Aegisub/aegisub/spline_curve.cpp

// Copyright (c) 2007, Rodrigo Braz Monteiro
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are met:
//
//   * Redistributions of source code must retain the above copyright notice,
//     this list of conditions and the following disclaimer.
//   * Redistributions in binary form must reproduce the above copyright notice,
//     this list of conditions and the following disclaimer in the documentation
//     and/or other materials provided with the distribution.
//   * Neither the name of the Aegisub Group nor the names of its contributors
//     may be used to endorse or promote products derived from this software
//     without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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// ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE.
//
// -----------------------------------------------------------------------------
//
// AEGISUB
//
// Website: http://aegisub.cellosoft.com
// Contact: mailto:zeratul@cellosoft.com
//


///////////
// Headers
#include "spline_curve.h"
#include "utils.h"


/////////////////////
// Curve constructor
SplineCurve::SplineCurve() {
	type = CURVE_INVALID;
}


/////////////////////////////////////////////////////////
// Split a curve in two using the de Casteljau algorithm
void SplineCurve::Split(SplineCurve &c1,SplineCurve &c2,float t) {
	// Split a line
	if (type == CURVE_LINE) {
		c1.type = CURVE_LINE;
		c2.type = CURVE_LINE;
		c1.p1 = p1;
		c1.p2 = p1*t+p2*(1-t);
		c2.p1 = c1.p2;
		c2.p2 = p2;
	}

	// Split a bicubic
	else if (type == CURVE_BICUBIC) {
		c1.type = CURVE_BICUBIC;
		c2.type = CURVE_BICUBIC;

		// Sub-divisions
		float u = 1-t;
		Vector2D p12 = p1*t+p2*u;
		Vector2D p23 = p2*t+p3*u;
		Vector2D p34 = p3*t+p4*u;
		Vector2D p123 = p12*t+p23*u;
		Vector2D p234 = p23*t+p34*u;
		Vector2D p1234 = p123*t+p234*u;

		// Set points
		c1.p1 = p1;
		c1.p2 = p12;
		c1.p3 = p123;
		c1.p4 = p1234;
		c2.p1 = p1234;
		c2.p2 = p234;
		c2.p3 = p34;
		c2.p4 = p4;
	}
}


//////////////////////
// Smoothes the curve
// Based on http://antigrain.com/research/bezier_interpolation/index.html
void SplineCurve::Smooth(Vector2D P0,Vector2D P3,float smooth) {
	// Validate
	if (type != CURVE_LINE) return;
	smooth = MID(0.0f,smooth,1.0f);

	// Get points
	Vector2D P1 = p1;
	Vector2D P2 = p2;

	// Calculate intermediate points
	Vector2D c1 = (P0+P1)/2.0f;
	Vector2D c2 = (P1+P2)/2.0f;
	Vector2D c3 = (P2+P3)/2.0f;
	float len1 = (P1-P0).Len();
	float len2 = (P2-P1).Len();
	float len3 = (P3-P2).Len();
	float k1 = len1/(len1+len2);
	float k2 = len2/(len2+len3);
	Vector2D m1 = c1+(c2-c1)*k1;
	Vector2D m2 = c2+(c3-c2)*k2;

	// Set curve points
	p4 = p2;
	p2 = m1+(c2-m1)*smooth + P1 - m1;
	p3 = m2+(c2-m2)*smooth + P2 - m2;
	type = CURVE_BICUBIC;
}