I'm trying to make it so when a sprite which is attached to a physics body overlaps another sprite on the level something happens. The second sprite is NOT attached to a physics body.
More specifically when the two sprites are overlapping I want the game to constantly check to see if the distance between the centers of the sprites is less than a certain amount or not. Then if the distance is small enough something will happen.
I'm trying to use collision checking as a way of optimizing the game so it doesn't have to constantly check distances between every single object of type A and B even if they're not even close. It will only check the distance when they're close enough to be overlapping.
Now what I am wondering is how can I do this? Is there a way to check collisions between sprites as part of AndEngine? Or would it be easier to attach a physics body to the second object also and then just use physics collision detection? But then if I do that can I make it so the collision will be detected but they won't actually physically "collide"?
Yes, see CollisionDetectionExample.java. I suggest you download the whole examples package, it is very useful in the absence of any documentation for AndEngine. Please note that collision detection is not pixel perfect, so it will still detect collisions of transparent parts of the Sprites. There is a library for that, but I am afraid it is outdated.
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I'm working on a simple game with libGDX and want to make the main character to be fixed in the center of the screen and the world move when I press a button. I was wondering how to do... I was thinking to add a physicsBody to the world that contains other bodies and apply impulses to it when the button is pressed, is this possible in libGDX? And if it is, can i apply other impulses or forces to the bodies contained in the world's physicsBody? I think this way would be the best for me if it is possible, because i have to work a lot with physics, but if you have other ideas tell me please
There's no need to think about applying forces to all the non-character objects, that's just going to get messy very quickly.
The simple solution is to move your camera so that it always looks at your character. So your game loop may look something like:-
Process input
Update physics, character and other entity positions.
Move camera to point at character's new position.
Render
This way, you can update your game world without having to think about the camera at all. Then, when it comes to rendering, you can position your camera and render your graphics without needing to know anything about the game physics. It keeps the physics and rendering relatively independent, and makes it much easier to change things in the future.
For example, you may later decide that you want the camera to follow your character for the most part, but then follow a baddy whilst it is their turn. This is now easy to do, you just specify the character / entity to look at in your game logic, and then position the camera to look at whatever target that is, before you render.
i am learning libgdx. i want to create a 2d fps game using libgdx, which is basically no physics environment. in that case lot of collision will be there (for example lot of bullets hitting multiple objects). i need to check intersecting of every sprite's rectangle with other sprites. in this way there may be thousand sprite's, checking every sprite with other 999 sprites in every time isn't definitely not a good idea.
libgdx has scene2d which has hit detection api's, is that solve my problem?
or
i should use box2d collision detection?
or
is there any other way to detect collision in libgdx?
i want to create a 2d fps game
As much as i know FPS means "First-Person-Shooter" -> a shooter with the first person perspective. That means, that it is 3D.
So pleas clarify what you mean.
Now to the collision detection question:
Scene2Ds hit detection is used for input like touch or
mouseevents. So it is used to detect, if an Actor is touched,
clicked...
Box2D is a 2D physic-engine which can not only do collision
detection for you, but it can also do the collision response as well
as the physics simulation (gravity and things like that).
Libgdx offers the Intersector class, which you could use for
overlap tests. The organization/the management of the collision
detection is up to you.
It would be better if you tell us how your game should work, how your world should be managed etc.
For example, if your world is tilebased, the collision detection between wall and player could be a simple check, if the tile is occupied -> collision, if not -> no collision.
Also it is important to know the shapes of your objects. A rectangle-rectangle collision detection is different from a rectangle-circle collision detection.
So now there are 3 solutions for your problem:
- Use Box2D and read tutorials on how to use it
- Do some research on collision detection, read tutorials and take a look at some sample projects
- Give us more informations about the game, its objects, their shapes etc.
My question is mostly related to the theory behind it. I make a 2D game for a project and i detect collisions by using the .overlaps method in the Rectangle class and the collisions are handled beautifully. First of all , is that considered to be a continuous or discrete collision technique. As i'm reading the theory i say it is discrete ,however i'm reading in online articles that the major disadvantage of discrete is that it detects collision after it actually happened. So,my question is the following : is it actually discrete and if it is why i see no disadvantages?
