How To Use The Camera On The Vive
Vive Pro AR (SRWorks) vs. ZED Mini
Since HTC's Vive Pro launched with two front-facing cameras, many developers have asked united states of america how using those cameras for pass-through augmented reality would compare to using our own ZED Mini. At present that HTC released their SRWorks AR SDK, we tested Vive Pro AR and ZED Mini AR side-by-side.
Summary
As you can meet, the Vive Pro's advantages as an AR headset primarily come from its forcefulness as a VR headset: it'south comfortable and integrated, and it'due south great if yous as well do VR development. The ZED Mini excels on nearly all AR-specific qualities. The i exception is vertical field of view, which we'll examine later.
General
Form Gene
The Vive Pro'due south class gene is peradventure its biggest advantage. It does not require a separate attachment or USB cablevision. At that place is no mounting process, and the headset is more comfy than either headset that the ZED Mini supports.
Minimum Requirements
You need a minimum of a GTX 1060 to utilise the ZED Mini, but only a GTX 970 for Vive Pro AR. This is because, with higher resolution and more than features, the ZED Mini is simply doing more at in one case. As we built the ZED SDK effectually NVIDIA CUDA, you lot can but use ZED Mini with NVIDIA GPUs. SRWorks is also restricted to NVIDIA GPUs and likely for the aforementioned reasons.
Cost
Ignoring VR purposes, the ZED Mini is technically more than cost-effective. If you own no previous VR hardware, and so the price of the required starter kit ($1,099) exceeds the combination of the ZED Mini with either compatible headset. You lot tin can buy the Vive Pro as a standalone headset for $799 if y'all already ain the base stations and controllers by ownership a Vive, but in that case, you lot only need to spend $449 to add together AR to your existing headset.
Prototype Quality 
Resolution
The ZED Mini's prototype is substantially sharper, given its 720p resolution over the Vive Pro's 480p. Like watching a low-res YouTube video on big screen, this affects the enjoyment of every moment in the headset.
The ZED Mini also renders real and virtual objects at the same resolution, whereas Vive Pro AR renders virtual objects at the full Vive Pro resolution of 2880×1600. This makes them look distinctly different from the 480p globe they are supposed to be a part of.
Vive Pro AR capture from desktop mirror
ZED Mini capture from desktop mirror (cropped for comparison)
Field of View
With the Vive Pro cameras' 96° and the ZED Mini's 90° horizontal field of view, both effectively fill the headset from left to correct. For vertical field of view, the Vive Pro's AR's is significantly higher, at 80° vs. sixty°. As a outcome, you lot can see blackness borders at the top and bottoms of the ZED Mini image when viewed from the headset, but not in Vive Pro AR.
This is a merchandise-off we deliberately fabricated at Stereolabs. We could have selected lenses with a wider field of view for the ZED Mini. Notwithstanding, this would have lowered the effective resolutionin the way your eye perceives information technology. The middle 60° of our eyesight – chosen Primal Vision – is where we have the nearly fretfulness and see the majority of the data that gets sent to our brains. As such, we establish it is worth chopping off part of the prototype exterior that range if it makes the image look ameliorate within it. Even so, that advantage is lost when the user looks at the edges of the screen, when the epitome borders enter Primal Vision.
Performance
Frame Rate
The frame charge per unit of each is tied more than to USB bandwidth than computing ability; stereo cameras have to send twice the information of a standard camera with the same resolution, so there are limitations on how fast these images can be sent through USB iii.0.
When set up to 480p, the limit is 90FPS for both cameras. The ZED Mini gets 60FPS at its default setting of 720p, however nosotros've found this to exist the most comfy remainder of resolution/frame rate.
Latency
The latency of Vive Pro AR is three.3x that of the ZED Mini, at 200ms and 60ms, respectively. The impact of latency varies with the feel. With slower, simpler apps, it may be bearable. With more than fast-paced apps, or any that require physical motion, 200ms will be impairing and may crusade motion sickness.
Below we've captured both the virtual and real versions of the Vive controller in a scene, where the virtual version's position is unaffected by the photographic camera's latency:
Vive Pro AR:
ZED Mini:
Synchronized capture of Vive Pro AR (left) and ZED Mini (correct). Audio levels from the HMD mics are visible to show synchronization.
