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mitsuba/src/sensors/telecentric.cpp

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/*
This file is part of Mitsuba, a physically based rendering system.
Copyright (c) 2007-2012 by Wenzel Jakob and others.
Mitsuba is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License Version 3
as published by the Free Software Foundation.
Mitsuba is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <mitsuba/render/sensor.h>
#include <mitsuba/render/medium.h>
#include <mitsuba/render/track.h>
#include <mitsuba/core/frame.h>
#include <mitsuba/core/warp.h>
MTS_NAMESPACE_BEGIN
/*!\plugin{telecentric}{Telecentric lens camera}
* \order{4}
* \parameters{
* \parameter{toWorld}{\Transform\Or\ATransform}{
* Specifies an optional sensor-to-world transformation.
* \default{none (i.e. camera space $=$ world space)}
* }
* \parameter{apertureRadius}{\Float}{
* Denotes the radius of the camera's aperture in scene units.
* \default{\code{0}}
* }
* \parameter{focusDistance}{\Float}{
* Denotes the world-space distance from the camera's aperture to the
* focal plane. \default{\code{0}}
* }
* \parameter{shutterOpen, shutterClose}{\Float}{
* Specifies the time interval of the measurement---this
* is only relevant when the scene is in motion.
* \default{0}
* }
* \parameter{nearClip, farClip}{\Float}{
* Distance to the near/far clip
* planes.\default{\code{near\code}-\code{Clip=1e-2} (i.e.
* \code{0.01}) and {\code{farClip=1e4} (i.e. \code{10000})}}
* }
* }
* \renderings{
* \rendering{The material test ball viewed through an telecentric camera.
* Note the orthographic view together with a narrow depth of field.}{sensor_telecentric}
* \medrendering{A rendering of the Cornell box. The red and green walls are partially visible
* due to the aperture size.}{sensor_telecentric_2}
* }
*
* This plugin implements a simple model of a camera with a \emph{telecentric lens}.
* This is a type of lens that produces an in-focus orthographic view on a
* plane at some distance from the sensor. Points away from this plane are out of focus
* and project onto a circle of confusion. In comparison to idealized orthographic cameras,
* telecentric lens cameras exist in the real world and find use in some computer
* vision applications where perspective effects cause problems.
* This sensor relates to the \pluginref{orthographic} plugin in the same way
* that \pluginref{thinlens} does to \pluginref{perspective}.
*
* The configuration is identical to the \pluginref{orthographic} plugin, except that
* the additional parameters \code{apertureRadius} and \code{focusDistance} must be provided.
*/
class TelecentricLensCamera : public ProjectiveCamera {
public:
TelecentricLensCamera(const Properties &props)
: ProjectiveCamera(props) {
m_type |= ENeedsApertureSample
| EOrthographicCamera
| EPositionSampleMapsToPixels;
/* World-space aperture radius */
m_apertureRadius = props.getFloat("apertureRadius", 0.0f);
}
TelecentricLensCamera(Stream *stream, InstanceManager *manager)
: ProjectiveCamera(stream, manager) {
m_apertureRadius = stream->readFloat();
configure();
}
void serialize(Stream *stream, InstanceManager *manager) const {
ProjectiveCamera::serialize(stream, manager);
stream->writeFloat(m_apertureRadius);
}
void configure() {
ProjectiveCamera::configure();
const Vector2i &filmSize = m_film->getSize();
const Vector2i &cropSize = m_film->getCropSize();
const Point2i &cropOffset = m_film->getCropOffset();
Vector2 relSize((Float) cropSize.x / (Float) filmSize.x,
(Float) cropSize.y / (Float) filmSize.y);
Point2 relOffset((Float) cropOffset.x / (Float) filmSize.x,
(Float) cropOffset.y / (Float) filmSize.y);
/**
* These do the following (in reverse order):
*
* 1. Create transform from camera space to [-1,1]x[-1,1]x[0,1] clip
* coordinates (not taking account of the aspect ratio yet)
*
* 2+3. Translate and scale to shift the clip coordinates into the
* range from zero to one, and take the aspect ratio into account.
