godot/core/math/transform_interpolator.cpp

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/*  transform_interpolator.cpp                                            */
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/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur.                  */
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#include "transform_interpolator.h"

#include "core/math/transform_2d.h"

void TransformInterpolator::interpolate_transform_2d(const Transform2D &p_prev, const Transform2D &p_curr, Transform2D &r_result, real_t p_fraction) {
	// Special case for physics interpolation, if flipping, don't interpolate basis.
	// If the determinant polarity changes, the handedness of the coordinate system changes.
	if (_sign(p_prev.determinant()) != _sign(p_curr.determinant())) {
		r_result.columns[0] = p_curr.columns[0];
		r_result.columns[1] = p_curr.columns[1];
		r_result.set_origin(p_prev.get_origin().lerp(p_curr.get_origin(), p_fraction));
		return;
	}

	r_result = p_prev.interpolate_with(p_curr, p_fraction);
}