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Subject: 
Re: Some Words To BFC
Newsgroups: 
lugnet.cad.dev
Date: 
Tue, 4 Apr 2000 11:29:42 GMT
Viewed: 
1671 times
  
If you 're able to correct wrong things in a model so BFC can be used, is it
than not possible to make a program that goes over al your parts once and
corrects all the parts so that all your models will be automatically
correct?


Michael Lachmann <michael.lachmann@maxmobil.at> schreef in berichtnieuws
FsHJv3.Bxr@lugnet.com...
Hy,

I finaly got internet-access here, and could follow the discussions about • BFC.
Some words I would like to say first:
I think it doesn't make sence to blame Steve about BFC stuff, since I • asked
him if the spec
is in a state that we could try it. Since it was (and I know that it's • still
not complete) I tried
implementing it into MLCad.
Steve and I did several tests, found missing things (matrix inversions) • and
corrected them.
So if someone likes to blame Steve, he should blame me as well since I did • the
coding and therefor
made the standard realistic.
I believe we should all play together, instead of writing crazy letters.

So ... no for the real stuff!

I warn everbody to put to much additional into BFC since I found out, that • the
BFC overhead is not to
underastimate. To much additional checks would cost drawing speed and • therefor
make BFCed file-drawing slower.

The performance gain in MLCad using BFC varies from 0% up to 30%. This is
influenced by e.g. the actual
viewing angle of the model and the sice of the areas removed by a BFC • check.
The bigger they are the more time
you win ... So in realy big models it might even happen that you need more
time drawing the model, than without
BFC statements!

My suggestion is to keep the BFC statements as simple as possible. Meaning • we
should rather correct wrong defined
parts than letting the software correct wrong definitions!!!!
As an example I take the matrix-repair statement:
Checking the matrix for bad definitions is easy, but then you have to find
out, which of the values is wrong, and correct it.
The additional code to do this correction is not much, but will cost
additional calculation time.
Someone might say thats not much, but an average model has arround 500000!
triangles and quads. So we have to multiply this
small time by 500000 and then we are somewhere in the second range!

I think the BFC standard (I know there is no real) is realy good already, • no
need to make additional effort and we should
try to make it even faster (not slower).

So my recomendation is: Just enjoy it, make use of it, make good parts and
everything is perfect!

Michael



Message has 1 Reply:
  Re: Some Words To BFC
 
(...) <SNIP> Sure that is possible, I could imagine having a seperate tool for this, or even implementing it as a helper-function inside MLCad which does something like a BFC conversion. This solution would definitly be a better aproach. Michael (24 years ago, 4-Apr-00, to lugnet.cad.dev)  

Message is in Reply To:
  Some Words To BFC
 
Hy, I finaly got internet-access here, and could follow the discussions about BFC. Some words I would like to say first: I think it doesn't make sence to blame Steve about BFC stuff, since I asked him if the spec is in a state that we could try it. (...) (24 years ago, 4-Apr-00, to lugnet.cad.dev)  

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