如何釋放在GLU_TESS_COMBINE回調中分配的內存

Question

我正在使用GLUtesselator填充一些非凸多邊形。

它做得很不錯，但與一些多邊形它抱怨它需要一個結合功能，所以我提供了一個非常簡單的GLU_TESS_COMBINE回調，其分配一個新的頂點，只是複製COORDS（它是2D純色，所以我不需要內插RGB值或任何東西）：

void CALLBACK tessCombine(GLdouble coords[3], GLdouble * vertex_data[4], GLfloat weight[4], GLdouble **outData) 
{ 
    GLdouble *vertex = new GLdouble[3]; 
    vertex[0] = coords[0]; 
    vertex[1] = coords[1]; 
    vertex[2] = coords[2]; 
    *outData = vertex; 
} 

現在一切都按預期呈現，但它顯然會泄漏內存。該文檔說：

分配另一個頂點，[0121]在調用gluTessEndPolygon之後的某個時間釋放內存。

但是在我找到的所有例子中，它們並沒有顯示如何處理內存。回調是免費的功能，無法釋放分配的內存，是嗎？

我能想到的唯一方法是將它們存儲在某個地方，然後自己刪除它們。這是正確的方法嗎？

Answer 1

看看this OpenGL Tessellation tutorial。

重點不是在回調中分配任何內存（否則你會得到內存泄漏）。相反，您應該將頂點數據複製到回調中的內存位置（因爲它在example中完成）。從您複製頂點數據的位置開始，由您決定。

這是回調函數看起來如何在他們example：

void CALLBACK tessCombineCB(const GLdouble newVertex[3], const GLdouble *neighborVertex[4], 
          const GLfloat neighborWeight[4], GLdouble **outData) 
{ 
    // copy new intersect vertex to local array 
    // Because newVertex is temporal and cannot be hold by tessellator until next 
    // vertex callback called, it must be copied to the safe place in the app. 
    // Once gluTessEndPolygon() called, then you can safly deallocate the array. 
    vertices[vertexIndex][0] = newVertex[0]; 
    vertices[vertexIndex][1] = newVertex[1]; 
    vertices[vertexIndex][2] = newVertex[2]; 

    // compute vertex color with given weights and colors of 4 neighbors 
    // the neighborVertex[4] must hold required info, in this case, color. 
    // neighborVertex was actually the third param of gluTessVertex() and is 
    // passed into here to compute the color of the intersect vertex. 
    vertices[vertexIndex][3] = neighborWeight[0] * neighborVertex[0][3] + // red 
           neighborWeight[1] * neighborVertex[1][3] + 
           neighborWeight[2] * neighborVertex[2][3] + 
           neighborWeight[3] * neighborVertex[3][3]; 
    vertices[vertexIndex][4] = neighborWeight[0] * neighborVertex[0][4] + // green 
           neighborWeight[1] * neighborVertex[1][4] + 
           neighborWeight[2] * neighborVertex[2][4] + 
           neighborWeight[3] * neighborVertex[3][4]; 
    vertices[vertexIndex][5] = neighborWeight[0] * neighborVertex[0][5] + // blue 
           neighborWeight[1] * neighborVertex[1][5] + 
           neighborWeight[2] * neighborVertex[2][5] + 
           neighborWeight[3] * neighborVertex[3][5]; 


    // return output data (vertex coords and others) 
    *outData = vertices[vertexIndex]; // assign the address of new intersect vertex 

    ++vertexIndex; // increase index for next vertex 
}