houdini hdk范例文件sop_dualstar中文注释笔记

这个范例主要介绍了在有两个输出端的时候怎么在第二个输出端分离出一个几何体。关键点就是创建一个新的gdh给定一个新的gdp。

头文件 SOP_DualStar.h

#ifndef __SOP_DualStar_h__
#define __SOP_DualStar_h__
#include 
namespace HDK_Sample {
class SOP_DualStar : public SOP_Node
{
public:
    static OP_Node      *myConstructor(OP_Network*, const char *,
                                OP_Operator *);
    static PRM_Template      myTemplateList[];
protected:
         SOP_DualStar(OP_Network *net, const char *name, OP_Operator *op);
    virtual ~SOP_DualStar();

    /// cookMySop does the actual work of the SOP computing, in this
    /// case, a star shape.
    virtual OP_ERROR         cookMySop(OP_Context &context);
    virtual GU_DetailHandle  cookMySopOutput(OP_Context &context, int outputidx, SOP_Node *interest);

    /// Actually build a star in the given geometry
    void    buildStar(GU_Detail *dst, OP_Context &context);
private:
    /// The following list of accessors simplify evaluating the parameters
    /// of the SOP.
    int     DIVISIONS(fpreal t) { return evalInt  ("divs", 0, t); }
    fpreal  XRADIUS(fpreal t)   { return evalFloat("rad", 0, t); }
    fpreal  YRADIUS(fpreal t)   { return evalFloat("rad", 1, t); }
    int     NEGRADIUS()     { return evalInt  ("nradius", 0, 0); }
    fpreal  CENTERX(fpreal t)   { return evalFloat("t", 0, t); }
    fpreal  CENTERY(fpreal t)   { return evalFloat("t", 1, t); }
    fpreal  CENTERZ(fpreal t)   { return evalFloat("t", 2, t); }
    int     ORIENT()        { return evalInt  ("orient", 0, 0); }
};
} // End HDK_Sample namespace

#endif

源文件 SOP_DualStar.h

#include "SOP_DualStar.h"

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

using namespace HDK_Sample;

//
// Help is stored in a "wiki" style text file.  This text file should be copied
// to $HOUDINI_PATH/help/nodes/sop/star.txt
//
// See the sample_install.sh file for an example.
//

///
/// newSopOperator is the hook that Houdini grabs from this dll
/// and invokes to register the SOP.  In this case we add ourselves
/// to the specified operator table.
///
void
newSopOperator(OP_OperatorTable *table)
{
    table->addOperator(new OP_Operator(
        "hdk_dualstar",                 // Internal name
        "Dual Star",                     // UI name
        SOP_DualStar::myConstructor,    // How to build the SOP
        SOP_DualStar::myTemplateList,   // My parameters
        1,                          // Min # of sources
        1,                          // Max # of sources
        //这里没有，如果有应该是给一个成员数据例如SOP_Star::myVariables
        0,      // Local variables
        //这里表示该节点需要生成一个新的几何体
        OP_FLAG_GENERATOR,        // Flag it as generator
    //**inputlabels
    //Note: The 'inputlabels' array is expected to be null-terminated
    0,
    //输出端数量
    2));    // Outputs.
}
//参数 复选框 是否使用负值半径
static PRM_Name     negativeName("nradius", "Negative Radius");
//                   ^^^^^^^^    ^^^^^^^^^^^^^^^
//                   internal    descriptive version
//默认值 细分数
static PRM_Default  fiveDefault(5);     // Default to 5 divisions
//默认值 内外半径
static PRM_Default  radiiDefaults[] = {
               PRM_Default(1),      // Outside radius
               PRM_Default(0.3)     // Inside radius
            };
//参数表
PRM_Template
SOP_DualStar::myTemplateList[] = {
    //细分数
    PRM_Template(PRM_INT,           // Integer parameter.//参数类型
        //No extended type given but export level given
        //这个导出类型的具体用途还不知道
         PRM_Template::PRM_EXPORT_TBX,  // Export to top of viewer
                        // when user selects this node
         1,         // One integer in this row/parameter//参数元素数量/整形即1，矢量即3
         &PRMdivName,   // Name of this parameter - must be static//默认值，需要传入地址//这里使用模板类
         &fiveDefault,  // Default for this parameter - ditto//这里使用上面定义的默认值
         0,     // Menu for this parameter//菜单样式//这里为空
         &PRMdivision2Range // Valid range//分段数范围//这里使用模板//该模板范围是2-50
         ),
    // 半径
    PRM_Template(PRM_XYZ,   2, &PRMradiusName, radiiDefaults),
    //是否使用负值半径
    PRM_Template(PRM_TOGGLE,    1, &negativeName),
    //中心点
    PRM_Template(PRM_XYZ,       3, &PRMcenterName),
    //方向
    PRM_Template(PRM_ORD,   1, &PRMorientName, 0, &PRMplaneMenu),
    PRM_Template()
};


