Function derivBSpline

tutorials/pathtracer/pathtracer_device.cpp:1068–1106

}

inline Vec3fa derivBSpline(const ISPCHairSet* mesh, const unsigned int primID, const float t, const float time)
{
  Vec3fa p00, p01, p02, p03;
  const int i = mesh->hairs[primID].vertex;
  
  if (mesh->numTimeSteps == 1)
  {
    p00 = mesh->positions[0][i+0];
    p01 = mesh->positions[0][i+1];
    p02 = mesh->positions[0][i+2];
    p03 = mesh->positions[0][i+3];
  }
  else
  {
    float f = mesh->numTimeSteps*time;
    int itime = clamp((int)floor(f),0,(int)mesh->numTimeSteps-2);
    float t1 = f-itime;
    float t0 = 1.0f-t1;
    const Vec3fa a0 = mesh->positions[itime+0][i+0];
    const Vec3fa a1 = mesh->positions[itime+0][i+1];
    const Vec3fa a2 = mesh->positions[itime+0][i+2];
    const Vec3fa a3 = mesh->positions[itime+0][i+3];
    const Vec3fa b0 = mesh->positions[itime+1][i+0];
    const Vec3fa b1 = mesh->positions[itime+1][i+1];
    const Vec3fa b2 = mesh->positions[itime+1][i+2];
    const Vec3fa b3 = mesh->positions[itime+1][i+3];
    p00 = t0*a0 + t1*b0;
    p01 = t0*a1 + t1*b1;
    p02 = t0*a2 + t1*b2;
    p03 = t0*a3 + t1*b3;
  }

  const float t0 = 1.0f - t, t1 = t;
  const float n0 = -0.5f*t1*t1;
  const float n1 = -0.5f*t0*t0 - 2.0f*(t0*t1);
  const float n2 =  0.5f*t1*t1 + 2.0f*(t1*t0);
  const float n3 =  0.5f*t0*t0;
  return Vec3fa(n0*p00 + n1*p01 + n2*p02 + n3*p03);
}

void postIntersectGeometry(const TutorialData& data, const Ray& ray, DifferentialGeometry& dg, ISPCGeometry* geometry, int& materialID)
{