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About shadow12345

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  1. shadow12345

    true randomness and quantum physics

    Quote: Radioactive beta decay is the prime example. Can you please explain this a bit more? edit: Quote: Oh, and something totally unrelated: I once read or heard that lightspeed has changed over the centuries, and also that how fast lightspeed is, depends on how much mass there is close to you (so lightspeed would be much faster if you'd go outside the milky way). Is this true? Well, it is my understanding that objects with macroscopic mass properties cannot reach the speed of light, as it takes infinite amounts of energy. The reason I say 'macroscopic mass properties' is that light *does* have mass properties, but only on a small scale. this relates to einstein's work on the photoelectric effect (where light bumps electrons off of metals) which is what he actually won his nobel prize for.
  2. shadow12345

    true randomness and quantum physics

    Quote: but the particles still HAVE both a unique velocity and a unique position, right? No, they are considered to *NOT* have a definite velocity/position (or any mixture of two inter related quantum variables) at the same time. This can be electron spin as well.
  3. shadow12345


    kill yourself
  4. shadow12345

    lost the passion

    Quote:Original post by Eelco yeah i very much recognize that. however, im too much of a perfectionist to let it go. that why i let go of doing big projects. i used to be a totally chaotic programmer, just sit down, open my IDE, and type away. my coding style has now evolved to a point where i do nothing but think about a project, read about the subjects, for months and months on end, after which i slowly write my program, with hardly any rewriting done. or i dont begin at all, knowing i cant do it or knowing its too easy. that happens most of the time really. its not so much the coding i enjoy, as the coming up with code. good thing i do not intend to do this for a living :). That's, like, *exactly* the same scenario with me. I think it has to do with your ability to solve problems. When you start off, and all of the math and complex subjects are completely new to you, you just want the damn code to WORK. After you do this for a while (for me, about two years) you consider yourself masterful in a large number of areas such that the actual implementation of things is seen as a smaller part of the overall system. I also pay respect to the idea of actually making a game though. I haven't really 'made a game' in the technical sense, and I'm trying to balance these two fields of thought so that the code I write is fairly robust but also I want to actually get something done.
  5. shadow12345

    Normal Homosexuality

    Oh no, the original poster might've started an intellectual discussion on homosexuality, BAN HIM...sheesshhh...you guys could spare us the innane 'uhh' comments so the people capable of having a mature discussion can take place.
  6. shadow12345

    Normal Homosexuality

    That certainly does sound interesting (rating ++). Quote: it grabs you by the balls, so to speak lmao so, how developed is asmat again? Maybe I need to reread your post. Well, it says south africa, but, south africa is actually more developed than the rest of the country I've heard.
  7. shadow12345

    Sort of a theoretical/philosophical question about math

    thanks dmytry, you have been helpful by the way, I just wanted to let you know that. The reason I haven't asked questions recently is I'm working on some 'other stuff' right now and I've put the whole matrix understanding thing off to the side. I really appreciate your help (and the help of the others that responded). I may just send a PM to you if that's all right. Thanks again Quote: Threads goes off-topic as soon as there's no questions from OP.... Yeah, you're right, so it is partially my fault.
  8. shadow12345

    Sort of a theoretical/philosophical question about math

    Quote: And also, proof is not even related to understanding. It's the level of understanding deep enough for what I want. All of this (what I consider) banter about understanding things even deeper than that is useless for people who are actually working on something. I really honestly think I summed all of this up about my comments about human abstractions which went basically ignored, and I'm upset because I'm forced to start a new thread if I have any more questions (this one's hijacked). I really should not have said 'philosophical' in the title, I think that screw this thread over. I hope you all have fun talking yourselves in circles (I've read one too many threads like this, and this is exactly what happens).
  9. shadow12345

    Sort of a theoretical/philosophical question about math

    This thread is going way off topic. Things in mathematics are about human abstractions and abstract ideas. Saying there are two socks on the floor is an abstract statement that only a human can make, because the socks are really just a bunch of collection of molecules, and only a human can distinguish these collections of molecules as two separate 'high level' entities, called socks. My questions about matrices were really questions about understanding the human abstractions involved in creating them. The appropriate response was what the first posters said about the fact that matrices have geometric interpretations (more human abstractions). I think that sums that up quite well. I wasn't trying to go THAT deep with this discussion, about trying to understand the fabric of the universe or whatever. Let me put it this way...it's sort of like I was using an equation without being able to prove it. Surely, we can all agree there's a big difference between copying an equation from a math book, and being able to prove the equation on paper. And surely we can agree that maybe there's a 'more fundamental level of understanding' deeper than being able to prove a math equation, but that being able to prove an equation on paper is good enough for all pragmatic purposes (i.e writing my damn rigid body physics modeling program)
  10. shadow12345

    Sort of a theoretical/philosophical question about math

    Hey all, I just wanted to say I appreciate the responses. I think all in all this makes a bit better sense (at least coming from the geometric side of things). Quote: Have you had a dedicated linear algebra course yet? A good linear algebra teacher should point out these geometric interpretations to you. No I haven't, and that very well may be part of the problem with the holes in my understanding. I have little formal training in any super advance topics, and I really hate the idea of waiting until I'm a sophomore or junior in college to get it...I hate school anyway :) Quote: Imagine you have axises/arrows in 3D pointing from origin , defined by columns of matrix (interpreting each column as vector) (assume you use matrix in openGL-like way, otherwise, rows) When would it be rows? Is it usually columns in the OpenGL like way, i.e in most math text books? I.e, vector one is column one, with each row being a different component (x component, y component, z component, etc)? EDIT: I'm looking at mathematics for 3d game programmign and computer graphics, and it seems it is the other way around, i.e each row is a vector. Maybe OpenGL is just backwards from the rest of the world in this regard? So basically, all in all, the key thing for me to understand is that a matrix is just a set of vectors. These vectors can mean different things, depending on what the matrix does, and that matrix operations are really just a bunch of vector operations. I read and liked all of your descriptions. I guess in a way this is stuff I 'sort of' knew, but after reading your responses I think I just 'get it' better. I think that on the geometric side of things I am pretty close to being satisfied with how I understand matrices, and the linear equations will just have to wait until I get that high up in mathematics at my university.
  11. shadow12345

    buoyancy formula by volume...

