scrolling a background

Unity Engine
1

I’m scrolling a cloud texture in a 2D game to give the appearance of clouds moving across the sky. I have it working but wondered if there were some tricks I was missing.

Essentially, I’m usng GUI.DrawTexture to draw the texture at a continually changing x coordinate and repeating the texture on the right. I thought there could be a better way, like a “wrapping” setting I could use. My code example is below.

Thanks,

Brian

var clouds : Texture2D;
var cloudPos : float = 0;

function OnGUI ()
{
	...

	GUI.DrawTexture(Rect(-cloudPos, 0, 480, 160), clouds, ScaleMode.ScaleAndCrop);
	GUI.DrawTexture(Rect(480 - cloudPos, 0, 480, 160), clouds, ScaleMode.ScaleAndCrop);

	if (cloudPos < 480)
		cloudPos += Time.deltaTime * 10;
	else
		cloudPos = 0;
}

[/code]

2

Have a separate camera draw your skybox. Rotate that camera. Moving clouds with minimal effort. If you wish you can also disconnect the skybox from the clouds, by having a camera inside a hemisphere with clouds drawn on it and rotate it, instead of your skybox.

3

I’m sure that will work, but this is a 2D game so I don’t think I need a sky box at all. At most, I need a “sky plane”. Knowing this, is there a better technique than the one I’m using?

Thanks,

Brian

4

Use a 3D plane with the texture on it, and scroll the UV offset. (Look up SetTextureOffset in the docs for an example.)

–Eric

5

Similar to what you’re doing, but different from using a GUItexture.

Create a plane, put your sky/cloud texture on it and scale it to fit.

function Update() {

var scrollSpeed = 0.5;
var offset = Time.time * scrollSpeed;

 renderer.material.mainTextureOffset = Vector2 (offset, 0);

}

This will constantly scroll and ‘wrap’ your texture to the right assuming it’s tileable. Myself i’d still use a skybox, otherwise you have to use a plane and texture oversized in the x direction, or it will get quite repetitive.

6

Thanks for the help. And just to show how green I am, can you clarify what is meant by the “main texture”? Is this the texture for a material whose shader uses additional textures? For shaders like diffuse, there is only one texture available, right?

– Brian

7

main texture is the texture that is on the plane, the first one you put on it.

8

Sorry, but I don’t understand this. Is there a way to put 2 textures on a plane? If I drag a 2nd texture to a plane it replaces the first one and uses the default “diffuse” shader. So if this is the “main texture”, what is an example of 2nd texture? Is this for a shader such as “decal” that uses more than one texture?

9

photoshop

combine the textures to put two on a plane

10

This doesn’t address my question, which asked about the significance of the “main texture” and how to add a 2nd texture to a plane so that it will be recognized a texture #2 by Unity. I’m not talking about graphical stuff here, which of course I know you can do in Photoshop. I’m talking about learning Unity data structures and programming.

– Brian

11

oh

12

Correct. Main texture references the diffuse map. You can however easily access the normal, specular and whatnot for shaders that use them with the following…

 renderer.material.GetTexture ("_BumpMap");

In fact, renderer.maintexture is just a shorthand equivalent for…

 renderer.material.GetTexture ("_MainTex");

Try looking around in the documentation for the Renderer Class to see all the goodies you have access to.