When you normally map to a sphere in gimp you get a pinching effect at the north/south axis (See Left Image), I have been internet searching and playing with gimp to try and get the faces to map evenly (See Right Image).



This tutorial will hopefully explain how I achieved the right side image and be a spring board for improvements of being able to map patterns and photo to a sphere without as much distortion.

1. Open Gimp and create a new image 1024px * 1024px and fill with Black.

2. Go Images>Guides>New Guides and add a Horizontal Guide at 512px and Vertical Guides at 256,512,768px. Go View and makes sure "Show Guides", "Snap To Guide" and "Snap To Canvas Edge" are ticked.

3. Go Layer>New Layer makes sure "Transparency" is checked and click O.K.



4. From Toolbox choose the "Rectangle Select" tool and draw a selection across the top half of the image and fill with white.



5. Still with the "Rectangle Select" tool draw a selection across the first bottom quarter of the image and fill with red.



6. Still using the "Rectangle Select" tool work across the image filling each bottom quarter with a different colour, I used Red, Green, Blue and Pink although it doesn't really matter. Once finished Go>Select>None to get rid of the selection. You should be looking similar to the image below.



7. Go>Layer>Transform>Offset and set X to 128 and check "Wrap Around" then click offset.



8. Go>Filters>Distort>Polar Coordinates and set "Circle Depth In Percentage" to 50, Also check "Map From Top" and "To Polar".



9. Go>Filters>Distort>Polar Coordinates and set "Circle Depth In Percentage" to 100, Also check "Map From Top" and uncheck "To Polar".



10. Go>Layer>Scale Layer and unlock the chain link and change "Height" to 256px (This is our original Height divided by 4) and click Scale.



11.From the Toolbox choose the "Move" tool and position the bottom of your layer onto the middle horizontal guide making sure you keep layer central.



12. Go Layer>Duplicate Layer then Layer>Transform>Flip Vertically, then using the "Move" tool, Position the top of your layer onto the middle horizontal guide making sure you keep layer central. Then Go>Layer>Merge Down. You should be looking similar to the image below.



13. The next part is purely cosmetic but if you Go>View and untick show guides, then Zoom into the image you will see that across the middle line where the two images where joined there are some artefacts left behind from the polar mapping. I basically created a Rectangle selection around these parts an filled with the appropriate colour. I also used the "Fuzzy Select" tool to select the bottom white section and changed the colour to yellow.



14. Time to Map the Sphere, Go>Filters>Map>Map Object, the only tabs we are concerned with is the "Options" and "Orientation". Under the "Options" tab set "Map To" to Sphere and check "Transparent Background". Under the "Orientation" tab set the "Position" value Z to 0.75000 and under "Rotation" change Y and Z to 15, But do have a play with these settings to see the sphere map in full.



15. Now you've probably noticed that our sphere is very elongated, don't worry. Go>Layer>AutoCrop then Go>Layer>Scale Layer and unlock the chain link and change "Height" to 837px (This should be the same dimension as the width), Then click "Scale".



16. That's our Sphere Cube finished.

Thanks for the tutorial, hearty! Looks very interesting. I'll give it a go sometime soon.

Rellik - Thanks for the comment.

So far I have managed to map a chequerboard pattern onto one face...

Pretty easy to follow there Hearty. No problems at all. Wanted to see what using gradients would do and messed around with the rotation settings abit.

Thanks, he4rty, for sharing this nice and very intelligible technique.

I had no problems with reproducing the steps of the tutorial.

I also tried to apply some texture to the lateral faces of the sphere, by putting into action the "CML explorer" filter, and this is the interesting outcome I achieved:

Very nice Gino, it looks like a beach ball.

Rellik - Nice work, curious about what stage during the tutorial you added the gradients.
Gino - Again nice work, I'll admit I've not heard of the cml explorer filter before.

Steps 5 & 6 he4rty. Instead of adding a solid color... I just used some gradients going from middle of selection to outer using bi-linear.

Wow, nice tutorial he4rty, I missed it, I was busy painting in MyPaint. I will make that tute into a pdf and try it some time this week. Kudo's

On a side note also... Using the gradients and getting rid of the artifacts in step#13 kinda of created a challenge, but the heal tool took care of that.

Nice one he4rty

Wow, cool alc. leave it to you.

Alc - Nice work on the ball animation.

good job Conbagui, looks like Walnut wood grain.

conbagui - Nice work on the ball and the wood effect looks great.

Nice tut. Going to play around with this one. All went well except I'll need to spend a little more time cleaning up the artifacts in step 13. Thanks

This is a fabulous tutorial! Thank you for sharing. The really nice thing for me is this can also be used when creating textures for 3D artwork because mapping square textures on spherical shapes can be difficult as well. Thank you!

Thanks for the comment, I have had more success mapping an image using gmic's polar filter rather than gimps, but only on the white face.

I suspect g'mic also works better on the bottom face, as well, because spherically mapped image have distortions at both the top and bottom. Thank you for the PM information. It was definitely helpful.

Art