Frustum.cpp

// Copyright © 2008-2018 Pioneer Developers. See AUTHORS.txt for details
// Licensed under the terms of the GPL v3. See licenses/GPL-3.txt

#include "Frustum.h"
#include "Graphics.h"

namespace Graphics {

// min/max FOV in degrees
static const float FOV_MAX = 170.0f;
static const float FOV_MIN = 20.0f;

// step for translating to frustum space
static const double TRANSLATE_STEP = 0.25;

Frustum::Frustum() {}

Frustum::Frustum(float width, float height, float fovAng, float znear, float zfar)
{
	//http://www.opengl.org/resources/faq/technical/transformations.htm
	const float fov = tan(DEG2RAD(Clamp(fovAng, FOV_MIN, FOV_MAX) / 2.0f));

	const float aspect = width/height;
	const float top = znear * fov;
	const float bottom = -top;
	const float left = bottom * aspect;
	const float right = top * aspect;

	m_projMatrix = matrix4x4d::FrustumMatrix(left, right, bottom, top, znear, zfar);
	m_modelMatrix = matrix4x4d::Identity();
	InitFromMatrix(m_projMatrix);

	m_translateThresholdSqr = zfar*zfar*TRANSLATE_STEP;
}

Frustum::Frustum(const matrix4x4d &modelview, const matrix4x4d &projection) : m_projMatrix(projection), m_modelMatrix(modelview)
{
	const matrix4x4d m = m_projMatrix * m_modelMatrix;
	InitFromMatrix(m);
}

void Frustum::InitFromMatrix(const matrix4x4d &m)
{
	// Left clipping plane
	m_planes[0].a = m[3] + m[0];
	m_planes[0].b = m[7] + m[4];
	m_planes[0].c = m[11] + m[8];
	m_planes[0].d = m[15] + m[12];
	// Right clipping plane
	m_planes[1].a = m[3] - m[0];
	m_planes[1].b = m[7] - m[4];
	m_planes[1].c = m[11] - m[8];
	m_planes[1].d = m[15] - m[12];
	// Top clipping plane
	m_planes[2].a = m[3] - m[1];
	m_planes[2].b = m[7] - m[5];
	m_planes[2].c = m[11] - m[9];
	m_planes[2].d = m[15] - m[13];
	// Bottom clipping plane
	m_planes[3].a = m[3] + m[1];
	m_planes[3].b = m[7] + m[5];
	m_planes[3].c = m[11] + m[9];
	m_planes[3].d = m[15] + m[13];
	// Near clipping plane
	m_planes[4].a = m[3] + m[2];
	m_planes[4].b = m[7] + m[6];
	m_planes[4].c = m[11] + m[10];
	m_planes[4].d = m[15] + m[14];
	// Far clipping plane
	m_planes[5].a = m[3] + m[2];
	m_planes[5].b = m[7] + m[6];
	m_planes[5].c = m[11] + m[10];
	m_planes[5].d = m[15] + m[14];

	// Normalize the fuckers
	for (int i=0; i<6; i++) {
		double invlen = 1.0 / sqrt(m_planes[i].a*m_planes[i].a + m_planes[i].b*m_planes[i].b + m_planes[i].c*m_planes[i].c);
		m_planes[i].a *= invlen;
		m_planes[i].b *= invlen;
		m_planes[i].c *= invlen;
		m_planes[i].d *= invlen;
	}
}

bool Frustum::TestPoint(const vector3d &p, double radius) const
{
	for (int i=0; i<6; i++)
		if (m_planes[i].DistanceToPoint(p)+radius < 0)
			return false;
	return true;
}

bool Frustum::TestPointInfinite(const vector3d &p, double radius) const
{
	PROFILE_SCOPED()
	// check all planes except far plane
	for (int i=0; i<5; i++)
		if (m_planes[i].DistanceToPoint(p)+radius < 0)
			return false;
	return true;
}

bool Frustum::ProjectPoint(const vector3d &in, vector3d &out) const
{
	// see the OpenGL documentation
	// or http://www.songho.ca/opengl/gl_transform.html
	// or http://cgit.freedesktop.org/mesa/glu/tree/src/libutil/project.c (gluProject implementation from Mesa)

	const double * const M = m_modelMatrix.Data();
	const double * const P = m_projMatrix.Data();

	const double vcam[4] = { // camera space
		in.x*M[0] + in.y*M[4] + in.z*M[ 8] + M[12],
		in.x*M[1] + in.y*M[5] + in.z*M[ 9] + M[13],
		in.x*M[2] + in.y*M[6] + in.z*M[10] + M[14],
		in.x*M[3] + in.y*M[7] + in.z*M[11] + M[15]
	};
	const double vclip[4] = { // clip space
		vcam[0]*P[0] + vcam[1]*P[4] + vcam[2]*P[ 8] + vcam[3]*P[12],
		vcam[0]*P[1] + vcam[1]*P[5] + vcam[2]*P[ 9] + vcam[3]*P[13],
		vcam[0]*P[2] + vcam[1]*P[6] + vcam[2]*P[10] + vcam[3]*P[14],
		vcam[0]*P[3] + vcam[1]*P[7] + vcam[2]*P[11] + vcam[3]*P[15]
	};

	if (is_zero_exact(vclip[3])) { return false; }

	const double w = vclip[3];
	out.x = (vclip[0] / w) * 0.5 + 0.5;
	out.y = (vclip[1] / w) * 0.5 + 0.5;
	out.z = (vclip[2] / w) * 0.5 + 0.5;

	return true;
}

double Frustum::TranslatePoint(const vector3d &in, vector3d &out) const
{
	out = in;
	double scale = 1.0;
	while (out.LengthSqr() > m_translateThresholdSqr) {
		out *= TRANSLATE_STEP;
		scale *= TRANSLATE_STEP;
	}
	return scale;
}

}