/*in the boolean flag case :
lets say aDistance and aAmount are both child of a compound in an array of
compound*/
MStatus myclass::setDependentsDirty(const MPlug &plug, MPlugArray &affect)
{
mayastream << "dirtying. .." << "\n";
if(plug.isChild() && plug.attribute() == aDistance )
{
e_distance_change= true ;
/*get index to target this attribute specifically will be
useful with MArrayDataHandle*/
m_element_idx = plug.parent().logicalIndex();
}
else
if(plug.isChild() && plug.attribute() == aAmount )
{
e_amount_change= true ;
/*get index to target this attribute specifically will be
useful with MArrayDataHandle*/
m_element_idx = plug.parent().logicalIndex();
}
return MPxNode::setDependentsDirty(plug , affect );
}
MStatus myclass::compute(...)
{
//typical moves:
cmp_array = datablock.inputArrayValue(aArray);
if( e_distance_change == true )
{
/* perform targeted calculations
use cmp_array.jumpToElement(m_element_idx)*/
}
else
if(e_amount_change == true )
{
/*perform targeted calculations
use cmp_array.jumpToElement(m_element_idx)*/
}
//...
}
/*in the use Plug case :
lets say aDistance and aAmount are both child of a compound in an array of
compound*/
MStatus myclass::setDependentsDirty(const MPlug &plug, MPlugArray &affect)
{
mayastream << "dirtying. .." << "\n";
m_dirty_plug = plug;
/*just one line and we can use the plug however we want
the benefit is we also have all the methods of MPlug
like .isConnected and so on , aslong as the method stay ) const
we can use it in compute without a problem...
we can use this to get index in array :
m_dirty_plug.parent().logicalIndex();
now to compute() ... */
return MPxNode::setDependentsDirty(plug , affect );
}
MStatus myclass::compute(...)
{
//things I never saw:
cmp_array = datablock.inputArrayValue(aArray);
if(m_dirty_plug.isChild() && m_dirty_plug.attribute() == aDistance )
{
/*perform targeted calculations
use all the cool const methods of MPlug
use cmp_array.jumpToElement(m_dirty_plug.parent().logicalIndex())*/
}
else
if(m_dirty_plug.isChild() && m_dirty_plug.attribute() == aAmount)
{
/*perform targeted calculations
use all the cool const methods of MPlug
use cmp_array.jumpToElement(m_dirty_plug.parent().logicalIndex())*/
}
/*...
optionnaly at the end you can if you want reset m_dirty_plug with
m_dirty_plug.setMObject(MObject::kNullObj) but it's not really required
because it
will be reassigned ... it allow to use .isNull() in particular cases tho
lot of things you can do with just a plug instead of 4 boolean flags, it's
also
way easier to maintain*/
}
Sent from Mail for Windows 10
From: Marcus Ottosson
Sent: Saturday, March 17, 2018 12:01 PM
To: [email protected]
Subject: Re: [Maya-Python] Why most people use boolean flags instead ofcatching
the MPlug ?
My question to you is, who is most people? Maybe if you share an example we
could more easily spot why the decision to use a boolean was made for that
particular case.
If I had to guess, then I'd think it's the same reason as to why it is ill
advised to store a reference to an MObject; they aren't built to last. That is
to say, storing an MObject, changing the Maya scenegraph, and later accessing
the MObject could yield unexpected results, and in some cases even lead to
crash, because the memory it points to is no longer what you think it is.
However if you know that there is no chance of the scenegraph to change for the
duration of you storing this member variable, then I would think you should be
fine. That is why I'm asking for examples, because odds are the examples you've
have been unable to guarantee such conditions.
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