Thanks for spinning the mat cap!
I wish I could say that, but right now it just rotates with the image facing forward. It should be able to rotate like a “sphere”, as you can see in the forger video I posted.
However, this is a minor issue compared to the greatness of this update, so please implement it next time if you have time!
While I’m sure I’ve seen some neural network ai stuff being done to extract a 3D model from a 2d image in order to extrapolate a lot of unknown information (in this case the possible other side of a sphere with completely random “shading”), that would be a considerable amount of work for what doesn’t seem to be much of a reason. Especially with user directed lights currently in the program.
Now that I think of it, Taron had created a matcap creation tool called Macrea back when Sculptris was still a thing. Something along those lines could be implemented a lot quicker. It kind of simulated a sphere in 2d. But, considering all the rest of the things likely in development, I’m not sure if it’s a high priority.
As a side note, Taron also made another program called Verve. If anyone is interested in watercolor like fluid mechanics painting, it’s quite fun to play around with (windows only though). You can change the fluid mechanics to come pretty close to oil and other paints as well.
It would be a lot of work to add such a feature, just being able to rotate like Forger is enough 
This is off topic, but I’m pursuing analog painting with digital, so verve’s story is very interesting to me. Thank you 
https://twitter.com/i/events/1243326675670065153?s=20
Yeah the way the matcap is rotating is bad, I won’t keep the way it is.
Unlike HDRI, you cannot rotate a matcap “like a sphere”.
Here’s how it looks like with an horizontal rotation, with visible bad seams/distortion.
In forger you can rotate the matcap in every direction, so this is a bit better but it’s still an hack. You can easily see seams and ugly distortion.
I’ll either remove this feature or allow very small degree of freedom.
Yes I still remember it, it looked very nice.
With a nice and simple tablet UI, I’m pretty sure it could be a big success as an iPad app right now.
Oh, that’s it! 
I like that better than the current planar rotation because it’s more adjustable.
Even if it is a bit weird, it should be useful for many people. If we can restore the default, we don’t need to limit it.
It could be a type of slider with X and Y sliders instead of 360°.
The distortion is very bad, Matcap are simply not meant to be rotated, at least not to that extent.
I don’t really want to add 2 sliders for a feature that is already bothering me.
I’ll experiment a few things but don’t get your expectation high 
Ok…I’ve been working with iPad only for a long time, so I’m happy to see the evolution of various apps.
By the way, I mainly use Paintstorm for painting. Other apps like Artset and Artrage are also good for analog reproduction.
https://twitter.com/i/events/885609810913251328