Qworkshop3 Tutorials

Star field Shader Tutorial by Crashmeplease

Ok, just to set the scene, here's the original post from RAWBEEFSKiN

Topic: shit.......we're not in Manchester anymore sanji !!
okay......i just had a idea.....there was one thing i liked about UT (that's unreal tournament...for those of u that can't memorize hundreds of abbreviations).....anyway the only thing i liked about UT was that level in a little spaceship.....i liked it because when u looked out of the windows that texture with stars zooming past made it really feel like you were going some place.....and not stuck in self-contained static arena....i think something like that would be pretty nice for Q3 (if i need to explain that you're in the wrong place).....I've had a couple of attempts but my knowledge of shaders n' stuff isn't that great........if any ones bored, bored, understands what i mean or bored and feels like having a go I'd be interested to see what ya come up with.....
------------------
<simplicity precedes equanimity>

Well as I was thinking to myself what a cool idea, I started drooling uncontrollably. it's so easy to add several 'planes' to a shader to give us an effective vision of perspective.

Ok, so you have no idea what im going on about. Think of it like this, imagine a fast moving object close to us, it wizzes past. Now think of the same object traveling at the same speed but this time further away from us, it's still traveling at the same speed, and will move the same distance, but it appears to move much slower.

Here's a little pic of what we're all on about.

A Bit crap but a good example on what we are trying to achieve

Catching on yet ?

The Beginning
First of all, I've put a new directory in the textures folder named starfield and created three simple, well quite poor, but hey they took me like 10 minutes to make :o) starlike looking jpg files.
Next creating a new shader script called starfield.shader and adding this to the shaderlist.txt file.

The start of the shader code looks like this :


textures/starfield/starfield-3p
{
	qer_editorimage textures/starfield/starfield-00a.tga
	surfaceparm nodlights
	surfaceparm noimpact

The name of the texture is starfield-3p and it lives in the textures > starfield directory.
The image we will all see in Radient is starfield-00a.tga.
A surface parameter of nodlights implies this shader will not be affected by dynamic lighting.
A surface parameter of noimpact implies that no projectiles will strike the surface, etc.

Somewhere in the Middle
Now comes the scrolling bit :


	{	
			map textures/starfield/starfield-00a.tga
			//      tcmod scroll <sSpeed><tSpeed>
			tcmod scroll 1 0
	}

Here we are using the starfield-00a.tga texture.
The tcmod scroll function allows us to scroll out texture around. In this instance right by 1 texture a second.

Almost the End
Thats the basic's done. Simple eh ?
We can now add as many planes as God will allow, by copying the middle shader stage and adding an add function, just like this :


	{
			map textures/starfield/starfield-01a.tga
			//      tcmod scroll <sSpeed><tSpeed>
			tcmod scroll 0.75 0
			blendfunc add
	}

First you will notice that we're using a different texture, this time starfield-01a.tga, cos it would get boring with the same texture.
And also the tcmod scroll speed has been reduced to 0.75.
Not forgetting the blendfunc add, this is responsible for combining all of our starfield images. Because the blendfunc add 'adds' the images together, stars passing over each other will appear brighter than they actually are. This gives quite a neat effect in my opinion.

The Final Script
Looks like this for a starfield with 3 planes. I don't think it's necessary for more planes, but you can add more it u like.


//
//  Moving Starfields by crashmeplease.
//				crashmeplease@yahoo.co.uk
//

//  This shader came from the Starfield Shader Tutorial from:
//	Q-workshop3		
//	http://qw3.gamedesign.net
//

//	A three pass starfield example
//
textures/starfield/starfield-3p
{
	qer_editorimage textures/starfield/starfield-00a.tga
	surfaceparm nodlights
	surfaceparm noimpact 
	// first pass
	{
		map textures/starfield/starfield-00a.tga
		//      tcmod scroll <sSpeed><tSpeed>
		tcmod scroll 1 0
		
	}	
	// second pass
	{
		map textures/starfield/starfield-01a.tga
		//      tcmod scroll <sSpeed><tSpeed>
		tcmod scroll 0.75 0
		blendfunc add
	}	
	// third pass
	{
		map textures/starfield/starfield-02a.tga
		//      tcmod scroll <sSpeed><tSpeed>
		tcmod scroll 0.5 0
		blendfunc add
	}	
}

Thats all there is to it. You can see that the first pass is the fastest, and the third pass the slowest. Why not play with the scrolling speeds yourself.
One other thing if your feeling brave is to add a little motion blur effect by stretching the texture out a little.

Oh and them images

starfield-00a.tga	starfield-01a.tga	starfield-02a.tga

This is the image for the close up stars.	This is the image for the in the middle stars.	This is the image for the farthest away stars.

They're a bit crap, but they serve their purpose well. You'd be well advised to make you're own, lol

Download here !
Rather than c'n'p you can download a zip file that contains the images and the shader.

Sign Off
Gee I'm a nice guy today. If u have any questions then mail me Crashmeplease.

Hit Counter