# Christopher Harris

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1. ## Impulse Physics confusion...

Oliii, do you have your physics examples back online yet? I'm really missing that source code... btw, Aressera, Thanks for the link, I've been trying to find that for a while now!
2. ## Impulse Physics confusion...

Ello, everyone. So I'm about to start programming a simple (2d) physics example. While I have worked with physics engines before, and know basically what's happening and when, This is my first time programming my own. I'd like to use impulse based physics, and for starters I'm only going to implement spheres. From there I'll add custom convex shapes (defined by a list of points). Most likely I'll use a seperating axis method for my collision detection. So here's my confusion. 1.) Assuming I'm using impulse physics, and all convex shapes, how many collision points would an object have (min, max)? I've seen examples where 2 objects are overlapping, and the collision point is somewhere inside the overlap. I've also seen examples where 2 points are located either both on the overlapping edges, or one inside the overlap and another on the edge. 2.) I just need to learn a lot more about impulse based physics. Anyone?
3. ## Slow motion without screwing up the physics timestep?

I believe fixed timesteps are usually held at 1/60, in otherwords if you have a constant velocity that velocity is applied over one second, and not one frame (assuming your framerate is a constant 60). If the framerate were to drop below, say, 30 then objects would be moving about twice as fast per frame, and the collision detection and response (aka, physics) would be less accurate. The same goes for if the framerate stays at 60, and you increase the timestep by two (effectively doubling your playing speed). However, if you were to DECREASE the timestep, and thus slowing gameplay (or the passing of time) objects would move much slower. Assuming all of your physics code is based on time, and it usually is, then this would INCREASE your collision detection and response accuracy. This is a good thing. Decreasing your timestep, at least in my experiences, has never hindered a physics engine's performance. If anything, it has always helped it. You shouldn't have a problem decreasing the time step. Just be careful if you want to speed it up.
4. ## Animating Sprites in 2D

Hey, guys. I've been programming a 2D game, and I've got a friend who can cartoon very well. The problem is neither of us know where to begin when developing sprites. Are there any tutorials you could direct us to, or possibly books you would suggest?
5. ## really simple question about rotation (managed dx)

We need to see the code that actually calls the draw function, and any other code that would effect the world/object/view matrices (unless you're straying away from them). I don't see any information relating to rotation in this code :/
6. ## 2D Collisions and Physics

I haven't tried it, but you might want to look at Physics2D.Net. As for engines NOT in C#, there's Erin Catto's Box2D. Considering the fact that it only handles boxes, it's pretty impressive that it's been shown at GDC twice. And inspired by Box2D, we also have Chipmunk. Chipmunk is written for the mac, but the videos are worth taking a look at :D Hope this helps. I found these at gphysics.com - edit - Hi, Oliii.
7. ## C++ Set to C# List... ?

Awesome. I know it's being sorted, so I'll look into sorted lists. Thanks :D And actually... how would I see if the "sorting behaviour" is being used?
8. ## C++ Set to C# List... ?

If anyone has seen Erin Catto's Box2D, then you know the code I'm trying to convert to C#. Here's the only part I'm having trouble with. I'm not familier with Set's in C++, so can someone tell me exactly what this code is doing, when it's being used, and possibly why... ? // This is used by std::set inline bool operator < (const Arbiter& a1, const Arbiter& a2) { if (a1.body1 < a2.body1) return true; if (a1.body1 == a2.body1 && a1.body2 < a2.body2) return true; return false; }
9. ## Walk the line - game idea - premise

I like it! Kind of simple, yeah... it would just be a sort of mini game. But the idea is solid. Four dimentions wouldn't be that hard to represent in certain ways. Other than time, you could just use size as the 4th dimention. I know, I know, size is made up of 3 dimentions, but if we were to have a world inside of a cube, and cubes inside of that world, and other worlds inside of those cubes with seamless scaling transitions to those worlds... That would be cool :) Kind of simulating a 4th dimention. I'm back to ramble on the boards again. lol Good idea, keep thinking stuff up!
10. ## DeviceLost

When a device becomes "lost" you are required to reset the device and recreate all of the resources that were stored on the device. If you had a texture in video memory and the device becomes lost, you must release that texture, reset the device, and recreate the texture. Simply checking the return code of "Present" will tell you what state the device is currently in. D3DERR_DEVICELOST means that the device was lost, and that it is still lost. while this flag is returned you cannot reset the device. D3DERR_DEVICENOTRESET means that the device is lost, but you can now reset it. This flag should tell you to reset your device and get things back to normal. Hope this helps... *edit Oh crap. It didn't occur to me that you were using managed code. I'll try to look up a solution for that.
11. ## XNA Framework on the way

Quote:Original post by Alpha_ProgDes Quote:Original post by Christopher Harris Am I going to have to use C# ? :( What's wrong with C#? Oh are you gonna start that managed code is slower than native code thing? And how C# doesn't do native code? Actually I just don't like C#... I'm used to C++, and I don't really want to learn another language. Yet.
12. ## XNA Framework on the way

Am I going to have to use C# ? :(
13. ## Sprite fighter gameplay video

AGOG, I wasn't trying to call the game easy to make, but rather, easy to make in comparison to an RPG, or an FPS, or possibly a puzzle game (I suck at writing logic). I wouldn't doubt if I were to make this game it would take me a year or more, but if I were to make an RPG, it might take me 4 years :D. Also, I was assuming it was all randomness... Scripted enemies would be a much harder challenge.
14. ## torque, pivot points, and friction

Net force would always be the same, if that object were to sit on the table and not push away or into it. so saying that the force applied when one vertex is touching should be devided by two when 2 vertices are touching would be correct, if you're applying that force to each vertex.
15. ## Time-Based movement is jittery...

Ok, so I was wondering if there was some other way to do timebased movement, other than euler's method. It seems a bit jittery. Anyone?