I weigh the rock in my hand, then toss it back to the ground. I run my hand across some tall grass, feeling the stems ripple, flatten and spring back. Then I reach out and take hold of a cloud and pull it toward me.

None of these objects exist. The rock, grass and cloud are all figments of virtual reality -- yet they feel completely real against the skin of my hand.

I'm trying the first public demo of a tactile glove from VR startup HaptX at the Sundance Film Festival in snowy Park City, Utah. The HaptX glove is designed to conquer one of virtual reality's most annoying limitations: You can see and hear the virtual world in your headset but, as MC Hammer might say, you can't touch this.

Currently available VR technology lets you interact with the virtual universe by waving hand controllers around, but these only solve half the problem. When you see what appears to be a solid object in VR, you merely have to wave your hand in that direction to feel there's nothing there. This lack of physical interaction breaks the illusion of reality, or "presence," that VR relies on.

HaptX

Several other VR experiences displayed at Sundance's annual dedicated VR event, including a psychedelic space adventure produced by filmmaker Darren Aronofksy and another by VR luminary Chris Milk, get around that by limiting your interaction to conjuring nebulous trails of light. HaptX goes one better.

I begin by sliding on the snug black glove made of a fabric with plastic thimbles clipped over each fingertip and flat plastic cables snaking over the back of my hand. A thick umbilical cable attaches the glove to a VR rig.

I don the VR headset -- in this case an HTC Vive -- which shows me a colorful virtual farmyard laid out in front of my eyes. I reach out to touch the red-painted wooden barn. It feels solid. I move my hand to where I can see animated gray rocks, and feel resistance. I close my fingers around where I can see a virtual rock, and it genuinely feels like I'm holding something in my hand. I touch rippling grass and spin the sails of a wooden windmill. All of them feel like I'm actually holding or brushing them with my hand.

The glove works by inflating and deflating more than 100 tiny blisters of air across the surface of your hand. HaptX calls them "tactors" -- a combination of tactile and actuator. The more of these little inflatable air pockets on the surface of the glove, the finer the feeling. For example, the demo allowed a virtual spider to walk across my hand, and its footsteps were as light and tickly as you'd expect. I also felt confetti and rain lightly sprinkle into my palm.

The air pockets give the illusion of shape and movement. But what really sells the illusion of solidity is the way the glove resists when you try to push against something. An exoskeleton on the outside gently pulls back on your fingers as you try to close them, stopping your hand from simply closing around thin air. This creates the feeling that there's something beneath your fingertips. Combine that with the evidence that I was looking at a three-dimensional object or a flat surface, I totally bought the illusion.

The only thing missing is the texture of the objects I'm touching. The feeling of rough or smooth texture is the vibration you feel when you run your fingers over something, and haptic vibration to simulate texture is something tech companies have been playing with for a while. HaptX hints that it has its own ideas about that avenue, but it isn't talking about it yet.

Training day

HaptX, founded in 2012, is one of a number of companies tackling touch and interaction with VR. Other similar VR wearables include the Sense Glove, on sale this year, and the Cerevo Taclim VR shoes.

So far, VR is widely recognized as a gaming thing, with PlayStation VR and other headsets marketed as gaming peripherals. But while gaming and related uses like theme park or movie theater VR installations could be in their future, the folks at HaptX are starting out by sharing a prototype with engineers and developers interested in VR training and simulation.

VR has real potential for training people who require muscle-memory-based skills in environments that are expensive or dangerous to simulate. That could include surgeons or military personnel for whom learning on the job might be risky to life and limb. It could include industrial workers who work in potentially dangerous environments, like oil rig roughnecks or deep sea divers. The advantage of VR in training is that it can be programmed -- so pilots can learn different planes on the same system, for example, instead of requiring multiple expensive physical simulators -- while still building the muscle memory required when holding actual scalpels, rifles or joysticks.

In the future, the system could be integrated into telerobotics, allowing operatives of drones or robots to "feel" what a machine is touching miles away. A full-body version is also potentially possible: The glove's air-pocketed fabric is light enough to make a suit giving the illusion of touch all over you, although the exoskeleton element would be heavier and more complicated.

At Sundance, HaptX also showed a demo that allowed you to feel temperature in virtual reality. It's less advanced than the glove, requiring you to put your hand in a fixed machine rather than having the freedom to move your arms around. But it's still pretty clever, running hot and cold water through fine pipes in the palm reader with enough precision to simulate different temperatures on different parts of your hand. The demo featured a dragon breathing blasts of fire and ice, and it was precise enough to convey the feeling of heat or cold sweeping across the surface of my hand from one side to the other.

There are many forms of virtual reality storytelling, from filmlike stories in which you're just an observer to fantastic games in which you direct the play. Not all of them need the element of touch. But HaptX goes further than most to make the virtual a reality.

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