Well said Kostya. Pedro - I defined the formula to get your normal above. A normal is a unit vector (a 3D vector of length 1.) Each vertex must have a normal for proper shading, as that's how light is calculated. The normal of a vertex of a sphere is a easy to calculate. Think of it as the direction from the center of the sphere through the vertex. That's your vector. I provided a formula, though you'll have to javafy it a little to make that work for you. If you're struggling to understand this, I suggest reading some 3D primer books before moving on. They are very, very helpful.
Cheers On Dec 27, 7:59 am, Kostya Vasilyev <kmans...@gmail.com> wrote: > Pedro, > > A normal is a unit vector (length == 1) that is perpendicular to the > surface. Normals are used for shading, so don't worry about them too > much for now. > > Texture coordinates, as was already pointed out here, are in 2D space, > i.e. two coordinates. The reason is that textures are 2-dimensional, and > texture coordinates specify which point within the texture should be > mapped to a particular vertex in 3D space. > > Imagine that the texture is a stretchable, initially square, piece of > fabric. Each UV coordinate represents a point within that square. > > For each vertex, the point within the texture specified for that vertex > by UV coordinates is "glued" to the vertex. Then the texture is allowed > to stretch between vertexes. > > What sort of texture coordinates you generate is entirely up to you. > > A simple way to texture map a sphere is to wrap the texture into a > vertical cylinder around the sphere, then pull the top and bottom > towards the sphere, so you have singularities at the top and bottom of > the sphere. > > If you generate your sphere as a bunch of horizontal bands, each having > equal angular size, and further subdivided around into equal patches, > then you can your use loop variables (band / patch index) to compute UV > coordinates. Just remember that UV are 0 to 1 (unless you want tiling). > > -- Kostya > > 27.12.2010 18:35, pedr0 пишет: > > > > > > > > > > > But normal.x what is it? > > > Is the abs(x) ? > > > On 23 Dic, 20:41, Robert Green<rbgrn....@gmail.com> wrote: > >> UV unwrapping/mapping is standard practice in 3d games. It's how the > >> artist lines up the textures onto the skin/model. > > >> You're doing UV coordinate generation, which is similar but is > >> mathematically specified instead of placed by a 3D modeling > >> application. > > >> On Dec 23, 12:37 am, pedr0<pulsarpie...@gmail.com> wrote: > > >>> What do you think about it? > >>>http://en.wikipedia.org/wiki/UV_mapping > >>> On 23 Dic, 09:19, pedr0<pulsarpie...@gmail.com> wrote: > >>>> Thanks a lot, > >>>> especially at Robert Green for his very good explanation! > >>>> The absurd thing is that the code which I posted above is 100% right > >>>> in a iPhone iOS, but when I port the same code on the Android platform > >>>> I have these issues. > >>>> I will try to do what you are talking about normals and I let you know > >>>> about my progress! > >>>> Thanks again. > >>>> pedr0 > >>>> On 23 Dic, 04:10, Mario Zechner<badlogicga...@gmail.com> wrote: > >>>>> On 22 Dez., 20:42, Robert Green<rbgrn....@gmail.com> wrote: > >>>>>> 3DVec normal = (sphereCenter - point).normalize(); > >>>>> 3DVec normal = (point - sphereCenter).normalize(); > >>>>> Or your world will be upside down. Unless my brain is totally > >>>>> borked :) (could well be, 4am here...) > > -- > Kostya Vasilyev -- WiFi Manager + pretty widget > --http://kmansoft.wordpress.com -- You received this message because you are subscribed to the Google Groups "Android Developers" group. To post to this group, send email to android-developers@googlegroups.com To unsubscribe from this group, send email to android-developers+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/android-developers?hl=en
