# Selenaut

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1. ## Collision Physics Question

Alright, shy of some bugs that I can fix relatively quickly (hopefully), I got it working. Thanks guys.   Selenaut   P.S.: Can anybody tell me why I have so many -1's?
2. ## physics help

Where did you get the equation for dW? It's very difficult to dissect the entirety of this problem without knowing where the equations came from.
3. ## Collision Physics Question

Are you saying that I can just use the x- and y-components to do the same thing? I figured it out but had to use a bit of trig... and the original method. XD   EDIT: ...Why the heck do I have like 7 -1's on this thread alone? (Not to mention they're my only -1's.) How am I supposed to report this?
4. ## Collision Physics Question

Unless you're planning on using non-right-angles for anything other than ramps... which I am. Also, nice oxymoron. ;) EDIT: I see what you mean, definitely less trig involved, even for my above statement. I'll convert all my classes, and tell you how it turns out. EDIT 2: Okay, how the heck to I program bouncing now? XD Selenaut
5. ## Collision Physics Question

I'm using angles because I'm using vectors and not keeping track of individual x- and y- axis motion, but rather speed in a direction. The use of angles also gives me the possibility of using angles other than right angles, e.g. 45- and 22.5-degree ramps. (I'm hoping to get to ramps in the future, but at the moment I'm only worrying about 90-degree angles; I'm just trying to write it so that it's easy to port later.)   EDIT: I forgot to mention the whole division thing: That's exactly what it is, and I can't believe I didn't realize that. I'll let you know if correcting that fixes the problem.   Thanks,   Selenaut   PS: I hate the quick edit feature. XD
6. ## Collision Physics Question

Okay, so I came up with this formula for finding the precise moment of impact. t = the amount of time one discreet timestep takes (currently set at 1/60 of a second) mv = magnitude of the velocity vector (x & y change each stimestep by t*velocity, with respect to each axis) p = the amount the moving object penetrated past the collision point as measured by the wall's normal (0 if it didn't collide) ?v = angle of the velocity vector ?w = the angle of the wall The amount of time the object should move is equal to t - (|p/sin(?v-?w)|/mv). Then it bounces, and runs the rest of the timestep. I'm almost certain this is correct, right? Well, I'm getting a bug where when it corrects, the object bounces, but flies off the screen when the bounce height gets near 0. Within a second, its coordinates are in the billions (bouncing off the walls of a 640*480-ish window - obviously a problem.) So, err..... Yeah. Any ideas? Selenaut
7. ## Most Important Mathematics in Advanced AI/Robotics

.......Why has nobody included basic calculus...?   Selenaut
8. ## Distance between parallel lines under transformation

Yeah, I dunno too much about affine transformations, I was kinda taking a stab in the dark there (just another example of how assumptions suck). However, as haegarr stated, I think you answered your own question.
9. ## Speeding Up A* Pathfinding Idea

Okay... Here's what I would reccommend: As previous posters have stated, use a multi-level A* algorithm. This means that you take groups of tiles and clump them together to make larger (and thus coarser) tiles that are easier to calculate. You can do this to as many levels as you like, but don't go to crazy. Calculate the weight of coarser tiles as the sum of the tiles that they're comprised of; continue until you reach the highest level. Find all entry and exit points at every level of tile to see which ones can be connected. Path at the highest level which areas you would move through to get to your desired location; then work your way down through the next level, pathing only the current area that the object to pathfind is in. For example, if you have a 16x16 grid, and that is made up of a higher level comprising of a 2x2 grid, only path within the tile on the 2x2 grid you're currently in. As soon as the pathfinding object makes their way to another section, restart the pathfinding process of steps 2-4. This is basically hierarchical A* pathfinding, as many before me have suggested. It's like level of detail, except for pathfinding. :D   Selenaut
10. ## The "every aspring game programmer coded that at some point" thread

Before I got into "real" programming, I loved screwing around in GM8 Lite. (I'd be lucky if I ever got something worth noting done though...)   Once I began learning Java (After C++; that was a strange transition, especially since I had no idea what OOP was), I began making more complex games. I even made a parody of Minesweeper where you literally have to walk around the map, rather than being able to click and stuff.   Oh, and I made an Asteroids clone for a school project once. ("AAAHHH VECTOR MATH" *Head explodes*)   Selenaut   EDIT: I can't believe I forgot about my procedural terrain generation forays.... They even used cellular automata to make it more believable (via comparing neighbor counts to a random weight function). They made pretty decent-sized maps too (1000*1000 px I think), in about 30 seconds.
11. ## I think the required Humanities courses in college are a waste of time

I still hold the belief that learning a little about things other than one's main focus is good. I mean, could you imagine how difficult life would be if literally all a person knew was all math known to man and nothing else? Times would most certainly be rough for him.   Obviously this is the most extreme case, but it applies for everything in between. Anyway, if you don't enjoy it, find a way to make it enjoyable: I often find that learning is much more interesting and satisfying if you relate it to things you like - like game development.   Selenaut
12. ## Distance between parallel lines under transformation

I don't understand how there could be a more direct measurement, unless you're looking for an equation. According to the definition from wolfram, an affine transformation is one that "preserves collinearity ... and ratios of distances." Thus if you're scaling everything, the distance will scale with the lines as well. Thus new h = old h * scale amount. Otherwise the h will stay the same. Hope this helps, Selenaut
13. ## I think the required Humanities courses in college are a waste of time

Note that in French if a noun ends in e, then it is quite often female, with a few exceptions (e.g. libre, meaning book).   Selenaut
14. ## Collision Physics Question

Okay, let me clarify this: I'm using an effective AABB for my object. I'm currently attempting to bounce it off the walls of the window (drawing using BufferedImage - it's in Java). Using my own motion system class, I have the program set up so that every tick (about 1/60 of a second, not the same as a frame) the object moves in relation to its current acceleration and velocity to its new position. Both velocity and acceleration are vectors (a custom class), and x and y are held as doubles for precision. I then check for whether the AABB is outside of the bounds of the window. The problem is somewhere in the collision position correction section, which I'm still telling you is the problem. My first go was something like "If the x-val of the AABB is out of bounds, move it so that the x-val is back in bounds; repeat for y." Then I used the bounce function. This obviously causes, as I've stated, the infinite bouncing problem (it also doesn't play nice with a "bounce" with restitution of 0). The problem is how I correct the position, and I have an idea of how to fix it: I can check for whether the next movewill put me out of bounds, if so how far; then using this, back up a specific amount so that the intersection amount becomes 0. I'm having troubles coding specifically this. Sorry if that sounded impatient, it's just that it's very difficult to explain it when I don't have the code to put up atm. Selenaut
15. ## Collision Physics Question

Yes, I realize this; what I've been trying to say is that I can't figure out how to correct the collision so that it is precisely set back to where the object is just barely touching the wall.   When I tried to correct it by simply placing it back into the bounds, it created the effect of an infinitely bouncing ball when its bounce height got small-ish. It never - literally, never - stopped bouncing.   So yes; How do I correctly, err... correct the collision?   Thanks,   Selenaut