Splitting the project in 3 parts along the curvey

[Stribor45]

I would like to split my canvas in 3 parts along the curve just like in the picture attached. Can someone point me for good tutorial how to do that please.

Thanks

[c.pfaffenbichler]

I would recommend using Groups and Vector Masks.

[Stribor45]

How do you make that curve and then copy it to make white curve area?

[c.pfaffenbichler]

Use the Pen Tool to create an appropriate Path.

To duplicate a Vector Mask to another Layer/Group alt-drag it in the Layers Panel.

[JJMack]

I would highly agree with using vector mask for you will be able to resize you layer document well when vectors are used like Text and shapes layers.

The Pen tool take some time to use well but can be very precise and edited.  In fact  to use the Pen tool well you will have to edit  the pen point you create.  Even when you have mastered the pen tool it takes time to use the pen tool to create a good path tracing an object.  Often you can save some time by letting Photoshop Create the path and edit Photoshop Path to make it better.  The Quick selection tool can often be used to quickly select the object to be traced and that selection Photoshop can quickly to a Path you can edit. 

[JJMack]

An other way to look at your project is layers. An Image file canvas can not be actually be split they are a single rectangular area. You should build you project composite using Photoshop layer. You can use Layer groups to compose your composite image in your three sections.