bool Disk::Intersect(const Ray &r, float *tHit, float *rayEpsilon,
DifferentialGeometry *dg) const {
// Transform _Ray_ to object space
Ray ray;
(*WorldToObject)(r, &ray);
// Compute plane intersection for disk
if (fabsf(ray.d.z) < 1e-7) return false;
float thit = (height - ray.o.z) / ray.d.z;
if (thit < ray.mint || thit > ray.maxt)
return false;
// See if hit point is inside disk radii and $\phimax$
Point phit = ray(thit);
float dist2 = phit.x * phit.x + phit.y * phit.y;
if (dist2 > radius * radius || dist2 < innerRadius * innerRadius)
return false;
// Test disk $\phi$ value against $\phimax$
float phi = atan2f(phit.y, phit.x);
if (phi < 0) phi += 2. * M_PI;
if (phi > phiMax)
return false;
// Find parametric representation of disk hit
float u = phi / phiMax;
float v = 1.f - ((sqrtf(dist2)-innerRadius) /
(radius-innerRadius));
Vector dpdu(-phiMax * phit.y, phiMax * phit.x, 0.);
Vector dpdv(-phit.x / (1-v), -phit.y / (1-v), 0.);
dpdu *= phiMax * INV_TWOPI;
dpdv *= (radius - innerRadius) / radius;
Normal dndu(0,0,0), dndv(0,0,0);
// Initialize _DifferentialGeometry_ from parametric information
*dg = DifferentialGeometry((*ObjectToWorld)(phit),
(*ObjectToWorld)(dpdu),
(*ObjectToWorld)(dpdv),
(*ObjectToWorld)(dndu),
(*ObjectToWorld)(dndv),
u, v, this);
// Update _tHit_ for quadric intersection
*tHit = thit;
// Compute _rayEpsilon_ for quadric intersection
*rayEpsilon = 5e-4f * *tHit;
return true;
}
bool Cylinder::Intersect(const Ray &r, Float *tHit, SurfaceInteraction *isect,
bool testAlphaTexture) const {
Float phi;
Point3f pHit;
// Transform _Ray_ to object space
Vector3f oErr, dErr;
Ray ray = (*WorldToObject)(r, &oErr, &dErr);
// Compute quadratic cylinder coefficients
// Initialize _EFloat_ ray coordinate values
EFloat ox(ray.o.x, oErr.x), oy(ray.o.y, oErr.y), oz(ray.o.z, oErr.z);
EFloat dx(ray.d.x, dErr.x), dy(ray.d.y, dErr.y), dz(ray.d.z, dErr.z);
EFloat a = dx * dx + dy * dy;
EFloat b = 2 * (dx * ox + dy * oy);
EFloat c = ox * ox + oy * oy - EFloat(radius) * EFloat(radius);
// Solve quadratic equation for _t_ values
EFloat t0, t1;
if (!Quadratic(a, b, c, &t0, &t1)) return false;
// Check quadric shape _t0_ and _t1_ for nearest intersection
if (t0.UpperBound() > ray.tMax || t1.LowerBound() <= 0) return false;
EFloat tShapeHit = t0;
if (tShapeHit.LowerBound() <= 0) {
tShapeHit = t1;
if (tShapeHit.UpperBound() > ray.tMax) return false;
}
// Compute cylinder hit point and $\phi$
pHit = ray((Float)tShapeHit);
// Refine cylinder intersection point
Float hitRad = std::sqrt(pHit.x * pHit.x + pHit.y * pHit.y);
pHit.x *= radius / hitRad;
pHit.y *= radius / hitRad;
phi = std::atan2(pHit.y, pHit.x);
if (phi < 0) phi += 2 * Pi;
// Test cylinder intersection against clipping parameters
if (pHit.z < zMin || pHit.z > zMax || phi > phiMax) {
if (tShapeHit == t1) return false;
tShapeHit = t1;
if (t1.UpperBound() > ray.tMax) return false;
// Compute cylinder hit point and $\phi$
pHit = ray((Float)tShapeHit);
// Refine cylinder intersection point
Float hitRad = std::sqrt(pHit.x * pHit.x + pHit.y * pHit.y);
pHit.x *= radius / hitRad;
