Interacting with Houdini Engine in Python | 使用Python与Houdini Engine交互
Houdini Engine是Houdini的一个无图形界面简化版，可以通过houdini engine与houdini内核交互，完成houdini fx中的操作。
官方有For Maya, For Max, For Unity, For Unreal四个插件，可以在这四个host程序中调用houdini engine。这是极好的，意味着开发的HDA资源可以直接应用在host程序中。不过笔者并不满足于此，是否可以不用host环境直接调用houdini engine？当然可以，官方提供了一套C API https://www.sidefx.com/docs/hengine/ . 只不过笔者看着它就头疼，主要两个问题
- 面向过程，不面向对象
- 语法繁琐
这也是笔者开发pyhapi的初衷，希望面向对象，简化语法。
怎么安装
已经发布到PyPI，安装直接使用pip即可
pip install pyhapi
要求py>3.6, 因为用了asyncio异步库
numpy>1.15
Houdini17.5测试没问题，需要commercial license. Houdini18尚未测试
当然要注意的是，请确保houdini dll路径在PATH中
使用
目前支持的功能:
- 实例化节点，HDA
- 节点连接操作
- 节点参数设置
- 节点异步cook
- 传入/出 曲线，模型
还不支持的：
- 传入/出 体素
- PDG
举例来说，如果想实例化一个HDA，传入参数，cook，可以这样：
# -*- coding: utf-8 -*-
"""Example of getting/setting params of HDA asset
Author : Maajor
Email : hello_myd@126.com
"""
import pyhapi as ph
def main():
session = ph.HSessionManager.get_or_create_default_session()
#load hda asset and instantiate
hda_asset = ph.HAsset(session, "hda/SideFX_spaceship.otl")
asset_node = hda_asset.instantiate(node_name="Spaceship")
#Set node's parameters
asset_node.set_param_value("seed", 1.0)
asset_node.set_param_value("rop_geometry1_sopoutput", "$HIP/spaceship.obj")
#Press button
asset_node.press_button("rop_geometry1_execute", status_report_interval=1.0)
session.save_hip("spaceship.hip")
if __name__ == "__main__":
main()
执行完以后就可以输出spaceship.obj模型啦
对比一下C API的官方案例Parameters.c
两百多行其实就干了一件事：实例化一个HDA，打印出它所有参数
#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 )
{
const char * hdaFile = argc == 2 ? argv[ 1 ] : "examples/SideFX_spaceship.otl";
HAPI_CookOptions cookOptions = HAPI_CookOptions_Create();
HAPI_Session session;
HAPI_CreateInProcessSession( &session );
ENSURE_SUCCESS( HAPI_Initialize( &session,
&cookOptions,
true,
-1,
nullptr,
nullptr,
nullptr,
nullptr,
nullptr ) );
HAPI_AssetLibraryId assetLibId;
ENSURE_SUCCESS( HAPI_LoadAssetLibraryFromFile( &session, hdaFile, true, &assetLibId ) );
int assetCount;
ENSURE_SUCCESS( HAPI_GetAvailableAssetCount( &session, assetLibId, &assetCount ) );
if (assetCount > 1)
{
std::cout << "Should only be loading 1 asset here" << std::endl;
exit ( 1 );
}
HAPI_StringHandle assetSh;
ENSURE_SUCCESS( HAPI_GetAvailableAssets( &session, assetLibId, &assetSh, assetCount ) );
std::string assetName = getString( assetSh );
HAPI_NodeId nodeId;
ENSURE_SUCCESS( HAPI_CreateNode( &session, -1, assetName.c_str(), "AnAsset", false, &nodeId ) );
ENSURE_SUCCESS( HAPI_CookNode( &session, nodeId, &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 );
HAPI_NodeInfo nodeInfo;
ENSURE_SUCCESS( HAPI_GetNodeInfo( &session, nodeId, &nodeInfo ) );
HAPI_ParmInfo * parmInfos = new HAPI_ParmInfo[ nodeInfo.parmCount ];
ENSURE_SUCCESS( HAPI_GetParameters( &session, nodeId, parmInfos, 0, nodeInfo.parmCount ) );
// Print parameter info
std::cout << "Parameters: " << std::endl;
for( int i = 0; i < nodeInfo.parmCount; ++i )
{
std::cout << "==========" << std::endl;
std::cout << " Name: "
<< getString( parmInfos[ i ].nameSH )
<< std::endl;
std::cout << " Values: (";
if ( HAPI_ParmInfo_IsInt( &parmInfos[ i ] ) )
{
int parmIntCount = HAPI_ParmInfo_GetIntValueCount( &parmInfos[ i ] );
int * parmIntValues = new int[ parmIntCount ];
ENSURE_SUCCESS( HAPI_GetParmIntValues( &session,
nodeId, parmIntValues,
parmInfos[ i ].intValuesIndex,
parmIntCount ) );
for ( int v = 0; v < parmIntCount; ++v )
{
if ( v != 0 )
std::cout << ", ";
std::cout << parmIntValues[ v ];
}
delete [] parmIntValues;
}
else if ( HAPI_ParmInfo_IsFloat( &parmInfos[ i ] ) )
{
int parmFloatCount = HAPI_ParmInfo_GetFloatValueCount( &parmInfos[ i ] );
