Houdini Engine 3.0
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Groups Sample

For documentation on the groups APIs, see Groups.

The example below shows how to create groups on an input node and query their membership. It will create a cube, marshal it in, and create a point group on the input geometry. It goes on to create a transform SOP, connect the two nodes together, and sets the parameters on the transform SOP such that it affects only the points in the group we created. The scene at this point is dumped, so that we can see the result in Houdini.

Finally, the transform SOP asset is cooked, we then query its geometry for group information and show via output that the group is intact and display the group membership.

#include <HAPI/HAPI.h>
#include <iostream>
#include <string>
#define ENSURE_SUCCESS( result ) \
if ( (result) != HAPI_RESULT_SUCCESS ) \
{ \
std::cout << "Failure at " << __FILE__ << ": " << __LINE__ << std::endl; \
std::cout << getLastError() << std::endl; \
exit( 1 ); \
}
#define ENSURE_COOK_SUCCESS( result ) \
if ( (result) != HAPI_RESULT_SUCCESS ) \
{ \
std::cout << "Failure at " << __FILE__ << ": " << __LINE__ << std::endl; \
std::cout << getLastCookError() << std::endl; \
exit( 1 ); \
}
static std::string getLastError();
static std::string getLastCookError();
static std::string getString( HAPI_StringHandle stringHandle );
int
main( int argc, char **argv )
{
HAPI_Session session;
ENSURE_SUCCESS( HAPI_Initialize( &session,
&cookOptions,
true,
-1,
nullptr,
nullptr,
nullptr,
nullptr,
nullptr ) );
HAPI_NodeId cubeNode;
ENSURE_SUCCESS( HAPI_CreateInputNode( &session, &cubeNode, "Cube" ) );
ENSURE_SUCCESS( HAPI_CookNode( &session, cubeNode, &cookOptions ) );
int cookStatus;
HAPI_Result cookResult;
do
{
cookResult = HAPI_GetStatus( &session, HAPI_STATUS_COOK_STATE, &cookStatus );
}
while (cookStatus > HAPI_STATE_MAX_READY_STATE && cookResult == HAPI_RESULT_SUCCESS );
ENSURE_SUCCESS( cookResult );
ENSURE_COOK_SUCCESS( cookStatus );
cubePart.faceCount = 6;
cubePart.vertexCount = 24;
cubePart.pointCount = 8;
ENSURE_SUCCESS( HAPI_SetPartInfo( &session, cubeNode, 0, &cubePart ) );
attrInfo.count = 8;
attrInfo.tupleSize = 3;
attrInfo.exists = true;
ENSURE_SUCCESS( HAPI_AddAttribute( &session, cubeNode, 0, "P", &attrInfo ) );
float positions[ 24 ] = { 0.0f, 0.0f, 0.0f, // 0
0.0f, 0.0f, 1.0f, // 1
0.0f, 1.0f, 0.0f, // 2
0.0f, 1.0f, 1.0f, // 3
1.0f, 0.0f, 0.0f, // 4
1.0f, 0.0f, 1.0f, // 5
1.0f, 1.0f, 0.0f, // 6
1.0f, 1.0f, 1.0f }; // 7
ENSURE_SUCCESS( HAPI_SetAttributeFloatData( &session, cubeNode, 0, "P", &attrInfo, positions, 0, 8 ) );
int vertices[ 24 ] = { 0, 2, 6, 4,
2, 3, 7, 6,
2, 0, 1, 3,
1, 5, 7, 3,
5, 4, 6, 7,
0, 4, 5, 1 };
ENSURE_SUCCESS( HAPI_SetVertexList( &session, cubeNode, 0, vertices, 0, 24 ) );
int face_counts [ 6 ] = { 4, 4, 4, 4, 4, 4 };
ENSURE_SUCCESS( HAPI_SetFaceCounts( &session, cubeNode, 0, face_counts, 0, 6 ) );
ENSURE_SUCCESS( HAPI_AddGroup( &session, cubeNode, cubePart.id, HAPI_GROUPTYPE_POINT, "pointGroup" ) );
int groupElementCount = HAPI_PartInfo_GetElementCountByGroupType( &cubePart, HAPI_GROUPTYPE_POINT );
int * pointMembership = new int[ groupElementCount ];
for ( int ii = 0; ii < groupElementCount; ++ii )
{
if ( ii % 2 )
{
pointMembership[ ii ] = 1;
}
else
{
pointMembership[ ii ] = 0;
}
}
ENSURE_SUCCESS( HAPI_SetGroupMembership( &session, cubeNode, cubePart.id, HAPI_GROUPTYPE_POINT,
"pointGroup", pointMembership, 0, groupElementCount ) );
ENSURE_SUCCESS( HAPI_CommitGeo( &session, cubeNode ) );
HAPI_NodeId xformNode;
ENSURE_SUCCESS( HAPI_CreateNode( &session, -1, "Sop/xform", "PointGroupManipulator", false, &xformNode ) );
