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Thread: ILDA Format BS

  1. #91
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    I think everyone should have a lumia wheel in their arsenal. I remember going to a laser show way back when and thinking that was the coolest effect in the whole show. One of the members on here, I can't remember who, cut me some round pieces of privacy glass that has waves in it. It makes a very nice effect. I haven't gotten around to it yet but I intend to make put a cheap green and homemade DVD red laser and it into a box and make it TTL controlled. It will be nice and self contained.

  2. #92
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    Quote Originally Posted by carmangary View Post
    I think everyone should have a lumia wheel in their arsenal. I remember going to a laser show way back when and thinking that was the coolest effect in the whole show. One of the members on here, I can't remember who, cut me some round pieces of privacy glass that has waves in it. It makes a very nice effect. I haven't gotten around to it yet but I intend to make put a cheap green and homemade DVD red laser and it into a box and make it TTL controlled. It will be nice and self contained.
    I'' save you some time of sorting through dozens of pieces of shower glass, as only a few work.

    get some of the acrylic sheet gnome depot sells for window replacement. GO outside when you do this. take a propane torch and ever so lightly bubble the surface. More bubbles = more dense lumia, bigger deeper bubbles = more divergence. Dont burn or brown the surface, and do it outside in the wind as THE FUMES ARE LETHAL.

    I'm debating on if I should reveal how to do wave lumia, there is a PL member trying to design those for low cost sale right now, and I'm wondering if I should conspire to help him by keeping that little jewel of a detail. Eh, whats 3 more months of not talkin about it.

    Steve
    Last edited by mixedgas; 01-14-2009 at 07:09.

  3. #93
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    The glass I got had large waves in it. It isn't the kind that looks like rain. It's the stuff used on front doors. It works fine.

    I have used the blow torch method before but using those clear spacers that come with blank CDs. They are already round so that is nice.

    What is wave lumia? Do you have a photo?

  4. #94
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    i can vouch for the silicone on plastic effect, its nice..
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    Quote Originally Posted by carmangary View Post
    I have used the blow torch method before but using those clear spacers that come with blank CDs. They are already round so that is nice.
    I've wondered about those clear plastic spacer things before. If you bounce light off them at an angle it's clear that they have some kind of structure to them. I suspect they may be CD-R blanks with the pregroove stamped in them but with no photodye or metal layer coated onto them. In which case, I wonder if one could use their diffractive effects to any advantage? I only get three lines out of my DPSS but maybe someone with a multiline Ar-Kr or Ar could get some nice effects that way.

  6. #96
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    yes they do defract .. which is not bad for a lumia effect..
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  7. #97
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    Hey Heroic...

    Quote Originally Posted by heroic View Post
    I hope you can go back and read what I read and see what I meant.

    I'm sure they're still innovating, I look forward to seeing what they come up with- it's a big world and there's room for all sorts of different approaches to the same fundamental medium!
    THAT'S THE SPIRIT!!! Sorry if I came across as 'shelling your beach', I was waaayy tired yesterday and, as-usual, doing way too much for one guy...

    Anyhoo, yeah, I can tell you this: The 'reincarnation' of Laserium promises to, yet again, bring smiles and 'that was GREAT'-s to thousands, if not millions... if we can just get this dang 'economy cloud' to just blow-over... ...Mankind NEEDS Great Laser Shows, don't they KNOW that???

    Anyhoo, peace and have-been enjoying the spirited 'tech discussions' about best-approach for DACs, etc... So 'back to the regularly scheduled program', here!...

    ciao
    j
    ....and armed only with his trusty 21 Zorgawatt KTiOPO4...

  8. #98
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    Regular? Scheduled? I don't know the meaning of the words.

    Quote Originally Posted by carmangary View Post
    What I don't like about current scanning is that you tell the scanner to go to point x0,y0 and then give it some time to get there then you tell it to go to point x1,y1, and then repeat this a gazillion times. If you look at what is going on inside the scanner amp, you see wicked accelation followed by wicked deceleration. It's basically like being at a stop light and going full throttle when the light turns green and then slamming on the brakes at the next light, then repeating.

