Virtual reality has yet to become a mainstream hit, but many companies, investors, and developers still have high hopes.

The potential for VR to become a huge hit, VR mergers and acquisition is too big for these boosters to pass up. Augmented reality and VR mergers and acquisition advisory firm Digi-Capital predicts that VR will become a $25 billion market by 2021.

For instance, despite recent setbacks for the Oculus Rift Headset that include smaller-than-expected sales and management issues , Facebook CEO Mark Zuckerberg is still pledging to spend billions of dollars on VR.

It's been a rough stretch for virtual reality over the past year, but there are some developments that show there are still signs of life, according to a survey of 600 VR developers released Thursday by the Virtual Reality Developers Conference.

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But challenges still persist like dealing with headsets that cause people to feel sick that the industry must overcome before the tech becomes a massive success. Heres a roundup of the survey's most interesting findings:

According to the survey, developers cite the uncomfortable feeling of motion sickness as a prominent issue thats impacting consumer adoption. People can often feel sick when wearing a VR headset because what they see in the virtual world doesnt sync up to their physical movements, in addition to problems with latency and frame-rate issues. The resulting incongruity can produce feelings similar to sea-sickness.

One coder that was surveyed said that nobody has developed a one-size-fits-all technique to alleviate motion sickness that VR app makers can use. As another developer bluntly put it, A lot of those [VR] experiences make people sick.

Video games still dominate when it comes to virtual reality, with 78% of survey respondents saying that they're dedicating time to developing games and related VR entertainment apps. The rest of the respondents said they're building VR business apps used for corporate training, marketing content like vacation apps, and industrial design.

Some developers said that the current focus on VR video games is misplaced, because businesses appear more interested in using the tech than mainstream consumers. One developer said that the overwhelming concentration on games and entertainment, gives the impression of [VR] being a toy instead of the world-changing technology that it really is.

Developers appear to be more optimistic about the future of augmented reality, in which digital imagery is overlaid onto the physical world, than virtual reality. The survey said that 77% of respondents believe AR apps will be more popular than VR apps in the long-term.

One developer said ARs advantage over VR is that it does not pose such a high risk of vertigo, motion sickness, or the other potential side effects of VR since people arent totally immersed in virtual world.

Our entire society would have to change to incorporate VR in daily life beyond situationally-specific contexts, said another respondent. "But augmented reality means that you can incorporate it virtually anywhere."

Several big tech companies like Apple ( aapl ) , Google ( goog ) , and Facebook ( fb ) have all debuted AR coding tools this year as a way to spur more developers to build compelling AR apps.

Among some of the survey respondents favorite VR and AR apps released this year include a version of Google Earth for virtual reality headsets that lets fly past awe-inspiring sights, including Yosemite National Park and Italys Florence cathedral.

A VR version of Google Street view also seemed to be a favorite, with one developer saying, Put someone in [VR] Street View of their childhood home and just let them walk around and talk.

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Several coders also mentioned last summers blockbuster game Pokmon Go as important in getting mainstream consumers interested in AR and VR technologies. It really made it easy for people to understand AR, said one developer.

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Virtual Reality Needs to Fix Stomach-Churning Experiences - Fortune