OP_Node *
SOP_DualStar::myConstructor(OP_Network *net, const char *name, OP_Operator *op)
{
    return new SOP_DualStar(net, name, op);
}

SOP_DualStar::SOP_DualStar(OP_Network *net, const char *name, OP_Operator *op)
    : SOP_Node(net, name, op)
{
    // We do not manage our ids, so do not set the flag.
}

SOP_DualStar::~SOP_DualStar() {}

OP_ERROR
SOP_DualStar::cookMySop(OP_Context &context)
{
    // We must lock our inputs before we try to access their geometry.
    // OP_AutoLockInputs will automatically unlock our inputs when we return.
    // NOTE: Don't call unlockInputs yourself when using this!
    OP_AutoLockInputs inputs(this);
    if (inputs.lock(context) >= UT_ERROR_ABORT)
        return error();
    //复制输入数据，需要指定输入端口
    duplicateSource(0, context);

    // Start the interrupt server
    //这里调用原有的gdp构建几何体是在输入几何体的基础上构建的
    //就是说直接显示节点会同时显示两个几何体
    buildStar(gdp, context);

    return error();
}

void
SOP_DualStar::buildStar(GU_Detail *dst, OP_Context &context)
{
    //get参数
    fpreal now = context.getTime();
    int divisions  = DIVISIONS(now)*2;  // We need twice our divisions of points

    int plane     = ORIENT();
    int negradius = NEGRADIUS();
    float tx      = CENTERX(now);
    float ty      = CENTERY(now);
    float tz      = CENTERZ(now);

    int xcoord, ycoord, zcoord;
    switch (plane)
    {
        case 0:         // XY Plane
            xcoord = 0;
            ycoord = 1;
            zcoord = 2;
            break;
        case 1:         // YZ Plane
            xcoord = 1;
            ycoord = 2;
            zcoord = 0;
            break;
        case 2:         // XZ Plane
            xcoord = 0;
            ycoord = 2;
            zcoord = 1;
            break;
    }
    //分段数小于4给出警告后把分段数设置为4
    //warning是手动给出的
    if (divisions < 4)
    {
        // With the range restriction we have on the divisions, this
        // is actually impossible, but it shows how to add an error
        // message or warning to the SOP.
        addWarning(SOP_MESSAGE, "Invalid divisions");
        divisions = 4;
    }
    //中断行为
    // Start the interrupt server
    UT_AutoInterrupt boss("Building Star");
    if (boss.wasInterrupted())
    {
        return;
    }

    // Build a polygon
    //这里的dst是传进来的gdp。div决定了创建多少个点。然后指定模型为封闭。接下来直接set点位置就好
    GEO_PrimPoly *poly = GEO_PrimPoly::build(dst, divisions, GU_POLY_CLOSED);
    float tinc = M_PI*2 / (float)divisions;

    // Now, set all the points of the polygon
    for (int i = 0; i < divisions; i++)
    {
        //用户中断
        // Check to see if the user has interrupted us...
        if (boss.wasInterrupted())
            break;

        // Since we expect the local variables to be used in specifying
        // the radii, we have to evaluate the channels INSIDE the loop
        // through the points...
        //根据循环次数设定temp
        float tmp = (float)i * tinc;
        //用‘按位和’运算判断循环奇偶数。一外一内就是星星的形状
        float rad = (i & 1) ? XRADIUS(now) : YRADIUS(now);
        //如果没有启用负值半径的情况下半径小于0那就把半径设置为0
        if (!negradius && rad < 0)
            rad = 0;
        //这里的xyzcoord不是字面的xyz位置。是索引号。在上面的switch确定下来的
        UT_Vector3 pos;
        //计算点位置。cos得到位置乘半径加中心点
        pos(xcoord) = SYScos(tmp) * rad + tx;
        pos(ycoord) = SYSsin(tmp) * rad + ty;
        //0加中心点
        pos(zcoord) = 0 + tz;
        //设置点位置
        GA_Offset ptoff = poly->getPointOffset(i);
        dst->setPos3(ptoff, pos);
    }

}
//设置第二个输出端
GU_DetailHandle
SOP_DualStar::cookMySopOutput(OP_Context &context, int outputidx, SOP_Node *interests)
{
    //创建一个新的gdh
    GU_DetailHandle result;
    //创建新的gdp
    GU_Detail       *dst = new GU_Detail();
    //设置gdh将其指向给定的gdp
    result.allocateAndSet(dst);
    //用新的gdh创建几何。这样子会丢掉输入的几何体
    buildStar(dst, context);
    //返回gdh
    return result;
}