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();
 }