user input or environmental feedback.
6. AR/MR Framework Limitations
Certain AR/MR frameworks or SDKs may have limitations when it comes to precise scaling, particularly in complex environments. These limitations could be due to inaccurate coordinate mapping, poor depth sensing, or insufficient data from the device’s sensors.
- Fix: Regularly update and patch AR/MR SDKs, or consider switching to more robust solutions that handle scaling issues more effectively.
Solutions & Best Practices for Correct Scaling
✅ 1. Use High-Precision Depth Sensors
Incorporate LiDAR, ToF, or structured light sensors to improve the system’s understanding of depth and physical dimensions, ensuring virtual objects are scaled appropriately to real-world sizes.
✅ 2. Accurate Calibration and Measurement Tools
Provide users with accurate calibration tools that help them set the scale based on their environment and physical dimensions. This could include automatic calibration based on the user’s height, device position, or real-world reference objects.
✅ 3. Use Real-Time Scale Adjustment
Implement real-time scale adjustment algorithms that allow the AR/MR system to continuously adjust the virtual object’s size based on dynamic environmental changes or depth sensor feedback.
✅ 4. Environment Scanning and Mapping
Encourage users to perform a thorough environment scan to allow the system to better understand the physical space. This scanning process helps ensure the environment is accurately mapped, allowing for more reliable object scaling.
✅ 5. Optimizing AR/MR Frameworks
Ensure that the AR or MR framework being used has robust scaling algorithms that adapt to varying environments. Use SDKs that handle scale adjustments dynamically based on real-time data.
✅ 6. Precise Model Creation and Importing
When designing virtual objects, make sure they are created with accurate real-world dimensions. When importing models, ensure they are properly scaled and tested for size consistency within the AR/MR application.
Example Use Case: AR Furniture Placement
A user is trying to place a virtual piece of furniture in their living room using an AR app. The virtual furniture, however, appears either too small or too large relative to the physical room and surrounding furniture.
Fix:
- Depth sensing and LiDAR are used to accurately measure the room’s dimensions.
- The user is prompted to perform environment scanning to capture the room layout.
- The app uses real-time scale adjustment to ensure the virtual furniture appears proportional to the room’s size.
Tools and Platforms for Correct Scaling
| Platform | Feature or Tool |
|---|---|
| ARKit (iOS) | Accurate world coordinate system mapping, depth sensing |
| ARCore (Android) | Environmental understanding, scaling adjustments |
| Vuforia | Image recognition, object scaling handling |
| Unity XR SDK | Real-world scaling tools, model adjustment APIs |
| HoloLens SDK | Depth sensing, coordinate alignment |
Summary Table
| Issue | Cause | Fix |
|---|---|---|
| Virtual objects too large or small | Faulty depth sensing, model scaling | Use high-precision sensors, real-time scale adjustment |
| Poor real-world alignment | Inaccurate world coordinate system | Improve coordinate alignment, world space transformations |
| Inconsistent user calibration | Incorrect user-specific data | Guide users through proper calibration, use automatic calibration |
| Virtual object misplacement | Inaccurate environmental scanning | Encourage thorough environment scanning |
| Model size inconsistencies | Incorrect model scaling | Ensure real-world dimensions during model creation, adjust scale within app |
Future Trends
- AI-powered scale adjustments that automatically detect and correct scaling issues in real-time.
- Advanced environmental understanding through cloud-based tools that enable seamless scale calibration across different devices and environments.
- Improved user-centric calibration where the device learns and adapts to the user’s measurements and the surrounding environment automatically.