Re: Image plot on back wall

[davidf(at)dfanning.com (David Fanning)]

Martin Schultz (m218003@modell3.dkrz.de) shows that the
Germans do too have a sense of humor when he writes:

> OK. I guess, I see clearer now: it's not objects that I don't like, but
> the applications that are built on objects! ... Nowadays it seems we have to *talk*
> to these machines and *ask* them to *please* try to accomplish at least
> a tiny fraction of what we had in mind. 

Even though your program didn't actually produce anything
on the display (typical for object graphics programs,
by the way) when I tried to run on my machine, it did
manage to capture some of the flavor of object graphics
programs. :-)

But RSI never claimed this stuff wasn't low level. They
just haven't come up with much in the way of higher level
tools. And I'm not sure we want them to anyway. Heck, you
will find *much* better IDL programs than RSI puts out
just by looking around the web. How come Liam Gumley
has to write a TV command that actually works on the
machines we run IDL on!? And images are IDL's thing,
for goodness sake.

But to give RSI some credit, they do have new things
in each new release that make object graphics easier
to use. In IDL 5.3, I think (I couldn't get my old
beta fired up for some reason, so I couldn't try this),
they now have these handle-like things you can put
around your lights. Sort of like the lights we use
in the theater. That way you can *see* the lights in
your scene and physically move them around and position
them. That will make things a LOT easier to work with.

The thing that absolutely makes object graphics so 
impossible on occasions is that you get absolutely
no feedback on what has gone wrong. Since *everything*
is possible, object graphics doesn't care if you
rotate the surface under the rug where it can't be
seen. Maybe that is where you intended to put it.
Meanwhile you sit and stare at an empty screen for
hours, whispering every incantation you know, hoping
upon hope that *something* might show up to give you
your bearings.

I'm telling you, I only have so much patience for
staring at a black rectangle on the display that is
suppose to be an image. I finally, yesterday, had
to ask RSI for an example that worked. At first
they pointed me to their Show3_Object example
in the example/objects directory, which I had
already examined, since that is exactly what I
was trying to do. But that example worked as
well as mine did: a black rectangle instead of
the image. Don't these people look at the output
of these programs before they pass them off as
examples of how to write programs!?

But eventually I did get a working example. That is
the only way I would have discovered, I think, that
a 24-bit image was required. I tend, like many
people, to be *way* to naive when it comes to 
believing what I read.

So, OK, it was a frustrating day. But I learned a
couple of new things, and knowledge that comes
too easy isn't fully appreciated. What I know will
help me sell books. What I can't figure out is why
RSI believes that their customers, who have no
such financial incentive to spend hours learning
this on their own, will be willing (or able) to 
give up direct graphics for this.

Cheers,

David
-- 
David Fanning, Ph.D.
Fanning Software Consulting
Phone: 970-221-0438 E-Mail: davidf@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com/
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