alice-teacher Screen goes dark when "Say" command used?

[Don Slater]

It is primarily a platform issue, although I am interested in the replies that it does not seem to be universally true. 

When Alice was first created, it was created for the PC platform, and the rendering engine for the runtime window was implemented with DirectX. When the Mac version of Alice 2 was created, the Mac did not  support DirectX, and so it was implemented with OpenGL.

There is not a direct correlation between DirectX calls and OpenGL calls, and so you will see artifacts such as the darkening of the background when the speech and thought bubbles appear, but also when billboards with some transparency elements (such as the fairy wings, the cloud effect) appear in a black box, because OpenGL deals with the alpha channel differently than DirectX.

We have been wrestling with this for some time, and short of rewriting the Alice 2 PC version so that it is also OpenGL we have not found a satisfactory solution.

Alice 3 is using OpenGL for all platforms.

All the best,
Don Slater

On Jan 23, 2012, at 8:23 PM, EILEEN PELUSO wrote:

> I rarely use Macs, but have seen the same phenomenon – pretty much all the time, as I recall – on that platform.  I’ve never seen it on our PCs.
>  
> From: alice-teachers-bounces+pelusoem=lycoming.edu at lists.andrew.cmu.edu [mailto:alice-teachers-bounces+pelusoem=lycoming.edu at lists.andrew.cmu.edu] On Behalf Of Roger Wistar
> Sent: Monday, January 23, 2012 10:15 AM
> To: alice-teachers at lists.andrew.cmu.edu
> Subject: alice-teacher Screen goes dark when "Say" command used?
>  
> One of my students noticed that the lighting in his program seems to go dark when certain "Say" commands are used. It doesn't happen all the time, and it does not seem to be a problem with the syntax of his program. Has anyone else noticed this problem, and is there some way to fix it?
>  
> The problem has only been noticed on Macs — is the platform the issue?
>  
> Sample program is attached.
>  
> Thanks!
>  
> Roger Wistar
> The Hotchkiss School
> rwistar at hotchkiss.org
> _______________________________________________
> alice-teachers mailing list
> alice-teachers at lists.andrew.cmu.edu
> https://lists.andrew.cmu.edu/mailman/listinfo/alice-teachers