Aggggh!
My head is about to explode from trying to follow videos!
I have a pdf tut on texturing but it does not show how to get to the material lab.
I've even tried to find out how in the user manual but still no go.
I want to do projection painting but it is not easy for my poor brain to grasp things in a video...sigh.
I totally understand. I tend to prefer something written I can scan for the information I want rather than a video I have to pause and rewind.
So, IMHO, materials have a lot of confusing legacy in Blender. I'm not sure what you mean by the "material lab," because there are two places you can go to mess with materials and at least two you can go to mess with textures. For me, the easiest way to deal with both materials and textures is to work with nodes. To do that, just select the item you want to work with, go to a window you don't need or make one, and choose "Node Editor" out of the pull-down list that defines the type of window you have open. You know, the one that lets you choose "3D View" or "Timeline".
Projection painting is actually a whole separate beast, because it's about _texture_ editing, not materials. They're connected, obviously, but separate.
Unfortunately, I'd say this is where a video will be invaluable, because it will show you all the places to click and the settings to choose. That said, every video I've come across gets into details that just aren't that helpful. So let me see if I can list what I think are the relevant points.
- Set up your interface. You'll want at least one UV/Image Editor window for the various textures you're working on. I find I often need a second for references. You'll obviously need a 3D View and a Properties window, with the Properties window generally being on Texture (the checker board) and set to either Brush or Brush Mask. Brush will give you the ability to give your brush a texture, which is what you want for projection painting. You probably want a Node Editor window, too. That way you can set up your materials, and do what you want with your textures.
- Either make a new image or load the image you want to edit in your main UV/Image Editor window. Either way, make sure to "Save As Image" before you get started, and to "Save Image" as you go along. There's a button in the Tool Panel of the 3D view that will save all your textures, but I find I never want to do that automatically. It might just be because I'm clumsy, though. I find that I need to check each image and make sure I haven't accidentally painted somewhere I didn't mean to. You know, like accidentally catching the shoulder when painting the head, accidentally catching the nails when painting the hand, etc. So I would rather go through and save by hand. That said, I've lost work that way.
- Select your object and if you haven't already, set up your materials. Add your images where they should be. For instance, if you just want to work on diffuse and bump, just make a plain Diffuse node (Principled nodes are more useful, but have _many_ more options), stick your diffuse color into the color slot, make a bump node, stick your bump texture into the Height input of the bump node, and the bump node into the normal of the Diffuse node, and the Diffuse node into the Surface input of the Material Output node. Set up all the material zones you want to paint across.
- With your object selected, in the 3D View, go into Texture Paint mode. Make sure you have the Tool panel open (press T to toggle it). If it's not already, select "Draw". Make sure your color is white. Scroll down to "Texture" and expand it. If projection source isn't loaded already, click "New" and give your new texture a name. Then go over to the Properties window (this is the bit I find annoying), switch to Texture, and select Brush from the top pull down menu, then select your new texture from the menu beneath that. Scroll down the Properties window until you come to Image, where you'll find a Pull down, a "New" button, and an "Open" button. IMHO, this is an annoying and unnecessary level of abstraction, but your texture can have whatever source you want to give it. Use Open to load the image you want to project from your hard drive.
- Back in the Tool panel, under Texture, you should now see your image. Pull down the Brush Mapping menu which probably says View Plane and change it to Stencil. If you put your mouse on the 3D View, you'll be able to see a transparent version of the projection image. I find I often need to click "Image Aspect" to give it the right proportions.
- Just to make sure, in the Tool panel, check out the second tab Slots. That's where you can see what image you're painting in. Don't worry about which material is selected, because it will just figure that out. Just make sure you're painting on the right image. Also, look at the the third tab, Options. Specifically the Project Paint settings. Make sure you've got a good sized bleed (4px or more- I use 8px). That's also where you set the angle to which you can paint, so change it if you find you're painting too much or too little on the faces that curve away from you.
That's the important stuff. I realize it sounds like a lot, but a lot of that is kind like describing how to copy and paste from one document to another- detail that's pretty intuitive after you've done it a couple of times. To control the projection paint image, you can use
short cuts that are in the documentation. Documentation I definitely recommend for when it's just not clear how something works. I'd still suggest looking at videos. I can suggest one if you'd like, but my experience has been that the right video depended on what I found confusing and what I was trying to do.