Image objects, known as SceneLayers in World of Goo and WoG Editor, are how you get graphics into your level. It is important to realise that images are not solid. Just because you add a picture of a cliff to your level, this doesn't mean the Goo Balls will sit on it. You need geometry objects to make things solid.

SceneLayers let you build up the visuals in a level, from the background image to what the walls and cliffs look like, and they let you add foreground objects, like bushes, which come between the player and the Goo Balls.

You cannot import image files directly onto a SceneLayer object, the image file must first be added to the resource list and given a unique id. You can then select this id from a list in the image attribute of the SceneLayer.

Once you have assigned an image the SceneLayer can be moved, rotated and resized using the mouse in the Level view, or by changing the center, rotation and scale attributes.

Images also have depth

This allows you to control which images appear in front or behind other images, the geometry and the Goo Balls. depth can be positive or negative (positive values are in front of the Goo Balls, negative values are behind), and can be a fractional number (1.234).

It also controls the "distance" to the image. Over a limited range (where depth is between -2 to +2) the only apparent effect is which things are in front and which are behind. On a larger scale a parallax scrolling effect can be seen. Objects with large negative depth (-1000 say) will appear to move more slowly around the screen as you scroll, simulating being further away. Objects with positive depth (+200) will be in the foreground, will move faster as you scroll and will appear between the player and the Goo Balls. [Embed Video]

Other useful SceneLayer attributes

alpha allows you to control the overall transparency of the image.

colorize allows you to change the color of an image.
The image will become tinted by the RGB color you enter [Technical Details Here]
A value of 255,255,255 will display the image unchanged, and 0,0,0 will display a completely black image.

tilex and tiley repeat the image across the whole level.
Used in the original World of Goo Corporation levels for the "infinite" sky and ground. Note:tilex and tiley should not be used with rotated images, see this example showing why not.

SceneLayers can also rotate/spin, see Making things spin, or can be animated. However, whilst this may make the images move, they will still not interact with the Goo Balls or Geometry objects. If you want to create a moving object which can affect things, see [Applying Images to Geometry]

Full details of all the SceneLayer attributes and their functions [Here]

Notes on depth

  • Images representing walls, cliffs should be as close to depth=0 as possible.
    This applies to all SceneLayers showing the image for any solid object created using geometry. If these images have a large positive or negative depth, then they will move relative to the geometry, and Goo Balls may appear to bounce off thin air, or fall through a cliff, rather than off the edge. This is because the balls and geometry themselves are at depth 0.
  • The absolute maximum foreground depth is +700
    This is where the camera is. Beyond this, the game considers the image to be behind the camera, but will still attempt to display the image. This causes some rather odd and disorientating effects.
    For foreground objects such as bushes, trees and rafters etc. depths in the range +100 - +300 are best.