/* * * * * * * * * * * * * Author's note * * * * * * * * * * * *\
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*                     http://www.humus.name                     *
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* This file is a part of the work done by Humus. You are free to   *
* use the code in any way you like, modified, unmodified or copied   *
* into your own work. However, I expect you to respect these points:  *
*  - If you use this file and its contents unmodified, or use a major *
*    part of this file, please credit the author and leave this note. *
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// I would like to thank Humus for giving away this code, it
// is very generous and makes my life easier.
// - Bill Whitacre

#include "frustum.h"

void Projection::ToMatrix(Matrix4x4 &mat)
{
	float top,bot,lft,rgt;
	top=(float)(znear*tan(180.0/(PI*(double)yfov)));
	bot=-top;
	lft=bot*aspect;
	rgt=top*aspect;

	mat.rows[0]=Vector4((2*znear)/(rgt-lft),0.0,(rgt+lft)/(rgt-lft),0.0);
	mat.rows[1]=Vector4(0.0,(2*znear)/(top-bot),(top+bot)/(top-bot),0.0);
	mat.rows[2]=Vector4(0.0,0.0,-((zfar+znear)/(zfar-znear)),-((2*zfar*znear)/(zfar-znear)));
	mat.rows[3]=Vector4(0.0,0.0,-1.0,0.0);

	/*return Matrix4x4(
		Vector4((2*znear)/(rgt-lft),0.0,(rgt+lft)/(rgt-lft),0.0),
		Vector4(0.0,(2*znear)/(top-bot),(top+bot)/(top-bot),0.0),
		Vector4(0.0,0.0,-((zfar+znear)/(zfar-znear)),-((2*zfar*znear)/(zfar-znear))),
		Vector4(0.0,0.0,-1.0,0.0));*/
}

void Frustum::LoadFrustum(const Matrix4x4 &mvp){
	planes[_FRUSTUM_LEFT  ] = Plane(mvp[12] - mvp[0], mvp[13] - mvp[1], mvp[14] - mvp[2],  mvp[15] - mvp[3]);
	planes[_FRUSTUM_RIGHT ] = Plane(mvp[12] + mvp[0], mvp[13] + mvp[1], mvp[14] + mvp[2],  mvp[15] + mvp[3]);

	planes[_FRUSTUM_TOP   ] = Plane(mvp[12] - mvp[4], mvp[13] - mvp[5], mvp[14] - mvp[6],  mvp[15] - mvp[7]);
	planes[_FRUSTUM_BOTTOM] = Plane(mvp[12] + mvp[4], mvp[13] + mvp[5], mvp[14] + mvp[6],  mvp[15] + mvp[7]);

	planes[_FRUSTUM_FAR   ] = Plane(mvp[12] - mvp[8], mvp[13] - mvp[9], mvp[14] - mvp[10], mvp[15] - mvp[11]);
	planes[_FRUSTUM_NEAR  ] = Plane(mvp[12] + mvp[8], mvp[13] + mvp[9], mvp[14] + mvp[10], mvp[15] + mvp[11]);
}

bool Frustum::PointInFrustum(const Vector3 &pos) const {
	for (int i = 0; i < 6; i++){
		if (planes[i].dist(pos) <= 0) return false;
	}
    return true;
}

bool Frustum::SphereInFrustum(const Vector3 &pos, const float radius) const {
	for (int i = 0; i < 6; i++){
		if (planes[i].dist(pos) <= -radius) return false;
	}
    return true;
}

bool Frustum::CubeInFrustum(const float minX, const float maxX, const float minY, const float maxY, const float minZ, const float maxZ) const {
    for (int i = 0; i < 6; i++){
		if (planes[i].dist(Vector3(minX, minY, minZ)) > 0) continue;
		if (planes[i].dist(Vector3(minX, minY, maxZ)) > 0) continue;
		if (planes[i].dist(Vector3(minX, maxY, minZ)) > 0) continue;
		if (planes[i].dist(Vector3(minX, maxY, maxZ)) > 0) continue;
		if (planes[i].dist(Vector3(maxX, minY, minZ)) > 0) continue;
		if (planes[i].dist(Vector3(maxX, minY, maxZ)) > 0) continue;
		if (planes[i].dist(Vector3(maxX, maxY, minZ)) > 0) continue;
		if (planes[i].dist(Vector3(maxX, maxY, maxZ)) > 0) continue;
        return false;
    }
    return true;
}