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Author Topic: Image Blending, Convergence?  (Read 6151 times)

Kellen Tyburski

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Image Blending, Convergence?
« on: March 27, 2011, 03:21:56 pm »

Hey all -

I'm interested in learning about blending images with multiple projectors or TV's... but having trouble finding info... I don't think I am using the right terms in my searches..

For example... The other day I saw 4 32" LCDTV's configured in a large square, but the image interacting between all of the screens (text bouncing from top to bottom, etc). What is this called, and any suggestions for learning how to do this?

Another example... 2 10x14 screens lined up next to eachother - with two projectors to cover the 28 ft across, but the image seems as though it is 1 10x28' image. What is this called?

Convergence, Image blending??
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Brad Weber

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Re: Image Blending, Convergence?
« Reply #1 on: March 28, 2011, 07:26:49 am »

The multiple flat panel concept seems to generally be referred to as tiling or arraying.  Some professional or commercial flat panels incorporate some integrated array functionality, in other cases this is accomplished using an external video processor.
 
The multiple projector approach noted seems to be referencing edge blending and again, some, typically higher end, projectors incorporate edge blending functionality but this is often handled via external processing and/or software.
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Gareth Marsh

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Re: Image Blending, Convergence?
« Reply #2 on: March 30, 2011, 02:02:43 am »

Hey all -

I'm interested in learning about blending images with multiple projectors or TV's... but having trouble finding info... I don't think I am using the right terms in my searches..

For example... The other day I saw 4 32" LCDTV's configured in a large square, but the image interacting between all of the screens (text bouncing from top to bottom, etc). What is this called, and any suggestions for learning how to do this?

Another example... 2 10x14 screens lined up next to eachother - with two projectors to cover the 28 ft across, but the image seems as though it is 1 10x28' image. What is this called?

Convergence, Image blending??

Blending, widescreen blending, etc refers to using multiple projectors to make up one large projected image.

This can, of course, be done horizontally or vertically, although horizontal is more usual.

Blending is sometimes done within the projectors themselves but usually it is done on the processing side of things, take a look at Vista Spyder for a hardware solution or Dataton Watchout for a computer based system. Both of these also do a heck of a lot more than blend though.

Projection blending is not that easy - there is a bit of calcualtion involved in getting the blend amount right and also working out your total pixel area - as you have the projectors overlapping it is not as simple as adding the resolution of the projectors together. The physical lineup can take quite a while too, not to mention tweaking the 'blend curve' which is the way that the projectors "fade" into each other. Getting colour and brightness matched up over the whole image to make it seamless is an artform, and when you put moving images or text across this it is even more important.

Then you get into things like curved blends, 3 dimensional surfaces, odd shapes, 360 degree screens.

Both the products mentioned above also handle plasma arrays, etc (you just dont turn the blending on). This is much easier to do, you just have to assign the panel location and size and map to media to it. It doesnt really have the same effect as a massive seamless image though.


Convergence, when referring to projection, usually refers to the alignment of the red, green and blue parts of the image in 3-chip projectors. You will notice that if you look at the image from some projectors closely that you can see, on a white line for instance, that there is a slight mis-alignment between the chips that causes one or more of the colours to be out of line with the others. This again is a very precise adjustment and not something to just jump into.



HTH


Gareth
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Kellen Tyburski

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Re: Image Blending, Convergence?
« Reply #3 on: April 06, 2011, 08:51:44 pm »

Thanks for the info guys, this helps a ton.

Your right, the plasma arrays dont have as much of an affect as the image blending on big screens, but I think it looks very cool for digital signage.

Reading your responses, I wonder how the "source image" is generated for one of these really long screens. On a computer, on a proprietary system? Some of these images I found of these screens look pretty complex...

For example...
http://www.youtube.com/watch?v=bNxU2LIUiUU&NR=1

the Powerpoint on both sides, with the IMAG in the middle..
very cool....Gareth, do you do this type of work?


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Gareth Marsh

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Re: Image Blending, Convergence?
« Reply #4 on: April 07, 2011, 03:00:53 am »

Thanks for the info guys, this helps a ton.

