Cylinder.cpp

/**
 @file Cylinder.cpp
  
 @maintainer Morgan McGuire, http://graphics.cs.williams.edu

 @created 2003-02-07
 @edited  2006-02-18

 Copyright 2000-2006, Morgan McGuire.
 All rights reserved.
 */

#include "G3D/platform.h"
#include "G3D/Cylinder.h"
#include "G3D/BinaryInput.h"
#include "G3D/BinaryOutput.h"
#include "G3D/LineSegment.h"
#include "G3D/CoordinateFrame.h"
#include "G3D/Line.h"
#include "G3D/AABox.h"

namespace G3D {

Cylinder::Cylinder(class BinaryInput& b) {
	deserialize(b);
}


Cylinder::Cylinder() {
}


Cylinder::Cylinder(const Vector3& _p1, const Vector3& _p2, float _r) 
	: p1(_p1), p2(_p2), mRadius(_r) {
}


void Cylinder::serialize(class BinaryOutput& b) const {
	p1.serialize(b);
	p2.serialize(b);
	b.writeFloat64(mRadius);
}


void Cylinder::deserialize(class BinaryInput& b) {
	p1.deserialize(b);
	p2.deserialize(b);
	mRadius = b.readFloat64();
}


Line Cylinder::axis() const {
	return Line::fromTwoPoints(p1, p2);
}



float Cylinder::radius() const {
	return mRadius;
}


float Cylinder::volume() const {
	return
		(float)pi() * square(mRadius) * (p1 - p2).magnitude();
}


float Cylinder::area() const {
	return
        // Sides
		(twoPi() * mRadius) * height() +

         // Caps
         twoPi() * square(mRadius);
}

void Cylinder::getBounds(AABox& out) const {
    Vector3 min = p1.min(p2) - (Vector3(1, 1, 1) * mRadius);
    Vector3 max = p1.max(p2) + (Vector3(1, 1, 1) * mRadius);
    out = AABox(min, max);
}

bool Cylinder::contains(const Vector3& p) const { 
    return LineSegment::fromTwoPoints(p1, p2).distanceSquared(p) <= square(mRadius);
}


void Cylinder::getReferenceFrame(CoordinateFrame& cframe) const {
    cframe.translation = center();

    Vector3 Y = (p1 - p2).direction();
    Vector3 X = (abs(Y.dot(Vector3::unitX())) > 0.9) ? Vector3::unitY() : Vector3::unitX();
    Vector3 Z = X.cross(Y).direction();
    X = Y.cross(Z);        
    cframe.rotation.setColumn(0, X);
    cframe.rotation.setColumn(1, Y);
    cframe.rotation.setColumn(2, Z);
}


void Cylinder::getRandomSurfacePoint(Vector3& p, Vector3& N) const {
    float h = height();
    float r = radius();

    // Create a random point on a standard cylinder and then rotate to the global frame.

    // Relative areas (factor of 2PI already taken out)
    float capRelArea  = square(r) / 2.0f;
    float sideRelArea = r * h;

    float r1 = uniformRandom(0, capRelArea * 2 + sideRelArea);

    if (r1 < capRelArea * 2) {

        // Select a point uniformly at random on a disk
        // @cite http://mathworld.wolfram.com/DiskPointPicking.html
        float a = uniformRandom(0, (float)twoPi());
        float r2 = sqrt(uniformRandom(0, 1)) * r;
        p.x = cos(a) * r2;
        p.z = sin(a) * r2;

        N.x = 0;
        N.z = 0;
        if (r1 < capRelArea) {
            // Top
            p.y = h / 2.0f;
            N.y = 1;
        } else {
            // Bottom
            p.y = -h / 2.0f;
            N.y = -1;
        }
    } else {
        // Side
        float a = uniformRandom(0, (float)twoPi());
        N.x = cos(a);
        N.y = 0;
        N.z = sin(a);
        p.x = N.x * r;
        p.z = N.y * r;
        p.y = uniformRandom(-h / 2.0f, h / 2.0f);
    }

    // Transform to world space
    CoordinateFrame cframe;
    getReferenceFrame(cframe);
    
    p = cframe.pointToWorldSpace(p);
    N = cframe.normalToWorldSpace(N);
}


Vector3 Cylinder::randomInteriorPoint() const {
    float h = height();
    float r = radius();

    // Create a random point in a standard cylinder and then rotate to the global frame.

    // Select a point uniformly at random on a disk
    // @cite http://mathworld.wolfram.com/DiskPointPicking.html
    float a = uniformRandom(0, (float)twoPi());
    float r2 = sqrt(uniformRandom(0, 1)) * r;

    Vector3 p(  cos(a) * r2,
                uniformRandom(-h / 2.0f, h / 2.0f),
                sin(a) * r2);

    // Transform to world space
    CoordinateFrame cframe;
    getReferenceFrame(cframe);
    
    return cframe.pointToWorldSpace(p);
}

} // namespace