I'm developing a game, as a tutorial, learning experience
Specs summary:
imagine something like icehockey, but with static obstacles on the field ( thumbtacks ).
turn based, each players shoots by dragging ball and applying linear impulse on opposite direction
all of this is MULTI-PLAYER
Basically, after you shoot, you tell the other player's app that it must apply "this" force to the ball. Considering it's the same engine, I imagined I would get the same result on both devices, therefore the only communication will envolve sending the force params when the time is right. This is correct AS LONG AS THEY HAVE THE SAME RESOLUTION. If I shoot a straight line, no obstacles, then everything seems fine ( I can't really see if there's a very small offset ), but with obstacles, collision etc. the motion is not the same ( not the same trajectory ) on different resolutions ( devices )
I need to know if there is some way I can make this work the same on all devices. I need to find a way so I can replicate in minute detail a movement ( complex, not straight line ) on different screen/resolution.
Some technical details:
I'm using the letterbox scale
1200w 800h resolution ( don't really know why I chose this :) ... it seems really dumb now ... but you get the picture, I'm using basically a resolution bigger than most of the devices I test on )
physics.setScale( 100 ) = this seemed important on some point.
PS: This is meant to be a tutorial; I'm aware that I can send the trajectory lines then compose the movement OR find another way to replicate the motion, but I need to understand EXACTLY this issue, since I'll have to confront it in future games.
I'm not sure if it works but you can try this:
( forceVariable / 1200 ) * display.contentWidth
( Assuming, your width is still 1200 px
It worked with images for me
Related
For some time now, I've been thinking about how games calculate physics. Take as an example the game TrackMania. There are special routes where you only have to accelerate from the beginning to get to the finish. As an example, I take the following YouTube video (https://www.youtube.com/watch?v=uK7Y7zyP_SY). Unfortunately, I'm not a specialist in game development, but I know roughly how an engine works.
Most engines use a game loop, which means they use the delta value between the last call and the current call. This delta value is used to move objects, detect collisions and so on. The higher the delta value, the farther the object must have moved. The principle works fine with many games, but not with TrackMania.
A PC that can only display 25 FPS would calculate the physics differently than a PC with 120 FPS, because the collision detection is more accurate (impact is detected earlier, speed adjusted accordingly, ...). Now you can assume that the delta value is always the same (as with Super Mario Maker, at least that's my assumption), then this would work. But that would cause problems similar to old games (https://superuser.com/questions/630769/why-do-some-old-games-run-much-to-quickly-on-modern-hardware/).
Now my question, why do such maps work on every PC and why is the physics always exactly the same? Did I miss any aspect of game development / engine development?
The answer is simple, first the physic of the game is predictable, based on the input the result will always be the same.
Then the physic loop is not the same as the render, the game ensure the physic loop will be call with exactly the same period every time during the whole execution. So, yes a delta is needed for the render part, but the physic as a constant time in ms between each iteration.
One last think : you wont find "Press Forward" maps on the multiplayer, these kind of maps will not work correctly, this is directly linked to specificities in the physic to avoid TAS (Tool Assisted Speedrun).
I have a 2D sidescrolling game. Right now, in order to jump, the player must be touching the ground. Therefor, I have a boolean, isOnGround, that is set to YES when the player collides with a tile object, and no when the player jumps. This generates a LOT of calls to didBeginContact method, slowing down the game.
Firstly, how can I optimise this by using one big physics body for the tiles on the floor (for example clustering multiple adjacent tiles into one single physics body)?
Secondly, is this even efficient? Is there a better way to detect if the play is on the ground? My current method opens up a lot of bugs, for example wall jumping. If a player collides with a wall, isOnGround becomes YES and allows the player to jump.
Having didBeginContact called numerous times should in no way slow down your game. If you are having performance issues, I suspect the problem is probably elsewhere. Are you testing on device or simulator?
If you are using the Tiled app to create your game map, you can use the Objects Layer to create a individual objects in your map which your code can translate into physics bodies later on.
Using physics and collisions is probably the easiest way for you to determine your player's state in relation to ground contact. To solve your wall issue, you simply make a wall contact a different category than your ground. This will prevent the isOnGround to be set to YES.
You could use the physics engine to detect when jumping is enabled, (and this is what I used to do in my game). However I too have noticed significant overhead using the physics engine to detect when a unit was on a surface and that is because contact detection in sprite kit for whatever reason is expensive, even when collisions are already enabled. Even the documentation notes:
For best performance, only set bits in the contacts mask for
interactions you are interested in.
So I found a better solution for my game (which has 25+ simultaneous units that all need surface detection). Instead of going through the physics engine, I just did my own surface calculation and cache the result each game update. Something like this:
final class func getSurfaceID(nodePosition: CGPoint) -> SurfaceID {
//Loop through surface rects and see if position is inside.
