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Generalized calculation of spiral curve tangent vector

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This commit is contained in:
Richard Brice
2023-12-07 08:01:31 -08:00
parent c562a52011
commit 4b933812a7
1 changed files with 8 additions and 24 deletions
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src/ifcgeom/mapping/IfcCurveSegment.cpp
+8 -24
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@@ -99,13 +99,13 @@ class segment_geometry_adjuster {
auto next = taxonomy::cast<taxonomy::piecewise_function>(mapping->map(next_inst));
start_of_next_inst_ = next->evaluate(0.0);
} else {
// there is not a next segment, however IfcGradientCurve and IfcSegmentedRefernceCurve
// there is not a next segment, however IfcGradientCurve and IfcSegmentedReferenceCurve
// have an optional EndPoint attribute that serves the same purpose as the zero-length
// "next segment" at the end of the curve. The Ifc specification is a little redundant
// in that the "zero length" segment is required thereby negating the need for EndPoint
// but some implementations use the EndPoint instead of the "zero length" segment
//
// Get the parent of this segment. If it is a IfcGradientCurve or IfcSegmentedRefernceCurve
// Get the parent of this segment. If it is a IfcGradientCurve or IfcSegmentedReferenceCurve
// look for the optional EndPoint attribute
auto curves = inst->UsingCurves();
if (curves && curves->size()) {
@@ -387,7 +387,7 @@ class curve_segment_evaluator {
}
}
void set_spiral_function(mapping* mapping_, const IfcSchema::IfcSpiral* c, double s, std::function<double(double)> signX, std::function<double(double)> fnX, std::function<double(double)> signY, std::function<double(double)> fnY, std::function<double(double)> fnSlope) {
void set_spiral_function(mapping* mapping_, const IfcSchema::IfcSpiral* c, double s, std::function<double(double)> signX, std::function<double(double)> fnX, std::function<double(double)> signY, std::function<double(double)> fnY) {
// determine the length of the spiral from the local origin to the end point
auto sign_s = binary_sign(start_);
auto sign_l = binary_sign(length_);
@@ -405,7 +405,7 @@ class curve_segment_evaluator {
auto segment_type = segment_type_;
auto transformation_matrix = taxonomy::cast<taxonomy::matrix4>(mapping_->map(c->Position()))->ccomponents();
geometry_adjuster = std::make_shared<GEOMETRY_ADJUSTER>(mapping_, segment_type_, inst_, next_inst_);
eval_ = [L, start, s, signX, fnX, signY, fnY, fnSlope, transformation_matrix, segment_type, geometry_adjuster = this->geometry_adjuster](double u) {
eval_ = [L, start, s, signX, fnX, signY, fnY, transformation_matrix, segment_type, geometry_adjuster = this->geometry_adjuster](double u) {
u += start;
@@ -419,21 +419,8 @@ class curve_segment_evaluator {
// From https://standards.buildingsmart.org/IFC/RELEASE/IFC4_3/HTML/lexical/IfcSpiral.htm, x = Integral(fnX du), y = Integral(fnY du)
// The tangent slope of a curve is the derivate of the curve, so the derivitive of an integral, is just the function
// Therefore, Dx/Du = fnX(u) and Dy/Du = fnY(u) which leads to du = Dx/fnX(u) and Dy = fnY(u)*Du = fnY(u)*Dx/fnX(u) so Dy/Dx = fnY(u)/fnX(u)
// However, Dx and Dy are not normalized. Recall that slope = rise/run
// If run = 1.0, then rise = Dy/Dx = fnY(u)/fnX(u) and l = sqrt((fnY(u)/fnX(u))^2 + 1.0^2)
// The direction ratios are dx = 1.0/l and dy = (fnY/fnX)/l;
//auto fy = fnY(u);
//auto fx = fnX(u);
//auto rise = fy / fx;
//auto run = 1.0;
//auto l = sqrt(run * run + rise * rise);
//auto dx = run / l;
//auto dy = rise / l;
auto slope = fnSlope(b);
auto dx = signX(u) * cos(slope);
auto dy = signY(u) * sin(slope);
auto dx = signX(u)*fnX(b)/s;
auto dy = signY(u)*fnY(b)/s;
Eigen::Matrix4d m;
if (segment_type == ST_HORIZONTAL) {
@@ -534,10 +521,8 @@ class curve_segment_evaluator {
auto sign_y = [A](double t) { return sign(t) == sign(A) ? 1.0 : -1.0; };
auto fn_x = [A, s](double t) -> double { return s * cos(PI * fabs(A) * t * t / (2 * fabs(A))); };
auto fn_y = [A, s](double t) -> double { return s * sin(PI * fabs(A) * t * t / (2 * fabs(A))); };
//auto fn_slope = [A](double t) -> double { return sqrt(PI) * t * t / (2 * abs(A)); };
auto fn_slope = [A, s](double t) -> double { return pow(t*s / A, 2) / 2; };
set_spiral_function(mapping_, c, s, sign_x, fn_x, sign_y, fn_y, fn_slope);
set_spiral_function(mapping_, c, s, sign_x, fn_x, sign_y, fn_y);
}
#endif
@@ -562,10 +547,9 @@ class curve_segment_evaluator {
auto fn_x = [theta](double t)->double {return cos(theta(t)); };
auto fn_y = [theta](double t)->double {return sin(theta(t)); };
auto fn_slope = [](double t)->double { return tan(t); };
double s = 1.0; // @todo: rb - this is supposed to be the curve length when the parametric value u = 1.0
set_spiral_function(mapping_, c, s, sign_x, fn_x, sign_y, fn_y, fn_slope);
set_spiral_function(mapping_, c, s, sign_x, fn_x, sign_y, fn_y);
}
#endif