float * parmFloatValues = new float[ parmFloatCount ];
ENSURE_SUCCESS( HAPI_GetParmFloatValues( &session,
nodeId, parmFloatValues,
parmInfos[ i ].floatValuesIndex,
parmFloatCount ) );
for ( int v = 0; v < parmFloatCount; ++v )
{
if ( v != 0 )
std::cout << ", ";
std::cout << parmFloatValues[ v ];
}
delete [] parmFloatValues;
}
else if ( HAPI_ParmInfo_IsString( &parmInfos[ i ] ) )
{
int parmStringCount = HAPI_ParmInfo_GetStringValueCount( &parmInfos[ i ] );
HAPI_StringHandle * parmSHValues = new HAPI_StringHandle[ parmStringCount ];
ENSURE_SUCCESS( HAPI_GetParmStringValues( &session,
nodeId,
true, parmSHValues,
parmInfos[ i ].stringValuesIndex,
parmStringCount ) );
for ( int v = 0; v < parmStringCount; ++v )
{
if ( v != 0 )
std::cout << ", ";
std::cout << getString( parmSHValues[ v ] );
}
delete [] parmSHValues;
}
std::cout << ")" << std::endl;
}
delete [] parmInfos;
char in;
std::cout << "Press any key to exit" << std::endl;
std::cin >> in;
HAPI_Cleanup( &session );
return 0;
}
static std::string
getLastError()
{
int bufferLength;
HAPI_GetStatusStringBufLength( nullptr,
HAPI_STATUS_CALL_RESULT,
HAPI_STATUSVERBOSITY_ERRORS,
&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;
HAPI_GetStatusStringBufLength( nullptr,
HAPI_STATUS_COOK_RESULT,
HAPI_STATUSVERBOSITY_ERRORS,
&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;
HAPI_GetStringBufLength( nullptr,
stringHandle,
&bufferLength );
char * buffer = new char[ bufferLength ];
HAPI_GetString ( nullptr, stringHandle, buffer, bufferLength );
std::string result( buffer );
delete [] buffer;
return result;
}
用pyhapi的话十行以内：
import pyhapi as ph
def main():
session = ph.HSessionManager.get_or_create_default_session()
#load hda asset and instantiate
hda_asset = ph.HAsset(session, "hda/SideFX_spaceship.otl")
asset_node = hda_asset.instantiate(node_name="Spaceship")
#Query node's parameters
for name in asset_node.get_param_names():
print("Query param: {0} has value: {1}".format(name, asset_node.get_param_value(name)))
if __name__ == "__main__":
main()
当然我们还可以把一个模型/曲线，传入/取出houdini engine，比如mesh_marshall_input.py这个例子，传进去一个方块，然后做了细分
# -*- coding: utf-8 -*-
"""Example of setting mesh data into hengine
Author : Maajor
Email : hello_myd@126.com
"""
import numpy as np
import pyhapi as ph
def main():
"""Main
"""
session = ph.HSessionManager.get_or_create_default_session()
#create an inputnode where you can set geometry
geo_inputnode = ph.HInputNode(session, "Cube")
#create a geomesh
cube_geo = ph.HGeoMesh(
vertices=np.array(
[[0.0, 0.0, 0.0],
[0.0, 0.0, 1.0],
[0.0, 1.0, 0.0],
[0.0, 1.0, 1.0],
[1.0, 0.0, 0.0],
[1.0, 0.0, 1.0],
[1.0, 1.0, 0.0],
[1.0, 1.0, 1.0]], dtype=np.float32),
faces=np.array(
[[0, 2, 6, 4],
[2, 3, 7, 6],
[2, 0, 1, 3],
[1, 5, 7, 3],
[5, 4, 6, 7],
[0, 4, 5, 1]], dtype=np.int32))
#set this geomesh as geometry of inputnode
geo_inputnode.set_geometry(cube_geo)
#create a node whose input is inputnode
ph.HNode(session, "Sop/subdivide", "Cube Subdivider").connect_node_input(geo_inputnode)
session.save_hip()
if __name__ == "__main__":
main()
内部怎么实现的？
Python可以和C很好地实现交互
类似其他几个平台，
Unity 用的c#，dllimport就行
Unreal就是cpp，include进来就行
Python用ctypes就能加载dll
sys = platform.system()
if sys == "Windows":
HAPI_LIB = ctypes.cdll.LoadLibrary("libHAPIL")
elif sys == "Linux":
HAPI_LIB = ctypes.cdll.LoadLibrary("libHAPIL.so")
这就直接可以调用libHAPIL的方法了
HAPI_LIB.HAPI_IsSessionValid(byref(session))
源码里hapi.py里全部是对libHAPIL的封装，hdata.py里全是houdini engine的struct
除此以外，hsession封装session对象，hnode封装node对象，hgeo封装geo对象，hasset封装HDA对象
总共就这六个文件
可以干什么？
为了Houdini Pipeline咯
可以做
- 资产自动化处理
- HDA自动化测试
- HDA管理
- etc...
祝读者春节快乐，百病不侵！