Recently I've been trying to create something I've always wanted, but never had the skill and time to do - a computer game. To be more precise, a homage / clone of one of many of my favourite games. To start with something simple I've decided to create a classic 2D platform based on the Castlevania series.
Being a Ruby programmer I've decided to use Gosu. Then I decided I don't want to reinvent the wheel so I'm going to use Chipmunk.
After a few days, I've ended up having inexplicable collision detection problems. I've added boundary-box drawing functions just to see what the hell is going on.
As you can see, Belmont collides with blocks of walls he's not remotely close to touching. Since the demo game included with gosu gem works fine, there must be something wrong I'm doing, I probably don't really udnerstand how a polygon Shape is defined and added to the space. I'm pretty sure it's not really where I draw it.
There's a public repo with the game, so you can see how walls (Brush < Entity) and player (Player < Entity) are defined and that they indeed have a simple, rectangular polygon shape. Walls are not added to the space (they are rogue), only the player is. I've tried debugging the game and see where the body position is, but all looked fine.
https://github.com/ellmo/castellvania
Player falls down slowly, but you can control him with up / left / right arrows. Tilde button (~) shows the boudning boxes and the collision boxes are supposed to be always visible.
I need some help trying to understand what am I doing wrong.
I probably don't really udnerstand how a polygon Shape is defined and added to the space. I'm pretty sure it's not really where I draw it.
That's it. Shape coordinates are added to the body position, not substracted from it.
In your Entity.boundaries replace the line
verts << CP::Vec2.new(#shape.body.p.x - #shape[vert].x, #shape.body.p.y - #shape[vert].y)
with
verts << CP::Vec2.new(#shape.body.p.x + #shape[vert].x, #shape.body.p.y + #shape[vert].y)
and you will get correct picture. (drawing will be still broken, but bounding boxes will be correct.
Related
I have a rather simple react-three-fiber setup that includes cannon.js-powered physics. In the scene there is a cup -- which is modelled as a cylinder whose top radius is bigger than the bottom one -- that is placed on a surface.
When I run the code, during the loading screen everything looks fine. But when physics kick in, the cup suddenly "sinks" into the ground. Why is that? I can't make sense of that...
One theory of mine was that the "physics shape" of the cylinder is not identical with the "optical shape" that gets rendered, but even then the movement I observe still doesn't make sense with any reasonable bounding box I can imagine...
Working example: https://codesandbox.io/s/amazing-proskuriakova-4slpq
Physics are finicky and really hard to debug because you're often trying to intuit the effects of an invisible system by its effects on whatever hybrid view you have.
I notice if i bring the mass downn to a more reasonable value, like 5, the object appears to roll around like a sphere or some other shape.. so I think your theory is sound. I don't know off the top of my head what the solution is, but I do know that the only physics engine I "trust" in the js space, except for very simple simulations, is Ammo.js. It's hard to use, but is an emscripten port of a truly amazing AAA quality library. https://threejs.org/examples/?q=phys#physics_ammo_break
I would start by getting a cube and a sphere working.. once you have verified that those work as expected.. ideally using real-ish world scale units, like a 1x1x1 cube, with a mass of 1. Use a texture on the sphere so you know that its rolling like you expect. Once you have verified the simpler primitives work, move onto the more complex geometries.
Best way forward would be to make an issue on the use-cannon GH. That lib and cannon-es are under active maintenance now. Meanwhile, i believe convexpolyhydron can also do it flawlessly, see: https://codesandbox.io/s/r3f-convex-polyhedron-cnm0s
I am making a game and i have come across a hard part to implement into code. My game is a tile-bases platformer with lots of enemies chasing you. basically, in theory, I want my enemies to be able to, every frame/second/2 seconds, find the realistic, and shortest path to my player. I originally thought of A-star as a solution, but it leads the enemies to paths that defy gravity, which is not good. Also, multiple enemies will be using it every second to get the latest path, and then walk the first few tiles of it. So they will be discarding the rest of the path every second, and just following the first few tiles of it. I know this seems like a lot, to calculate a new path every second, all at the same time, if their is more than one enemy, but I don't know any other way to achieve what i want.
This is a picture of what I want:
Explanation: The green figure is the player, the red one is an enemy. the grey tiles are regular, open, nothing there tiles, the brown tiles being ones that you can stand on. And finally the highlighted yellow tiles represents the path that i want my enemy to be able to find, in order to realistically get to the player.
SO, the question is: What realistic path-finding algorithm can i use to acquire this? While keeping it fast?
EDIT*
I updated the picture to represent the most complicated map that their could be. this map represents what the player of my game actually sees, they just use WASD and can move around and they see themselves move through this 2d plat-former view. Their will be different types of enemies, all with different speeds and jump heights. but all will have enough jump height and speed to make the jumps in this map, and maneuver through it. The maps are generated by simply reading an XML file that has the level data in it. the data is then parsed and different types of tiles are placed in the tile holding sprite, acording to what the XML says. EX( XML node: (type="reg" graphic="grass2" x="5" y="7") and so the x and y are multiplied by the constant gridSize (like 30 or something) and they are placed down accordingly. The enemies get their frame-by-frame instruction from an AI class attached to them. This class is responsible for producing this path and return the first direction to the enemy, this should only happen every second or so, so that the enemies don't follow a old, wrong path. Please let me know if you understand my concept, and you have some thought/ideas or maybe even the answer that i'm looking for.
ALSO: the physics in this game is separate from the pathfinding, they work just fine, using a AABB vs AABB concept (the player and enemies also being AABBs).
