I was reading your description of how you make the nebulas. Ive got a few questions on this topic.
It's a variety of techniques. I usually start by laying down a base of several different Cloud filters in different colors on different layers. A useful texture to create in Photoshop is a pseudo-Perlin-turbulence. Start with a canvas 2048 pixels square. Create a black-white cloud texture on it. Shrink the canvas to 1024 pixels, and create a second cloud texture on a new layer. Repeat for 512 and 256 pixel squares. Order the layers so that the first one (that was originally 2048 pixels) is on the top and the last one is on the bottom. Set the opacities for all the layers to something like 12%, 25%, 50%, and 100% from top to bottom.
Then I manually paint in highlights on on other layers using the airbrush. To get a 3D effect, it is helpful to paint in both light and dark colors for each feature on different layers, as if you were seeing a 3D pillar of cloud lit on one side and shadowed on another. I also add very fine grained trails of "dust" using a dark color and just dotting them in with a fine airbrush. Set that layer's blend to "multiply".
The most important part of the effect is to create a separate layer that is used as an alpha-channel by the game engine. The edges of this layer must be completely black so that you don't see polygon seams at the edges of the texture. I usually hand-paint this layer with the airbrush as well. Sometimes I add some variance to the alpha by using a stippled brush pattern in the airbrush. Just a little gray stippling helps to add some texture to the body of the texture. This layer gets saved out as a separate greyscale PCX file that the game engine will recognize as containing alpha values for the main texture.
I paint the nebulae on a 512x256 pixel canvas, and then squash the image to 256 square to make a texture out of it.
The geometry of the nebula model is like a movie screen: twice as wide as it is high, and wrapped around the 3D origin point so that all the polygon normals are oriented toward the viewer. Because of the way magic works, I actually stretch the texture over the geometry while it is still flat, and then bend the framework around the center point. You have to be careful to keep all the quad polys flat while you do this or you will see unsightly texture shearing when the polys get near the edge of the viewport in the game.
1. What is the reason to you rescaling the canvas between rendering each layer?
2. The alpha layer. Im kind of confused here. Ok you create a top layer with black edges and airbrush the edges so that you get a smoother transition. Thats fine. But Then you say ". This layer gets saved out as a separate greyscale PCX file that the game engine will recognize as containing alpha values for the main texture". I dont get this at all. PCX format does not support layers and needs the image to be flattend. So how does this layer get saved out???? Do you save it manually as a separate file and in that case what do you name it ??
3. The 3d model for the nebula what kind of shape do you use? You say that you bend a flat geometry that you bend. Do you just create a square polygon for this or what? Then finally how do you bend it? Just by splitting it up and moving the vertexes? How much do you bend it?
Reason Im puzzled here is because Ive been playin with this and find it hard to get a good nebula. The texture is ok but for the nebula Ive been using a sphere shape that I invert the faces on. This works but doesnt give me a result that Im too happy with as it really does feel like Im flyin inside a fish bowl.
Actually would you mind attaching a sample MAG file?
Thanks for reading.
Tex
