A fast way to remove point in HDK

[eko]

Hi, all
I am trying to delete points in HDK using the

Code:

gdp->destroyPointOffsets(GA_Range(*delgroup));

There are about 30000000 points in delgroup. It works fine but it seems "gdp->destroyPointOffsets" method is very slow.
I found if I use the "Blast" Sopnode in houdini and select the delgroup. It works much faster（about 50 times） than "destroyPointOffsets" function in hdk.
I wonder that is there any ways to makes delete points faster in HDK.
Thanks!

[edward]

How many points total? The Blast SOP needs to make a copy of the geometry anyhow, so in certain cases, it will *copy* the points you want to keep instead (via mergePoints()). It might also be faster if you convert the point group to a primitive group first and then delete by primitives. However, it depends on the actual geometry that you have.

[eko]

Hi,thanks for reply!

There are about 70,000,000 points total! There are all points and no primitive. I take your advises and use gdp->appendPointBlock() for adding points and used multi thread For setting Postion of these points. But There are some points that I don't want.

I try these:

gdp->destroyUnusedPoints(pointgroup);
gdp->deletePoints(*pointgroup);
gdp->destroyPointOffsets(GA_Range(*pointgroup));

But they are not fast as the Blast Sop.

[edward]

No, I mean to try copying the points you want to keep instead of deleting the points.

const GU_Detail &input_geo = *inputGeo(/*input_index*/0, context);
pointgroup->toggleEntries(); // pointgroup is now the points to keep
gdp->stashAll();
gdp->mergePoints(input_geo, pointgroup, /*keepgrps*/true, /*internal*/false);
gdp->destroyStashed();

Or if you don't have an input gdp to copy from, then perhaps something like this (but likely slow):

pointgroup->toggleEntries(); // pointgroup is now the points to keep
GU_Detail geo;
geo.mergePoints(*gdp, pointgroup, /*keepgrps*/ true, /*internal*/ false);
gdp->duplicate(geo, /*unused*/0, GA_DATA_ID_CLONE);

 

[eko]

Hi, Edward. It's almost the same number between keep and deleting the points.

Thanks for your help. I got it. It' works very well.

I use

pointgroup->toggleEntries(); // pointgroup is now the points to keep
GU_Detail geo;
geo.mergePoints(*gdp, pointgroup, /*keepgrps*/ true, /*internal*/ false);
gdp->duplicate(geo, /*unused*/0, GA_DATA_ID_CLONE);