*
* 4+5. Translate and scale the coordinates once more to account
* for a cropping window (if there is any)
*/
m_cameraToSample =
Transform::scale(Vector(1.0f / relSize.x, 1.0f / relSize.y, 1.0f))
* Transform::translate(Vector(-relOffset.x, -relOffset.y, 0.0f))
* Transform::scale(Vector(-0.5f, -0.5f*m_aspect, 1.0f))
* Transform::translate(Vector(-1.0f, -1.0f/m_aspect, 0.0f))
* Transform::orthographic(m_nearClip, m_farClip);
m_sampleToCamera = m_cameraToSample.inverse();
/* Position differentials on the near plane */
m_dx = m_sampleToCamera(Point(m_invResolution.x, 0.0f, 0.0f))
- m_sampleToCamera(Point(0.0f));
m_dy = m_sampleToCamera(Point(0.0f, m_invResolution.y, 0.0f))
- m_sampleToCamera(Point(0.0f));
/* Clip-space transformation for OpenGL */
m_clipTransform = Transform::translate(
Vector((1-2*relOffset.x)/relSize.x - 1,
-(1-2*relOffset.y)/relSize.y + 1, 0.0f)) *
Transform::scale(Vector(1.0f / relSize.x, 1.0f / relSize.y, 1.0f));
const Transform &trafo = m_worldTransform->eval(0.0f);
m_normalization = 1.0f / (
trafo(m_sampleToCamera(Vector(1, 0, 0))).length() *
trafo(m_sampleToCamera(Vector(0, 1, 0))).length());
m_scale = Vector(
trafo(Vector(1, 0, 0)).length(),
trafo(Vector(0, 1, 0)).length(),
trafo(Vector(0, 0, 1)).length());
m_aperturePdf = 1 / (M_PI * m_apertureRadius * m_apertureRadius);
m_maxRotation = 360/M_PI * std::atan(m_apertureRadius/(m_focusDistance * m_scale.x));
}
/**
* \brief Compute the percentage of overlap between an arbitrary disk and a
* rectangle that is centered at the origin
*
* \remark To restrict the possible number of cases to a sane amount, the
* implementation here assumes that <tt>size.{x,y}/2 < radius</tt>.
*
* \param center
* Center of the disk
* \param radius
* Radius of the disk
* \param size
* Total width and height of the rectangular region
* \author Wenzel Jakob
*/
Float convolve(const Point2 &center, Float radius, const Vector2 &size) const {
/* Coordinates of the lower right rectangle corner in the disc frame */
Float invRadius = 1.0f / radius,
x = (0.5f * size.x - std::abs(center.x)) * invRadius,
y = (0.5f * size.y - std::abs(center.y)) * invRadius;
if (x < -1 || y < -1 || (x < 0 && y < 0 && x*x+y*y > 1)) {
return 0.0f; /* No coverage at all */
} else if (x >= 1 && y >= 1) {
return 1.0f; /* Full coverage */
} else if (x >= 0 && x <= 1 && y >= 0 && y <= 1 && x*x+y*y > 1) {
/* There are four intersections. Area = full circle - 2 circular segments */
return INV_PI * (x * std::sqrt(1-x*x) + y * std::sqrt(1-y*y) + std::asin(x) + std::asin(y));
} else if (x*x + y*y <= 1) {
/* There are two intersections (case 1): area = 1 circular segment + 1 triangle. */
Float yt = -std::sqrt(1-x*x), xt = -std::sqrt(1-y*y),
ct = x*xt + y*yt;