The trick with using A* here is how you link tiles together to form available paths. Take for example the first gap the red player would need to cross. The 'link' to the next platform (aka brown tile to the left) is actually a jump action, not a move action. Additionally, it's up to you to determine how the nodes connect together; I'd add a heavy penalty when moving from a gray tile over a brown tile to a gray tile with nothing underneath just for starters (without discouraging jumps that open a shortcut).
There are two routes I see personally: running a quick prediction of how far the player can jump and where they'd jump and adjusting how the algorithm determines node adjacency or accept the path and determine when parts of the path "hang" in the air (no brown tile immediately below) and animate the enemy 'jumping' to the next part of the path. The trick is handling things when the enemy may pass through brown tiles in the even the path isn't a parabola.
I am not versed in either solution; just something I've thought about.
You need to give us the most complicated case of map, player and enemy behaviour (including jumping up and across speed) that you are going to either automatically create or manually create so we can give relevant advice. The given map is so simple, put the map in an 2-dimensional array and then the initial player location as an element of that map and then first test whether lower number column on the same row is occupied by brown if not put player there and repeat until false then same row higher column and so on to move enemy.
Update: from my reading of the stage generation- its sometime you create- not semi-random.
My suggestion is the enemy creates clones of itself with its same AI but invisible and each clone starts going in different direction jump up/left/right/jump diagonal right/left and every time it succeeds it creates a new clone- basically a genetic algorithm. From the map it seems an enemy never need to evaluate one path over another just one way fails to get closer to the player's initial position and other doesn't.
I'm using Farseer and XNA on on WP7. I have 2 objects in my game. The first one is a wall generated from a bitmap. The second one is a player controller - in fact it's just a circle object. This circle follows player's finger.
I need a certain behavior - probably it's very basic, but I can't figure out how to google it. It's a collision detection that just wouldn't allow the controller to come into the wall. It shouldn't bounce. It should just try to follow the finger but not enter the wall.
I know it's not hard to implement it on my own, but if I'm using a physics engine and it happens to offer such a functionality it would be a shame not to take advantage of it. :)
you need to use a BoundingBox object, and check collision VS the object (you should create a BoundingSphere wrapping it)
http://www.riemers.net/eng/Tutorials/XNA/Csharp/Series2/Collision_detection.php
Right, I'm making a 2d car racing game. So far I've got the car moving etc (with a little help of course) and was wondering how do I go about adding collision detection in XNA. I've taken a bumper part (from the whole track), and made it as a separate .png file. And I was thinking of adding a collision detection box around it (so if 'car' hits 'bumper' move back by so and so). How do I add collison detection to the bumper, and integrate it with the car? Thank you!
Try this tutorial: http://create.msdn.com/en-US/education/catalog/tutorial/collision_2d_perpixel
Source code for the tutorial is in Downloads, under the two (ugly) blue boxes.
It seems this would be a lot easier if the cars were always straight--not rotated. If they were rotated you wouldn't be able to use rectangles to help.
If you do, then you could instead have the bumper included in car.png.
Then you could use the coordinates of the car and add certain values to get the length and width of the region for the bumper.
You can then do
Rectangle bumperBoundingBox = new Rectangle
(
(int)X_COORDINATE_OF_CAR,
(int)Y_COORDINATE_OF_CAR,
(int)X_COORDINATE_OF_CAR + WIDTH_OF_BUMPER,
(int)Y_COORDINATE_OF_CAR + HEIGHT_OF_BUMPER
);
Rectangle otherCarBoundingBox = new Rectangle( \* x, y, ... *\ );
bool carIsTouchingBumper = otherCarBoundingBox.Intersects(bumperBoundingBox);
This may not be perfectly perfect, as in the parameters for rectangle might be in a different order or something like that. But once you have it, you can use carIsTouchingBumper and do stuff.
If you want the bumper to be a separate image, you could do the same thing as above, except use the coordinates of the bumper instead. Also you would have to make the bumper follow the car.
I am still shiny new to XNA, so please forgive any stupid question and statements in this post (The added issue is that I am using Visual Studio 2010 with .Net 4.0 which also means very few examples exist out on the web - well, none that I could find easily):
I have two 2D objects in a "game" that I am using to learn more about XNA. I need to figure out when these two objects intersect.
I noticed that the Texture2D objects has a property named "Bounds" which in turn has a method named "Intersects" which takes a Rectangle (the other Texture2D.Bounds) as an argument.
However when you run the code, the objects always intersect even if they are on separate sides of the screen. When I step into the code, I noticed that for the Texture2D Bounds I get 4 parameters back when you mouse over the Bounds and the X, and Y coordinates always read "X = 0, Y = 0" for both objects (hence they always intersect).
The thing that confuses me is the fact that the Bounds property is on the Texture rather than on the Position (or Vector2) of the objects. I eventually created a little helper method that takes in the objects and there positions and then calculate whether they intersect, but I'm sure there must be a better way.
any suggestions, pointers would be much appreciated.
Gineer
The Bounds property was added to the Texture2D class to simplify working with Viewports. More here.
You shouldn't think of the texture as being the object itself, it's merely what holds the data that gets drawn to the screen, whether it's used for a Sprite or RenderTarget. The position of objects or sprites and how position/moving is handled is entirely up to you, so you have to track and handle this yourself. That includes the position of any bounds.
The 2D Rectangle Collision tutorial is a good start, as you've already found :)
I found the XNA Creator Club tutorials based on another post to stackoverflow by Ben S. The Collision Series 1: 2D Rectangle Collision tutorial explains it all.
It seems you have to create new rectangles, based on the original rectangles moving around in the game every time you try to run the intersection method, which then will contain the updated X and Y coordinates.
I am still not quite sure why the original object rectangles position can not just be kept up to date, but if this is the way it should work, that's good enough for me... for now. ;-)