Thanks
This is discreet because we only know if two bounding boxes collided after we check if the imaginary/invisible boxes intersected meaning they already overlapped. So by the time you take action (update) due to that collision, the objects are not in the collided position. Worse case, if they are not in relative speed, they can pass through. Think of the classic helicopter game where you dodge obstacles by going up and down. Say you put the velocity of the chopper on x really high, depending on your frame rate which depends on the hardware, you will see different positions of actual collision. For continuous, one object has to be aware of the physics properties of the other objects it may collide with to predict possible collision.
In reality, for 2d games like the helicopter game I mentioned, it really doesn't matter much. You can simulate the result of the collision by doing changes on an object's rotation, velocity, gravity and through some nice animations. If your game objects have abstract shapes, you should use something like box2d. There's a good Intersector class as well.
Also, you can experiment with different bounding box sizes (bounds) of an object rather than creating the bounding box of the object equal to its width and height.
Im making small 2D game and i would like how should, theoretically work jumping and standing on objects.
For jumping should there be some kind of gravity?Should i use collision detection?
Good example of what i want to undestand is jumping in Mario.
I think for jumping it would be best to create some simple model which use "game time". I would personally create some physical model based on gravity, but you can go for whatever you want.
If you want your character to "stand" on object, you will have to create some collision detection. Good start is to approximate object by one or more circles (or lines) compute collision of them and in case the approximation collides determine the final state by some more precise method.
In terms of should there be gravity and collision detection - personally for such a thing I'd say yes and yes! It doesn't have to be complicated but once you have those things in place the pseudocode for the "main loop" becomes relatively simple:
if not colliding with object underneath, apply gravity
if user presses jump key and not colliding with surface //i.e. if we're in the air already, don't jump again
apply upward velocity
That is of course oversimplified and there are other corner cases to deal with (like making sure when you're coming down after jumping, you don't end up embedded or potentially going through the floor.
You might want to take a look at Greenfoot which handles a lot of things like all the Java2d stuff, collision detection etc. for you. Even if you don't stick with it it'd be a good platform for building a prototype or playing around with the ideas talked about.
Standing on objects implies collision detection, you can approximate the characters and the environment objects with primitive shapes (rectangles, circles etc.).
To check if to shapes are colliding, check axis one by one (X and Y axis in your case). Here is an explanation of the "separating axis theorem" (Section 1).
I'm new to OpenGL. I'm using JOGL.
I would like to create a sky for my world that I can texture with clouds or stars. I'm not sure what the best way to do this is. My first instinct is to make a really big sphere with quadric orientation GLU_INSIDE, and texture that. Is there a better way?
A skybox is a pretty good way to go. You'll want to use a cube map for this. Basically, you render a cube around the camera and map a texture onto the inside of each face of the cube. I believe OpenGL may include this in its fixed function pipeline, but in case you're taking the shader approach (fixed function is deprecated anyway), you'll want to use cube map samplers (samplerCUBE in Cg, not sure about GLSL). When drawing the cube map, you also want to remove translation from the modelview matrix but keep the rotation (this causes the skybox to "follow" the camera but allows you to look around at different parts of the sky).
The best thing to do is actually draw the cube map after drawing all opaque objects. This may seem strange because by default the sky will block other objects, but you use the following trick (if using shaders) to avoid this: when writing the final output position in the vertex shader, instead of writing out .xyzw, write .xyww. This will force the sky to the far plane which causes it to be behind everything. The advantage to this is that there is absolutely 0 overdraw!
Yes.
Making a really big sphere has two major problems. First, you may encounter problems with clipping. The sky may disappear if it is outside of your far clipping distance. Additionally, objects that enter your sky box from a distance will visually pass through a very solid wall. Second, you are wasting a lot of polygons(and a lot of pain) for a very simple effect.
Most people actually use a small cube(Hence the name "Sky box"). You need to render the cube in the pre-pass with depth testing turned off. Thus, all objects will render on top of the cube regardless of their actual distance to you. Just make sure that the length of a side is greater than twice your near clipping distance, and you should be fine.
Spheres are nice to handle as they easily avoid distortions, corners etc. , which may be visible in some situations. Another possibility is a cylinder.
For a really high quality sky you can make a sky lighting simulation, setting the sphere colors depending on the time (=> sun position!) and direction, and add some clouds as 3D objects between the sky sphere and the view position.