ENSURE_SUCCESS( HAPI_ConnectNodeInput( &session, xformNode, 0, cubeNode ) );
// Set xform parameters
HAPI_NodeInfo xformInfo;
ENSURE_SUCCESS( HAPI_GetNodeInfo( &session, xformNode, &xformInfo ) );
HAPI_ParmInfo * parmInfos = new HAPI_ParmInfo[ xformInfo.parmCount ];
ENSURE_SUCCESS( HAPI_GetParameters( &session, xformNode, parmInfos, 0, xformInfo.parmCount ) );
int groupParmIndex = -1;
int tParmIndex = -1;
for ( int ii = 0; ii < xformInfo.parmCount; ++ii )
{
std::string parmName = getString( parmInfos[ ii ].nameSH );
if ( parmName == "group" )
{
groupParmIndex = ii;
}
if ( parmName == "t" )
{
tParmIndex = ii;
}
}
if ( groupParmIndex < 0 || tParmIndex < 0 )
{
std::cout << "Error: couldn't find required parameters group or t" << std::endl;
exit( 1 );
}
float tParmValue[ 3 ] = { 0.0f, 1.0f, 0.0f };
ENSURE_SUCCESS( HAPI_SetParmFloatValues( &session, xformNode, tParmValue, parmInfos[ tParmIndex ].floatValuesIndex, 3 ) );
ENSURE_SUCCESS( HAPI_SetParmStringValue( &session, xformNode, "pointGroup", groupParmIndex, 0 ) );
ENSURE_SUCCESS( HAPI_CookNode( &session, xformNode, &cookOptions ) );
int xformCookStatus;
HAPI_Result xformCookResult;
do
{
xformCookResult = HAPI_GetStatus( &session, HAPI_STATUS_COOK_STATE, &xformCookStatus );
}
while (xformCookStatus > HAPI_STATE_MAX_READY_STATE && xformCookResult == HAPI_RESULT_SUCCESS );
ENSURE_SUCCESS( xformCookResult );
ENSURE_COOK_SUCCESS( xformCookStatus );
ENSURE_SUCCESS( HAPI_SaveHIPFile( &session, "examples/groups.hip", false ) );
HAPI_GeoInfo xformGeoInfo;
ENSURE_SUCCESS( HAPI_GetGeoInfo( &session, xformNode, &xformGeoInfo ) );
int numGroups = HAPI_GeoInfo_GetGroupCountByType( &xformGeoInfo, HAPI_GROUPTYPE_POINT );
std::cout << "Number of point groups on xform: " << numGroups << std::endl;
HAPI_PartInfo partInfo;
ENSURE_SUCCESS( HAPI_GetPartInfo( &session, xformNode, 0, &partInfo ) );
int numElementsInGroup = HAPI_PartInfo_GetElementCountByGroupType( &partInfo, HAPI_GROUPTYPE_POINT );
std::cout << numElementsInGroup << " points in pointGroup" << std::endl;
int * membership = new int[ numElementsInGroup ];
ENSURE_SUCCESS( HAPI_GetGroupMembership( &session, xformNode, partInfo.id, HAPI_GROUPTYPE_POINT,
"pointGroup", nullptr, membership, 0, numElementsInGroup ) );
for ( int ii = 0; ii < numElementsInGroup; ++ii )
{
if ( membership[ ii ] )
{
std::cout << "Point " << ii << " is in pointGroup" << std::endl;
}
}
HAPI_Cleanup( &session );
return 0;
}
static std::string
getLastError()
{
int bufferLength;
&bufferLength );
char * buffer = new char[ bufferLength ];
HAPI_GetStatusString( nullptr, HAPI_STATUS_CALL_RESULT, buffer, bufferLength );
std::string result( buffer );
delete [] buffer;
return result;
}
static std::string
getLastCookError()
{
int bufferLength;
&bufferLength );
char * buffer = new char[ bufferLength ];
HAPI_GetStatusString( nullptr, HAPI_STATUS_COOK_RESULT, buffer, bufferLength );
std::string result( buffer );
delete[] buffer;
return result;
}
static std::string
getString( HAPI_StringHandle stringHandle )
{
if ( stringHandle == 0 )
{
return "";
}
int bufferLength;
stringHandle,
&bufferLength );
char * buffer = new char[ bufferLength ];
HAPI_GetString ( nullptr, stringHandle, buffer, bufferLength );
std::string result( buffer );
delete [] buffer;
return result;
}

The output from a run of the application is as follows:

Number of point groups on xform: 1
8 points in pointGroup
Point 1 is in pointGroup
Point 3 is in pointGroup
Point 5 is in pointGroup
Point 7 is in pointGroup

The HIP file that was saved as part of the program can also be seen here. Note that only points 1,3,5,7 have been moved up by the transform SOP:

HAPI_Groups_OutputOfMarhalGroupsIn.png