axmol/core/math/CCVertex.cpp

/****************************************************************************
 Copyright (c) 2010-2012 cocos2d-x.org
 Copyright (c) 2011 ForzeField Studios S.L
 Copyright (c) 2013-2016 Chukong Technologies Inc.
 Copyright (c) 2017-2018 Xiamen Yaji Software Co., Ltd.

 https://axis-project.github.io/

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 of this software and associated documentation files (the "Software"), to deal
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 all copies or substantial portions of the Software.

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 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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#include "math/CCVertex.h"
#include "base/ccMacros.h"

NS_AX_BEGIN

void ccVertexLineToPolygon(Vec2* points, float stroke, Vec2* vertices, unsigned int offset, unsigned int nuPoints)
{
    nuPoints += offset;
    if (nuPoints <= 1)
        return;

    stroke *= 0.5f;

    unsigned int idx;
    unsigned int nuPointsMinus = nuPoints - 1;

    for (unsigned int i = offset; i < nuPoints; i++)
    {
        idx     = i * 2;
        Vec2 p1 = points[i];
        Vec2 perpVector;

        if (i == 0)
            perpVector = (p1 - points[i + 1]).getNormalized().getPerp();
        else if (i == nuPointsMinus)
            perpVector = (points[i - 1] - p1).getNormalized().getPerp();
        else
        {
            Vec2 p2 = points[i + 1];
            Vec2 p0 = points[i - 1];

            Vec2 p2p1 = (p2 - p1).getNormalized();
            Vec2 p0p1 = (p0 - p1).getNormalized();

            // Calculate angle between vectors
            float angle = acosf(p2p1.dot(p0p1));

            if (angle < AX_DEGREES_TO_RADIANS(70))
                perpVector = p2p1.getMidpoint(p0p1).getNormalized().getPerp();
            else if (angle < AX_DEGREES_TO_RADIANS(170))
                perpVector = p2p1.getMidpoint(p0p1).getNormalized();
            else
                perpVector = (p2 - p0).getNormalized().getPerp();
        }
        perpVector = perpVector * stroke;

        vertices[idx].set(p1.x + perpVector.x, p1.y + perpVector.y);
        vertices[idx + 1].set(p1.x - perpVector.x, p1.y - perpVector.y);
    }

    // Validate vertexes
    offset = (offset == 0) ? 0 : offset - 1;
    for (unsigned int i = offset; i < nuPointsMinus; i++)
    {
        idx                     = i * 2;
        const unsigned int idx1 = idx + 2;

        Vec2 p1 = vertices[idx];
        Vec2 p2 = vertices[idx + 1];
        Vec2 p3 = vertices[idx1];
        Vec2 p4 = vertices[idx1 + 1];

        float s;
        // BOOL fixVertex = !ccpLineIntersect(Vec2(p1.x, p1.y), Vec2(p4.x, p4.y), Vec2(p2.x, p2.y), Vec2(p3.x, p3.y),
        // &s, &t);
        bool fixVertex = !ccVertexLineIntersect(p1.x, p1.y, p4.x, p4.y, p2.x, p2.y, p3.x, p3.y, &s);
        if (!fixVertex)
            if (s < 0.0f || s > 1.0f)
                fixVertex = true;

        if (fixVertex)
        {
            vertices[idx1]     = p4;
            vertices[idx1 + 1] = p3;
        }
    }
}

bool ccVertexLineIntersect(float Ax, float Ay, float Bx, float By, float Cx, float Cy, float Dx, float Dy, float* T)
{
    float distAB, theCos, theSin, newX;

    // FAIL: Line undefined
    if ((Ax == Bx && Ay == By) || (Cx == Dx && Cy == Dy))
        return false;

    //  Translate system to make A the origin
    Bx -= Ax;
    By -= Ay;
    Cx -= Ax;
    Cy -= Ay;
    Dx -= Ax;
    Dy -= Ay;

    // Length of segment AB
    distAB = sqrtf(Bx * Bx + By * By);

    // Rotate the system so that point B is on the positive X axis.
    theCos = Bx / distAB;
    theSin = By / distAB;
    newX   = Cx * theCos + Cy * theSin;
    Cy     = Cy * theCos - Cx * theSin;
    Cx     = newX;
    newX   = Dx * theCos + Dy * theSin;
    Dy     = Dy * theCos - Dx * theSin;
    Dx     = newX;

    // FAIL: Lines are parallel.
    if (Cy == Dy)
        return false;

    // Discover the relative position of the intersection in the line AB
    *T = (Dx + (Cx - Dx) * Dy / (Dy - Cy)) / distAB;

    // Success.
    return true;
}

NS_AX_END