Advice 
Author Message
 Advice

Hello,

Can somebody give me a name (with url) of a good application for creating
vrml worlds?

Thank you very much
delarou



Mon, 06 May 2002 03:00:00 GMT  
 Advice


Quote:
> Hello,

> Can somebody give me a name (with url) of a good application for
creating
> VRML worlds?

> Thank you very much
> delarou

Check www.parallelgraphics.com
--
Tima
http://www.orc.ru/~timofeev/index_en.htm
"When things are going well,
      something will go wrong."

Sent via Deja.com http://www.deja.com/
Before you buy.



Tue, 07 May 2002 03:00:00 GMT  
 Advice
Hi everyone,

Today I was playing with programming rules for piling boxes in VRML.
See stack.wrl  at http://www.bk.tudelft.nl/users/stelling/internet/stack.wrl

If you look at the code, you see many quite difficult conditions which form
the logic for some gravity and piling behaviour of just three boxes.
I was wondering if JavaScript provides language structures (special ways of
programming) in order to make such rules more general?
If I have 10 or even 1000 boxes, how can I program the general rules for
piling?
What programming concepts are used to evaluate a whole structure if the
structure is too complex for a programmer to pre-think the whole chain of
individual events and their effects?

I hope this is not too far from the VRML topic, anyway, I hope you like
playing with the boxes.

Martijn Stellingwerff.



Thu, 09 May 2002 03:00:00 GMT  
 Advice

Quote:

> Today I was playing with programming rules for piling boxes in VRML.
> See stack.wrl  at http://www.bk.tudelft.nl/users/stelling/internet/stack.wrl

Very clever.  About the only thing I'd suggest changing is
to change the bitwise ANDs "&" to logical ANDs "&&".  While

        if (x==1) & (y==2)

will return the right result because of the way the
interpreter evaluates TRUE conditions, when you start
NOTing you can run into trouble.  It's usually better
to use

        if (x==1) && (y==2)

from the git-go and get into a good habit.

And (from my old fortran days) I like to parenthesize
everything:

        if ((x==1) && (y==2))

but that's just because I don't trust compilers and
interpreters.  Adding the parentheses clarifies the job
the interpreter has to do.

Quote:
> If you look at the code, you see many quite difficult conditions which form
> the logic for some gravity and piling behaviour of just three boxes.
> I was wondering if JavaScript provides language structures (special ways of
> programming) in order to make such rules more general?

Yup.  When you have a number of items that are identical
and are subject to identical operations, you can use arrays.
In this case, since the thing that discriminates between
each data object is really numeric -- first box, second
box, etc. -- there's even a good match between the problem
space and the array construct.  MyMFVec3f[0] is really the
first box (zeroth, actually -- ECMAScript, like many C-based
programming languages starts all arrays at zero), and so
on.

In your case, you could substitute an MFVec3f for your
SFVec3f's and use an index in a loop expression:

        for (i=0; i<numBoxes; i++) {
            MyMFVec3f[i] = whatever;
        }

You should read what the spec says about adding elements
to MFvariables.  It generally works the way you want it
to.  For example,

        MyMFVec3f[numBoxes++] = new SFVec3f(1.0,2.0,3.0);

will add on a new element to the tail end of the array,
increment the number of boxes you now have, and allocate
the space for the new element automatically.

Quote:
> If I have 10 or even 1000 boxes, how can I program the general rules for
> piling?

I didn't see anything there that couldn't (at first glance)
be put into arrays.

Quote:
> What programming concepts are used to evaluate a whole structure if the
> structure is too complex for a programmer to pre-think the whole chain of
> individual events and their effects?

Some say object-oriented programming defers the need to
think about problems, sometimes indefinitely.  The same
people say that there are two classes of problems: object-
oriented problems, and problems that have been solved.

There really isn't any substitute for thinking about the
problem and then unambiguously telling the computer what
to do about it.
--
Bob Crispen
crispen at hiwaay dot net
What we're looking for: destinations.
What we end up getting: journeys.



Fri, 10 May 2002 03:00:00 GMT  
 
 [ 5 post ] 

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