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# roundedbox.cpp Example File
demos/boxes/roundedbox.cpp

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     #include "roundedbox.h"

     //============================================================================//
     //                                P3T2N3Vertex                                //
     //============================================================================//

     VertexDescription P3T2N3Vertex::description[] = {
         {VertexDescription::Position, GL_FLOAT, SIZE_OF_MEMBER(P3T2N3Vertex, position) / sizeof(float), 0, 0},
         {VertexDescription::TexCoord, GL_FLOAT, SIZE_OF_MEMBER(P3T2N3Vertex, texCoord) / sizeof(float), sizeof(QVector3D), 0},
         {VertexDescription::Normal, GL_FLOAT, SIZE_OF_MEMBER(P3T2N3Vertex, normal) / sizeof(float), sizeof(QVector3D) + sizeof(QVector2D), 0},

         {VertexDescription::Null, 0, 0, 0, 0},
     };

     //============================================================================//
     //                                GLRoundedBox                                //
     //============================================================================//

     float lerp(float a, float b, float t)
     {
         return a * (1.0f - t) + b * t;
     }

     GLRoundedBox::GLRoundedBox(float r, float scale, int n)
         : GLTriangleMesh<P3T2N3Vertex, unsigned short>((n+2)*(n+3)*4, (n+1)*(n+1)*24+36+72*(n+1))
     {
         int vidx = 0, iidx = 0;
         int vertexCountPerCorner = (n + 2) * (n + 3) / 2;

         P3T2N3Vertex *vp = m_vb.lock();
         unsigned short *ip = m_ib.lock();

         if (!vp || !ip) {
             qWarning("GLRoundedBox::GLRoundedBox: Failed to lock vertex buffer and/or index buffer.");
             m_ib.unlock();
             m_vb.unlock();
             return;
         }

         for (int corner = 0; corner < 8; ++corner) {
             QVector3D centre(corner & 1 ? 1.0f : -1.0f,
                     corner & 2 ? 1.0f : -1.0f,
                     corner & 4 ? 1.0f : -1.0f);
             int winding = (corner & 1) ^ ((corner >> 1) & 1) ^ (corner >> 2);
             int offsX = ((corner ^ 1) - corner) * vertexCountPerCorner;
             int offsY = ((corner ^ 2) - corner) * vertexCountPerCorner;
             int offsZ = ((corner ^ 4) - corner) * vertexCountPerCorner;

             // Face polygons
             if (winding) {
                 ip[iidx++] = vidx;
                 ip[iidx++] = vidx + offsX;
                 ip[iidx++] = vidx + offsY;

                 ip[iidx++] = vidx + vertexCountPerCorner - n - 2;
                 ip[iidx++] = vidx + vertexCountPerCorner - n - 2 + offsY;
                 ip[iidx++] = vidx + vertexCountPerCorner - n - 2 + offsZ;

                 ip[iidx++] = vidx + vertexCountPerCorner - 1;
                 ip[iidx++] = vidx + vertexCountPerCorner - 1 + offsZ;
                 ip[iidx++] = vidx + vertexCountPerCorner - 1 + offsX;
             }

             for (int i = 0; i < n + 2; ++i) {

                 // Edge polygons
                 if (winding && i < n + 1) {
                     ip[iidx++] = vidx + i + 1;
                     ip[iidx++] = vidx;
                     ip[iidx++] = vidx + offsY + i + 1;
                     ip[iidx++] = vidx + offsY;
                     ip[iidx++] = vidx + offsY + i + 1;
                     ip[iidx++] = vidx;

                     ip[iidx++] = vidx + i;
                     ip[iidx++] = vidx + 2 * i + 2;
                     ip[iidx++] = vidx + i + offsX;
                     ip[iidx++] = vidx + 2 * i + offsX + 2;
                     ip[iidx++] = vidx + i + offsX;
                     ip[iidx++] = vidx + 2 * i + 2;

                     ip[iidx++] = (corner + 1) * vertexCountPerCorner - 1 - i;
                     ip[iidx++] = (corner + 1) * vertexCountPerCorner - 2 - i;
                     ip[iidx++] = (corner + 1) * vertexCountPerCorner - 1 - i + offsZ;
                     ip[iidx++] = (corner + 1) * vertexCountPerCorner - 2 - i + offsZ;
                     ip[iidx++] = (corner + 1) * vertexCountPerCorner - 1 - i + offsZ;
                     ip[iidx++] = (corner + 1) * vertexCountPerCorner - 2 - i;
                 }

                 for (int j = 0; j <= i; ++j) {
                     QVector3D normal = QVector3D(i - j, j, n + 1 - i).normalized();
                     QVector3D offset(0.5f - r, 0.5f - r, 0.5f - r);
                     QVector3D pos = centre * (offset + r * normal);

                     vp[vidx].position = scale * pos;
                     vp[vidx].normal = centre * normal;
                     vp[vidx].texCoord = QVector2D(pos.x() + 0.5f, pos.y() + 0.5f);

                     // Corner polygons
                     if (i < n + 1) {
                         ip[iidx++] = vidx;
                         ip[iidx++] = vidx + i + 2 - winding;
                         ip[iidx++] = vidx + i + 1 + winding;
                     }
                     if (i < n) {
                         ip[iidx++] = vidx + i + 1 + winding;
                         ip[iidx++] = vidx + i + 2 - winding;
                         ip[iidx++] = vidx + 2 * i + 4;
                     }

                     ++vidx;
                 }
             }

         }

         m_ib.unlock();
         m_vb.unlock();
     }