MyGUI_GeometryUtility.cpp

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/*
 * This source file is part of MyGUI. For the latest info, see http://mygui.info/
 * Distributed under the MIT License
 * (See accompanying file COPYING.MIT or copy at http://opensource.org/licenses/MIT)
 */

#include "MyGUI_Precompiled.h"
#include "MyGUI_GeometryUtility.h"

namespace MyGUI
{

    namespace geometry_utility
    {

        VectorFloatPoint cropPolygon(FloatPoint* _baseVerticiesPos, size_t _size, const IntCoord& _cropRectangle)
        {
            VectorFloatPoint resultVerticiesPos;
            resultVerticiesPos.resize(_size);
            for (size_t i = 0; i < _size; ++i)
            {
                resultVerticiesPos[i] = _baseVerticiesPos[i];
            }

            cropPolygonSide(resultVerticiesPos, _cropRectangle.left, Left);
            cropPolygonSide(resultVerticiesPos, _cropRectangle.right(), Right);
            cropPolygonSide(resultVerticiesPos, _cropRectangle.top, Top);
            cropPolygonSide(resultVerticiesPos, _cropRectangle.bottom(), Bottom);

            return resultVerticiesPos;
        }

        void cropPolygonSide(VectorFloatPoint& _verticies, int _sideCoord, Side _side)
        {
            VectorFloatPoint newVerticies;
            int invert = (_side == Right || _side == Bottom) ? -1 : 1;
            for (size_t i = 0; i < _verticies.size(); ++i)
            {
                FloatPoint& v0 = _verticies[i];
                FloatPoint& v1 = _verticies[(i + 1) % _verticies.size()];
                switch (_side)
                {
                case Left:
                case Right:
                    // both inside
                    if (invert * v0.left >= invert * _sideCoord && invert * v1.left >= invert * _sideCoord)
                        newVerticies.push_back(v0);
                    // intersect side (1st vertex in)
                    else if (invert * v0.left >= invert * _sideCoord && invert * v1.left < invert * _sideCoord)
                    {
                        newVerticies.push_back(v0);
                        float c = (v0.left - _sideCoord) / (_sideCoord - v1.left);
                        newVerticies.push_back(FloatPoint((float)_sideCoord, (v0.top + c * v1.top) / (c + 1)));
                    }
                    // intersect side (2nd vertex in)
                    else if (invert * v0.left <= invert * _sideCoord && invert * v1.left > invert * _sideCoord)
                    {
                        float c = (v0.left - _sideCoord) / (_sideCoord - v1.left);
                        newVerticies.push_back(FloatPoint((float)_sideCoord, (v0.top + c * v1.top) / (c + 1)));
                    }
                    // else don't add any verticies
                    break;
                case Top:
                case Bottom:
                    // both inside
                    if (invert * v0.top >= invert * _sideCoord && invert * v1.top >= invert * _sideCoord)
                        newVerticies.push_back(v0);
                    // intersect side (1st vertex in)
                    else if (invert * v0.top >= invert * _sideCoord && invert * v1.top < invert * _sideCoord)
                    {
                        newVerticies.push_back(v0);
                        float c = (v0.top - _sideCoord) / (_sideCoord - v1.top);
                        newVerticies.push_back(FloatPoint((v0.left + c * v1.left) / (c + 1), (float)_sideCoord));
                    }
                    // intersect side (2nd vertex in)
                    else if (invert * v0.top <= invert * _sideCoord && invert * v1.top > invert * _sideCoord)
                    {
                        float c = (v0.top - _sideCoord) / (_sideCoord - v1.top);
                        newVerticies.push_back(FloatPoint((v0.left + c * v1.left) / (c + 1), (float)_sideCoord));
                    }
                    // else don't add any verticies
                    break;
                }
            }

            _verticies = newVerticies;
        }

        FloatPoint getPositionInsideRect(const FloatPoint& _point, const FloatPoint& _corner0, const FloatPoint& _corner1, const FloatPoint& _corner2)
        {
            FloatPoint result;

            FloatPoint point = _point - _corner0;
            FloatPoint dirX = _corner1 - _corner0;
            FloatPoint dirY = _corner2 - _corner0;

            float div = dirX.left * dirY.top - dirX.top * dirY.left;
            if (div == 0.0f)
                return FloatPoint();
            return FloatPoint(
                (point.top * dirX.left - point.left * dirX.top) / div,
                (point.left * dirY.top - point.top * dirY.left) / div);
        }

        FloatPoint getUVFromPositionInsideRect(const FloatPoint& _point, const FloatPoint& _v0, const FloatPoint& _v1, const FloatPoint& _baseUV)
        {
            return FloatPoint(
                _baseUV.left + _point.left * _v0.left + _point.top * _v1.left,
                _baseUV.top  + _point.left * _v0.top  + _point.top * _v1.top);
        }

    } // namespace geometry_utility

} // namespace MyGUI