Depth Sensing
To understand the 3D earth, both headsets calculate depth to every pixel in view. This is necessary for whatever case where a virtual object must act on a existent object in 3D space. Both sensors calculate depth the way the human being eye does, using stereo triangulation from ii different views of the earth.
Depth estimation in Vive Pro is done in software, but like the ZED Mini. HTC seems to use open-source stereo depth estimation techniques, which is very noisy indoors with sparse measurements. The ZED Mini uses in-house stereo depth sensing engineering which has been developed over the years at Stereolabs. Encounter the video below for comparison.
Depth maps from Vive Pro AR (summit) and ZED Mini (bottom)
Depth accurateness, range and abyss are very different betwixt the two. College accuracy means objects will behave every bit expected; virtual shadows cast on the existent world will appear at the right angle, virtual assurance will bounce correctly on your floor, etc. With less accuracy, lighting effects tin appear noisy, and a virtual object might wing through a existent i when information technology should collide with information technology. Beyond the maximum range of a depth sensor, no spatially enlightened interactions can occur. Finally, without a complete depth, AR occlusions cannot happen in dynamic environments.
Features 
Platforms
Developers can build applications for either Vive Pro AR or ZED Mini, straight with their SDK or through Unity or Unreal plugins. The ZED Mini's SDK is more than expansive, however it was designed for full general purpose use, and then developing pass-through AR without the plugins will probable accept more implementation than with the Vive Pro SDK.
The ZED Unity plugin currently has more features to simplify development. As these are public, high-level features, advanced developers could implement any such features present in one plugin but not the other.
Spatial Mapping
Both are capable of spatial mapping for proper physics and other applications just the ZED Mini can scan faster and at a longer range.
Vive Pro AR Spatial Mapping
ZED Mini Spatial Mapping
SRWorks requires pre-scanning an environment for a number of features whereas the ZED Mini doesn't require pre-scanning for most of the features. See below.
Visual Furnishings Both ZED Mini and Vive Pro AR back up depth occlusion – having real objects hibernate virtual objects backside them – and casting virtual shadows on real objects. Notation that just the ZED Mini delivers both these features without any pre-scanning unlike the Vive Pro AR.
Vive Pro AR occlusion
Vive Pro AR shadows
ZED Mini does not require pre-scanning for either feature, instead deriving the proper effects from its live depth map in real fourth dimension. Besides convenience, this too allows occlusions and shadows to work with moving real objects.
ZED Mini occlusion and shadows
The ZED Mini tin use realistic virtual lighting to objects in existent-time. SRWorks does non support this characteristic at the moment.
ZED Mini virtual low-cal projection in the existent globe
Physics
Equally both have admission to a depth map, both can utilise a Z-test to observe if a moving object has hit the real world or not. This technique doesn't provide enough data for proper physics simulation merely is useful for things similar projectiles.
As of version 2.4, the ZED Mini supports real-time plane detection, allowing you lot to plow flat surfaces into virtual meshes near-instantaneously, consummate with a collider. This lets y'all accurately bounce or place objects off of existent flat surfaces without the pre-scanning. SRWorks just includes airplane detection internally to assist with pre-scanning.
ZED Mini aeroplane detection
Tracking
The ZED Mini can piggyback onto the headset's tracking or use its own. However, as the Vive Lighthouse tracking system is the nigh authentic available, information technology will near always be the best choice if already constrained to a tracked environment (which is most situations).
If using the Oculus Rift, the ZED Mini's tracking tin can allow users to apply the headset without base stations, technically assuasive for world-scale AR.
Determination
Creating AR for a headset is hard. It ways solving countless issues from capture to rendering to display, where each solution has to be implemented perfectly to make the experience conceivable–and endurable. Things like calibration, depth calculation, optimization, latency mitigation and the many nuances of how the eye expects the globe to look. Each takes time and experience to solve.
AR is not the primary part of the Vive Pro, and SRWorks simply needs more time. The claiming is software, non hardware. Stereo vision is an unforgiving scientific discipline that takes years to get correct. But with companies like HTC walking downwardly that path, it validates a bright hereafter for stereovision and laissez passer-through augmented reality. For now, if you lot're looking for a comfortable, interactive and realistic AR experience, effort ZED Mini with your Rift or Vive.
Source: https://www.stereolabs.com/blog/vive-pro-ar-zed-mini/
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