pHit.y *= radius / hitRad;
phi = std::atan2(pHit.y, pHit.x);
if (phi < 0) phi += 2 * Pi;
if (pHit.z < zMin || pHit.z > zMax || phi > phiMax) return false;
}
// Find parametric representation of cylinder hit
Float u = phi / phiMax;
Float v = (pHit.z - zMin) / (zMax - zMin);
// Compute cylinder $\dpdu$ and $\dpdv$
Vector3f dpdu(-phiMax * pHit.y, phiMax * pHit.x, 0);
Vector3f dpdv(0, 0, zMax - zMin);
// Compute cylinder $\dndu$ and $\dndv$
Vector3f d2Pduu = -phiMax * phiMax * Vector3f(pHit.x, pHit.y, 0);
Vector3f d2Pduv(0, 0, 0), d2Pdvv(0, 0, 0);
// Compute coefficients for fundamental forms
Float E = Dot(dpdu, dpdu);
Float F = Dot(dpdu, dpdv);
Float G = Dot(dpdv, dpdv);
Vector3f N = Normalize(Cross(dpdu, dpdv));
Float e = Dot(N, d2Pduu);
Float f = Dot(N, d2Pduv);
Float g = Dot(N, d2Pdvv);
// Compute $\dndu$ and $\dndv$ from fundamental form coefficients
Float invEGF2 = 1 / (E * G - F * F);
Normal3f dndu = Normal3f((f * F - e * G) * invEGF2 * dpdu +
(e * F - f * E) * invEGF2 * dpdv);
Normal3f dndv = Normal3f((g * F - f * G) * invEGF2 * dpdu +
(f * F - g * E) * invEGF2 * dpdv);
// Compute error bounds for cylinder intersection
Vector3f pError = gamma(3) * Abs(Vector3f(pHit.x, pHit.y, 0));
// Initialize _SurfaceInteraction_ from parametric information
*isect = (*ObjectToWorld)(SurfaceInteraction(pHit, pError, Point2f(u, v),
-ray.d, dpdu, dpdv, dndu, dndv,
ray.time, this));
// Update _tHit_ for quadric intersection
*tHit = (Float)tShapeHit;
return true;
}
bool Hyperboloid::Intersect(const Ray &r, Float *tHit,
SurfaceInteraction *isect) const {
Float phi, v;
Point3f pHit;
// Transform _Ray_ to object space
Vector3f oErr, dErr;
Ray ray = (*WorldToObject)(r, &oErr, &dErr);
// Compute quadratic hyperboloid coefficients
// Initialize _EFloat_ ray coordinate values
EFloat ox(ray.o.x, oErr.x), oy(ray.o.y, oErr.y), oz(ray.o.z, oErr.z);
EFloat dx(ray.d.x, dErr.x), dy(ray.d.y, dErr.y), dz(ray.d.z, dErr.z);
EFloat a = ah * dx * dx + ah * dy * dy - ch * dz * dz;
EFloat b = 2.f * (ah * dx * ox + ah * dy * oy - ch * dz * oz);
EFloat c = ah * ox * ox + ah * oy * oy - ch * oz * oz - 1.f;
// Solve quadratic equation for _t_ values
EFloat t0, t1;
if (!Quadratic(a, b, c, &t0, &t1)) return false;
// Check quadric shape _t0_ and _t1_ for nearest intersection
if (t0.UpperBound() > ray.tMax || t1.LowerBound() <= 0) return false;
EFloat tShapeHit = t0;
if (t0.LowerBound() <= 0) {
tShapeHit = t1;
if (tShapeHit.UpperBound() > ray.tMax) return false;
}
// Compute hyperboloid inverse mapping
pHit = ray((Float)tShapeHit);
v = (pHit.z - p1.z) / (p2.z - p1.z);
Point3f pr = (1 - v) * p1 + v * p2;
phi = std::atan2(pr.x * pHit.y - pHit.x * pr.y,
pHit.x * pr.x + pHit.y * pr.y);
if (phi < 0) phi += 2 * Pi;
// Test hyperboloid intersection against clipping parameters
if (pHit.z < zMin || pHit.z > zMax || phi > phiMax) {
if (tShapeHit == t1) return false;
tShapeHit = t1;
if (t1.UpperBound() > ray.tMax) return false;
// Compute hyperboloid inverse mapping
pHit = ray((Float)tShapeHit);
v = (pHit.z - p1.z) / (p2.z - p1.z);
