One of the scenarios that could happen inside the airplane is the cabin filling with smoke due to inside or outside fire. This changes how the stewards should operate the door and work with the passengers. Not to mention this adds a lot of stress to the situation as a whole which could impact on how the steward handles and reacts. For these reasons we decided that a "smoke situation" would be one of the first scenarios to work out.
Making particles in Unity is fairly easy. Making performance efficient particles that look good is a lot more difficult. Especially when creating for VR applications where the rendering path is different. This all depends on what shader material is assigned to the particles texture. To test the different results on looks and performance I created four different particle systems to compare. Alpha Blend: After rendering the screen the alpha value of the texels are calculated to see what color is behind the texture. The two values are blended together to give the illusion there is transparency. Altough giving good looking results, Alpha Blending is relatively heavy on the performance. Vertex Lit: This shader only calculates light over the vertices of the mesh or texture. Therefor pixel-based rendering is not happening. As a result the center of your image will appear a lot darker than the corners, dependent on the size of the image and the distance to the light source. On that note, the vertex lit shader is incredibly low cost and produces decent results. As an added plus it changes color dependant on the direction of source lights. However, when in complete shadow it appears as complete black. Unlit Transparent: This is a combination of the latter two where transparency is calculated over the texels with lower alpha values. Lighting however is not calculated and the resulting product is a smoke plume that looks like the provided texture. This means that no mather the direction of the light source. The smoke will always appear the same as if it's receiving an equal amount of light from all corners. Standard Specular: A shader that is generally used for Physically Based Rendering and metallic surfaces due to the way it handles lighting calculations and applying gloss. With the cutout setting it takes away a percentage of the transparent edges of the smoke texture giving more rigid outlines. Though efficient and having a nice cartoon look it doesn't convey a proper smoke feel. The reasoning behind trying this was that it reduces the drawcalls to calculate the transparent layers which became an issue when placed inside the smoke cabin. However the thick layer of smoke completely hid everything in sight the moment the smoke came in. Given the fact that we're currently pushing the concept of making the simulation look real we chose to make use of the alpha blend shader for the smoke. The impact in the airplane scene is pretty high but a lot of overhead comes from rendering the plane itself because most of the meshes aren't properly grouped and optimized. Redoing most of the models is on the to-do list. After that, depending on the resulting runtime performance, we can change the smoke shader. One of the goals for the project was to implement a form of mixed reality. Mixed reality is the idea of combining the real world with the virtual world. Walking around in VR space where the walls are in the same location as the real world is a form of mixed reality. In our case we wanted to translate the airplane door to the virtual space so that the trainees would actually have to hold on to a door handle. Enforcing the idea of opening the door and developing muscle memory, hence it is a training simulation. Research started with figuring out how the HTC Vive controller work and how they are tracked within Unity projects with the use of the VRTK toolkit. The Vive website has an extensive article of the inner workings of the controllers (link) outlining the guidelines for developers. The SteamVR plugin handles all of the tracking and correctly showing the controllers in Unity. Therefor to get the position and orientation of the controllers is as easy as retrieving the transform component from the controller objects. No extra work. I explored a few options on how to track other objects in virtual space. This could be done with the Vive controllers itself or third-party tracking sensors. However the latter would require different products and another toolkit next to the already in-use SteamVR and VRTK toolkits which is an unnecessary overhead. With the available resources I went with the first approach of using the Vive controllers. The Vive had two options when it comes to tracking. The Vive controller and the Vive trackers (as pictured above). The Vive controllers are mainly used for interaction from the player in the virtual space. However the trackers have the benefit that they can be mounted on any object making that object trackable in VR. At this point in time the trackers are sadly not available to consumers yet. So we had to make do with two Vive controllers. One for the player and one to track an object. To create the illusion that an object in reality is also in VR the position, shape and scaling all have to be the same for it to feel real. For the example I used a bottle of terpentine that had a fairly generic shape and recreated that object in VR trying to get the same dimensions. One problem arrose: the player needs their hands free to pick up the bottle and the only free hand is the one not being tracked. With the headset on the player would not know where his or her hand is. So a new question took priority: how can we track the show the player's hands position in VR while keeping the hands free? During research into the Manus VR gloves a picture of an early development build of the gloves came up where Vive controllers were attached to the users forearms. This gave us a direction to experiment with. Over the weekend I created a simple controller mount with scraps of foam and velcro and developed a scene in Unity that has a table, with the same dimensions as the table in the VR room, and a bottle, to which the other controller is mounted. Now the position of the users hand is approximately being tracked and has the hands free. And the object is being tracked. That is all there is to it given that the tracking of the controllers happens already, the positions of objects is by itself already in the same position as in reality. The picture above is the resulting product. The user no long has the ability to use any of the buttons on the controller but has full control of their hands. Given that the human brain is excellent in replacing your arms with some other appendage, simply having a sphere in the headset as your arm is enough.
I asked a couple of students to try out the project with the bottle and all of them mentioned that it works better than anticipated. Even though the users don't see a proper hand in VR, the fact that they can see their hand is close to the bottle they instinctively open their hand to grab it. It felt natural. With this conclusion I started researching interaction with more complex objects for mixed reality purposes. In case of the KLM project: a door handle.
Having arrived with the whole team we sat around the table with one of the co-founders and briefly discussed the project we're developing and the benefits of using the Manur VR gloves. After a tour around the office we got a hands-on with the gloves themselves. The development team has created a small room with some objects the user can toy around with. Some balls and cube to pick up and throw around, a pole, a sort of DJ table with records that can be span and a few buttons.
