# Screen Spanning with Projectors



## PatrickAngle (Nov 14, 2010)

I am the lighting designer for our school's production of 'White Christmas', and I am current trying to figure out how to set up two projectors to project images onto our stage's back wall. The biggest issue is how to trick our Mac into thinking that the two projectors are really one big screen, as Keynote does not support presenting across multiple screens. Our budget is low, so purchasing a device like Matrox's DualHead2Go is not an option, I'm instead looking for a software solution to solve the problem. Any help or advice would be appreciated!


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## skienblack (Nov 14, 2010)

I know we used Isadora to do something similar. I have little experience with it, but I know we drove 3 projectors and our display on a mac pro.


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## ruinexplorer (Nov 14, 2010)

The issue that you are dealing with is taking a single output and splitting it into two different images (that are later combined to create one image). Since you have a low budget, I expect that your projectors are also more in lines with boardroom projectors, am I correct? I think that the Matrox is probably the cheapest way to do this.

How do you plan on blending the images? Or are you planning on just butting up the images without a blend?


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## ssss2art (Nov 15, 2010)

I Agree that the cheapest way to do this is using a dual or Triple head to go box.
Perhaps you can rent one. My recommendation (based on your budget) would be to create a black stripe between the 2 screens so you dont have to try to align the two images. this could be done using a painted 1x2 or even gaffers tape. most people will just ignore the line.

Stewart


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## museav (Nov 15, 2010)

Does your Mac have multiple video outputs, not multiple connectors or formats but literally multiple outputs? If not then a software solution doesn't seem feasible without some additional hardware.

If the $210-$220 price of the Matrxo DualHead2Go device is too high to be considered then the $275 educational cost of Isadora or any similarly priced software is probably also out of the question. That also gets into the issue of what level of quality is desired or acceptable for the result, for example is a noticeable division between images or a brighter area where they overlap acceptable?


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## PatrickAngle (Nov 16, 2010)

Thanks for all the suggestions! I have solved our problem by writing some in-house software to do our effects, that can use multiple display, instead of just one.


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## metti (Nov 21, 2010)

PatrickAngle said:


> Thanks for all the suggestions! I have solved our problem by writing some in-house software to do our effects, that can use multiple display, instead of just one.


 
What exactly does your software do? Would you be interested in sharing it with others.


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## shiben (Nov 21, 2010)

> I Agree that the cheapest way to do this is using a dual or Triple head to go box.
> Perhaps you can rent one.



I jump in on this after the fact, but you might consider in the future using Qlab. Keynote is great, but its for making slideshows. Using Qlab, you can control up to 8 outputs (the practical limit of most computer tower's video slots anyhow), and you can rent it for 1 buck a day educational. So you can make all your slides and stuff, get the rental license, and then pay only however many days you need it, making it one of the most cost effective systems I have ever used. Having used Isadora, its probably not the best option for you, its a decent program, but for making whats basically a complicated slideshow, you want something like Qlab. Also, you can then do your sound effects, and if you need to, trigger your lighting console as well, reducing the number of operators involved.


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## PatrickAngle (Nov 28, 2010)

metti said:


> What exactly does your software do? Would you be interested in sharing it with others.


The software allows a Mac or Windows machine to run effect across multiple projectors. Currently it is capable of showing still pictures, movies, and some other basic effects that involve smaller objects moving with momentum. The software is very primitive in terms of interface, and currently requires effects to be created manually as text files. I do, however, hope to release the software to the community once I've written a decent effect creator. If there are any features anyone would like to see in the software, feel free to contact me in some way.


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