Stars%20Tutorial.pdf

Making a Star World in Blender

Blender’s star world feature produces some pretty corny results

when it comes to animations. Even in a simple panning shot, the stars

don’t look right, because they move past the camera at different rates of

speed. This tutorial, which assumes that you have a basic knowledge of

the Blender software, will show you how to quickly and easily produce

a much more realistic star ield. We’ll be using a technique very similar

to the “sky dome” technique. When we’re done, we’ll have a camera in

the center of a sphere with stars mapped onto it. The camera will be able

to rotate in any direction, and still see stars - plus, the stars will all move

at the same rate of speed when the camera pans. We’ll be able to “alpha

over” our star animations almost any space scene we need.

For this tutorial, I used Blender 2.47, but I think older versions

would work just as well.

* * *

We’ll start by making a preliminary map for the sky dome

we’re going to build shortly. Open a new Blender scene, and de-

lete the default cube. Next, change the World color to black, and

turn the Stars button on. Use these settings:

Star Distance: 2

Minimum Distance: 40

Size: .06

I left the “Colnoise” at 0, but if you want a more colorful star

ield, you can bump it up a little.

Next, go to the Node editor, and add in a Soften ilter with a

value of 1. (Of course, turn on the Do Composite button, in the

Scene panel.) Set the size of the render to 2500 x 1200 pixels,

and render. Save the map to your project directory (I’m assuming

that you have one since you’re an organized individual).

Open a new Blender scene. Delete everything except

the camera, and center the camera at the origin (the center of

Blender’s 3D world). Next, add in an icosphere (also centered at

the origin), with subdivision of 4 and radius of 1. In the Trans-

form Properties window (hit ‘n’ key to open), set the X, Y, and

Z scales to about 84 (well, somehow mine ended up at 84.281).

Give the sphere a new material, change the color to white, and

turn on the Shadeless button. Turn off the Traceable, Shadowbuf,

and Shadow buttons, and set Relectivity to 0. Set Specularity to

0 with Hard value of 1.

Add an image texture, and load the star map we rendered

earlier. Change the map type to Spherical (under Map Input tab).

Change the Size X, Y, and Z to 6. Note that we are not perform-

ing a true spherical mapping procedure - but the method we’re

using will get perfectly ine results.

Add another texture beneath the irst one, and choose the

Noise texture type. Under the Colors tab, set Bright to 0, and

Contrast to 1.233.

Add a second noise texture. This time, use a Brightness level

of .2, with a Contrast level of 1.23. Under the Map To tab, set the

color to white for both noise textures.

In the node editor, add in a Brightness/Contrast node, fol-

lowed by a Sharpen node, between the input and output. The val-

ues for these two nodes make all the difference in our star world.

You can use whatever settings you want, depending on what kind

of a star world you’re going for. I used a Brightness value of -15,

with a Contrast value of 2, and a Sharpen value of .1.

You’re ready to render! You can disable Ray Tracing, Envi-

ronment Map Rendering, and Shadow Calculation for this scene

- they’re not necessary. This star world gives a good effect if

you’re dealing with small renders - 800x600, for example. It’s

the technique I’m currently using for my stop-motion ilm, Mis-

sion to Deimos . However, for more serious productions, I use a

slightly different approach.

* * *

Save our star project as a new project, and delete all the textures of

the star sphere except the irst two. Turn off the Shadeless button for the

sphere’s material, and set the Emit value to 1.2.

Change the Map Input Size X, Y, and Z of the irst texture to 7.

Add a new noise texture into the third texture slot, with Brightness

and Contrast values of 1. Under Map To tab, set the Col value to .5.

Add another noise texture. Use a Brightness level of .2, and a Con-

trast level of 1.23. Make sure the Map To color is white for all noise

textures.

Add a inal texture, and load the stars map again. Under Map input,

set the Size X, Y, and Z to 12 and turn on Spherical mapping.

Next, set the Nodes to look like the screenshot below:

Render, and you’ll get what I think is a pretty good-looking star ield.

