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Keet
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Experiments with texturing a sphere

The default sphere from the Sweet Home 3D catalog is a UV sphere as it is created with Blender. You can set a texture to this sphere, for example to create a wooden ball.
But sometimes we want the texture to be different. We we can shift the texture along the X and Y axis in Sweet Home 3D and we can adjust the angle and scale of the texture . But that usually distorts the texture in ways we don't want. For the exmaples I used two different wooden textures and a white marble texture. The wooden textures clearly show how the texture is mapped on the sphere: like disks of wood glued together.


Wrapped and Unwrapped
Since we can't change more than the mentioned options in Sweet Home 3D we have to resort to another application to change the way the texture is mapped on the sphere. The first try is what is called UV unwrapping. “UV” is not an acronym for Ultra Violet, UV's are coordinates on the 2D texture image. Since X,Y, and Z are already used for defining points in the 3D space (vertices) and W is used for quaternion rotations, U and V are the letters chosen for the coordinates on 2D surfaces.
In Blender we can “UV unwrap” the texture mapping of an object. In simple terms that means we unfold the 3D surface image to a flat 2D image. Using that unfolded image give a very different result as is shown on the right side in the image. With the shown textures the result is very different and for some textures useful. For these three I would say that the result is worse than the original. The marble texture... well it looks a little like marble but wrapped or unwrapped it's a mess.

Different Projections
What other options can we try? Again using Blender we can change the projection of the texture on the object. In the image you can see the how different projections change how the texture is mapped on the sphere. I added the sphere with the irises to better show what the cube projection does: the image is repeated for each “side of a cube”.

The sphere and cylinder projections look very similar but notice the stretched knot at the arrow. The cylinder projection is useful when you have a texture image with a text that must be wrapped around the sphere so the text remains a horizontal word. The sphere projection seems the best choice with the marble texture, maybe also the cylinder projection. The “Projection from view” looks like it useless. The image is faded. You don't want the mapping to change the look of the used texture image.



Apparently Blender takes the view into account when you export the object. It exports “as you see it”. Notice in the image with the four different projections that the sphere and cylinder projections show the top as if it is tilted a little to the left. The next image shows the sphere and cylinder projection with the view set as “Front Ortho”, i.e. front in front and without perspective. This better shows the texture mapping and is more useful as a base for other textures. Now the top really is the top.


Different spheres
These are the options using Blender that present different ways to map a texture on a sphere. The five different spheres (unchanged, unwrapped, cube projection, sphere projection, and cylinder projection) are added to the shapes library. With these you can simply choose a different sphere and see what gives the best result for your texture.
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[Dec 13, 2024, 6:36:25 PM] Show Printable Version of Post    View Member Profile    Send Private Message [Link] Report threatening or abusive post: please login first  Go to top 
GaudiGalopin3324
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applause Re: Experiments with texturing a sphere

Keet Bravo!
[Dec 13, 2024, 7:11:35 PM] Show Printable Version of Post    View Member Profile    Send Private Message [Link] Report threatening or abusive post: please login first  Go to top 
captaincook
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Re: Experiments with texturing a sphere

Beau travail, en effet, Keet.
Intéressant et utile.
Merci pour ces nouvelles fournitures.

Je me suis amusé à comparer les résultats sur les 5 différentes sphères et avec un cube.
L'image utilisée sur tous les objets est une photo de paysage montagneux.
Tous les objets ont la même taille (diamètre 100 et 100*100*100 pour le cube).
L'image est appliquée comme texture dans la section Matériaux et avec les mêmes réglages pour tous ( Echelle 100% et 0 pour les décalages angulaires X et Y ainsi que l'angle).



Dans ce cas particulier, la sphère cylindre projection semble la mieux adaptée, je pense.
[Dec 14, 2024, 12:02:14 PM] Show Printable Version of Post    View Member Profile    Send Private Message [Link] Report threatening or abusive post: please login first  Go to top 
Keet
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Re: Experiments with texturing a sphere

Dans ce cas particulier, la sphère cylindre projection semble la mieux adaptée, je pense.
Oui, la projection cylindrique est particulièrement utile pour les textures qui ont une orientation horizontale comme une ligne de texte ou, comme dans votre exemple, pour une image qui ne doit pas être déformée dans le plan vertical mais qui doit s'enrouler autour de la sphère dans une ligne horizontale. Une bonne image pour montrer les différences.

[English]
In this particular case, the projection cylinder sphere seems the most suitable, I think.
Yes, the cylinder projection is especially useful with textures that have a horizontal orientation like a line of text or, as in your example, with an image that should not be distorted in the vertical plane but should wrap around the sphere in a horizontal line. A good image to show the differences.
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[Dec 14, 2024, 12:20:22 PM] Show Printable Version of Post    View Member Profile    Send Private Message [Link] Report threatening or abusive post: please login first  Go to top 
Keet
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Re: Experiments with texturing a sphere

Texturing Spheres Part 2

Besides the UV spheres there are Ico Spheres. The difference is in how the faces of the sphere are organized. On the left a UV sphere and on the right a Ico sphere.

The Ico sphere looks very different but the image shows a Ico Sphere with only 2 subdivisions. Using Blender you can create Ico Spheres with more subdivisions making the sphere much smoother:

The smoothed Ico Sphere with 4 subdivisions looks exactly like a UV sphere but the object size is smaller (103.2kB vs 78.6kB). Significant if you are using a lot of spheres in a project. The Ico Sphere is build out of triangles instead of the quads of the UV sphere. No translation needed for quads to triangles. Rendering should be faster.

Just like the UV spheres we can use different projections for the spheres:

The unchanged sphere with the text shows the slices that are 'glued' together to form the sphere, just like the unchanged UV sphere. The cylinder projection shows it's value again for textures that need to retain a horizontal line.
I especially like the Ico Sphere with 2 subdivisions unwrapped and with a wood texture. The wood grains in the triangles look really nice!

Eight Ico Sphere models are added to the Shapes library:

Ico Sphere 2sd (sd = sudivisions)
Ico Sphere 3sd
Ico Sphere 4sd
Ico Sphere 4sd smoothed

Ico Sphere 2sd unwrapped
Ico Sphere 2sd cube projection
Ico Sphere 2sd sphere projection
Ico Sphere 2sd cylinder projection
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[Dec 14, 2024, 2:07:51 PM] Show Printable Version of Post    View Member Profile    Send Private Message [Link] Report threatening or abusive post: please login first  Go to top 
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