Sunset Lake Software - Comments for "3-D rotation without a trackball"

Unfortunately, there is no

Unfortunately, there is no good way that anyone has found for capturing a 3-D transformation in Core Animation without using the private UIGetScreenImage(). It's a frequent question on Stack Overflow, and I've not seen a solution for it.

File an enhancement request for this functionality and maybe Apple will add it in the next SDK version.

One problem that after I few

One problem that after I few days I haven't been able to come up with a solution.

When using this technique, I can find literally no way to properly capture the screen as a UIImage, the CATransform3D is not applied by renderInContext, so it's all flat.

Any ideas? There must be a way besides rewriting my app in OpenGl, especially because using UIGetScreenImage() to take an image of CATransform3D works like a charm.

Hi , if i wanna make the

Hi , if i wanna make the sides clickable and on tapping of the user i open a new view relative to the side he tapped on . what should i do ?

Hi I was playing with the

I was playing with the pinch example and noticed a bug. If you pinch and bring them toward the center and then continue the motion the image will disappear. The problem is the calculated distance becomes negative. I made this change to line 129 or MyView.m to fix it. Basically I take the absolute value of the calculation and feed that to sqrt.

	return (sqrt(abs((point1.x - point2.x) * (point1.x - point2.x) + (point1.y - point2.y) * (point1.y - point2.y))));

Great example! Keep up the good work.

Here is the version of

Here is the version of Molecules that I've been porting to iPhone OS 3.0. It includes the CATransform3D logic in its rotation, scaling, and translation code. I'm sorry that I got a little sidetracked with other things and haven't updated the application yet.

the point is that usually

the point is that usually translation and rotation is allways done from the original perspective as a starting point...(if I am not mistaken-> still a beginner in OpenGL)
now, when you replace the modelview matrix (by glLoadMatrixx(currentModelViewMatrix);) at each frame and do a incremental translate/rotate this implies that you lose your original orientation and hence do not know where to go with a translate once one rotation has been applied

would be interesting how you solved that problem...the molecules code of dec08 does not use the CATransform3D mechanism as far as i can see.

can you post the code snipped

can you post the code snipped of the translation?
i had a look at a molecules version (maybe older one?) that did not use the CATransform3D matrix for translation.

Yes, it does, but that's the

Yes, it does, but that's the behavior you'd expect. For Molecules, I use this same technique, and let people pan across the 3-D structure. If they go to pan it left, they'll want the model to be displaced left from their current perspective on the object, not the object's original orientation.

I see a problem with this

I see a problem with this technique (Manipulation of a temporary copy of the modelview matrix and overwriting it with the original one @ rendering): Ever used translate and rotate function both with it?
Say ... lets do a translate 180 degrees around the y axis and later on the user wants to move the model to the right. Its moving to the left instead (and vice versa)