    There is no method of telling the scanner amp that it has to go to point x0,y0 but don't slow down when you get there because the next step is still on the same path. But, with a smarter scanner you could do that and it could maintain (at least more closely) a constant velocity throughout the image. This would get rid of hot spots (bright dots) where there shouldn't be.
    I solved this for my rotating polygons exercises. But I have no idea how ILDA compatible it might be. I also used it to draw a clock hand that rotated round a central point at one end, so I know it will work for arbitrary frame point data.

    The method is to start with a fullscale value for either axis, say ±32767 to use all the 16 bit range available. I used integers. Calculate the next point, and distance to it from the current point (Pythagoras). To draw at constant rate, I interpolated a number of substeps whose count was line length divided by a constant step size. Each substep was one sample at a given fixed frequency.* That allows arbitrary change of direction while preventing a visible hotspot at the join of two draws that appeared as one straight line. Curves would be made by using a small number of straight segments, as in many CAD programs, but there is no need to specify a number of points in a long straight line as seems to be required in standard practise, because the interpolator takes care of this at output sample rate at all times. Dwell points were a simple addition of a fixed number of equal samples inserted, usually 9 of them for WideMoves, though the number would change to suit other galvos or output sample rates. As it's based on a constant draw rate, the dwell time can also be fixed, though should no doubt change if draw rate is also variable.

    That's as far as I got. I was contemplating an ILDA test frame but I got thoroughly dischuffed with WideMove inaccuracy for fine detail at this point, so I stopped work on it. Can't assess performance properly in those conditions. If I get some DT-40's I'll resume. One thing that I considered was a possible need to switch off the interpolator for any line that was to be blanked, but even better would be to change the step size in realtime, as this would also allow a nice (but limited) way to modify the apparent lineweight of the draw as well as giving me full control of draw speed up to the scan system maximum. As far as that maximum is concerned, this is where I delegate all responsibility to the scanner. I trust it to know how to damp and gain and do whatever it takes to do this as best possible. All I do is tune my output sample rate up till I get the best speed that doesn't cause inaccuracy to appear in corners, (or the ILDA circle/square, which I tested in pre-drawn waves, but not in my own code as I lost motivation to continue at that point, as I described).

    * Usually 30 KHz, as this sample rate fitted WideMove specs well in practise. Adjusting the draw rate to get the circle in the square in an ILDA test pattern would be done by adjusting the output devices' sample rate, which is why Layla 24 was nice, it can specify exact sample rates to 1 Hz increments.

    Doctor, I don't know why you are so opposed to that idea or why you think it adds so much complexity and cost. All of this type of technology already exists all around us and it isn't expensive or out of our reach. What I am talking about is the improvement that we saw when we went to radios and TVs with knobs for tuners to push button digital tuners. Everyone can still afford tvs and radios just fine and we don't have to twiddle knobs in order to get a decent signal anymore.
    Not against it, just sidestepped it, I think. Instead of trying to understand what ILDA files did, I just looked at the hardware, and worked out how I was going to make it draw arbitrary shapes as fast as accurately as possible with WideMoves and rotate them as they were drawn. Note! I did not use a frame at all because the 'frame' length and therefore rate would vary with the total length of lines to be drawn in whatever pattern was to be drawn. To rotate a pattern I calculated (trigonometry) the new location for a point and let the interpolator work as usual. This meant that the shape rotation appeared fluent instead of jerking round one small step with each complete trace of its outline. It also meant that the arbitrary 'frame' length wasn't an issue, as everything was governed by the prime requirement of a steady draw rate (or one whose rate was controlled to allow line weight modification. This whole method avoided the problems you've outlined, and further, allowed some limited line intensity modulation even for a fixed output TTL modulated laser, which is a nice extra that comes free with this design method, although it's better to modulate that directly if it has analog mod. What remains to be tested is whether this scheme has incompatibility with the current standard concept of frames and points. As far as I can tell, it probably doesn't. I can't work on this now though because it would be like trying to do chemistry with only a book. Haven't got things set up for it, I'd have to do more than I have means to do right now to fix that.
    Last edited by The_Doctor; 01-14-2009 at 15:08.

  9. #99
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    Quote Originally Posted by carmangary View Post
    I think everyone should have a lumia wheel in their arsenal. I remember going to a laser show way back when and thinking that was the coolest effect in the whole show.
    Man, that is so right on, I had to start this thread

    Thanks!

    -Mike


  10. #100
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    Gary, did you see that last post of mine? I took some time to get it right so I'm making sure it doesn't get lost.

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