Simon,
Thank you so much for the tutorials! They are very well done and extremely useful. I have only been working with OpenGL ES for a week now and they have helped me a great deal. I look forward to many more!
To anyone who may be interested,
I have spent quite a bit of time over this last week trying to get an object to rotate around it's origin with touch input from the user. Countless Google searches turned up page after page of "lecture notes" on angle/axis, quaternions, and rotation matrices, but nothing to tie it all together -- at least for me. It had been quite a few years since I had to deal with those concepts, and it was pretty rough trying to cram all of that back into my head. But, as I read more, and derived quite a bit on my own, I began to understand most of it. I was almost done implementing my own algorithms (though they had a few issues) when I revisited an example I had seen previously. The difference this time was that I actually understood what it was doing.
So, using Simon's OpenGL ES 10 Tutorial as a starting point, and the code I found at
opengl.org, I was able to get the cube to rotate around it's origin the way I wanted. You can download the source files I used from my web site (
BizarreSoftware.com) and use them with the
tutorial #10 from Simon's site.
Please let me know if there is a better way to do the rotations. It looks like it's working, but I know things are not always as they seem.
Jim