Point3f pr = (1 - v) * p1 + v * p2;
phi = std::atan2(pr.x * pHit.y - pHit.x * pr.y,
pHit.x * pr.x + pHit.y * pr.y);
if (phi < 0) phi += 2 * Pi;
if (pHit.z < zMin || pHit.z > zMax || phi > phiMax) return false;
}
// Compute parametric representation of hyperboloid hit
Float u = phi / phiMax;
// Compute hyperboloid $\dpdu$ and $\dpdv$
Float cosPhi = std::cos(phi), sinPhi = std::sin(phi);
Vector3f dpdu(-phiMax * pHit.y, phiMax * pHit.x, 0.);
Vector3f dpdv((p2.x - p1.x) * cosPhi - (p2.y - p1.y) * sinPhi,
(p2.x - p1.x) * sinPhi + (p2.y - p1.y) * cosPhi, p2.z - p1.z);
// Compute hyperboloid $\dndu$ and $\dndv$
Vector3f d2Pduu = -phiMax * phiMax * Vector3f(pHit.x, pHit.y, 0);
Vector3f d2Pduv = phiMax * Vector3f(-dpdv.y, dpdv.x, 0.);
Vector3f d2Pdvv(0, 0, 0);
// Compute coefficients for fundamental forms
Float E = Dot(dpdu, dpdu);
Float F = Dot(dpdu, dpdv);
Float G = Dot(dpdv, dpdv);
Vector3f N = Normalize(Cross(dpdu, dpdv));
Float e = Dot(N, d2Pduu);
Float f = Dot(N, d2Pduv);
Float g = Dot(N, d2Pdvv);
// Compute $\dndu$ and $\dndv$ from fundamental form coefficients
Float invEGF2 = 1 / (E * G - F * F);
Normal3f dndu = Normal3f((f * F - e * G) * invEGF2 * dpdu +
(e * F - f * E) * invEGF2 * dpdv);
Normal3f dndv = Normal3f((g * F - f * G) * invEGF2 * dpdu +
(f * F - g * E) * invEGF2 * dpdv);
// Compute error bounds for hyperboloid intersection
// Compute error bounds for intersection computed with ray equation
EFloat px = ox + tShapeHit * dx;
EFloat py = oy + tShapeHit * dy;
EFloat pz = oz + tShapeHit * dz;
Vector3f pError = Vector3f(px.GetAbsoluteError(), py.GetAbsoluteError(),
pz.GetAbsoluteError());
// Initialize _SurfaceInteraction_ from parametric information
*isect = (*ObjectToWorld)(SurfaceInteraction(pHit, pError, Point2f(u, v),
-ray.d, dpdu, dpdv, dndu, dndv,
ray.time, this));
*tHit = (Float)tShapeHit;
return true;
}
bool Cone::Intersect(const Ray &r, float *tHit, float *rayEpsilon,
DifferentialGeometry *dg) const {
float phi;
pbrt::Point phit;
// Transform _Ray_ to object space
Ray ray;
(*WorldToObject)(r, &ray);
// Compute quadratic cone coefficients
float k = radius / height;
k = k*k;
float A = ray.d.x * ray.d.x + ray.d.y * ray.d.y -
k * ray.d.z * ray.d.z;
float B = 2 * (ray.d.x * ray.o.x + ray.d.y * ray.o.y -
k * ray.d.z * (ray.o.z-height) );
float C = ray.o.x * ray.o.x + ray.o.y * ray.o.y -
k * (ray.o.z -height) * (ray.o.z-height);
// Solve quadratic equation for _t_ values
float t0, t1;
if (!Quadratic(A, B, C, &t0, &t1))
return false;
// Compute intersection distance along ray
if (t0 > ray.maxt || t1 < ray.mint)
return false;
float thit = t0;
if (t0 < ray.mint) {
thit = t1;
if (thit > ray.maxt) return false;
}
// Compute cone inverse mapping
phit = ray(thit);
phi = atan2f(phit.y, phit.x);
if (phi < 0.) phi += 2.f*M_PI;
// Test cone intersection against clipping parameters
if (phit.z < 0 || phit.z > height || phi > phiMax) {
if (thit == t1) return false;
thit = t1;
if (t1 > ray.maxt) return false;
// Compute cone inverse mapping
phit = ray(thit);
phi = atan2f(phit.y, phit.x);
if (phi < 0.) phi += 2.f*M_PI;
