Bob wrote:

> Miguel, could this be associated with going to an integer z-buffer?

I do not think that what I am seeing is related to the conversion from
shorts to ints for the z-buffer. see more below.

> One thing to check might be whether the slowness is related to the
> applet height and width -- larger size, more pixels, right?
>
> I haven't been noticing a problem at this page -- have others?

My linux laptop has a 1.6 Ghz Pentium M ... about 2 years old.

Even with a larger window, the trunk build seems snappier than the XTALX
applet.

I am wondering if it is related to something with the event model changes.

Q: Which code was the XTALX applet built from?

Nico wrote:
>> My own observation was not that rotation was sluggish but that it was
>> much more CPU intensive, so yes probably sluggish on slower computers
>> (the CPU usage was multiplied by something like 3 when "spin on"

The spin code tries to maintain a high frame rate.

Each time the screen paints it must clear the screen to the background
color and clear the zbuffer to "infinite" distance. This is a very simple
loop, but it is a somewhat expensive operation. It used to be the case
that each pixel was 6 bytes (4 byte color + 2 byte z-buffer). Now each
pixel requires 8 bytes (4 byte color + 4 byte z-buffer). That is a 2/6 ->
1/3 increase in the amount of memory that we are clearing.

Later, we do a lot of z-buffer testing, and we are wading through twice as
much memory.

The size of the CPU cache has a non-linear impact in many cases.

Putting it all together, it sure does't seem to me that this change should
account for a 3-fold increase in CPU usage.

So, my answer is ... I don't know :-(


Q: Nico, are you consistently seeing this 3-fold increase in CPU usage
with spin?


I will see how difficult it will be for me to revert back to shorts in
order to understand what is going on ... not that going back to shorts is
an option.


Miguel



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