Texturing with GIMP: welding seams

[thorst]

Hello,

from time to time I work a bit on a tutorial on how to color/recolor models in
GIMP. In the last hours I started texturing a small tank model and did welding
seams, I think I found a nice easy and fast method which is described in the
following. Please tell me what you think; if it's useful or if I should include
more pictures and so on for the booklet.

Now let's start!

Setup begins with a black&white outline. Above this, a new layer in grey is
created and layer mode is set to "multiply", so the lines will shine through.
Above, another two layers (transparent, with layer mode "value") are
created. The one below will contain the shadows, the one at the top the
highlights.


The first step is to paint some stripes perpendicular to the seam.
Therefore, take the airbrush-tool with a smooth brush shape, set size to
5px and choose black as color. Select the "Shadow" layer and paint the
stripes.


Don't take care too much on regularity! Afterwards, decide where the light
comes from. In the example, it comes from top-right. So draw an irregular
line on the other side of the seam as well as about 1/4 of the seamwidth
from the side towards the light.

(the outline layer is set to invisible now for clarity).

Now select the "Highlight" layer and pick white color. Use the same brush
to paint on irregular lines now on the side of the seam towards the light
source as well as 1/4th of the seamwidth away from the shadow side.


That's all!

With the setup as described here, you only have to substitute the grey
layer with one containing the camouflage sheme, the layer mode "value" of
the shadow/highlight layers will then add the impression of three-
dimensionality of the seam to the color behind.
If the seam looks to hard, just set the opacity of the layers to a smaller
value.
Try it, it works pretty well!

Of course, I couldn't describe all basics in this short post, but it will all be
covered in the tutorial, when it's finally finished.

I hope to hear some criticism so I can include more helpful information in
the future!

Best regards,
Thorsten

[richkat]

Thank you VERY much for this thread Thorsten, I know GIMP can do a lot but I don't have a clue how. I want to learn how to do this........Rich

[gillman]

Thorst, this was a good tutorial for the task. If you're doing alot of the lines for the welds for this project or others, you might want to create your own brush for the task. There are a number of YouTube tutorials about creating brushes that can change direction automatically when you're going around a curve.

Richkat, GIMP is great, but it has a steep learning curve (again, lots of pretty good tutorials on YouTube). I've been using it as a hobbyist for 7 or 8 years and I'm nowhere close to being able to use all the tools available. But I will say it's a great tool for Paper Models, especially once you get comfortable with the layers Thorst mentioned. Being able to work on individual parts of a project (camo paint, seam lines, glass areas, etc.) without overwriting other elements will make life alot easier.

[thorst]

gillman, thanks, I will look into the brush creation task! However I did it
the hard way and finished the shading for the parts. To illustrate the
advantage of layers, here is the part in two different color shemes.

Red:

and a three-tone camo (not finished):
The only thing which had to be edited was the color layer(s), in fact,
every color has got a seperate layer, so that contrast adjustments can be
done very easily. To improve the highlights, the layer mode was changed
to "hard light" on this layer.

Now the same can be done with weathering effects.

And to show another nice possibility of what can be done (and how crazy I am ;-) ):

Here, I mapped photos of the real vehicle all around the development of
the part, and set the layer style to "multiply", so I can trace the real color
sheme for authenticity

Thorsten

[whulsey]

Thanks, I use GIMP but primarily for editing photos. Need to really start looking at more of its capability.

[Art Deco]

Thorsten, it's great that you are learning a powerful graphics tool, you are already achieving some very nice results!

Does GIMP have "layer styles" like Photoshop does? In Photoshop, when I want to do something like this, I use the "Emboss" layer style. That automatically creates the highlights and shadows. Much less work!

To take Gillman's excellent advice about custom brush tips, you could create a brush with an oval tip that varies the tip size as it moves. This will create lines with uneven widths.

To make the seam appear "lumpy", set the brush to slightly vary the lightness/darkness as it moves. Then adjust the "spacing" so the brush creates overlapping "blobs" of color. (Note: I use Photoshop, I hope GIMP has these same controls.) You can make it more irregular by setting the roundness of the brush tip to vary, or adding some "scatter" so the blobs are a bit out of line.

Using a brush tip like that with the GIMP-equivalent of "Emboss layer style", you could make a realistic welding seam with a single brush stroke along the seam path.

I'm attaching a graphic to show what I described above. Each of those "weld seams" is a single brush stoke. I changed some of the settings for each stroke to give an idea of the possibilities. I repeated the last stroke without color or embossing to show what the brush is actually painting.

That brush tip took only a few minutes to design, custom brush tips are really worth the time to learn!

Keep up the great graphics work!

[thorst]

Art Deco,

thanks for the reply!

Yes, gimp has layer styles, they are called "modes" here. But the emboss-style is not included, at least in my version. But it seems that it is nothing different than the combined "Hard light" and "value" (or "multiply" for bw-layers) mode.

But I have a question: If i draw the seams by hand, I can adjust the direction from where the light is coming as I go around and on other parts. Can this be automated with such a brush?

Best regards,
Thorsten

[Art Deco]

Originally Posted by thorst

If i draw the seams by hand, I can adjust the direction from where the light is coming as I go around and on other parts. Can this be automated with such a brush?

Thorsten, I use Photoshop CS2 version 9, which is several versions out of date, so I cannot answer this question with certainty for the latest release of Photoshop, much less GIMP (which I know nothing about).

However, the principles are probably the same. In Photoshop ver 9, if you are using an Emboss layer style to make things 3D, the light can only come from one angle for everything on that layer. For multiple light angles, you would need to separate the weld seams into multiple layers (which you could keep together in a single folder). That should still be vastly easier than hand-drawing shadows.

Besides, keeping the 3D effect separate from the brushwork gives you the advantage of being able to easily change it later.

Imagine that you later decide that all the weld seams look a little too tall, or that the weld seam shadows need to be darker to show up better on an alternate camo style. If you can adjust that through a "mode" or some other independent effect, that might be an easy change to make. If the 3D effect is part of the brushwork itself, you might have to re-do all the brushwork to make that change. It's the same thinking as this:

every color has got a seperate layer, so that contrast adjustments can be done very easily.

Yeah! That's the beauty of layers, they let you keep graphical elements isolated from each other, allowing you to build up highly complex images or textures while still retaining control over the individual elements.

[thorst]

Originally Posted by Art Deco

Besides, keeping the 3D effect separate from the brushwork gives you the advantage of being able to easily change it later.

Imagine that you later decide that all the weld seams look a little too tall, or that the weld seam shadows need to be darker to show up better on an alternate camo style. If you can adjust that through a "mode" or some other independent effect, that might be an easy change to make. If the 3D effect is part of the brushwork itself, you might have to re-do all the brushwork to make that change.

Yes, that's why I also have the shadows and highlights in a separate layer. It doesn't cost any extra work to keep everything on it's own layer, but it can save sooo much time if one realizes that one should change the weights.

Thorsten