Building and Using Nebulae: (Photoshop)
Now that we have built the geometry and prepared the surface attributes for our nebula, we must get on with the really important part of the nebula and paint the image map.
One quick note about painting nebulae (and any other organic or freeform textures for that matter). The one tool that will make this task a thousand times quicker and easier is a pressure sensitive graphics tablet. It doesn't matter what size, all that matters is the pressure sensitivity and the ability to make more natural 'brush strokes'. Don't let size put you off, the little A6 Wacom Graphire tablets are absolutely superb and cost a fraction of the price of the bigger tablets. If you have some spare cash and are looking to get into some texturing, get a tablet.
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Open Photoshop, or whatever image editing package you prefer and make a new image whose size conforms to the aspect ratio required, which we worked out earlier.
My required aspect ratio was roughly 5:1 so I am going to create an image of 3000 x 600 pixels. An image of this size is quite a strain on the system, so you may want to create a smaller image of say, 1500 x 300 pixels. Much smaller than this, however, and the image will look rather flat and without detail when you render it out as a nebula.
If it isn't already, clear the background to black. To do this, press Ctrl+a to select the entire canvas, next, set the background colour to be black so that your toolbar looks like this:
Finally, press Delete on your keyboard to clear the background to black.
|photoshop screen ready for painting|
Hopefully, you will now have your canvas ready to paint your nebula.
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The first thing we will do is to put down some very basic colours to use as the basis for our nebula.
We will make use of Photoshop's layers to keep our colours separate from the background, which will make later operations much simpler.
Create a new layer by pressing Ctrl+Shift_n. Call this new layer Colours 1.
|creating a new layer|
Pick a basic colour for your nebula. I will be painting a blue nebula here, so I am going to use 5,13,92 (RGB) as my first colour. I always paint nebulae in very vivid colours, because it is easy to remove saturation and brightness from an image at a later stage, but it is much more tricky to add saturation and brightness to an image.
Next, create a large, soft-edged brush by clicking on a blank area in the brushes palette. Use settings similar to those in the image below.
|new brush settings|
We are now ready to get painting.
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Select the brush or airbrush tool and put down some basic shapes. It is very important that you leave a decent sized black border around whatever you paint here, or horrible things will happen when we try to use this image as a nebula in Lightwave.
Try not to be confined to the rectangular shape of the canvas, paint some thin bits, wiggly bits and jagged bits.
NB: This is the part where a tablet comes into its own, as you can set the size and opacity of the brush to be affected by the pressure of the strokes you make.
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When you are happy with what you have painted here, try applying a few filters. The most useful of these at this point is the Gaussian Blur. I applied a Gaussian blur with a radius of 25 pixels, and I also applied a small 'Twirl' filter from the Distort group of filters.
|blurred and twirled|
There are no hard and fast rules for what you can and can't do here. Just experiment and see what looks good. At this point though, try to avoid filters that add small details to the image.
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Now create another new layer (Ctrl+Shift+n) and call it Colours 2.
|another new layer|
Pick a slightly smaller brush than you used before and lower the opacity of the brush strokes if you are not using a tablet. Also, pick a slightly lighter shade of the colour that you were using before. In my case, this colour will be 31,40,136.
Now put some paint down over some of the areas where the first layer could do with some more excitement.
This is the contents of my 'Colours 2' layer on its own (Colours 1 is swiched off so you can see Colours 2 by itself).
|contents of layer: Colours 2|
And switching Colours 1 back on again, this is the image so far.
|the nebula so far|
Is your nebula taking shape yet? If you think that some of the brush strokes in your nebula are too sharp or obvious, just use the blur tool or apply a few filters until you like what you've got.
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Create a third new layer, called Colours 3 and choose a lighter colour. I chose to paint with 90,93,127 and 179,183,223 and this is what I came up with.
|contents of layer: Colours 2|
With the other layers turned on, this is the image as it stands.
|contents of layer: Colours 2|
I think that this the new parts of the image look a little too blobby and are over-bright, so I'm going to work a little detail into Colours 3.
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The first thing I'm going to do is sort out the over-brightness. I think that the image needs some more build-up in the blue before we start putting almost white areas in... so here's a cool trick.
In the Layers pallets, change the compositing option for Colours 3 to Colour Dodge rather than Normal.
You will see that this changes the way that the colours in Colours 3 are added to the layers below. My nebula now looks like this:
|layer: colours 3 changed to colour dodge mode|
I like that a lot more, but the blobiness is still quite obvious, so let's deal with that now.
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Temporarily turn the compositing option for Colours 3 back to Normal so that you can see it more clearly.
