Using Photoshop's Dodge & Burn to Fake Ray-Tracing by gascooker

[BarbyW]

The aim of this document is to explain some of the methods you can employ to improve your gmax textures. It should help you make your buildings appear more realistic and get them to sit more comfortably with the original SC4 style and pallette.

Requirements and notes about this article

You will need a copy of photoshop 4.0 or greater and the ability to squint your eyes so the world appears blurry.

Although most of the concepts in this document are fairly obvious, there are few people making custom SC4 content who seem to be using them. Furthermore, it must be stated that this tutorial is design led and consequently any photoshop settings, decisions and values are subjective. This ain't science, this is art.

You should be familar with the following specific photoshop terms: tone; hue; neutrals; saturation; and highlights, shadows and midtones.

The world is a big fat tonal gradient

In real life, light bounces off an object onto other objects, changes colour and then gets reflected back onto your original object, absorbed, twisted and refracted and then eventually enters your eyes. The result is: what your brain knows to be the face of a pure white cube, is actually made up of a complex web of tonal gradients and colour casts.

In 3D computer modelling this can be simulated using ray tracing. This is an advanced method of determining light interaction, such as reflection and refraction and although may yield realistic results, is highly computationally intensive.

By understanding a few basic concepts of how light behaves you can side-step the need to use ray-tracing in gmax, thus saving you years of rendering time, but still get your textures looking more realistic.



The white cube on the left is a normal gmax rendering but the equally textureless cube on the right shows subtle tonal gradients and colour casts that would perhaps occur in real-life due to the mechanics of light. Other than black holes and supernovas, nothing much else in our universe is made of flat colour. In terms of SC4, none of your prominent textures should be tonally flat. They should all have some form of gradient tone.

Dodging, Burning and Sponging

There are three tools in photoshop which will allow you to do this: the dodge tool, the burn tool and the sponge tool. Think of them as brushes or live painting tool equivilents of the brightness-contrast, HSL and Levels sliders.

Here are the photoshop tone tools:



Using the dodge and burn tool is similar to painting with the airbrush or paintbrush tools. Select the Dodge tool. You will notice that a set of options for this tool appear on the toolbar.

Select the brush you want to use from the pulldown brush menu. You will nearly always need a very soft-edged brush,
with hardness set to zero. Tip: you can alter the size of your brush with the [ and ] keys dynamically while painting.

Depending on the texture you are working on, select the range you want the tool to effect, ie, if you want to make something dark, lighter, then select "shadows". The tool will then lighten all of the pixels it considers to be shadows. If you want to lighten the midtones or highlights, select these instead. You can see how it effects the tonal range in the image below.

The exposure setting will give you control over the tool. Choosing a low value such as 10-20% will effect the image less, each time you paint with it. A lower setting will mean you will have to dodge the image several times to get it how you want it. A high setting will likely bleach out the entire image to white in one stroke.

The airbrush mode button will make the brush act like an airbrush. (You should be experienced in using airbrushes if you want to
use this tool - I recommend you use the brush tool as its more precise)




The burn tool works in exactly the same way, except it will darken your image.



Making a gradient pitched roof texture

If you look closely at pitched roofs in real-life they are not tonally flat. If you look at the pitched roofs in SC4, they are not tonally flat. In real life light tends to be reflected more fom the higher points of the slope. However, depending on the material and its surroundings it sometimes can be reflected more from the lower points of the slope. The important lesson here is that it is not tonally flat.



To create a more realistic roof, open a flat roof texture such as the standard MAXIS rooftiles file: MaxisPitchedRoof.jpg. It has no tonal gradient.

Select the dodge tool and choose a large feathered brush. For the best results in SC4 always select highlights as the range as this will also desaturate the image and prevent any need for the use of the sponge. (This tonal-saturation effect will be discussed in greater detail in another document dealing with photoshop Levels and white-point capping)

Move the brush back and forth over the top of the image to lighten it. Then, select the burn tool, and with a large feathered brush move back and forth over the bottom of the image to darken it slightly as shown below.

