Hi,
Sorry that I am still not understand it clearly, let’s begin with follow
example:
If I have a vertex array as bellow:
GLint vert[4 * 3] = {
-1, 1, 0,
-1, -1, 0,
1, 1, 0,
1, -1, 0 };
And a rectangle will be drawn by:
glEnableClientState(GL_VERTEX_ARRAY);
glVertexPointer(3, GL_FIXED, 0, vert);
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
And if I want to bind a texture to this object without rotation, so how to
decide the coordinator of the texture ?
Thanks,
Song
From: [email protected]
[mailto:[email protected]] On Behalf Of ext
Till Oliver Knoll
Sent: Saturday, December 29, 2012 10:09 PM
To: Qt Project
Subject: Re: [Interest] About the coordinator between the texture and vertex in
opengl
Am 29.12.2012 um 12:52 schrieb
<[email protected]<mailto:[email protected]>>:
...
The problem is about binding a texture to an object, but i am quite not
understanding how is the texture coordinator decided according to the vertex
coordinator ?
Your question is indeed a little bit off-topic, but your assumption about
OpenGL experts here on this list is probably true (disclaimer: it's been quite
some while I did some OpenGL code, and that was back when OpenGL 1.4 was
current, so "expert" doesn't necessarily include me ;)).
If you haven't done already study this example:
http://doc.qt.digia.com/qt/opengl-textures.html
specifically
http://doc.qt.digia.com/qt/opengl-textures-glwidget-cpp.html
In GLWidget::makeObject you'll see how for every vertex (world coordinates are
usually denoted as X, Y, Z) a corresponding texture coordinate (usually denoted
U, V) is specified. That data is then passed on to OpenGL as array with
glTexCoordPointer (the "non-OpenGL ES 2 code path") or as array attribute to
the GL shader program.
Cheers,
Oliver
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