I am going to make simple 2D game in Defold game engine and I am new in this area. My question is, I have 2 game objects every object has sprites in it. A sprite in the first game object must be background for sprites of second object. I have designed it well but when I run (or render, I don't know how to call properly) it sometimes sprites of second game object are invisible and some times everything is OK.
The same issue if I set main backgruon image for the game. Please share your experiences with me. Thanks beforehand.
You posted the same question on the official Defold forum so I'm going to replicate the answer you got there here on SO as well. The solution is to make sure that the depth of two game objects that overlap isn't the same. If two objects have the same depth and overlap you might sometimes see one in front of the other and sometimes vice versa. The default render script allows a z-range of -1 to 1 (you can use fractional z-values to get fine grained control), but you can copy it from builtins and increase the range if you want to. Something like -10 to 10 is usually a good enough value.
Is it possible to calculate small distances with CoreMotion?
For example a user moves his iOS device up or down, left and right and facing the device in front of him (landscape).
EDIT
Link as promised...
https://www.youtube.com/watch?v=C7JQ7Rpwn2k position stuff starts at about 23 minutes in.
His summary...
The best thing to do is to try and not use position in your app.
There is a video that I will find to show you. But short answer... No. The margin for error is too great and the integration that you have to do (twice) just amplifies this error.
At best you will end up with the device telling you it is slowly moving in one direction all the time.
At worst it could think it's hurtling around the planet.
2020 Update
So, iOS has added the measure app that does what the OP wanted. And uses a combination of accelerometer and gyroscope and magnetometer in the phone along with ARKit to get the external reference that I was talking about in this answer.
Iām not 100% certain but if you wanted to do something like the OP was asking you should be able to dig into ARKit and find some apis in there that do what you want.
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At first I think my question should have been asked before, but I didn't find what I want.
One element of this iOS app I'm developing is break a 8x8 grid into Tetris pieces (every piece is made of 4 blocks). Two particular question I have are:
what is the best way to represent a Tetris piece in objective-C?
what algorithm to present the grid into random Tetris pieces (and later on how to check if two pieces fits together).
Edition on 01/28
#livingtech, I think I implemented pretty much what you say, except the point of "having a hole". My code works with no hole at simple stage when Tetris block is two blocks only (yes, two squares, connected either horizontally or vertically), but at 3-square Tetris block, I would get holes. I just tested and out of 1000 running, I would get one without a hole. So definitely I need some mechanism to check if next square will be a singleton.
I been trying to do the same thing for my game. Though I am a total beginner, and I'm using XNA and C#.
But the way I'm trying to go about it is: 4x6 grid array
--y123456
X1-000000
X2-000000
X3-000000
X4-000000
Here,
0 signifies no block
1 defines a block
Algorithm
Start by taking the very first 0 in the array ( top left corner )
and randomly pick a 0 or a 1.
Randomly choose the coordinates based on x1/x2-y1/y2, decide 1 or 0.
If it is 1, then decide coordinated based on where that 1 was put.
If it was 1 on x2 y1, then decide if a 1 should go on next touching
coordinate.
If you just have to code in what coordinates touch and which don't,
and the logic will roll through.
I have mine set up bit different. But this is the basic foundation of my random Tetris engine.
I also found that making it like that really helps to have a whiteboard and make a drawing of the grid and label with your coordinates.
since ur board is 8*8, i think u can use a int64 to represent the board. each bit of the int64 represents whether the specific grid is filled or not.
Implementing Tetris is a hobby of mine. First implemented it in Windows/C. Then in Perl/Tk! Last implementation I did in Obj-C/Cocoa (Mac). In all cases, the game logic is the same. Only the UI stuff changes. I treat every little box separately and have a two-dimensional array which contains the presence (and color) of every "set" box on the board. Standard board size I use is 10 boxes wide by 20 boxes high.
Separately I keep track of the "dropping" piece: it's location and what kind of piece it is. Based on a timer, try to make the piece drop. If any of the boxes where the "dropping" piece would drop is already set, then stop dropping the piece and add the piece boxes to the "set" part of the board. Create a new piece, and start over.
It may not be the best way to implement it, but it makes sense in my head. From a pure OO perspective, each shape of a dropping piece could be a subclass of a generic shape class. Override functions that check whether the shape can drop, the offsets of the individual boxes in the shape, etc.
I don't think anybody has taken a stab at your question #2 yet here, so I'm going to outline what I would do.
Setup:
You'll need to represent your grid as an array of some kind. At the very least, you'll want some kind of boolean values, to denote whether each coordinate in the grid is "occupied".
You'll need to keep track of the pieces on your grid. This could be another array, this time holding references to the four coordinates for each piece.
You'll need a variable or variables to keep track of a coordinate in your grid where you'll start filling in pieces, (I would probably populate these with a corner to start).
Set up a "pool" of all possible Tetris pieces and rotations. (You'll want to keep track of which ones you've already checked on every iteration outlined below.)
Iterate:
Get a random piece from your pool that will fit into your starting coordinate. (If you want to get fancy, you could be smart about which ones you choose, or you could just go totally random. As pieces don't fit, mark them checked, so you don't keep checking randomly forever. If you get to a point where you've checked all the pieces, you have a solution that doesn't work, either back up an iteration, or start over.)
Make sure the Tetris piece you selected didn't leave a "hole", or empty space with less than 4 squares. (I don't know your requirements for solving this problem, so I can't say whether you should focus on speed or ease of coding, but you may be able to skip this step if you want, and "brute force" the solution.)
"Place" the piece, by writing it to your piece array and marking the coordinates filled.
Check for "finished" condition, in which all your spaces are filled.
Pick a new coordinate in your grid and repeat #1. (I would pick an empty one next to the previous coordinate.)
If this actual yet, I wrote test tetris app on Objective-C few months ago https://github.com/SonnyBlack/Test-Demo-Tetris . I think my algorithm not very well, but it working. =)
iam working in a project that i take a vedio by a camera and convert this vedio to frames (this part of project is done )
what iam facing now is how to detect moving object in these frames and differentiate them from the background so that i can distinguish between them ?
I recently read an awesome CodeProject article about this. It discusses several approaches to the problem and then walks you step by step through one of the solutions, with complete code. It's written at a very accessible level and should be enough to get you started.
One simple way to do this (if little noise is present, I recommend smoothing kernel thought) is to compute the absolute difference of two consecutive frames. You'll get an image of things that have "moved". The background needs to be pretty static in order to work. If you always get the abs diff from the current frame to the nth frame you'll have a grayscale image with the object that moved. The object has to be different from the background color or it will disappear...
I've got a problem: i need to add a powerup to a racegame, using collision detection.
so i drawed the powerup, but the problem is: It has to be drawn after every 5 rounds and it needs to be placed ramdomly on the track.
Someone with any good advice?
Thanks.
Thats a bit vague. So here is my best shot at an answer.
You would want to use the c# Random class, here are the docs
For a simple game, using rectangular collision should be all you need (I assume thats what you are using) - If you want to randomly generate the power-up position, you will want to create a new Vector2 (the powerups position) with the random generator.
You can use the Next function, to pass in a low, and high variable - which you would need to configure the the bounds you wish the powerup to appear.
My advice as a game designer on the other hand, tells me that randomly located power-ups aren't always the go. It makes it harder to control the games flow and balance, and can very easily result in a flawed final product.
So my advice is a hard coded set of possible weapon spawn points - using a random generator to pick one to place.