You can easily change its brightness by adjusting the Emit value of the

star sphere.

Here’s how I use this star world in my animations: after I’ve ani-

mated a space shot, I import the shot’s camera into my star world scene.

Then I add a Copy Location constraint to the star sphere, and target the

camera. After making sure the camera’s clipping Start and End values

will work with the star sphere, I render the animation. Now, I have a star

animation with a rotation that matches my space shot perfectly. I next

render my space shot, using the star animation as the background via the

Video Sequence Editor.

Notice that when you’re working with a star world, animating the

rotation of the star world is usually all that matters when it comes to

space scenes. In real life, no matter how fast you ly a spaceship, you’re

not going to notice the stars getting any closer!

* * *

Let’s throw in a nebula effect, just for kicks. I designed this tech-

nique with still shots in mind, but a similar technique would probably

work well in animations. Open the star ile we just completed, and save it

as a new project. Delete all the textures for the sphere, and Set Relectiv-

ity to 1. Give the material an Emit value of 2, and an Alpha of .6. Turn on

Z Transparency, and give the sphere a color of black.

Add a distorted noise texture, and change the Noise Basis to Original

Perlin. Add a color ramp, set according to the screenshots below.

Under Map To tab, turn off the Col button and turn on the Emit but-

ton. Change Texture Blending Mode to Add, and set Var to .5.

Next, add a Marble texture to the sphere, with these values:

Noise Size: .3

Noise Depth: 6

Turbulence: 8.2

Add a colorband with these values:

Turn on Alpha (no yellow) under the Map To tab, and set the Var

value to .5.

Add a inal texture to the sphere - this time, we’ll use a Blend tex-

ture. Under the Blend tab, turn on the Sphere button. In the Map Input

tab, make sure the Win button is turned on instead of the Orco button.

Under Map To tab, turn of Col button and turn on Alpha (no yellow).

Change the Texture Blending Mode to Mix. The sole purpose of this

texture is to keep our nebula from covering the whole space backdrop.

By changing the properties of this texture, we can change the shape/size/

position of our nebula effect.

Duplicate the nebula sphere, and make a “single-user copy” of its

duplicated material. For the irst texture channel, make a single-user copy

of the distorted noise texture, and change the Noise Basis to Blender

Original. Make a single-user copy of the second texture, and change the

texture type to Clouds. Change the Noise Basis to Original Perlin, set

Noise Size to .2 and Noise Depth to 6. Use the following colorband:

Change the Var value to .75 in the Map To tab. The third (blend) tex-

ture doesn’t need to be changed at all, since we need a consistent mask-

ing effect.

There’s one inal step that we can take, to give more realism to our

still shot. Add in a UV sphere, with 32 rings and segments and radius

of 1. Center the sphere at the origin. Turn off Traceable and Shadowbuf

buttons, give the sphere a color of white, and turn on the Halo button. Set

Halo size to .1 with Hard at 127. Give the sphere a new particle system,

with Amount and Life values at 500, Start frame at 1, and End frame at

100. Set the sphere to emit from Random Vertices. In the Physics tab,

set Random velocity to 40 and Brownian motion to 50. Enter Edit mode

and Hash the sphere’s vertices. Set our camera’s Clipping Start to 40.

Now, depending on which frame # we render, we have a few stars in the

foreground, to give a feeling of depth to our shot.

In the Video Sequence Editor, set our scene to alpha over the star

background we rendered earlier. Turn on the Do Sequence button in the

Scene panel, turn on the Premul button instead of the Sky button, ad-

vance to frame 100 or so, and we’re ready to render!

There’s really no limit to the variety of stars and nebulae you can

render with this method. You can easily change all the color schemes,

colorbands, texture types, alpha values, etc. that we used in this example.

If you want more of an artistic look to the particle stars, turn on Rings,

Lines, and Star options, and adjust the halo and alpha settings.

Have fun with your stars. I hope this tutorial has been helpful.

William Chamberlin

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