三角形风扇的纹理坐标

Question

我试图“填充”我绘制的某些几何图形的表面。我正在使用GL_TRIANGLE_FAN原语。 （例如：1个枢纽（中心）点和12个其他点）。我已经计算了间隔0-1中每个顶点的纹理坐标。但结果我得到这个，它有点困惑。我希望得到像那样的结果image。请帮忙，这里有什么不对？ 如何计算正确的纹理在这样的三角坐标（GL_TRIANGLE_FAN）在image红点 是我的观点

*码 - 段：

assert(("CROSS type intersection needs only 5 vertices : center point and " 
     "rest points in anticlockwise order", (lp->size() > 5) && (lp->size() < 5))); 
osg::Vec3 vAlong_1,vAlong_2; 
vAlong_1 = (*lp)[1] - (*lp)[4]; 
vAlong_2 = (*lp)[1] - (*lp)[2]; 
eps = ((*lp)[2] - (*lp)[4]).length() * 0.2/2; 
vAlong_1.normalize(); 
vAlong_2.normalize(); 

_edgeCoords->push_back((*lp)[0]); 
_edgeCoords->push_back((*lp)[1]); 
if (CMF::euclidDistance((*lp)[0],(*lp)[1]) <= CMF::euclidDistance((*lp)[0],(*lp)[2])) { 
    float cosAlpha = -(vAlong_1 * vAlong_2); 
    float extraLength = ((*lp)[2] - (*lp)[1]).length() * cosAlpha; 
    _edgeCoords->push_back((*lp)[1] + vAlong_1 * (eps + extraLength)); 
    _edgeCoords->push_back((*lp)[2] + vAlong_1 * eps); 
} else { 
    float cosAlpha = (vAlong_1 * vAlong_2); 
    float extraLength = ((*lp)[2] - (*lp)[1]).length() * cosAlpha; 
    _edgeCoords->push_back((*lp)[1] + vAlong_1 * eps); 
    _edgeCoords->push_back((*lp)[2] + vAlong_1 * (eps + extraLength)); 
} 
_edgeCoords->push_back((*lp)[2]); 
if (CMF::euclidDistance((*lp)[0],(*lp)[2]) <= CMF::euclidDistance((*lp)[0],(*lp)[3])) { 
    float cosAlpha = -(vAlong_1 * vAlong_2); 
    float extraLength = ((*lp)[3] - (*lp)[2]).length() * cosAlpha; 
    _edgeCoords->push_back((*lp)[2] - vAlong_2 * (eps + extraLength)); 
    _edgeCoords->push_back((*lp)[3] - vAlong_2 * eps); 
} else { 
    float cosAlpha = (vAlong_1 * vAlong_2); 
    float extraLength = ((*lp)[3] - (*lp)[2]).length() * cosAlpha; 
    _edgeCoords->push_back((*lp)[2] - vAlong_2 * eps); 
    _edgeCoords->push_back((*lp)[3] - vAlong_2 * (eps + extraLength)); 
} 
_edgeCoords->push_back((*lp)[3]); 
if (CMF::euclidDistance((*lp)[0],(*lp)[3]) <= CMF::euclidDistance((*lp)[0],(*lp)[4])) { 
    float cosAlpha = -(vAlong_1 * vAlong_2); 
    float extraLength = ((*lp)[4] - (*lp)[3]).length() * cosAlpha; 
    _edgeCoords->push_back((*lp)[3] - vAlong_1 * (eps + extraLength)); 
    _edgeCoords->push_back((*lp)[4] - vAlong_1 * eps); 
} else { 
    float cosAlpha = (vAlong_1 * vAlong_2); 
    float extraLength = ((*lp)[4] - (*lp)[3]).length() * cosAlpha; 
    _edgeCoords->push_back((*lp)[3] - vAlong_1 * eps); 
    _edgeCoords->push_back((*lp)[4] - vAlong_1 * (eps + extraLength)); 
} 
_edgeCoords->push_back((*lp)[4]); 
if (CMF::euclidDistance((*lp)[0],(*lp)[1]) <= CMF::euclidDistance((*lp)[0],(*lp)[4])) { 
    float cosAlpha = -(vAlong_1 * vAlong_2); 
    float extraLength = ((*lp)[4] - (*lp)[1]).length() * cosAlpha; 
    _edgeCoords->push_back((*lp)[4] + vAlong_2 * eps); 
    _edgeCoords->push_back((*lp)[1] + vAlong_2 * (eps + extraLength)); 
} else { 
    float cosAlpha = (vAlong_1 * vAlong_2); 
    float extraLength = ((*lp)[4] - (*lp)[1]).length() * cosAlpha; 
    _edgeCoords->push_back((*lp)[4] + vAlong_2 * (eps + extraLength)); 
    _edgeCoords->push_back((*lp)[1] + vAlong_2 * eps); 
} 
_edgeCoords->push_back((*lp)[1]); 

_tCoords->push_back(osg::Vec2(0.5,0.5)); 
_tCoords->push_back(osg::Vec2(0.666,0.666)); 
_tCoords->push_back(osg::Vec2(0.666,1.0)); 
_tCoords->push_back(osg::Vec2(0.333,1.0)); 
_tCoords->push_back(osg::Vec2(0.333,0.666)); 
_tCoords->push_back(osg::Vec2(0.0,0.666)); 
_tCoords->push_back(osg::Vec2(0.0,0.333)); 
_tCoords->push_back(osg::Vec2(0.333,0.333)); 
_tCoords->push_back(osg::Vec2(0.333,0.0)); 
_tCoords->push_back(osg::Vec2(0.666,0.0)); 
_tCoords->push_back(osg::Vec2(0.666,0.333)); 
_tCoords->push_back(osg::Vec2(1.0,0.333)); 
_tCoords->push_back(osg::Vec2(1.0,0.666)); 
_tCoords->push_back(osg::Vec2(0.666,0.666)); 

Answer 1

尽量保持2D位置总是等于纹理坐标为每个顶点。这将确保您的几何图形显示为纹理未被扭曲的切口。然后，您可以根据需要重新调整和居中网格，而不会通过将变换应用于顶点位置来扭曲纹理。

做到这一点的一种方法是创建一个函数，它可以推动单个顶点，接受顶点的2D坐标以及任何要应用的变换。该函数然后将2d坐标推送为texcoords，然后转换它们并将结果推送为位置。