Plane.cpp

/*----------------------------------------------------------
* COSC363  Ray Tracer
*
*  The Plane class
*  This is a subclass of Object, and hence implements the
*  methods intersect() and normal().
-------------------------------------------------------------*/

#include "Plane.h"
#include <math.h>


/**
* Checks if a point pt is inside the current polygon
* Implement a point inclusion test using 
* member variables a, b, c, d.
*/
bool Plane::isInside(glm::vec3 pt)
{

	//=== Complete this function ====
	glm::vec3 ua = b - a;
	glm::vec3 va = pt - a;
	glm::vec3 ub = c - b;
	glm::vec3 vb = pt - b;
	glm::vec3 uc = d - c;
	glm::vec3 vc = pt - c;
	glm::vec3 ud = a - d;
	glm::vec3 vd = pt - d;
	
	glm::vec3 n = normal_internal(pt);
	
	float uavaDotn = glm::dot(glm::cross(ua, va), n);
	float ubvbDotn = glm::dot(glm::cross(ub, vb), n);
	float ucvcDotn = glm::dot(glm::cross(uc, vc), n);
	float udvdDotn = glm::dot(glm::cross(ud, vd), n);
	
	if (uavaDotn > 0 && ubvbDotn > 0 && ucvcDotn > 0 && udvdDotn > 0) {
		return true;
	} else {
		return false;
	}
	
}

/**
* Plane's intersection method.  The input is a ray (pos, dir). 
*/
float Plane::intersect_internal(glm::vec3 posn, glm::vec3 dir)
{
	glm::vec3 n = normal_internal(posn);
	glm::vec3 vdif = a - posn;
	float vdotn = glm::dot(dir, n);
	if(fabs(vdotn) < 1.e-4) return -1;
    float t = glm::dot(vdif, n)/vdotn;
	if(fabs(t) < 0.0001) return -1;
	glm::vec3 q = posn + dir*t;
	if(isInside(q)) return t;
    else return -1;
}

/**
* Returns the unit normal vector at a given point.
* Compute the plane's normal vector using 
* member variables a, b, c, d.
* The parameter pt is a dummy variable and is not used.
*/
glm::vec3 Plane::normal_internal(glm::vec3 pt)
{
	glm::vec3 n = glm::vec3(0);

	//=== Complete this function ====
	n = glm::cross((b - a), (d - a));
	
	n = glm::normalize(n);

    return n;
}