Your right, the plasma arrays dont have as much of an affect as the image blending on big screens, but I think it looks very cool for digital signage.

Reading your responses, I wonder how the "source image" is generated for one of these really long screens. On a computer, on a proprietary system? Some of these images I found of these screens look pretty complex...

For example...
http://www.youtube.com/watch?v=bNxU2LIUiUU&NR=1

the Powerpoint on both sides, with the IMAG in the middle..
very cool....Gareth, do you do this type of work?

The setup you refer to was done with Vista Spyder. There are several things going on here:

1. The moving widescreen background. This was probably created as a high res and very widescreen video file then run through something like Watchout, which then needs an input for each projector into the spyder system which then blends the outputs and sends them to the projectors.

2. The powerpoint will be a laptop put directly into Spyder, and then mapped to 2 windows on the next layer. You can create 2 windows from one input like this.

3. Then comes the imag, again into spyder, probably over SDI. This gets mapped to another window and mixed in and out as necessary.

As above, the media for widescreen is usually custom made to the exact pixel dimensions of the blended output. When you are trying to line up 2 or more projectors pixel for pixel you really don't want to be scaling the media that you are running across it - I've never done it but I imagine that moving graphics wouldn't match up across your blends if you could even line them up in the first place.

You can't use keystone or anything like that if you want to get your blends looking good (not that I use keystone normally).

I have done shows very similar to the video you linked, but usually incorporating a few more elements.


Gareth
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Brad Weber

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Re: Image Blending, Convergence?
« Reply #5 on: April 07, 2011, 07:36:41 am »

1. The moving widescreen background. This was probably created as a high res and very widescreen video file then run through something like Watchout, which then needs an input for each projector into the spyder system which then blends the outputs and sends them to the projectors.
Dataton WATCHOUT could handle all the display processing as well so if it was used it would likely be used for everything.  Both WATCHOUT and Vista Spyder are combination hardware and related software approaches that let you define display spaces and then video windows within those display space(s) to which you can assign various graphics files and sources, with varying levels of transitions, movement of windows, etc. allowed.  Both are also more expensive and complex than may be desired for simply edge blending a single image across multiple displays or for inserting multiple windows in a single image.
 
As far as scaling, I believe such systems are scaling, that is how they map pixel-to-pixel when addressing different resolution sources and varying resolution windows.
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Gareth Marsh

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Re: Image Blending, Convergence?
« Reply #6 on: April 08, 2011, 05:43:48 am »

Dataton WATCHOUT could handle all the display processing as well so if it was used it would likely be used for everything.  Both WATCHOUT and Vista Spyder are combination hardware and related software approaches that let you define display spaces and then video windows within those display space(s) to which you can assign various graphics files and sources, with varying levels of transitions, movement of windows, etc. allowed.  Both are also more expensive and complex than may be desired for simply edge blending a single image across multiple displays or for inserting multiple windows in a single image.
 
As far as scaling, I believe such systems are scaling, that is how they map pixel-to-pixel when addressing different resolution sources and varying resolution windows.


You could indeed do all of this in Watchout. The limitation being that it has to be put into a timeline whereas Spyder can be cue based. I think Watchout also has a greater latency for things like Imag, although this is probably related to capture hardware to some extent.

I am used to creating the main backgound media to the resolution of the entire blended image, akin to designing standard presentiations in the resolution that they will be shown at. With windows you will no doubt be scaling them to make them the size you want them to be.

Another versatile piece of software is ProPresenter. With the right hardware it is quite powerful, although ultimately limited to 3 outputs. The configurable stage display is also a nice feature. The blending is nowhere near as good as either of the other 2 though.
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Brad Weber

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Re: Image Blending, Convergence?
« Reply #7 on: April 08, 2011, 08:31:01 am »

Another versatile piece of software is ProPresenter. With the right hardware it is quite powerful, although ultimately limited to 3 outputs. The configurable stage display is also a nice feature. The blending is nowhere near as good as either of the other 2 though.
QLab and Isadora are other software based options that seem to work for many less complicated applications.
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