if (phit.z < 0 || phit.z > height || phi > phiMax)
return false;
}
// Find parametric representation of cone hit
float u = phi / phiMax;
float v = phit.z / height;
// Compute cone $\dpdu$ and $\dpdv$
Vector dpdu(-phiMax * phit.y, phiMax * phit.x, 0);
Vector dpdv(-phit.x / (1.f - v),
-phit.y / (1.f - v), height);
// Compute cone $\dndu$ and $\dndv$
Vector d2Pduu = -phiMax * phiMax *
Vector(phit.x, phit.y, 0.);
Vector d2Pduv = phiMax / (1.f - v) *
Vector(phit.y, -phit.x, 0.);
Vector d2Pdvv(0, 0, 0);
// Compute coefficients for fundamental forms
float E = Dot(dpdu, dpdu);
float F = Dot(dpdu, dpdv);
float G = Dot(dpdv, dpdv);
Vector N = Normalize(Cross(dpdu, dpdv));
float e = Dot(N, d2Pduu);
float f = Dot(N, d2Pduv);
float g = Dot(N, d2Pdvv);
// Compute $\dndu$ and $\dndv$ from fundamental form coefficients
float invEGF2 = 1.f / (E*G - F*F);
Normal dndu = Normal((f*F - e*G) * invEGF2 * dpdu +
(e*F - f*E) * invEGF2 * dpdv);
Normal dndv = Normal((g*F - f*G) * invEGF2 * dpdu +
(f*F - g*E) * invEGF2 * dpdv);
// Initialize _DifferentialGeometry_ from parametric information
const Transform &o2w = *ObjectToWorld;
*dg = DifferentialGeometry(o2w(phit), o2w(dpdu), o2w(dpdv),
o2w(dndu), o2w(dndv), u, v, this);
// Update _tHit_ for quadric intersection
*tHit = thit;
// Compute _rayEpsilon_ for quadric intersection
*rayEpsilon = 5e-4f * *tHit;
return true;
}
bool Hyperboloid::Intersect(const Ray &r, float *tHit,
float *rayEpsilon, DifferentialGeometry *dg) const {
float phi, v;
Point phit;
// Transform _Ray_ to object space
Ray ray;
(*WorldToObject)(r, &ray);
// Compute quadratic hyperboloid coefficients
float A = a*ray.d.x*ray.d.x +
a*ray.d.y*ray.d.y -
c*ray.d.z*ray.d.z;
float B = 2.f * (a*ray.d.x*ray.o.x +
a*ray.d.y*ray.o.y -
c*ray.d.z*ray.o.z);
float C = a*ray.o.x*ray.o.x +
a*ray.o.y*ray.o.y -
c*ray.o.z*ray.o.z - 1;
// Solve quadratic equation for _t_ values
float t0, t1;
if (!Quadratic(A, B, C, &t0, &t1))
return false;
// Compute intersection distance along ray
if (t0 > ray.maxt || t1 < ray.mint)
return false;
float thit = t0;
if (t0 < ray.mint) {
thit = t1;
if (thit > ray.maxt) return false;
}
// Compute hyperboloid inverse mapping
phit = ray(thit);
v = (phit.z - p1.z)/(p2.z - p1.z);
Point pr = (1.f-v) * p1 + v * p2;
phi = atan2f(pr.x*phit.y - phit.x*pr.y,
phit.x*pr.x + phit.y*pr.y);
if (phi < 0)
phi += 2*M_PI;
// Test hyperboloid intersection against clipping parameters
if (phit.z < zmin || phit.z > zmax || phi > phiMax) {
if (thit == t1) return false;
thit = t1;
if (t1 > ray.maxt) return false;
// Compute hyperboloid inverse mapping
phit = ray(thit);
v = (phit.z - p1.z)/(p2.z - p1.z);
Point pr = (1.f-v) * p1 + v * p2;
phi = atan2f(pr.x*phit.y - phit.x*pr.y,
phit.x*pr.x + phit.y*pr.y);
if (phi < 0)
phi += 2*M_PI;
if (phit.z < zmin || phit.z > zmax || phi > phiMax)
return false;
}
// Compute parametric representation of hyperboloid hit
float u = phi / phiMax;
// Compute hyperboloid $\dpdu$ and $\dpdv$
float cosphi = cosf(phi), sinphi = sinf(phi);
Vector dpdu(-phiMax * phit.y, phiMax * phit.x, 0.);
Vector dpdv((p2.x-p1.x) * cosphi - (p2.y-p1.y) * sinphi,
