ILD file implementation specifications Q&A

[mixedgas]

Respectfully, Au Contraire,

Total information content is relevant. Ignore the time domain and think about the spatial domain for a second.

Steve

[Avi]

two or three points added at a hard stop or 90 degree turn in a image

since all points in a frame connect, all points are angles, not sure what a "hard stop" is.
so i need so compute the angle between every 3 non dwell points and duplicate the point n times where n=(angle/90)*3. (duplicate in colour, or in blank? i guess blank so you don't make a bright dot)

Anchor point: two or three points added at a hard stop or 90 degree turn in a image.

What was prohibited by convention is "pulling" points to pre-distort a image when transferring the data in a ILDA file. You send what the finished image should look like, not a image pre-compensated for the quirks of a given galvo pair. It is OK to add anchor, blanking, and guide points, and to optimize the spacing of points in a line or curve, but It is not OK to predistort an image to fit a given projector.

That sounds conflicting, even guide points really should be handled in software and/or hardware, since it has nothing to do with the design of the artwork itself, neither does anchor points.

[mixedgas]

It's not conflicting. Back then this was a artistic venture done mostly by hand. Adding a few points per the conventions used by hand was easy. Images were drawn, not computed. You could do a 3x3 or 9x9 matrix Around each point and see if there is a major angle change. No big deal. There are other techniques for looking for a change angle change using simple trig. Matrix is only one method, commonly used in raster graphics. This is a highly sophisticated artform, not a LCD monitor, there is a difference. I'm boarding my flight, I'll scan in the docs tomorrow. Steve

[Avi]

Since angles are made by separate X and Y galvos, and not a singular moving mirror, shouldn't the decision to add anchor points at corners be based on the speed of deceleration of X or Y rather than an angle?

[james]

Both of the galvos are locked together in time. So either one or the other will have to decelerate to a stop before ripping off in another direction.

The most severe angle you will find in 3D vector art is in 2D. All angles are 2D and it is 180 degrees. That would be a line that doubles back onto itself.

Yes. You look at three consecutive vertices to see the angle of the one in the middle. You don't need to use a matrix. Trigonometry will answer your question. Three vertices makes a simple 2D triangle in any plane.

You can choose to add lit or blank dwell points or a combination of both. There are settings for this too in LaserBoy. That's what lit dwell overhang is all about.

Also remember there is a huge difference in the outcome of optimizing 3D vs. 2D art. There are some reasons to optimize art in 3D but in most cases, you should flatten Z before you optimize the art for display on a 2D, X, Y system.

The real purpose of 3D art is to use it as a starting point to make animations of rotations. Those animations can be flattened before they are displayed.

James.

[JohnYayas]

Another reason not to get too caught up in optimizing frames too early is that as soon as you apply some effect to the frame, it becomes a new frame, with new points and angles. In many cases, when a frame is added to a laser show, it isn't even projected in its native format. It gets resized or warped and what was optimized when it was drawn is not optimized for the current incarnation. Another reason to represent frames with minimal points and let the computer do the work. Computers back then could not handle real time optimization but they can today.

[Avi]

it only... If i do that, at least in quickshow, nothing comes out on the physical projector how i intended, not even close, really. Looks fine on screen though.
That is why i am trying to work out whats the minimum things that are required to be in the file to get it to come out right, even to get 2 lines to come out correct would be good, then perhaps a square, and a dot.

[JohnYayas]

it only... If i do that, at least in quickshow, nothing comes out on the physical projector how i intended, not even close, really. Looks fine on screen though.
That is why i am trying to work out whats the minimum things that are required to be in the file to get it to come out right, even to get 2 lines to come out correct would be good, then perhaps a square, and a dot.

I didn't mean you should create ILDA files with minimal points and use them in other software. I was talking about if were to create some time of real time optimizer that consumed them.

[Avi]

I was talking about if were to create some time of real time optimizer that consumed them.

Oh, no, i am just making ILD files, i have no idea about USB stacks and what not to control a DAC.

[cfavreau]

Since Avi is talking about creating frames for use in QuickShow maybe someone with Pangolin/QuickShow experience should chime in on what are the best practices for that software.

BTW... this is a very good thread. It has a lot of great information in it.