super-snuvi/src/me/hammerle/supersnuvi/util/Utils.java

package me.hammerle.supersnuvi.util;

import me.hammerle.supersnuvi.tiles.Tile;

public class Utils 
{
    public static float interpolate(float from, float to, float factor)
    {
        return from + (to - from) * factor;
    }
    
    public static int toBlock(float c)
    {
        return (int) (c / Tile.SIZE);
    }

    public static float toCoord(int b)
    {
        return b * Tile.SIZE;
    }
    
    public static float getSquaredDistance(float x1, float y1, float x2, float y2)
    {
        return (x1 - x2) * (x1 - x2) + (y1 - y2) * (y1 - y2);
    }
    
    public static Face getCollidingFace(
            float xMin1, float yMin1, float xMax1, float yMax1, 
            float xMin2, float yMin2, float xMax2, float yMax2)
    {
        float diffUp = yMax1 - yMin2;
        float diffRight = xMax2 - xMin1;
        float diffDown = yMax2 - yMin1;
        float diffLeft = xMax1 - xMin2;
        
        float min = diffUp;
        
        Face f = Face.UP;
        if(min > diffRight)
        {
            min = diffRight;
            f = Face.RIGHT;
        }
        if(min > diffDown)
        {
            min = diffDown;
            f = Face.DOWN;
        }
        if(min > diffLeft)
        {
            f = Face.LEFT;
        }
        
        int c = 0;
        c += (min == diffUp) ? 1 : 0;
        c += (min == diffRight) ? 1 : 0;
        c += (min == diffDown) ? 1 : 0;
        c += (min == diffLeft) ? 1 : 0;
        if(c >= 2)
        {
            return Face.NULL;
        }
        
        return f;
    }
    
    public static boolean intersect(float x11, float y11, float x12, float y12, float x21, float y21, float x22, float y22)
    {
        if(compareFloats(x11, x12))
        {
            if(compareFloats(x21, x22))
            {
                return false;
            }
            else
            {
                if(!isBetween(x11, x21, x22))
                {
                    return false;
                }
                float k = (y21 - y22) / (x21 - x22);
                float d = y22 - k * x22;
                float y = d + x11 * k;
                return isBetween(y, y11, y12) && isBetween(y, y21, y22);
            }
        }
        else
        {
            if(compareFloats(x21, x22))
            {
                if(!isBetween(x21, x11, x12))
                {
                    return false;
                }
                float k = (y11 - y12) / (x11 - x12);
                float d = y12 - k * x12;
                float y = d + x21 * k;
                return isBetween(y, y11, y12) && isBetween(y, y21, y22);
            }
            else
            {
                float k1 = (y11 - y12) / (x11 - x12);
                float k2 = (y21 - y22) / (x21 - x22);
                if(compareFloats(k1, k2))
                {
                    return false;
                }
                float d1 = y12 - k1 * x12;
                float d2 = y22 - k2 * x22;
                
                float x = (d1 - d2) / (k2 - k1);
                if(!isBetween(x, x11, x12) || !isBetween(x, x21, x22))
                {
                    return false;
                }
                float y = k1 * x + d1;
                return isBetween(y, y11, y12) && isBetween(y, y21, y22);
            }
        }
    }
    
    private static final float ERROR = 1.0f / 512.0f;
    
    private static boolean isBetween(float y, float y1, float y2)
    {
        float min = Math.min(y1, y2) - ERROR;
        float max = Math.max(y1, y2) + ERROR;
        return y >= min && y <= max;
    }
    
    private static boolean compareFloats(float a, float b)
    {
        return Math.abs(a - b) < ERROR;
    }
}