Sometimes when the burn tool is used, the texture may become too saturated. If this occurs you will need to use the sponge tool to
correct this. It works in exactly the same way as the dodge and burn tools, except you must choose saturate or desaturate from the range menu.


feathering is photoshop term used to describe a the process of softening the edges of an image in the foreground so that it blends into the background image with less contrast. A feathered brush is a brush with a low hardness setting. Feathering a selection will soften or blur that selection.




When using these methods in texture creation, the size of the texture must be considered to prevent tiling overlaps in gmax. Therefore, it is likely that textues will need to be customized for each building you create. You will need to use the UVW map gizmo to line textures up, and ensure that tiling doesn't create a repeat of the light top bit, half way through your roof.



This roof texture has no gradient and resembles nothing like the
intentions of the original SC4 designers' style.

It is flat, harsh and unrealistic. Most of the user-created BATs appear like this.



This roof texture has a subtle gradient. Already the building is starting to resemble the SC4 pallette and style. Although it still requires a bit of adjustment, the gradient brings the building to life. Even the slightest tonal difference can make a huge impact.



This roof texture is in reverse, yet still fits into the SC4 pallette. It is darker at the top and lighter at the bottom, unlike most SC4 renderings. However, the principle of the gradient tone
is what achieves this, not neccessarily its direction. In fact light is so unpredictable that anything goes.

Using Gradient Masks to stop your walls looking like Supernovas


If you look closely at the walls of buildings, and in particular tall buildings, they are not tonally flat. If you look at the walls of buildings in SC4, they are also not tonally flat. Once again, In real life light tends to be reflected more fom the higher points of a building.
You can see this below:




We can use the dodge and burn tools to create a gradient tone and simulate ray tracing, however, in this instance a gradient mask
will also do the same trick and is better for larger scaled textures.

Create a new photoshop document of similar proportions to the wall onto which it will be applied or open an existing wall texture. As you can see the texture shown below produces a flat unsuitable render in gmax.



To remedy this we are going to create a gradient mask effect.

In photoshop, duplicate the texture onto a new layer, by using the pull-down sub menu at the side of the layers pallette. Then, select the layer so it is highlighted and press the "add new layer mask" button at the bottom.

The new white box linked to your new texture layer is where the gradient mask will live. It will partially hide or show the layer called "background copy", whose appearance we will shortly change. It works like a greyscale alpha channel. Anything drawn in white on this layer mask will reveal the layer, anything drawn in black will hide the layer, and anything in between black and white will show the linked layer as translucent.

The mask/layer icon indicates whether you are currently working on the layer mask or the actual texture. The screen shot below shows the mask is currently active. A paintbrush icon will appear when you are working on the actual layer artwork itself. To work on the mask select the mask thumbnail and to work on your actual texture click on the layer thumbnail.



Ensure you are working on the mask by selecting the mask thumbnail. Now make sure that the foreground and background colours are set to black and white and finally choose the gradient tool from the toolbar. Draw a line with the gradient tool from the bottom to the top of your image, like shown below.



The gradient mask is now complete and can be seen in the thumbnail but nothing has changed to the texture!
" I want my money back, its rubbish!", I hear you cry...

To see the effects, select the layer thumbnail to return to working on the actual artwork on the layer called "background copy".
Choose Brightness-Contrast from the IMAGE > ADJUSTMENTS sub menu. You can now make the whole layer darker and because of the mask, the image will grade from light to dark giving a gradient tone to your texture. How dark or light you make it is up to you, but subtle effects will work best as fake ray-tracing and coarser effects will make the texture look dirty.

If you drew your gradient the other way round then the top will get darker; remember black is masking, white is revealing.


The below image shows the improvement in the gmax render:
(no .acv colour correction or white-point capping has been used in this render - hence the yellowness!)



Posted by BarbyW for gascooker.

[WillG_75]

Good tutorial!