It seems there is a desire for functionality, on-line DRC, I fear it cannot 
be delivered in the immediate future without impacting upon performance.
Every thing added to on-line DRC kills performance.

At the company I work for we have been using QualEcad for a couple of years 
now. We don't bother creating or maintaining 3D library models,
we just import heights for footprints from our database. It literally takes 
a few seconds to do. When we want to look at a height issue (Assuming
you've put some rooms down. Not hard to do) we just choose to view it. It 
all happens in Protel and takes "seconds" to do. You do need a good
video card supporting OpenGL. To do this while placing is not that big a 
deal. Not for us anyway.

This is so simple I don't think I want Protel to come up with anything 
else. Not just yet anyway. With the instrumentation we make we deal with
a lot of height issues and have not had a need for anything as elaborate as 
on-line DRC. I agree it is logical to do it but I think the capability for
Protel to get it right with their current system and performance issues, is 
quite some time off.

Passing note: In over 12 years I have only came across two CAD vendors that 
have provided me with excellent service, CAM350 (not much good
now though, prices have gone through the roof now Innoveda took over) and 
QualEcad. Well done John.

At 12:27 PM 8/02/2002 -0500, you wrote:
>QualECAD has been highly recommended by users. Yes, it appears that 
>QualECAD allows the assignment of a height attribute to rooms, and it 
>detects height violations based on the footprint 3-D models (and QualECAD 
>gives users, if I am correct, gives users access to the models).
>However, this is, if I am correct, a viewer. On-line DRC of height 
>restriction would be *much* more useful in a practical sense. Being able 
>to pick up a component and see immediately -- by the appearance of the 
>error color -- that there is a height violation -- cuts out a huge amount 
>of work.
>It is like on-line DRC in general. The original CAD DRCs were batch 
>programs run after the design was done. That was a great improvement, but 
>on-line DRC was a true productivity boon. Fixing errors could take ten 
>times as much time as making things right in the first place. Sometimes 
>late discovery of an error is a major disaster, if a lot of work has been 
>done that depends, say, on components location. Even if routing has been 
>postponed to get approval of placement, many components might need to be 
>moved to fix a problem. Much, much better if the height violation is 
>avoided from the beginning.
>This is a *placement* tool, thinking of 3-D in terms of viewing and 
>checking is quite limited, it is the placement assistance that is truly 
>important. Autoplace would necessarily respect height rules as well. It is 
>difficult to think of a more central operation to PCB design than placement!
>Abdulrahman Lomax
>Easthampton, Massachusetts USA


Colin Weber

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