(p2.x-p1.x) * sinphi + (p2.y-p1.y) * cosphi,
p2.z-p1.z);
// Compute hyperboloid $\dndu$ and $\dndv$
Vector d2Pduu = -phiMax * phiMax *
Vector(phit.x, phit.y, 0);
Vector d2Pduv = phiMax *
Vector(-dpdv.y, dpdv.x, 0.);
Vector d2Pdvv(0, 0, 0);
// Compute coefficients for fundamental forms
float E = Dot(dpdu, dpdu);
float F = Dot(dpdu, dpdv);
float G = Dot(dpdv, dpdv);
Vector N = Normalize(Cross(dpdu, dpdv));
float e = Dot(N, d2Pduu);
float f = Dot(N, d2Pduv);
float g = Dot(N, d2Pdvv);
// Compute $\dndu$ and $\dndv$ from fundamental form coefficients
float invEGF2 = 1.f / (E*G - F*F);
Normal dndu = Normal((f*F - e*G) * invEGF2 * dpdu +
(e*F - f*E) * invEGF2 * dpdv);
Normal dndv = Normal((g*F - f*G) * invEGF2 * dpdu +
(f*F - g*E) * invEGF2 * dpdv);
// Initialize _DifferentialGeometry_ from parametric information
const Transform &o2w = *ObjectToWorld;
*dg = DifferentialGeometry(o2w(phit), o2w(dpdu), o2w(dpdv),
o2w(dndu), o2w(dndv), u, v, this);
// Update _tHit_ for quadric intersection
*tHit = thit;
// Compute _rayEpsilon_ for quadric intersection
*rayEpsilon = 5e-4f * *tHit;
return true;
}
bool Rectangle::Intersect(const Ray &r, float *tHit, float *rayEpsilon,
DifferentialGeometry *dg) const {
// Transform _Ray_ to object space
Ray ray;
(*WorldToObject)(r, &ray);
// Compute plane intersection for disk
// Checks if the plane is parallel to the ray or not
// We can get the direction of the ray
// If the Z component of the direction of the ray is zero
// then, the ray is parallel to the plane and in such case
// there is no intersection point between the ray and the plane.
if (fabsf(ray.d.z) < 1e-7)
return false;
// Now, the direction of the ray is not parallel to the plane
// We have to check if the intersection happens or not
// We have to compute the parametric t where the ray intersects the plane
// We want to find t such that the z-component of the ray intersects the plane
// The ray "line" equation is l = l0 + (l1 - l0) * t
// l1 - l0 will give us the distance between the two points on the plane
// Then t is the ratio and in such case it should be between 0 and 1
// Considering that the rectangle completely lies in the z plane
/// distance = l1 - l0
/// thit = (l - l0) / distance
// But since we assume that the plane is located at height
// Then, the point l is at height on the plane
/// l = height
float thit = (height - ray.o.z) / ray.d.z;
// Then we check if the thit is between the ratio of 0 and 1 that is mapped
// between ray.mint and ray.maxt, if not retrun false
if (thit < ray.mint || thit > ray.maxt)
return false;
// Then we see if the point lies inside the disk or not
// Substitute the thit in the ray equation to get hit point on the ray
Point phit = ray(thit);
// We have to make sure that the interesction lies inside the plane
if (!(phit.x < x/2 && phit.x > -x/2 && phit.y < y/2 && phit.y > -y/2))
return false;
// Assuming that the plane is formed from the following 4 points
// P0, P1, P2, P3
//
// p0 *---------------* p1
// | |
// | |
// | |
// | O |
// | |
// | |
// | |