During one of the Virtual Technology classes the teacher mentioned that the human brain is great at substituting limbs that aren't yours and/or connected. Seeing your hands and fingers in VR move the way you move them in reality with the Manus Gloves is a great example of this feat. The moment I put on the Vive headset it felt natural. Instinctively you close your fingers to pick up objects and the same goes for in VR. When pressing buttons, we generally do so with our index fingers and once again, same works in VR. The gloves work as intuitive as we had researched beforehand and interaction with the world comes natural without having to explain the user any controls or mechanical rules. While the other team members got their chance to try out the gloves I had the chance to talk with one of the developers. The Manus VR team works with Unity3D aswell and provide an extensive library that comes with the gloves.
Knowing this and having experienced the gloves ourselves we we're convinced that adding Manus VR to the project is a worthwhile investment. Both for KLM as for us. The KLM and it's employees have a much more accessible simulation experience with a drop-in drop-out principle where controls don't have to be explained. And for us to work and learn with a new technology and thereby also discovering and research new topics made possibly by using the gloves. In the field, will the gloves really give that extra immersion? Will it still feel right without actually having the physical objects present? Audio is always an important part of a game, even more so in training simulations. Generally audio is done binaural, panning between the left and right ears to give a sense of hearing the direction of which the sound is emmitting. The last Virtual Technology class' subject was about spatial audio in Virtual Reality. With Virtual Reality it becomes that much more important to have a proper audio system to immerse the user into the world. There is a lot to learn when looking at how sounds and the human ears work in real life. One of the biggest aspects is how sounds are perceived differently depending on the direction it comes from. So called HRTFs (Head-Related Transfer Functions) are a sort of filter that changes the way the sound is perceived (YouTube video showcasing the difference between audio with and without HRTF in Counterstrike: Global Offensive can be found here). Another thing to take into account is how sound travels through space. Air itself already has effect on soundwaves, but so does every other material. Concrete absorbs and transfers sound differently that a piece of cloth does. There's even a difference in concrete that's connected to the world or disconnected. The students were tasked with finding a way to replicate some of these features in Unity and see how Unity handles audio. From itself Unity has a rather lacking audio feature. There's an option to enable 3D sound which opens up the option to use spatial audio, panning, rolloff, doppler effect and some other settings. Above all of this, hidden in the project settings, the audio source can be set to make use of HRTF filters, provided by Microsoft. Unity audio is relatively wholesome for simple average projects but lacks in features like reverbing sound from surfaces and materials. For our project we wanted to delve deeper into audio and Virtual Reality.
To demonstrate the differences and pros and cons between Steam Audio and Unity audio I created a scene with a concrete room and a few walls. Within this room there are two spheres that can be turned on and off. One uses Steam Audio and the other uses Unity audio. The spheres circle around the player, passing behind the concrete walls in its path. In case of the Unity audio sphere no difference can be heard when the sphere dissapears behind the concrete walls in the middle. The only noticible feature is the HRTF filters and the direction the audio comes from. The Steam Audio sphere on the other hand loses a lot of it's volume and higher pitches once it travels behind the walls. Sound becomes more clear once the sphere reaches the corners of the walls before being visible again. During the next Virtual Technology I let the teacher and some other students try the application and listen to the differences. With both spheres everybody was able to tell where the audio was coming from. Wether it was above or below them. The added value of Steam Audio however is the fact that the perceived sound changes based on the position of the source and the objects between the source and the player. Steam Audio offers more features like placing sound probes in the rooms where sound can in fact travel to better replicate the HRTF filters. For the KLM training simulation we decided to continue using Steam Audio. An airplane muffles sound in an interesting manner due to use of materials and shapes and Steam Audio has the power to simulate these filters.
For the class Virtual Technology I was tasked to do research into a subject of choice, related to virtual or augmented reality. During that time the team has been discussing the idea of having gesture recognition in the training simulation as a means of communicating with other characters. Gestures and poses to block passengers from passing, beckoning passengers to move over here or sending them somewhere else. We have discussed this concept with the KLM aswell and they mentioned that it would not have any priority to the training but could be an extra functionality towards pushing the realism of the training. Gesture recognition in virtual reality is relatively new and not a lot of information is available as of yet. A few games have implemented a basic version of gesture recognition where the players can wave at a character and the character will wave back. Another example, Left-Hand Path, takes it a step further and implemented different motions to cast different spells. This would require a form of recognizing the different motions of the controllers and compare them to a library of pre-set motions. After having done some research into available tools and examples (the full research can be found at the bottom of this entry in pdf-format) I called upon the VR Technology teacher, Juriaan, to discuss gesture recognition. Juriaan mentioned that there is a distinct difference between gestures and poses. A pose defines a stationary, single frame, stature. Like crossing arms in front of you. A gesture is a series of poses over time. A motion like beckoning. Looking for a gesture would require having knowledge of the position and orientation of the controllers and having to compare these to pre-set values of a gesture. A problem with this is the decrepancy in margins of the motions. Someone could make a beckoning motion while having the controller pointed downards while it is meant to trigger an event when it is pointing forwards. It's a difficult task to make a clear difference between when something is a gesture or an accident. For the time being I have set this aside as more pressing mathers are at hand. However, we still keep the idea in tha back of our heads should the project be at a state it is finished and we have spare time to explore gesture recognition more. Gesture Recognition in Virtual Reality
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