我已经在这方面工作了几个星期,但一直无法使我的算法正常工作,我的智慧结束了。以下是我所取得的成就:
如果一切正常,我希望最后有一个完美的圆形/椭圆形。
每次添加新控制点(黄色)时,都会重新计算我的采样点(白色)。在4个控制点,一切看起来都很完美,再次在第一个东西上面加上第5个看起来没问题,但是在第6个它开始偏离侧面而在7日它跳到原点!
下面我将发布我的代码,其中calculateWeightForPointI
包含实际算法。作为参考 - here is the information i'm trying to follow.如果有人可以看看我,我会非常感激。
void updateCurve(const std::vector<glm::vec3>& controls, std::vector<glm::vec3>& samples)
{
int subCurveOrder = 4; // = k = I want to break my curve into to cubics
// De boor 1st attempt
if(controls.size() >= subCurveOrder)
{
createKnotVector(subCurveOrder, controls.size());
samples.clear();
for(int steps=0; steps<=20; steps++)
{
// use steps to get a 0-1 range value for progression along the curve
// then get that value into the range [k-1, n+1]
// k-1 = subCurveOrder-1
// n+1 = always the number of total control points
float t = ( steps / 20.0f ) * ( controls.size() - (subCurveOrder-1) ) + subCurveOrder-1;
glm::vec3 newPoint(0,0,0);
for(int i=1; i <= controls.size(); i++)
{
float weightForControl = calculateWeightForPointI(i, subCurveOrder, controls.size(), t);
newPoint += weightForControl * controls.at(i-1);
}
samples.push_back(newPoint);
}
}
}
//i = the weight we're looking for, i should go from 1 to n+1, where n+1 is equal to the total number of control points.
//k = curve order = power/degree +1. eg, to break whole curve into cubics use a curve order of 4
//cps = number of total control points
//t = current step/interp value
float calculateWeightForPointI( int i, int k, int cps, float t )
{
//test if we've reached the bottom of the recursive call
if( k == 1 )
{
if( t >= knot(i) && t < knot(i+1) )
return 1;
else
return 0;
}
float numeratorA = ( t - knot(i) );
float denominatorA = ( knot(i + k-1) - knot(i) );
float numeratorB = ( knot(i + k) - t );
float denominatorB = ( knot(i + k) - knot(i + 1) );
float subweightA = 0;
float subweightB = 0;
if( denominatorA != 0 )
subweightA = numeratorA / denominatorA * calculateWeightForPointI(i, k-1, cps, t);
if( denominatorB != 0 )
subweightB = numeratorB / denominatorB * calculateWeightForPointI(i+1, k-1, cps, t);
return subweightA + subweightB;
}
//returns the knot value at the passed in index
//if i = 1 and we want Xi then we have to remember to index with i-1
float knot(int indexForKnot)
{
// When getting the index for the knot function i remember to subtract 1 from i because of the difference caused by us counting from i=1 to n+1 and indexing a vector from 0
return knotVector.at(indexForKnot-1);
}
//calculate the whole knot vector
void createKnotVector(int curveOrderK, int numControlPoints)
{
int knotSize = curveOrderK + numControlPoints;
for(int count = 0; count < knotSize; count++)
{
knotVector.push_back(count);
}
}
答案 0 :(得分:2)
您的算法似乎适用于我尝试过的任何输入。您的问题可能是控制点不在应有的位置,或者它们尚未正确初始化。它看起来有两个控制点,低于左下角的一半高度。