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  1. Artlav

    I Relativistic doppler shifted blackbody color?

    Real physics, ye cruel thing, you took away my starbow? Then here is my starsmile, adherent fully to your code. ( Going perpendicular to the galaxy at 0.8c ) No, certainly not. I only got the idea to add relativity a few week ago.
  2. Artlav

    I Relativistic doppler shifted blackbody color?

    Starbow, hm? Oddly enough, that's exactly the kind of an effect i got at first, and felt that it's pretty, but unrealistic. Got the article, it's pretty much exactly what i was looking for. Turns out i got most of the things right on the second try, except for the intensity factor - it's not...
  3. Artlav

    I Is there a point during star formation when gas is 1 atm?

    But will the temperature be anywhere near survivable? The thought that piqued my curiosity was that there could be a longer-than-instant period where such survivable conditions could exist inside such a collapsing nebula.
  4. Artlav

    I Relativistic doppler shifted blackbody color?

    I take the frequencies of red, green and blue, doppler shift them, convert each result back to RGB, then mix in the same proportion than in the original. This gives odd results for random colors, but works ok for near-white ones the stars tend to have. If you know of a better way, i'd like to...
  5. Artlav

    I Relativistic doppler shifted blackbody color?

    I'm trying to render the sky as it would appear from a starship moving at some large part of the speed of light. Geometry was straightforward, but colors are the problem. How would the doppler effect change the color of a star? The expectation is that the stars behind are red and the ones ahead...
  6. Artlav

    I Is there a point during star formation when gas is 1 atm?

    I have been reading about and contemplating the early stages of star formation lately. An interstellar cloud collapses under it's own gravity to form a star. There is much data about what could trigger it, and what happens when the gas heats up or starts fusing. However, i couldn't find...
  7. Artlav

    Ray transformation of a 3d lens?

    Ah. Skew rays was the googleable term i was looking for. Thanks. I'm just exploring what can be done with raytracing, making one myself. Since it's not for anything important or for profit, i find it more valuable to (re-)invent things myself rather than look at things already done and figured...
  8. Artlav

    Ray transformation of a 3d lens?

    Imagine a lens in front of you, on a table you're sitting at. It's at an angle to you. Look at it's center. Now shift that line of sight to the side. You will get a ray that passes through a lens, and yet it's not coplanar with the axis of the lens (the line that is perpendicular to the plane of...
  9. Artlav

    Ray transformation of a 3d lens?

    Greetings. I'm working on a raytracer, and got stuck with trying to model a lens analytically. Given is a thin lens at position p with the axis n, radius r and a focal distance f, a ray hits it at position p1 going in the direction d. Which way would the ray be going on the other side of the...
  10. Artlav

    Article on texture generation - can't get the math

    There is an article on procedural texture generation by example. I'm trying to implement it, and got lost in the mathematics. http://graphics.cs.kuleuven.be/publications/LVLD10PISTE/ The outline of the algorithm is thus: We start with a noise-like photo. Do a 2D DFT of it: Compute the power...
  11. Artlav

    How to convert air flow into pressure?

    I know. But that is not what the question is about.
  12. Artlav

    How to convert air flow into pressure?

    It's a centrifugal "pump" like the image below, used to fill up air mattresses. It produces a lot of air flow, but almost no pressure. That is, it can quickly inflate a garbage bag, but won't force any air into a regular party balloon. The latter is what i was thinking of using it for.
  13. Artlav

    How to convert air flow into pressure?

    Let's say i have an air pump which produce plenty of air flow, but almost no pressure. Is there a simple way to turn this high flow, low pressure into high pressure, low flow? I'm thinking something akin to a gearbox turning fast spin, low torque of a motor into a high torque, slow spin output...
  14. Artlav

    Calculating optical properties of an arbitrary gas?

    Hm, interesting. Two directions then. First, how do you compute it for a helium atom, even approximately? I'm looking for key words. Second, is there enough empirical data to calculate a refractive index for common gasses at given conditions? I found data sets online (i.e...
  15. Artlav

    Calculating optical properties of an arbitrary gas?

    Hello. Is there a way to calculate properties of a gas, given only it's composition? I.e. let's say i want to know what would a planet look like with an atmosphere of a mix of 50% gaseous sulphur and 50% gaseous mercury, at 500*C and surface pressure of half that of Earth. How would i go about...
  16. Artlav

    Decoding AM station from SDR into sound?

