openrw/rwengine/include/render/ViewFrustum.hpp

#ifndef _VIEWFRUSTUM_HPP_
#define _VIEWFRUSTUM_HPP_
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>

class ViewFrustum
{
public:
	
	class ViewPlane
	{
	public:
		glm::vec3 normal;
		float distance;
	};
	
	float near;
	float far;
	float fov;
	float aspectRatio;

	ViewPlane planes[6];
	
	ViewFrustum(float near, float far, float fov, float aspect)
	: near(near), far(far), fov(fov), aspectRatio(aspect)
	{
		
	}
	
	glm::mat4 projection()
	{
		return glm::perspective(fov / aspectRatio, aspectRatio, near, far);
	}
	
	void update(const glm::mat4& proj)
	{
		for(size_t i = 0; i < 6; ++i)
		{
			float sign = (i%2==0) ? 1.f : -1.f;
			int r = i / 2;
			planes[i].normal.x = proj[0][3] + proj[0][r] * sign;
			planes[i].normal.y = proj[1][3] + proj[1][r] * sign;
			planes[i].normal.z = proj[2][3] + proj[2][r] * sign;
			planes[i].distance = proj[3][3] + proj[3][r] * sign;
			
			auto l = glm::length(planes[i].normal);
			planes[i].normal /= l;
			planes[i].distance /= l;
		}
	}
	
	bool intersects(glm::vec3 center, float radius)
	{
		float d;
		bool result = true;

		for(size_t i = 0; i < 6; ++i)
		{
			d = glm::dot(planes[i].normal, center) + planes[i].distance;
			if( d < -radius ) result = false;
		}

		return result;
	}
};

#endif