Photoshop in Blender, Part 3: Creating an Alpha Mask

In the previous tutorial, Part 2, we saw how the alpha mask of the scene was used so it could work as the foreground image in the AlphaOver node, to combine a foreground with a background. In this tutorial, I will show you how to use The Gimp to create an alpha mask for my locomotive JPEG image, which does not have an alpha channel. In a future tutorial, I will show you how to create an alpha mask in Blender.
The first step is to separate the locomotive from its background, using the various selection tools the Gimp (and Photoshop as well) offer. The Gimp has 7 different selection tools - it’s a time consuming and detail oriented process - and of course the more detailed the selection the better the result. I don’t own Photoshop. I suspect there may be even more selection tools in it. Regardless, the process is the same.

Photoshop in Blender, Part 2: Transparency

In Part 1 of the Photoshop in Blender tutorial series, I introduced you to Blender’s compositor node setup. In this tutorial, we are going to combine an image that I took with my digital camera - an antique Vermont Railway locomotive, displayed at the White River Junction, Vermont, railroad station - with Suzanne in front of it. You’re looking at the final result. We’ll discover how transparency works in Blender, and why understanding and controlling image transparency, and the concept of the alpha channel, which is crucial in combining images in the compositor.
We’ll also pretend that we are creating this image for HD TV. In this case, the resolution of the image I took was 2592 x 1944 pixels.

Actually, when video is edited, it’s basically a sequence of images. Each image is called a frame. So we’re just editing one video frame. In later tutorials, I’ll show you how to edit videos with full motion, but that’s getting ahead of our story. In this tutorial, I will introduce a number of composite nodes, the viewer node, the Mix node, the Alpha Over node, and the Scale node, to accomplish the job. I hope you will become more comfortable with using Blender’s composite nodes after watching this tutorial.

Photoshop in Blender

This is the first in a series of I don’t know how many tutorials on how to do 2D image editing with Blender, more specifically with Blender’s composite node system. I’m using Version 2.63, although in general these tutorials should work with any version of Blender, from 2.6 on, and probably with recent 2.5 builds as well. I say “perhaps” because I haven’t tested this tutorial in any version except 2.63. What will be fun about these is that we are going to totally ignore the 3D characteristics of Blender. We’re going to use Blender as if it were Photoshop or The Gimp, as an image editor. I happen to use The Gimp, but I titled the tutorials Photoshop in Blender because more people, for whatever reason, use Photoshop. After watching these videos, you can then evaluate what part of your image editing workflow actually needs to be in Photoshop or The Gimp, and how much can actually be done in Blender.

In Part 1, we will set up the environment and do some simple image processing.