}
What I ended up doing was handling my own surface detection by checking if the bottom point of my unit was inside any of the surface frames. And if your frames are axis-aligned (your rectangles are not rotated) you can perform even faster checks to see if the point is inside the frame.
This is more work in terms of level design because you will need to build an array of surface frames either dynamically from your tiles or manually place surface frames in your world (this is what I did).
Making this change reduced the cpu time spent on surface detection from over 20% to 0.1%. It also allows me to check if any arbitrary point lies on a surface rather than needing to create a physics body (which is unnecessary overhead). However this solution obviously won't work for you if you need to use contact detection.
Now regarding your point about creating one large physics body from smaller ones. You could group adjacent floor tiles using a container node and recreate a physics body that fits the nodes that are grouped. Depending on how your nodes are grouped and how you recycle tiles this can get complicated. A better solution would be to create large physics bodies that just overlap your tiles. This would reduce the number of total physics bodies, as well as the number of detections. And if used in combination with the surface frames solution you could really reduce your overhead.
I'm not sure how your game is designed and what its requirements are. I'm just giving you some possible solutions I looked at when developing surface detection in my game. If you haven't already you should definitely profile your game in instruments to see if contact detection is indeed the source of your overhead. If you game doesn't have a lot of contacts I doubt that this is where the overhead is coming from.
I am working on a game which was developed by some other guy earlier. I am facing a problem that when player(with camera) start running on the road the buildings are not being shown up in their regular shape and as we move forward (more closer to the buildings) they gain their original shapes, and some times the buildings present on either side of the road are not visible by camera ( empty space ) and when we move closer to the building it comes up as visible object suddenly. I think it may be some unity3d setting problem (rendering , camera or quality). May be, it was being done due to increase performance on mobile devices.
can anybody know what may be the issue or how to resolve it.
Any help will be appreciated. Thanks in advance
This sounds like it's a problem with the available LODs for each building's 3D model.
Basically, 3d games work by having 2-3 different versions of each 3D model, with varying *L*evels *O*f *D*etail. So for example, if you have a house model which uses 500 polygons, you'll probably have another 2 versions (eg 250 polys and 100 polys), which are used depending on the distance between the player and the object. The farther away he is, the simpler the version used will be.
The issue occurs when developers use automatically generated LOD models, which will look distorted or won't appear at all. Unity probably auto generates them, but I'm unsure where you'll find the settings for this in unity. However I've seen 3d models on the unity store offering models with different LODs, so unity probably gives you the option to set your own. The simplest solution would be to increase the distance the LODs change at, while the complicated solution would be to fix custom versions of the 3D models for larger distances, with a lower poly count.
I have resolved the problem. This was due to the LOD (level of details) used for objects (buildings) in Unity3d to enhance the performance on the slower device. LOD provides many level of details (of an object) which you can adjust according to your need . In my specific problem the buildings were suddenly appear due to the different (wrong) position for LOD1, i.e. for LOD1 the building was at wrong place but for LOD0 it was at its right place. So when my camera see from the distance it see LOD1 which was at wrong place thence it sees empty space with no building at the expected position. But when camera comes closer it sees LOD0 in which building is at the right position and it seems that buildings are suddenly come or become visible.
Does anyone have any idea what technique I should use to make the display video shift left, right, up and down as in the video below? I want to achieve this with a Kinect but with a different idea.
Thanks in advance.
http://www.youtube.com/watch?v=V2hxaijuZ6w
EDIT:
Now that I'm awake, I'll go into better detail about this (it apparently took me a week to wake up).
So the Winscape project connects a real and virtual world by giving windows from the real world into a virtual world. The way it does this is act like the real world is part of the virtual world, and then changes the display of the monitors (disguised to look like windows) to replicate the view a person should see if they existed in the virtual world.
Imagine your virtual world. It doesn't necessarily have an end to it, but there's a point where you stop trying to render stuff into it, so let's say the world in enclosed in a box that contains all the rendered elements. Now what Winscape does is make it appear that the virtual world actually exists in the real world, and that you can see it through the monitors.
First step is obviously to create your virtual world. For starters, I'd suggest just creating a literal box. Make each wall a difference color, or put color gradients on the walls. Make something simple. If you haven't already decided on a 3D framework to handle this, I'd suggest XNA. It's C#, which works with the Kinect SDK, and it's got a ton of tutorials online to help you. Once you've created your world, use XNA to place a camera inside the box and add some simple controls to rotate the camera. This will allow you to look around the box from the inside, to make sure the rendering is working as expected.
Once you've done that, you need to decide where to put your windows. These will be the viewpoints into your 3D scene. To demonstrate this concept, here's a picture I took from an XNA camera tutorial.