return INV_TWOPI * ((x-xt) * (y-yt) + math::safe_acos(ct) - math::safe_sqrt(1-ct*ct));
} else {
/* There are two intersections (case 2): area = 1 circular segment only */
Float h = std::min(x, y);
return INV_PI * (std::acos(-h) + h*std::sqrt(1-h*h));
}
}
Spectrum sampleRay(Ray &ray, const Point2 &pixelSample,
const Point2 &otherSample, Float timeSample) const {
Point2 diskSample = Warp::squareToUniformDiskConcentric(otherSample)
* (m_apertureRadius / m_scale.x);
ray.time = sampleTime(timeSample);
/* Compute the corresponding position on the
near plane (in local camera space) */
Point focusP = m_sampleToCamera.transformAffine(Point(
pixelSample.x * m_invResolution.x,
pixelSample.y * m_invResolution.y, 0.0f));
focusP.z = m_focusDistance/m_scale.z;
/* Compute the ray origin */
Point orig(diskSample.x+focusP.x,
diskSample.y+focusP.y, 0.0f);
/* Turn these into a normalized ray direction, and
adjust the ray interval accordingly */
const Transform &trafo = m_worldTransform->eval(ray.time);
ray.setOrigin(trafo.transformAffine(orig));
ray.setDirection(normalize(trafo(focusP - orig)));
ray.mint = m_nearClip;
ray.maxt = m_farClip;
return Spectrum(1.0f);
}
Spectrum sampleRayDifferential(RayDifferential &ray, const Point2 &pixelSample,
const Point2 &otherSample, Float timeSample) const {
Point2 diskSample = Warp::squareToUniformDiskConcentric(otherSample)
* (m_apertureRadius / m_scale.x);
ray.time = sampleTime(timeSample);
/* Compute the corresponding position on the
near plane (in local camera space) */
Point focusP = m_sampleToCamera.transformAffine(Point(
pixelSample.x * m_invResolution.x,
pixelSample.y * m_invResolution.y, 0.0f));
focusP.z = m_focusDistance/m_scale.z;
/* Compute the ray origin */
Point orig(diskSample.x+focusP.x,
diskSample.y+focusP.y, 0.0f);
/* Turn these into a normalized ray direction, and
adjust the ray interval accordingly */
const Transform &trafo = m_worldTransform->eval(ray.time);
ray.setOrigin(trafo.transformAffine(orig));
ray.setDirection(normalize(trafo(focusP - orig)));
ray.mint = m_nearClip;
ray.maxt = m_farClip;
ray.rxOrigin = trafo(orig + m_dx);
ray.ryOrigin = trafo(orig + m_dy);
ray.rxDirection = ray.ryDirection = ray.d;
ray.hasDifferentials = true;
return Spectrum(1.0f);
}
Spectrum samplePosition(PositionSamplingRecord &pRec,
const Point2 &sample, const Point2 *extra) const {
const Transform &trafo = m_worldTransform->eval(pRec.time);
Log(EError, "The telecentric lens camera is currently incompatible "
"with bidirectional rendering algorithms!");
/* This function should sample from a rectangle that has been
convolved with a circle, but using only two random numbers.
Turns out that this is actually fairly difficult to do.
