intersect.cpp

/*
 * ______________________ _______    ________ ___  ___
 * \__    ___/\_   _____/ \      \  /  _____/|   | |  \
 *   |    |    |    __)_  /   |   \/   \  ___|   | |  |
 *   |    |    |        \/    |    \    \_\  \   |_|  |
 *   |____|   /_______  /\____|__  /\______  /________/
 * Game Engine.       \/         \/        \/
 *
 * (c) 8BitPimp (2013)
 */
#include "intersect.h"


//
// if [x1,y1] lies inside the box then this will fail
//
//
bool intersect_line_box
(
    sRayBox *i
)
{
    // find x1 x2 dimension style box
    float bx1 = i->bx - i->bw * 0.5f;
    float bx2 = i->bx + i->bw * 0.5f;
    float by1 = i->by - i->bh * 0.5f;
    float by2 = i->by + i->bh * 0.5f;
    //
    if ( i->x2 < i->x1 ) { swapf( &bx1, &bx2 ); }
    if ( i->y2 < i->y1 ) { swapf( &by1, &by2 ); }
    //
    float dx = (i->x2 - i->x1);
    float dy = (i->y2 - i->y1);
    //
    float t1x = (bx1 - i->x1) / dx;
    float t2x = (bx2 - i->x1) / dx;
    float t1y = (by1 - i->y1) / dy;
    float t2y = (by2 - i->y1) / dy;
    //
    if ( maxf( t1x, t1y ) < minf( t2x, t2y ) )
    {
        //
        float d = maxf( t1x, t1y );
        //
        if ( d > 1.0f ) return false;
        if ( d < 0.0f ) return false;
        //
        i->ix = i->x1 + d * (i->x2 - i->x1);
        i->iy = i->y1 + d * (i->y2 - i->y1);
        //
        return true;
    }
    //
    return false;
}

//
bool intersect_ray_box
(
    sRayBox *i
)
{
    // find x1 x2 dimension style box
    float bx1 = i->bx - i->bw * 0.5f;
    float bx2 = i->bx + i->bw * 0.5f;
    float by1 = i->by - i->bh * 0.5f;
    float by2 = i->by + i->bh * 0.5f;
    // swap to find the closest planes
    if ( i->x2 < i->x1 ) { swapf( &bx1, &bx2 ); }
    if ( i->y2 < i->y1 ) { swapf( &by1, &by2 ); }
    // differences
    float dx = (i->x2 - i->x1);
    float dy = (i->y2 - i->y1);
    //
    float t1x = (bx1 - i->x1) / dx;
    float t2x = (bx2 - i->x1) / dx;
    float t1y = (by1 - i->y1) / dy;
    float t2y = (by2 - i->y1) / dy;
    //
    if ( maxf( t1x, t1y ) < minf( t2x, t2y ) )
    {
        //
        float d = maxf( t1x, t1y );
        //
        i->ix = i->x1 + d * (i->x2 - i->x1);
        i->iy = i->y1 + d * (i->y2 - i->y1);
        //
        return true;
    }
    //
    return false;
}