    Figured it out. Two ways to do it, good and bad. 1. The bad. Produce the sound as beat frequency of the carrier. Sound sample = input sample (as a complex number I,Q) multiplied by sin(wt)+i*cos(wt), where w is 2*PI*Fcarrier. This results in a sound, but the sound is quite bad. Also, you...
  17. Artlav

    Decoding AM station from SDR into sound?

    In short, how do you decode AM signal from I/Q samples into sound? In details, i made a software defined radio that uses a PC sound card as ADC. The local oscillator on it is set to 700KHz, there is a radio station at 731KHz. With existing software i verified that the hardware works - the...
  18. Artlav

    What can be used to measure liquid nitrogen temperature?

    Hi. I'm looking for a common electronic component that can be used to determine a temperature between room temperature and that of liquid nitrogen. -Multimetre probe failed, getting stuck at -135*C -Common NTC thermistors rapidly ascent past gigaohm range, even from 1Ω-5Ω initial values...
  19. Artlav

    Green LED in liquid nitrogen turns yellow

    I wondered about similar thing, if it's a good idea to raise this old thread. Putting red, UV or blue LED in LN does not change their colour visibly. White LED stops working. But green LED turns orange. Videos i seen of that show an orange LED turn green - an opposite direction to my green...
  20. Artlav

    Axial flux alternators and motors design?

    I see, thanks. Two things i found experimenting: -An axial flux alternator does make a motor, however the windings good for a motor aren't as good for the generator, and vice-versa (at the same voltages), -Glue the magnets down. :) The motor mode spins much faster, and their mutual...
  21. Artlav

    Axial flux alternators and motors design?

    Axial flux alternator is an easy to make pancake of stationary coils between spinning permanent magnets. Having made one and played with it, i ended up with a few questions. Would it make a good motor? There are axial flux motors for sale, and my alternator spins nicely when hooked up to a...
  22. Artlav

    Constant current boost converter problems

    5Ω resistive load. The traces are across current feedback output - 20:1 amp of current across 0.01Ω sense resistor, with RC filter of 100Ω and 0.1μF. The ignitor transformer? It's 200μH worth of choke in series with the load. All in all, i'm likely to give up on this design, and try a CV...
  23. Artlav

    Constant current boost converter problems

    I think i am loosing my mind. Something is working backwards in here. Let's start back where we left. The flat line with RC filter was due to the zenner on the current sense input, which draws considerable leakage current, overwhelming the RC filter. Without it, things started happening. More...
  24. Artlav

    Constant current boost converter problems

    Helps quite a lot. :) The first one in particular, since it gave me a few ideas - i haven't realized that you might get away with a buck converter if you use a diode-isolated boost for initial ignition, instead of a 64V battery or something impractical like that. That might be something to...
  25. Artlav

    Constant current boost converter problems

    Yeah, i'm going through them slowly. Quite a bit of it is irrelevant, but many things from the second one are. For example, i found out that i can reliably switch between modes of wrongness by moving the current feedback wires a tiny bit relative to each other. This is so wrong... The...
  26. Artlav

    Constant current boost converter problems

    Ok, i'm making progress even though i'm still moving ahead blindly. I've rearranged the components as shown below. There is a 30uF capacitor before the sense resistor and a 100uF one after it, the sense resistor have a 10nF capacitor across it. This makes it much more stable, but still far...
  27. Artlav

    Constant current boost converter problems

    Here is what i see across the current sense resistor (with 10nF capacitor at the input), with the arc lamp and current set to 5A (0.5V on the amp input). I think it sort of averages to 0.5A, but it does not look good at all, and DC meter shows 8-9A. So, no whine does not equal no problem...
  28. Artlav

    Constant current boost converter problems

    Hm, moving big output capacitor negative end to after the sense resistor makes the whine go away. It still gives out 8A instead of 5A it's set to, but the input is now 15A instead of 21A.
  29. Artlav

    Constant current boost converter problems

    Overview of the build attached. I don't see any obvious current loops to interfere with the sensing. The lamp refuses to ignite without considerable output capacitance. Even so, the "clumping" also happen with a resistive load, and even in constant voltage mode. So whatever is wrong here is...
  30. Artlav

    Constant current boost converter problems

    Clumping sounds about right. If i put a 50Ω load at full voltage it would whine with a clean high sound, and the gate would get a regular missed pulse (first attach). If i get it into constant current at 2A, then it starts making a much lower tone with some surging, but similar picture of...
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