The new Keystone feature is a great addition to the Present3D stereoscopic toolbox. First of all, it makes it really simple to align a dual projector stereo system, but then it also allows the projectors to be setup off axis, so not center of screen, but off to one side, thus keeping all of the equipment and cabling out of the audience space. This is really great for mobile dual projector systems, or even fixed systems where the projector mount doesn't give fine grain adjustment.

Stacked Dual Projector Setup

Even though you are going to use the Keystone feature for alignment, you do still want to get the best physical alignment of your projectors to one another and positioned so they are just slightly overscanning the projection surface, as this will retain the greatest image resolution.

As mentioned above, you can choose to position the projectors off axis, this will increase the overscan required and thus reduce the final resolution of the projected image, however with decent projectors the effect isn't noticable and the flexibility of projector placement can make this feature indispensible. 


Using Keystone

To use the Keystone feature you need to add some additional options to your run Present3D  command, for stereo you will type the following

present3D myfile.p3d --keystone path/to/left.osgt --keystone path/to/right.osgt

Where path/to/ is replaced with the path to where you want the keystone .osgt files to be saved. 

Once your P3D show has loaded, you can bring up the alignment grid by using the ctrl  and g keys.

You should now see a red grid for one eye/screen and a green grid for the other.

To align the two grids, move your cursor to the bottom lhs corner, hold down the ctrl key and left mouse button and drag this corner till it aligns with the corner of your screen surface, you can now do the same with each of the corners for one eye/screen, then do the same with the other eye/screen, but this time align to the first screens grid, until you have a single yellow grid and both screens are aligned.

You can now use ctrl s to save alignment grid settings in the .osgt files and ctrl g again will hide the grids.


You can now continue with this P3D show, or use this alignment for other P3D shows by starting using the same command as above just changing the name of the show and the path to the left.osgt and right.osgt files as required, or you can use a setenv in your .tcshrc file and the this alignment will be applied to all P3D shows that you run.

When moving the system to a new location, you can remove the previous settings by using the ctrl r keys and align again as above.


Known issues :

a : You can't use with a .cfg config file, so if you have a .cfg specified in your .tcshrc you will need to comment out before using this feature.

b : Some click to run  / cursor issues



Set Environmental Variable in .tcshrc :

You can set an environmental variable in your .tcshrc file so that all P3D shows will load using the alignment set in the left.osgt and right.osgt files. Just add the following lines to your .tcshrc file.

setenv OSG_KEYSTONE_FILES  /path/to/left.osgt:/path/to/right.osgt.


Automator Script : 

To make it easier to start a P3D show you can create an Automator app that can be on your desktop and when clicked will fire off the commands required to start your show. We will cover that in How to: Use Automator to Start Shows.