強制GLUtesselator只生成GL_TRIANGLES？

Question

如果我只想使用一個頂點數組格式，那麼渲染我生成的數據相當困難。

我試圖提供GLU_TESS_EDGE_FLAG_DATA回調，但它使我的程序崩潰。 （在最後也嘗試沒有「_DATA」，效果相同）。

我怎樣才能得到它只生成GL_TRIANGLES？

Answer 1

gluTessCallback()，GLU_TESS_EDGE_FLAG：

...如果提供一個非空邊緣標誌回調...風扇和帶被轉換爲獨立的三角形。

這是我一直使用的是什麼：

struct TessContext 
{ 
    ~TessContext() 
    { 
     for(size_t i = 0; i < combined.size(); ++i) 
     { 
      delete[] combined[i]; 
     } 
    } 

    typedef std::pair< double, double > Point; 
    std::vector<Point> pts; 
    std::vector< GLdouble* > combined; 
}; 

#ifndef CALLBACK 
#define CALLBACK __stdcall 
#endif 

void CALLBACK tess_begin(GLenum) {} 
void CALLBACK tess_edgeFlag(GLboolean) {} 
void CALLBACK tess_end() {} 

void CALLBACK tess_vertex 
    ( 
    void*   data, 
    TessContext* ctx 
    ) 
{ 
    GLdouble* coord = (GLdouble*)data; 
    ctx->pts.push_back(TessContext::Point(coord[0], coord[1])); 
} 

void CALLBACK tess_combine 
    ( 
    GLdouble  coords[3], 
    void*   vertex_data[4], 
    GLfloat   weight[4], 
    void**   outData, 
    TessContext* ctx 
    ) 
{ 
    GLdouble* newVert = new GLdouble[3]; 
    ctx->combined.push_back(newVert); 

    newVert[0] = coords[0]; 
    newVert[1] = coords[1]; 
    newVert[2] = coords[2]; 
    *outData = newVert; 
} 

template< typename Vec > 
std::vector<Vec> Triangulate 
    ( 
    const vector<Vec>& aSimplePolygon 
    ) 
{ 
    std::vector<GLdouble> coords; 
    for(size_t i = 0; i < aSimplePolygon.size(); ++i) 
    { 
     coords.push_back(aSimplePolygon[i].x()); 
     coords.push_back(aSimplePolygon[i].y()); 
     coords.push_back(0); 
    } 

    GLUtesselator* tess = gluNewTess(); 
    gluTessCallback(tess, GLU_TESS_BEGIN,   (void (CALLBACK *)()) tess_begin  ); 
    gluTessCallback(tess, GLU_TESS_EDGE_FLAG,  (void (CALLBACK *)()) tess_edgeFlag ); 
    gluTessCallback(tess, GLU_TESS_VERTEX_DATA, (void (CALLBACK *)()) tess_vertex ); 
    gluTessCallback(tess, GLU_TESS_END,   (void (CALLBACK *)()) tess_end  ); 
    gluTessCallback(tess, GLU_TESS_COMBINE_DATA, (void (CALLBACK *)()) tess_combine ); 
    gluTessNormal(tess, 0.0, 0.0, 1.0); 

    TessContext ctx; 

    gluTessBeginPolygon(tess, &ctx); 
    gluTessBeginContour(tess); 

    for(size_t i = 0; i < aSimplePolygon.size(); ++i) 
    { 
     gluTessVertex(tess, &coords[i*3], &coords[i*3]); 
    } 

    gluTessEndContour(tess); 
    gluTessEndPolygon(tess); 

    gluDeleteTess(tess); 

    std::vector<Vec> ret(ctx.pts.size()); 
    for(size_t i = 0; i < ret.size(); ++i) 
    { 
     ret[i].x() = static_cast<Vec::Scalar>(ctx.pts[i].first); 
     ret[i].y() = static_cast<Vec::Scalar>(ctx.pts[i].second); 
    } 

    return ret; 
} 

我傾向於使用Eigen::Vector2f爲Vec。