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<[email protected]> 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<[email protected]> wrote:
What do you think about it?
http://en.wikipedia.org/wiki/UV_mapping
On 23 Dic, 09:19, pedr0<[email protected]> 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<[email protected]> wrote:
On 22 Dez., 20:42, Robert Green<[email protected]> 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
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