Hello everyone, I am quite new to Touchdesigner and I haven’t gone beyond running 2 Projectors on my laptop with very basic projects, so I am not quite sure what to expect, so please bear with me.
I’d like to use Touchdesigner to run projection-mapping in a room with about 6 Projectors, maybe even more in the future. At the moment, the projectors are whatever was lying around, so there is lots of different aspect ratios and resolutions. Most of them are 1080p or similar, but one is a more modern 4k model.
Do I need to run them all from a single computer, or is it possible to keep them all in sync with multiple computers running them?
If I end up using a single computer, I will probably need to buy multiple graphics cards, since each of the ones I know supports only 4 monitors max.
My Budget is about 1000 Euros, but I already have the Projectors and a bunch of old gaming hardware.
My questions are:
- Is CPU performance a concern, or can I get away with ~8 year old gaming hardware?
- Can I just use any old gaming GPUs, i.e. an Nvidia 1080 or do I need Quadro Cards?
- Can both cards be used for computation, or is one card just used for extra outputs?
- Do I need to use Crossfire / SLI ?
- Nvidia Quadro P6000, the latest Quadro Card, [has been released 10 years ago, the documentation mentions only Quadro and AMD with Crossfire]( Using Multiple Graphic Cards - Derivative ), can newer Nvidia Cards be used as well to drive more than 4 Displays, if so do I need to buy enterprise cards, or do gaming cards work as well?
One Quadro P6000 goes for about 250€ on eBay, is buying two of them a (and an old SLI bridge) reasonable idea?
Some answers:
Is CPU performance a concern, or can I get away with ~8 year old gaming hardware?
Hard to answer as this depends on what you’re going to build in TD. If that is yet unknown, I would recommend to just start with what you have, and upgrade CPU once you notice the load you put on it is heavier than what your cpu can deliver.
Can I just use any old gaming GPUs, i.e. an Nvidia 1080 or do I need Quadro Cards?
You don’t need quadro’s for home use.
Can both cards be used for computation, or is one card just used for extra outputs?
Do I need to use Crossfire / SLI ?
This is all answered on the page you linked to.
Nvidia Quadro P6000, the latest Quadro Card, [has been released 10 years ago, the documentation mentions only Quadro and AMD with Crossfire]( Using Multiple Graphic Cards - Derivative ), can newer Nvidia Cards be used as well to drive more than 4 Displays, if so do I need to buy enterprise cards, or do gaming cards work as well
Nvidia retired the Quadro brandname several years ago. These days the Quadro cards are called RTX Pro. And yes you can use any modern card to drive multiple outputs.
A cheap option for more outputs is buying a splitter such as Matrox Triplehead. It takes one input which is for instance (3 x 1920×1080) resolution and it has 3 separate 1920×1080 outputs. Combine that with a single geforce1080 card (if you already have that laying around, otherwise perhaps shop for second hand faster geforce) and you are already good to go for your first experiments. Then you can upgrade videocard to faster model once you notice your GPU needs are higher. (again, same as with CPU, your GPU needs fully depends on what you will write in TD).
Hope this helps you on your way with your experiments, have fun!
Thanks a lot for your reply 
While the documentation contains answers to most of my questions, it is a bit vague and I wanted to hear what the community recommends before I go and spend a lot of money on 10 year old hardware.
The setup I wanna build is semi-professional. We don’t have a lot of money unfortunately, but a lot of old projectors and a lot of crooked white walls that are perfect for projection mapping.
I guess the performance question is a bit of a chicken and egg problem, when programming yields a laggy setup, then I will probably have gone too far for the hardware I have. I hope that we can buy a proper fast PC in the future, but with how the hardware market is looking right now we will probably have to wait.
The Matrox splitter is a nice recommendation, but does that work with projectors that all have different resolutions?
Also it is 250 Euros where I live, which is about the same as another Graphics Card, but without actually adding any compute. Then again, it is probably easier to upgrade one Graphics Card and it simplifies the wiring.
What I couldn’t understand from the docs was if linking Quadro cards using SLI would yield more performance, or are the other cards just used as additional outputs?
Note that linking multiple cards to act as one does not provide extra compute. See this paragraph from that page:
Although multiple GPUs are used in this mode, the extra GPUs do not add performance to the system. In fact, using this mode will actually result in worse performance than an identical output canvas on a single GPU. This is because a every GPU is duplicating the work, and simply showing the sub-portion of the final output they need from their outputs. The cost of synchronizing this duplicated work is extra cost that a single GPU configuration doesn’t have. It is however useful in some situations where you need more pixels than is possible to output from a single GPU, but don’t want to deal with multi-GPU/multi-process sync issues.
If the number of pixels you want to output can be done with the 4-6 outputs your single GPU has, then a splitter such as a DataPath splitter can be used with a single GPU instead of multiple GPUs. This will perform better than using multiple GPUs
So a splitter will be more performant than 2 GPU’s linked as one.
Another (more complicated) option is to stick 2 GPU’s in the machine and start 2 TD processes, and bind each process to its own GPU (GPU Affinity, see same page). This will require setting up syncing of all CHOP/TOP/POP etc signals between the two processes and so it will take more development work to setup and be synced.