A video screen can grab content from either a canvas or a thrower. When it is grabbing content from a canvas you have to manually set which part of the canvas the content will be grabbed from. On the other hand, when it is grabbing content from a thrower, the part of the content that will be grabbed, is determined by the relative position of both the thrower and the screen in the Visualizer.
So let’s describe both approaches in more detail.
How to grab content from a canvas
When you want a video screen to grab content from a canvas you should open its Source tab and select the canvas you want the content to be grabbed from.
If you open the Canvas setup window of that canvas by either double-clicking on the canvas or going to its View tab and checking Show setup window checkbox.
After you’ve selected this canvas in the Source tab of your video screen, you should see the video screen on the left hand side of the setup window.
In order to map it to the canvas, right-click on the screen on the left and select Place on canvas. You should see a red rectangle appearing on the right-hand side.
It represents the area the video screen will grab the content from.
You can freely move it around or scale it and you should see the content on the screen in the Visualizer change accordingly.
How to get content from a thrower
Using throwers in connection with video screens is useful when you have lots of screens with gaps in between. To illustrate how this is done, let’s insert 2 video screens in the Visualizer and 1 thrower. Finally, you should also insert 1 canvas.
Create a layer and set it up so that the entire canvas is filled with some content. I am going to import an image and use it in conjunction with an Image reader node.
Now select the thrower and in its Source tab, select our canvas as the source.
Open the Canvas setup window by either double-clicking on the canvas or, after selecting it, opening its View tab and checking Show setup window checkbox.
In that window, you should see your thrower on the left side. Right-click on it and select Place on canvas.
You should see a red rectangle appearing on the canvas on the right side. It represents the area the thrower will grab the content from. You can freely move it around or scale it and you should see the content on the thrower in the Visualizer change accordingly. You can close this window when you are done.
Go back to the Visualizer and in the Source tab of both of the screens select your thrower as the source.
Depending on their relative positions you should see a part of the content from the thrower appearing on the screens.
A word of explanation about the image above. As you can see both Screen 1 and Screen 2 get their content from the thrower. But as the surface of Screen 2 is not parallel to the thrower the pixels are stretched.