    Quote: Parachutes just slow down the air moving past you during the fall. Yeah you are right, my mistake! Thanks for pointing that out.
  12. Now, this does relate to games, because what I want to talk about is something that every game programmer must use, the matrix. But, this doesn't directly relate to a specific game programming problem so if it gets closed I will understand and I will take it elsewhere. Part of the reason I am posting this is when I went to read the proof for the outer product (cross product) on mathworld: http://mathworld.wolfram.com/CrossProduct.html as you will see, the 'cross product can be written in shorthand notation in the form of a determinant', where a determinant is a matrix thing which I never really understood. Matrices are an essential tool to use, and they have all sorts of neat properties that math buffs love. The problem is, I only know how to use them, I don't *really* understand how, or why, they work. I'm talking about understanding this at a very fundamental level. To me, it seems that just saying 'well, to multiply matrices together, you multiply matrix1's rows by matrix2's columns, and that in order to multiply two matrirces together, the number matrix1's columns must equal the number of matrix 2's rows' doesn't really mean that I understand why they work. This is what I call methodology, where I know the method for getting something to work (which is great if you can actually get stuff to work), but I want to *really* understand stuff. That's what I hate about school: our physics course is about the methods for manipulating equations, but they never really talk about how/why things work (so basically my university physics course is just algebra, except with trickier equations). For example, I understand the proof for rotations, and I can see where the rotation matrices come from, and I can see that multiplying the rotation matrix by a point rotates that point (because it equals the original equation when you do the matrix multiplication out), but I still get the feeling that I can understand matrices at an even more fundamental level. So, is there a more fundamental level to understanding how/why matrices work, or are they really just a more convenient way of organizing otherwise nasty equations?
  13. shadow12345

    buoyancy formula by volume...

    EDIT: I kind of rambled on down below, it's useful information but I didn't directly answer the question: Quote: Now the question is: does this volume formula generalize to more complex models than just simple symmetric cubes and alike? I can't come up with a proof or any kind of intuitions on the subject, but I believe the words of experts =) The problem with that equation is finding the volume of the fluid displaced, especially when the object is not entirely submerged. If you were to implement this in a computer program, the steps would like like this: 1) Determine the plane of water with respect to your object (the water essentially 'slides' through your object) 2) Compute the volume of the water displaced. This would be no easy task, even with the simplest objects, because objects partially in, say, water are typically oriented in a weird manner. 3) Compute the weight of the water displaced 4) Apply this force at the geometric center of the submerged part of the object. Step 2 is especially difficult, and lends itself to a numerical solution. In physics for game developers, it gives you methods for computing volumes of meshes using triple vector products, although I'm not sure which method best balances speed and accuracy that you would want. Now for the rest of my ramble: Saying the buoyant force is equal to the integral of pressure over the surface is correct, but it boils down to what the OP said: Quote: Then it shows, constructively, that for a rectilinear object, this boils down to a buoyancy force formula that depends only on the volume of the object (so that integration through the surface isn't needed). It's incorrect to say 'integration through the surace isn't needed', because in the strictest sense this is what is really happening. However, in general, it's this equation which is easiest to remember the buoyant force on an object: Quote: (that is, F = fluid_density * gravitational_constant * volume) That equation basically just says that the buoyant force is equal to the weight of the fluid displaced, and it acts at the geometric center of the part of the object submerged in the fluid. For example, bourg's book (I assume you mean physics for game developers) shows how to predict the behavior of ship hulls and submarine hulls based on the object's center of mass versus center of volume submerged in the water. This works for all fluids, i.e, you currently have a buoyant force acting on you because of atmosphere pressure, you are displacing air, and therefore it is pushing you back up. This is how parachutes work, because they displace a lot of air, about equal to the weight of you and your equipment load. The reason that there is a net force upward is because of pascal's law which says the pressure at a point is zero. How this works, I don't know to be honest, but it's true and it has been proven. The implication for this, however, is what dmitry mentioned, that the vertical pressure gets greater as you travel downward in the fluid (when you go down in water, your eardrums hurt because of the increase in pressure). When you put a box into water, you've got a pressure at the top of the box pushing down, and you've got a greater pressure at the bottom of the box pushing up (because the pressure increases the further you go down). The pressure at the sides cancel (otherwise a box would move funky side to side when submerged). The pressure difference between the pressure at the top and the pressure at the bottom always yeilds a yet difference equal to the weight of the fluid displaced.
  14. shadow12345

    Diploma Thesis "Game Engine for a 3D Space Simulation"

    That's really cool. I played the game for about 15 minutes and enjoyed it (although it sometimes becomes hard when I can't control the spacecraft). I also looked at the source, overall I'd say very good job!
  15. shadow12345

    Mass moment of inertia about arbitrary axis

    I just wanted to thank you both for replying and for the link. I suppose it's sort of silly of me to actually think I could've come up with a method that is that easy which would work for all objects (if it worked, it would've been published already...it's unlikely something like that would've easily been missed).
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