Building in GMAX - texturing

Once again, I need to mention that there are usually a number of different ways to get to the same result when modelling with GMAX, and texturing is no different. However I will only show one method here. This method assumes we are both working towards the same result -- a photographically accurate model to represent an actual building or object at a real airport (or elsewhere.) If you are working towards something else (such as using generic, default or third-party textures) then it may not relate to your needs.

First up, we need a texture. As this is an introduction to modelling, I won't cover the intricacies of creating good textures, as this is covered in other tutorials on this site.

I will say, however, that the way I create my scenery relies more on finely crafted textures than finely crafted 3D models. In this tutorial we started building the model first, but I would never work that way in reality. For me, the first step is always to create the texture. So we are assuming here that we've already created the texture:)

And here it is:

This is the actual texture sheet which I'll use to texture my model,
but it has been saved here as a JPG image. If you wish to follow the
tutorial in GMAX, you may wish to save the image and convert it to
a BMP image for use in GMAX.

First, we'll talk about a couple of relevant points regarding this particular texture, and textures in general.

This texture is the top right corner of a texture which is included in my Real New Zealand Marlborough payware scenery, as this building is part of the scenery. The original texture size was 1024 x 512 pixels, and this one is 512 x 256 pixels. As part of a payware scenery, by the way, the texture is copyright, and is not available for use in any scenery. It is, however, available for use in this tutorial.

The Power of 2
No, not the title of a love song, but an important consideration when creating flightsim textures. Each dimension of our texture -- height and width -- needs to be a power of 2. For those who skipped that at school, or like me have forgotten most of what we learned all those years ago, this is a number progression which starts at one and each subsequent number is double the previous one. So our power of 2 numbers look like this:

2x2=4
2x2x2=8
2x2x2x2=16
2x2x2x2x2=32
2x2x2x2x2x2=64
2x2x2x2x2x2x2=128
2x2x2x2x2x2x2x2=256
2x2x2x2x2x2x2x2x2=512
2x2x2x2x2x2x2x2x2x2=1024
etc.

The dimensions of the texture we're using here is 512 and 256, which both appear on the list above. This is a requirement of flightsim textures! Although it is more a requirment of graphics rendering hardware in general than flightsim in particular.

So how do we determine the size of our texture, from all these choices? In reality, the smallest usable texture size in FS is 16 x 16 pixels, and the largest is 1024 x 1024. That still leaves a big range, though. As we are dealing with design, there is no objective answer. This is one of the joys of scenery design, figuring out these things for yourself! However I do have a few basic principles to determine the size of the texture I use.

First, you need to understand what I mean by a 'texture'. It is kind of obvious when we look at the texture shown at the top of this page -- it has a photo image of the front, back, each side and roof of the actual builiding we are modelling. Howeve the original texture -- of which this is a quarter of the area -- includes a number of different buildings. So our texture can include more than one object. This differs from most of the default textures included in the simulator -- in that each of these includes one image or one object, whether it is the side of a building, an iron roof, or a cloud.

So it may be more accurate to refer to the whole texture image -- shown above -- as a texture sheet, and each individual image as a texture. Our texture sheet can include any number of textures -- as many as would fit. So when we consider texture size, we need to consider two different things -- the size of the texture sheet, and the size of each texture within it.

I normally use texture sheets of 1024x1024, which gives me more flexibility. A large building may best be textured with an image which covers the entire width -- 1024 pixels -- of the texture sheet, or indeed it may be made up of multiple texture sheet widths. Microsoft recommend putting more textures into less texture sheets for better performance.

I said earlier that when I start a modelling project, I always begin with the texture, and don't start the modelling until the texture is finished. However this relates to the texture, rather than the texture sheet. The texture sheet may just include one building in the corner at first, and the rest won't be added till later, but the actual building texture is finished. As long as I leave the completed textures in the same place, and don't cover them up, they are 'finished' for that model.

I also said that in this particular scenery, the texture sheet was 1024 pixels wide by 512 pixels high. That's simply because the airport is so small that that's all the space I required. Note that I can mix and match texture sheet dimensions slightly -- they don't need to be square, but they do need to be powers of 2.

To begin with, it may be useful to start with a smaller texture sheet, working on the premise that while large equals flexible, small equals simple. Which is another reason why I have started here with a part of the original texture, 512 x 256 pixels.

So, we still haven't answered the big question -- how do we determine the size of each texture, which in this case represents each side of our building?

The simplest answer:
I like to use the smallest sized image, which still shows the detail that I wish to show in my model.

This will vary depending on the model. In this case, I want to read the big text, and see the logo, but I don't need to read the smaller text. I could have used a texture which allowed me to read the hand-written 'graffiti', but I chose not to.

Other considerations are whether the model will generally be viewed up close, and how 'important' it is to the finished airport. A building with a fuel pump attached, for instance, will be viewed very closely when refuelling, so the texture may be a lot bigger than a building at the rear of the airport, which you normally won't taxi up to.

Remember, larger textures use more flightsim resources, and reduce performance. Smaller textures perform better, but don't look as good. You need to find a good balance.

You'll know when your image becomes too small -- you will no longer be able to see the detail you want in your finished model. Shrinking images for textures is part science, part art, so be prepared to experiment and explore the options offered by your graphics software.


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