yade-users team mailing list archive

[Bruno Chareyre <bruno.chareyre@xxxxxxxxxxx>]

> I modified 2 or 3 lines in TriaxialCompressionEngine in order to 
> update the friction angle from compactionFrictionDeg to FrictionDeg 
> when the state transition is performed manually (by editing the .xml 
> file) from Iso_compaction to Triax_loading. (but I am not sure to 
> respect the idea of the person who written this part of the code)
It makes sense. I will review your changes when you will have them 
committed.


> In addition, during the state transition, I would like to update the 
> tangent of friction angle for all interaction and not only "real" 
> interaction
Why?!
By design, interactions which are not "real" have really no reason to be 
considered. See them as if they don't even exist. They will be seen as 
"new" interactions if, by any chance, they become real again. So, they 
will be re-initialized anyway, and your updated values will be 
overwritten before they can be actually used.
Did you try it already? I suspect it would lead to some i->friction = x 
with i the null pointer, then Yade crash.
> (from a discussion between Jerome and Bruno I understood that the 
> transition (isReal = 0 and isNew = 0) => (isReal = 1 and isNew = 0) 
> will not happen, but I would prefer to have several "protections" than 
> only one).
Sticking with the current design rule is the best way to avoid problems 
if you ask me. If this transition from (0,0) to (1,0) could occure, it 
would be a major bug, and a correct value of friction would not help a 
lot (think about the tangential displacement, which would be totally 
wrong : current_position - position_when_the_contact_was_lost).

> My question: I may want to submit code modifications in opposition 
> with previous developments. Thus, what is the philosophy? submit 
> directly these modifications to svn, or via a yade developer who will 
> filter the modifications?
Personnaly, I'd prefer people to at least point it out when they modify 
some code that I'm developping/using (Triaxial and related classes). 
Exactly like you just did. The commit itself can (should) be done by the 
one who modified the code (you).

To summarize :
1/ For changing friction after manual editing - or any other change 
consistent with current philosophy : let you commit your change.
2/ For accessing unreal values, it is really not consistent with the 
current contact logic. If you really want this behaviour, or anything 
else in opposition with previous logic, it is better to create your own 
separate class.

An important point when you modify an existing class : your changes must 
keep the default behaviour unchanged (might sound obvious).
One usual way for this is :

class C {

+ bool newFeatureActivation;
}

in the constructor : newFeatureActivation = false, and then define the 
modified behaviour in a if (newFeatureActivation) { ... }.

This precaution is not needed for your friction update though, as it is 
already doing nothing by default.

Bruno


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Chareyre Bruno
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