Since the precision requirements are modest, we can get away
with the following *terrible* hack, which makes four random
numbers out of two and then does convolution the "trivial" way */
#if defined(SINGLE_PRECISION)
uint32_t tmp1 = union_cast<uint32_t>(sample.x + 1.0f) & 0x7FFFFF;
uint32_t tmp2 = union_cast<uint32_t>(sample.y + 1.0f) & 0x7FFFFF;
float rand1 = (tmp1 >> 11) * (1.0f / 0xFFF);
float rand2 = (tmp2 >> 11) * (1.0f / 0xFFF);
float rand3 = (tmp1 & 0x7FF) * (1.0f / 0x7FF);
float rand4 = (tmp2 & 0x7FF) * (1.0f / 0x7FF);
#else
uint64_t tmp1 = union_cast<uint64_t>(sample.x + 1.0) & 0xFFFFFFFFFFFFF;
uint64_t tmp2 = union_cast<uint64_t>(sample.y + 1.0) & 0xFFFFFFFFFFFFF;
double rand1 = (tmp1 >> 26) * (1.0 / 0x3FFFFFF);
double rand2 = (tmp2 >> 26) * (1.0 / 0x3FFFFFF);
double rand3 = (tmp1 & 0x3FFFFFF) * (1.0 / 0x3FFFFFF);
double rand4 = (tmp2 & 0x3FFFFFF) * (1.0 / 0x3FFFFFF);
#endif
Point2 aperturePos = Warp::squareToUniformDiskConcentric(Point2(rand1, rand2))
* (m_apertureRadius / m_scale.x);
Point2 samplePos(rand3, rand4);
if (extra) {
/* The caller wants to condition on a specific pixel position */
pRec.uv = *extra + samplePos;
samplePos.x = pRec.uv.x * m_invResolution.x;
samplePos.y = pRec.uv.y * m_invResolution.y;
}
Point p = m_sampleToCamera.transformAffine(Point(
aperturePos.x + samplePos.x, aperturePos.y + samplePos.y, 0.0f));
pRec.p = trafo.transformAffine(
Point(p.x, p.y, 0.0f));
pRec.n = trafo(Vector(0.0f, 0.0f, 1.0f));
pRec.pdf = m_aperturePdf; /// XXX
pRec.measure = EArea;
return Spectrum(1.0f);
}
Spectrum evalPosition(const PositionSamplingRecord &pRec) const {
Log(EError, "The telecentric lens camera is currently incompatible "
"with bidirectional rendering algorithms!");
return Spectrum((pRec.measure == EArea) ? m_aperturePdf : 0.0f);
}
Float pdfPosition(const PositionSamplingRecord &pRec) const {
Log(EError, "The telecentric lens camera is currently incompatible "
"with bidirectional rendering algorithms!");
return (pRec.measure == EArea) ? m_aperturePdf : 0.0f;
}
Spectrum sampleDirection(DirectionSamplingRecord &dRec,
PositionSamplingRecord &pRec,
const Point2 &sample, const Point2 *extra) const {
Log(EError, "The telecentric lens camera is currently incompatible "
"with bidirectional rendering algorithms!");
const Transform &trafo = m_worldTransform->eval(pRec.time);
/* Compute the corresponding position on the
near plane (in local camera space) */
Point nearP = m_sampleToCamera(Point(
sample.x, sample.y, 0.0f));
/* Turn that into a normalized ray direction */
Vector d = normalize(Vector(nearP));
dRec.d = trafo(d);
dRec.measure = ESolidAngle;
dRec.pdf = m_normalization / (d.z * d.z * d.z);
return Spectrum(1.0f);
}
inline Float pdfDirection(const DirectionSamplingRecord &dRec,
const PositionSamplingRecord &pRec) const {
Log(EError, "The telecentric lens camera is currently incompatible "
"with bidirectional rendering algorithms!");
if (dRec.measure != ESolidAngle)
return 0.0f;
return 1.0f;
}
Spectrum evalDirection(const DirectionSamplingRecord &dRec,
const PositionSamplingRecord &pRec) const {
Log(EError, "The telecentric lens camera is currently incompatible "
"with bidirectional rendering algorithms!");
if (dRec.measure != ESolidAngle)
return Spectrum(0.0f);
return Spectrum(1.0f);
}
Spectrum sampleDirect(DirectSamplingRecord &dRec, const Point2 &sample) const {
Log(EError, "The telecentric lens camera is currently incompatible "
"with bidirectional rendering algorithms!");
