compute()

vec2f fl::CatmullRomPath::compute ( float alpha )

overridevirtual

Implements fl::XYPathGenerator.

Definition at line 275 of file xypath_impls.cpp.

                                         {
    const auto &points = params().points;
 
    // Need at least 2 points to define a path
    if (points.size() < 2) {
        // Return origin if not enough points
        return vec2f(0.0f, 0.0f);
    }
 
    // If only 2 points, do linear interpolation
    if (points.size() == 2) {
        return vec2f(points[0].x + alpha * (points[1].x - points[0].x),
                     points[0].y + alpha * (points[1].y - points[0].y));
    }
 
    // For Catmull-Rom, we need 4 points to interpolate between the middle two
    // Scale alpha to the number of segments
    float scaledAlpha = alpha * (points.size() - 1);
 
    // Determine which segment we're in
    int segment = static_cast<int>(scaledAlpha);
 
    // Clamp to valid range
    if (segment >= static_cast<int>(points.size()) - 1) {
        segment = points.size() - 2;
        scaledAlpha = static_cast<float>(segment) + 1.0f;
    }
 
    // Get local alpha within this segment [0,1]
    float t = scaledAlpha - static_cast<float>(segment);
 
    // Get the four points needed for interpolation
    vec2f p0, p1, p2, p3;
 
    // Handle boundary cases
    if (segment == 0) {
        // For the first segment, duplicate the first point
        p0 = points[0];
        p1 = points[0];
        p2 = points[1];
        p3 = (points.size() > 2) ? points[2] : points[1];
    } else if (segment == static_cast<int>(points.size()) - 2) {
        // For the last segment, duplicate the last point
        p0 = (segment > 0) ? points[segment - 1] : points[0];
        p1 = points[segment];
        p2 = points[segment + 1];
        p3 = points[segment + 1];
    } else {
        // Normal case - we have points before and after
        p0 = points[segment - 1];
        p1 = points[segment];
        p2 = points[segment + 1];
        p3 = points[segment + 2];
    }
 
    // Perform Catmull-Rom interpolation
    auto out = interpolate(p0, p1, p2, p3, t);
    return out;
}

References interpolate(), params(), fl::CatmullRomParams::points, x, and y.

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