Note that, if you read the actual tutorial, they won't say the exact same thing as me because I'm just hijacking the picture to demonstrate my meaning. So, the (0,0,0) point is where your "eye" is. The pink rectangle would represent your window. Looking at the window, four lines are drawn from the eye to the corners of the pink window. These four lines are extended forward until they collide with the background, creating the green rectangle. This would be the rectangle that your eye can see through the window.
Note that XNA will actually handle a LOT of this for you. You simply need to create a camera in your virtual scene and move it around, doing some math to aim it directly at your window. You'll want that camera to be in the virtual space in a way that represent your location in the real world. You can do this by using the Kinect to get your real world coordinates in relation to itself, then configure your application to know where your Kinect is in relation to your windows. Combing that data, you can get the location of your eyes in relation to your monitors in the real world, and since the monitors are represented by the windows in the virtual world, you can figure out where you exist in the virtual world. So place the virtual camera where your head is in the virtual world, point it at the windows, and do some magic to make sure only the window is viewed by the camera.
Original semi-lucid rant:
Okay, I'm going to take a shot at this (it's almost 1 AM, so let me know if I did a less than brilliant job and I'll come back to it when I wake up).
First, it'll involve quite a bit of math that I'm just going to skim over. You have, essentially, three layers.
Person ---- "Windows" (Monitors) ---- Scene
The scene, of course, doesn't really exist. You have to kind of incorporate the person into a virtual world where the scene, which is really just a flat image, exists behind a wall. The only way the person can see said scene is through the windows in the wall, which in reality is faked by monitors.
So, here comes the math. The Kinect can calculate where you're standing in the room, and more importantly, where your head is. From this you can get a general sense of where your eyes are. You'll need to take this point (your eyes) and translate it into the coordinates you're using in your virtual world. Then, calculate what those eyes should be able to see through the virtual windows. You can do this by projecting lines from the eyes to each corner of a window, all the way through until it hits the "scene" picture. Each window will correspond to a rectangular area on the background picture. This rectangle is what needs to be drawn to the screen.
The trickiest part is going to be setting up virtual world to nearly perfectly mimic the real world. Essentially, a lot of configuration ("okay, this window is 1.5 meters above the Kinect.. and .25 meters to its left.."). I'm also not sure how far back you should put the scene picture. If I think of something, I'll come back to this, but you can certainly just try it out and figure out a distance that works well for your set up.
Oh wait, now I know why I couldn't figure out the distance. It's because that example is using a 3D simulation. Pretty nifty. So you'd just need to figure out where you want to play your windows in the simulation or whatnot.
There are multiple techniques based on what setup you want to use (KinectDSK, libfreenect, OpenNI, etc.) and how accurate you want this to be.
OpenNI for example has a function called GetCoM which returns the centre of mass for a user (it doesn't need to track a skeleton at this point) which can be used. It looks like OpenNI was used in the video but they still use an old version. The newer version allows skeleton tracking without the 'psi'(ψ) pose.
Note that it doesn't look like it takes the user's head direction. The body could point in one direction and the head in another for example. G.Fanelli and his team have done quite a bit of research in the area. For Kinect check out Real Time Head Pose Estimation from Consumer Depth Cameras
I've played a bit with the KinectSDK and a Kinect for Windows and noticed there's a Face Tracker included.
In the end, based on to how loose or precise do you want the tracking to be, what's your ideal setup (maximum distance covered, content used, etc.) you can figure out what SDK/library will suit you best. Also, I imagine this also depends a bit on your experience with programming, in which case, also look for wrappers easier to tackle (e.g. Unity, MaxMSP/Jitter, Processing, openFrameworks, etc.)
I'm wondering, does the Kinect detects joints correctly when it's put on the top (on the ceiling).
I don't have necessary equipment to attach it to ceiling and test, but was wondering whether it reliably detects human. I'm ok even if it confuses the joints, actually.
Has anybody tested this?
From what I've seen while using it, the skeleton detection is iffy from any angle other than directly pointing at a person's front or back. A Kinect pointed straight down with people walking under it would almost certainly not detect anyone, because the human form from above does not look anything like it does from the front. I have had the Kinect pick up random people around me in odd positions (sitting, viewed from the side, etc), but the joints were largely spastic. If you have it mounted on the ceiling and pointed downwards at a sufficient angle to still see people from the front instead of from above.. it could do a fairly good job of picking them up.
So when you say on the ceiling do you mean pointing straight down or still looking at a fairly horizontal angle?
I did a little bit of testing with the Kinect mounted in a very high position (2.5 m, 70° to the ground). As answered by Coeffect it just doesn't work. It doesn't work with Microsoft SDK nor with OpenNI. What I can add is that the skeleton recognition only works if the user is facing the camera with her/his whole body-front. Even worse, both frameworks seem to expect the head at the top of the depth-frame.