Help with Projection Mapping

[richie4k2k]

Hey guys. I'm going to do my first projection mapping on a festival and need some help. I read this article: https://resolume.com/manual/en/r5/projectionmapping

But I'm missing something. How do I calculate the size of the screen. Lets say I have just one screen with some areas where I dont want to project. The projector is full hd 1920x1080. How big should the screen I project to be? And how do I convert the distance from one point to another where I dont want to project in pixels, so I can make a good map for resolume?

Thanks for help

[pfelberg]

It is not the screen size that matters. Actually the screen size is your projection size, which is already fixed by default, meaning you are projecting over a fixed architecture, structure or object.
The key is to calculate the proper distance of the projector and its lens value, so the projected image fits at least the entire region of the parts you wish to project.
The closer you can fit the projected image boundaries around your projection surface target, the best image quality you will get concerning resolution.
The smaller the parts being projected and if they are too apart from each other, the loss will be bigger since you will get less pixels available to project on each part. In that case, another projector would be necessary.

So far so good?

[richie4k2k]

Well lets say I want to project on something like this http://www.derivative.ca/Events/2013/Pr ... Cubes4.jpg

I know how big it is in real life. But how do I model it in cinema 4d. In which proportion? Do I just take the picture in cinema 4d an do it roughly? And later with the lens of the projector I try to fit the correct spot? How can I calculate the distance of the projector before going to the gig, so I dont have to try out so much?

[pfelberg]

I know how big it is in real life. But how do I model it in cinema 4d. In which proportion? Do I just take the picture in cinema 4d an do it roughly? And later with the lens of the projector I try to fit the correct spot? How can I calculate the distance of the projector before going to the gig, so I dont have to try out so much?

There are a few things to consider if you want to proceed this way (there are others ; ))

First you need to visit the location, simulate the structure size and calculate possible projectors positions.
If you know what projector is going to be used, you probably know what are the lenses available, if it is exchangeable.
If you don't understand the math on lens type, distances and image sizes, I suggest http://www.projectorcentral.com/
They have online tools that will help you with that, using your own projector attributes.

Once you find out the best position to install your projector on location, it is important to take "that scene information" into Cinema 4D. You should position your camera and model your object according to the real world the best way possible. Your camera is your projector. Distances, angles and lenses should be the same.

I never did that way anyway. I find that to be too difficult, specially if the people responsible for the real model construction are not reliable, considering measures, scales and build up.

In your example I would consider at least two projectors, because of possible shadows, great side distortions and also some focus issues.
But if 3D simulation effects are not a must have, I'd proceed in an entirely different way. I would create 2 flat video content, one for each each cube side (I am ignoring the top faces at this time). Then I would create all slices for cube faces.