Correct . However it is expensive(for a dev) to do it that way when you know
you can just use one unsigned int that get assigned in every call of
setdepdirty() , and it goes also with the fact that you only have to worry
about one attribute change at a time , and it is not necessary to store every
indices like that , the use of MArrayDataHandle::jumpToArrayElement() with
MArrayDataHandle::elementIndex() is a recommended combo to iterate over the
array of compounds/element even in the documentation , and you will need to
call MDataBlock::inputArrayValue() once you are in compute anyway so … this
m_element_index thing is just here so I know what element is tingling so that I
don’t have to do expensive complete calculations, it’s lazy evaluation if you
want
Sent from Mail for Windows 10
From: Rob Engle
Sent: Saturday, March 17, 2018 7:40 PM
To: Python Programming for Autodesk Maya
Subject: Re: [Maya-Python] Why most people use boolean flags insteadofcatching
the MPlug ?
My question is slightly off topic to this thread but motivated by the posted
code sample...
I was under the impression that setDependentsDirty can be called any number of
times with different arguments before compute is called (if ever). This would
mean that storage of m_element_index (or caching of any information from
setDependentsDirty) would need to store more than just the one call. This
could be solved by making m_element_index an array of cached values and compute
handling all of them. Is this right?
Rob
On Saturday, March 17, 2018 at 7:03:16 AM UTC-7, justin hidair wrote:
/*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*/
}
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