Using the Smudge tool you can now push and pull areas of colour around until the blobs have more random, streaky edges. Do this as much as you like, but try to respect the shapes defined by the colours in the lower layers.
This is what my Colours 3 now looks like.
|layer: colours 3 after smudging|
I then applied a small Gaussian Blur to the layer and set it back to Colour Dodge mode.
|layer: colours 3 after smudging|
Okay, now we have some much more vivid areas of colour, I think it's safe to add some more light areas to the nebula.
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Now you can start to add more and more detail to the nebula image, each time creating a new layer to work on, so that we can easily edit the image later.
For the purposes of this tutorial, I only painted two more layers, one with a very light blue colour, and the other with an almost white-blue.
|two more colour layers added|
Note that as your colours get lighter, you must add more small details to the shapes to avoid 'blobiness'. After I had applied my layers, I applied a Gaussian Blur to them to kill any sharp edges.
You can continue adding layers until you are happy...
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Once you have finished adding colour layers, you could leave your nebula as it is, but I wanted my nebula to have a cloudy, volumetric look to it, rather than just being areas of flat colour.
We can add get this effect very quickly using a few Photoshop tricks.
Create a new layer above all of your other layers and name it Texture 1.
Choose the Paint Bucket (fill) tool and fill the layer with any colour (it does not matter what colour).
Now set the background colour to be black and the foreground colour to white.
From the Filters menu, select Render \ Difference clouds. This will fill your layer with a fractal noise pattern with colours graduating from black to white.
|difference clouds applied to layer: Texture 1|
As you can see, this filter completely covers our nebula image... which is no good at all. What we really want this image to do is lightend and darken the layers below... applying the texture to our colour layers.
The way to do this is to change the compositing mode for Texture 1 to Overlay.
compositing mode changed
This change makes applies the fractal texture to all the colour layers below...
|texture applied to colour layers|
The effect is rather pleasing, but not really enough.
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We can add more texture detail to our nebula by adding more layers, applying difference clouds or clouds to each of these, and setting their compositing mode to Overlay.
For some interesting variations, I applied a few filters to each of my texture layers, such as Twirl and Wave.
This image has three layers of clouds, the second has a slight Twirl filter and the third has a slight Wave applied.
You can very quickly add detail using this method.
When you render out your nebula later, you may find that your nebula just isn't detailed enough, or if you find that the texture created by the 'clouds' from Photoshop is not quite to your taste, don't forget that you have at your disposal an almighty texturing tool: Lightwave!
When I decided that I wanted a little more detail in my nebula, I rendered a 3000x600 pixel image of some Lightwave procedural textures mapped onto a large polygon, (a mixture of Lightwave  'Puffy Clouds' and 'Fbm' noise) to give me a nice texture that I applied to my nebula image in Photoshop in the same way as I had used the 'clouds' filter.
|a small section from my Lightwave-generated texture for the nebula|
This gives you more control than the 'clouds' filters in Photoshop.
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You should save your nebula now. Lightwave can read Photoshop .psd files, so you have the advantage of being able to retain the layers information for a later date.
I'm going to extend the tutorial slightly here, because we can easily create a different coloured nebula using the blue one we have here. The pinky/red nebula at the head of this page started life as a blue nebula much like the one we have painted in this tutorial.
|the blue nebula that gave rise to the pink one at the top of the page.|
After some quick modifications, this blue nebula became this pink/red version:
|blue nebula after some colour modifications|
The process to change the colours in the nebula invloves simply playing with some sliders in Photoshop's colour correction controls.
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Let's begin with the bottom layer, Colours 1. Select this layer by clicking on it in the layers pallete.
select layer: Colours 1
With the layer now selected, press Ctrl+u to access the Adjust Hue/Saturation controls.
I shifted the Hue of my Colours 1 layer by +124 to shift it towards red, and decreased the brightness a little, which resulted in Colours 1 looking like this:
|contents of layer: Colours 1 before colour adjustment|
|contents of layer: Colours 1 after Hue adjustment|
Now click on each of your other Colour layers in turn and shift their hue values until you have something that you like.
After some quick tweaking with the Hue/Saturation and Colour Balance controls, my previously blue nebula has rapidly evolved into this new orange version.
If you have created a new nebula as I have, save your image now (with a different name from the blue one, obviously).
Here are a couple of nebulae painted by other people using this technique in the period while I was writing these tutorials. Both were painted in Photoshop without the use of a tablet.
This nebula was painted by Matt Tarling
|nebula by Matt 'Drakh' Tarling|
And this one was painted by Craig A Clark
|nebula by Craig A Clark|
|© 2000 Kier Darby and Alternate Perspective 3D Ltd.|