Search the Community

Hey guys I have a simple enough problem i wanted to solve in HDK, and i managed to do it, however im sure there has to be a more elegant solution with enough knowledge of HDK classes. I wanted to do a simple sop that compares the same user chosen attribute from two different inputs, and either groups the difference as points group, or deletes points that have the same attrib value across both inputs. Basically i just have the same point cloud on both inputs, the second input has a timeshift node that looks up the previous frame. Its a simple enough exercise, however i have to ask if anyone knows if im reinventing the wheel, if the interface for doing stuff like this is more simple to use, or could give me some hints on how to do it better. Now the problem i came across was how would one define an array to hold values of an attribute of type we dont know in advance? Ive used a hacky solution where i would do the following in cookMySop() //get ptrs to our input geoconst GU_Detail *firstInput = inputGeo(0); const GU_Detail *secondInput = inputGeo(1); //find if attr exist in those geos, lookup is our string that holds the attr name user chose from the UI const GA_Attribute *fattr = firstInput->findAttribute(GA_ATTRIB_POINT, lookup); const GA_Attribute *sattr; //get our total numpts std::cout << "total num of pts (1): " << firstInput->getPointMap().indexSize() << std::endl; // std::cout << (GA_StorageClass)fattr->getStorageClass() << std::endl; //if we have hooked a second input, find attrs and get total numpts if(secondInput) { sattr = secondInput->findAttribute(GA_ATTRIB_POINT, lookup); std::cout << "total num of pts (2): " << secondInput->getPointMap().indexSize() << std::endl; } // If source attribute doesn't exist, error. if (!fattr || !sattr) { addError(SOP_ATTRIBUTE_INVALID, (const char *)lookup); return error(); } //define our arrays UT_ValArray<int32> ptNumListFirst; UT_ValArray<int32> ptNumListSecond; UT_ValArray<int32> ptNumListDiff; //only if our attr is not string shall we compare, have no idea how to figure out string yet if(fattr->getStorageClass() == GA_STORECLASS_INT) { std::cout << "Yes it is a numeric!" << std::endl; //feed our list of attr values in the array FIRST GEO gdp->getPointAttributeAsArray(fattr,gdp->getPointRange(), ptNumListFirst); //if we have connected the second geo if(secondInput) { //feed our list of attr values in the array SECOND GEO secondInput->getPointAttributeAsArray(fattr,secondInput->getPointRange(), ptNumListSecond); //compare our first and second input list and feed the diff in the third input //this is our class method compareUTArrays(ptNumListFirst, ptNumListSecond, ptNumListDiff); } } I actually dont allow the user to pick an attrib from the list thats not int or the node errors out, so basically im forcing the user to choose an int attr. Im sure there is a better way of doing this. Also i tried using the sortedIntersection() method of the UT_ValNumeric array type, however i could never get the difference to be calculated so i had to write my own implementation of the method (compareUTArrays()). Also in the end i use this approach to get the pts in an array that either needed to be grouped or deleted, im not entirely sure if its the "proper" way of doing things: //if we ticked new group, create a new group for pts if(newGrp || deletePts) { //create our new group GA_PointGroup *diffGrp; diffGrp = gdp->newPointGroup(grpName, false); //create a temp group we will delete later if we need to delete points GA_PointGroup *delGrp = gdp->newPointGroup("__tempDelGrp__", false); //get the handle to our int attribute //would prefer if i could somehow make the handle type recognize the attr data type GA_ROHandleI lookup_attr(fattr); int32 value; //iterate thru all points for(GA_Iterator it(gdp->getPointRange()); !it.atEnd(); ++it) { GA_Offset offset = *it; value = lookup_attr.get(offset); std::cout << value << " is value of pts attr" << std::endl; //iterate thru the array and if we have found same attr value add it to the group for(UT_ValArray<int32>::const_iterator itarr = ptNumListDiff.begin(); itarr != ptNumListDiff.end(); ++itarr) { if(value == *itarr) { diffGrp->addOffset(offset); continue; } } } //the diff between the first and second input is found in the diff array //however we need to delete everything thats not the diff, and that is the second inputs members translated into first for(GA_Iterator it(secondInput->getPointRange()); !it.atEnd(); ++it) { GA_Offset offset = *it; delGrp->addOffset(offset); } if(deletePts) { gdp->destroyPointOffsets(GA_Range(*delGrp)); gdp->destroyGroup(delGrp); } } Now i guess i can use the GA_Attribute.getStorageClass and a switch or if statement and initialize my arrays according to the type, but like i said somehow im sure there has to be a more intelligent way of doing this Also im a bit confused about the bumpDataId, what should i do in this case? If i just group my points and dont even modify the geo or attrib values, should i signal houdini to bumpDataId and whats the syntax for doing that? If i delete points however im sure i have to inform houdini that ive modified geo, which class or method should i use to do something like that? I hope all of this makes sense, let me know if it doesnt ill try and elaborate better Any help would be greatly appreciated Thanks Serge