Help
and asked "How?" so I'll try to tell you. If there is anything I haven't made clear please ask
To begin: Create new image. For the purpose of this tut I've used 600 x 600 with a transparent background. The original was made with a much larger (can't remember how much larger) image.Alternatively use a white background then open a new transparent layer. The white background can make it easier to see what you are doing and you can delete it at the end.
I've used a square image because when Gimp maps object to sphere it keeps the proportions the same. If you want your spheroid to have different axis ratios choose a different size opening image. I want a true sphere so I need the
vertical and horizontal axes to be the same.
Now do Filters/Render/Grid.
To get a cage we need it to match up in both directions so the spacing settings need to be a factor of the image size. In this case the image is 600 x 600 and the spacing settings are (H) 60=600/10 and (V) 30=600/20. So why are the horizontal and vertical settings different?
As I said before when Gimp maps object to sphere it keeps the proportions the same. It does this by maping the vertical axis from North Pole to South Pole and the horizontal axis to the equator. So the vertical axis goes halfway round the sphere while the horizontal axis goes the whole way round. This stretches the horizontal axis so the setings in the grid box need to reflect this. So if you want to finish up with a square cage the horizontal Width and Spacing settings need to be twice the vertical settings. What seems a liitle illogical is that to get the vertical spacing wider you increase the horizontal spacing. This is because horizontal and vertical in this context refer to the bars not the axes. So increasing the spacing for the horizontal(bars) increases the spacing in the vertical axis.
The offset settings are a matter of choice. I've set the horizontal spacing to 12 because I don't want one of the bars of the cage coming dow the centre of the image. But neither do I want a hole in the bars centred. Have a play, see what looks good.
I finished up with this.
Now I wanted to make t look a bit metallic, Now I'm sure the artistic guys here could do a lot better but for quick and simple lets do Alpha to selection, Filter /Noise/ Hurl,Filter/Gaussian Blur. H=3 v=0, Layer/colour/desaturate. Ain't great but it's quick and easy. I'm sure you can do better.
OK that's the artistic bit over. The rest is easy.
What we want to do is render the front and the back of the sphere as seperate layers. Duplicate the gris layer and call the top one “front and the bottom one “back”. When Gimp maps object to sphere it uses the centre half of the image as the front and the left and right quarters as the back. So we need to duplicate the grid layer then cut out the relevant parts. We could do this using the rectangualr selection tool and fiddling about until we found point 299,0 but let's do this the easy way.
Open a new image with a solid background that is the same height but half the width of your grid image (in this case 300 x 600)
Edit/Copy visible then go back to your grid image and paste. Your pasted layer will be shown as “floating” so hit the new layer button at the bottom of the layers tab to keep it as a seperate layer. Just for housekeeping delete the new 300 x 600 image.
On your pasted layer do Alpha to Selection. For your back section you only want the outside quarters so select that layer and ctrl+K or edit/clear.The on your front later so ctrl+I or select/invert the ctrl+k.
Now delete the pasted layer.
Your layers should look something like this.
Although I've fiddled a bit for clarity.
Now we have to get a little artistic again. Open the render you want to put in the centre of the cage. If it has an obvious light source (as mine does)
You're going to want your cage to match that. If it doesn't and you want to give it one. If not don't. Your choice.
Go to the front layer of your grid image. Select all then filter/map/map object. Map to sphere. Select transparent background.If you are going to play with the lighting do it now. Then hit OK.
Go to the “back” layer and filter/map/map object. Gimp is kind and has kept all the settings since you last did it with the front layer so just hit OK.
Your sphere is much smaller than your original imge. In fact it's almost half the size (as opposed to 2/pi times the size which it should be. Gimp cheats.). You need to resize your inner image to fit. Do so. Then copy it, go back to the grid image and paste, then, as before, put it on a new layer. Move your render layer so that it is below your front layer and above your back layer and voila!
Just for tidiness, on your front or back layer, alpha to selection then image/crop image. No point in wasting space.
Not nearly as good as the original but the principles are sound. I should have made the bars thinner and inverted the colurs on the metallic grid. Just play with the artistic bits to get the result you want. What would be good would be to make the front layer shiny but the back layer rusty (you can't polish the inside of a cage can you?)