Transform trafo = m_worldTransform->eval(dRec.time),
invTrafo = trafo.inverse();
Float f = m_focusDistance / m_scale.z,
apertureRadius = m_apertureRadius / m_scale.x;
Point localP = invTrafo.transformAffine(dRec.ref);
Float dist = localP.z * m_scale.z;
if (dist < m_nearClip || dist > m_farClip) {
dRec.pdf = 0.0f;
return Spectrum(0.0f);
}
/* Circle of confusion */
Float radius = std::abs(localP.z - f) * apertureRadius/f;
radius += apertureRadius;
/* Sample the ray origin */
Point2 disk = Warp::squareToUniformDiskConcentric(sample);
Point diskP(disk.x*radius+localP.x, disk.y*radius+localP.y, 0.0f);
/* Compute the intersection with the focal plane */
Vector localD = localP - diskP;
Point intersection = diskP + localD * (f/localD.z);
/* Determine the associated sample coordinates */
Point uv = m_cameraToSample.transformAffine(intersection);
if (uv.x < 0 || uv.x > 1 || uv.y < 0 || uv.y > 1) {
dRec.pdf = 0.0f;
return Spectrum(0.0f);
}
dRec.uv = Point2(uv.x, uv.y);
dRec.p = trafo(diskP);
dRec.n = normalize(trafo(Vector(0, 0, 1.0f)));
dRec.d = dRec.p - dRec.ref;
dRec.dist = dRec.d.length();
dRec.d /= dRec.dist;
dRec.measure = ESolidAngle;
dRec.pdf = dist*dist / (-dot(dRec.n, dRec.d)
* M_PI * radius*radius);
return Spectrum(m_normalization);
}
Float pdfDirect(const DirectSamplingRecord &dRec) const {
return 0.0f;
}
Transform getProjectionTransform(const Point2 &apertureSample,
const Point2 &aaSample) const {
Point2 offset(
2.0f * m_invResolution.x * (aaSample.x-.5f),
2.0f * m_invResolution.y * (aaSample.y-.5f));
Float angle1 = (apertureSample.x-.5f)*m_maxRotation;
Float angle2 = (apertureSample.y-.5f)*m_maxRotation;
return m_clipTransform *
Transform::translate(Vector(offset.x, offset.y, 0.0f)) *
Transform::scale(Vector(1.0f, m_aspect, 1.0f)) *
Transform::glOrthographic(m_nearClip, m_farClip)*
Transform::scale(Vector(1.0f, 1.0f, m_scale.z)) *
Transform::translate(Vector(0.0f, 0.0f, -m_focusDistance)) *
Transform::rotate(Vector(1.0f, 0.0f, 0.0f), angle1) *
Transform::rotate(Vector(0.0f, 1.0f, 0.0f), angle2) *
Transform::translate(Vector(0.0f, 0.0f, m_focusDistance));
}
AABB getAABB() const {
AABB bounds;
bounds.expandBy(m_sampleToCamera(Point(0, 0, 0)));
bounds.expandBy(m_sampleToCamera(Point(1, 1, 0)));
return m_worldTransform->getSpatialBounds(bounds);
}
std::string toString() const {
std::ostringstream oss;
oss << "TelecentricLensCamera[" << endl
<< " apertureRadius = " << m_apertureRadius << "," << endl
<< " focusDistance = " << m_focusDistance << "," << endl
<< " nearClip = " << m_nearClip << "," << endl
<< " farClip = " << m_farClip << "," << endl
<< " worldTransform = " << indent(m_worldTransform.toString()) << "," << endl
<< " sampler = " << indent(m_sampler->toString()) << "," << endl
<< " film = " << indent(m_film->toString()) << "," << endl
<< " medium = " << indent(m_medium.toString()) << "," << endl
<< " shutterOpen = " << m_shutterOpen << "," << endl
<< " shutterOpenTime = " << m_shutterOpenTime << endl
<< "]";
return oss.str();
}
MTS_DECLARE_CLASS()
private:
Transform m_cameraToSample;
Transform m_sampleToCamera;
Transform m_clipTransform;
Float m_apertureRadius;
Float m_aperturePdf;
Float m_normalization;
Vector m_scale;
Float m_maxRotation;
Vector m_dx, m_dy;
};
MTS_IMPLEMENT_CLASS_S(TelecentricLensCamera, false, ProjectiveCamera)
MTS_EXPORT_PLUGIN(TelecentricLensCamera, "Telecentric lens camera");
MTS_NAMESPACE_END
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