// p2 *---------------* p3 -> X
//
// P0 @ (-x/2, y/2)
// P1 @ (x/2, y/2)
// P2 @ (-x/2, -y/2)
// P3 @ (x/2, -y/2)
Point P0(-x/2, y/2, height), P1(x/2, y/2, height);
Point P2(-x/2, -y/2, height), P3(x/2, -y/2, height);
/// Now, we have to find the parametric form of the plane in terms of (u,v)
/// Plane equation can be formed by at least 3 points P0, P1, P2
/// P0 -> P1 (vector 1)
/// P0 -> p2 (vector 2)
/// An arbitrary point on the plane p is found in the following parametric form
/// P = P0 + (P1 - P0) u + (P2 - P0) v
/// Now we need to express two explicit equations of u and v
/// So, we have to construct the system of equation that solves for u and v
///
/// Since we have found the intersection point between the plane and the line
/// we have to use it to formalize the system of equations that will be used
/// to find the parametric form of the plane
/// Plane equation is : P = P0 + (P1 - P0) u + (P2 - P0) v
/// Ray equation is : l = l0 + (l1 - l0) * thit
/// But l = P, then
/// l0 + (l1 - l0) * thit = P0 + (P1 - P0) * u + (P2 - P0) * v
/// l0 - P0 = (l0 - l1) * thit + (P1 - P0) * u + (P2 - P0) * v
/// MAPPING : l0 = ray.o
/// [l0.x - P0.x] = [l0.x - l1.x P1.x - P0.x P2.x - P0.x] [t]
/// [l0.y - P0.y] = [l0.y - l1.y P1.y - P0.y P2.y - P0.y] [u]
/// [l0.z - P0.z] = [l0.z - l1.z P1.z - P0.z P2.z - P0.z] [v]
///
/// Then, we should find the inverse of the matrix in order to
/// solve for u,v and t for check
// System AX = B
float a11 = ray.o.x - 0;
float a12 = P1.x - P0.x;
float a13 = P2.x - P0.x;
float a21 = ray.o.y - 0;
float a22 = P1.y - P0.y;
float a23 = P2.y - P0.y;
float a31 = ray.o.y - height;
float a32 = P1.z - P0.z;
float a33 = P2.z - P0.z;
float b1 = -7;
float b2 = -2;
float b3 = 14;
float x1 = 0;
float x2 = 0;
float x3 = 0;
Imath::M33f A(a11,a12,a13,a21,a22,a23,a31,a32,a33), AInverted;
Imath::V3f X(x1, x2, x3);
Imath::V3f B(b1,b2, b3);
// This operation has been checked and working for getting
// the correct inverse of the matrix A
AInverted = A.invert(false);
x1 = AInverted[0][0] * B[0] +
AInverted[0][1] * B[1] +
AInverted[0][2] * B[2];
x2 = AInverted[1][0] * B[0] +
AInverted[1][1] * B[1] +
AInverted[1][2] * B[2];
x3 = AInverted[2][0] * B[0] +
AInverted[2][1] * B[1] +
AInverted[2][2] * B[2];
/// Then we have u = something, and v = something
///
/// Then we come for the derivatives, so we have to find the derivatives
/// from the parametric forms defined above for the plane equations
/// dpdu = (P1 - P0)
/// dpdv = (P2 - P0)
///
/// For the normal we have the always fixed direction in y
/// So the derivative for the normal is zero
/// dndu = (0, 0, 0) dndv = (0, 0, 0)
///
/// Then we can construct the DifferentilGeometry and go ahead
// Find parametric representation of disk hit
float u = x2;
float v = x3;
Vector dpdu(P1.x - P0.x, P1.y - P0.y, P1.z - P0.z);
Vector dpdv(P2.x - P0.x, P2.y - P0.y, P2.z - P0.z);
Normal dndu(0,0,0), dndv(0,0,0);
// Initialize _DifferentialGeometry_ from parametric information
const Transform &o2w = *ObjectToWorld;
*dg = DifferentialGeometry(o2w(phit), o2w(dpdu), o2w(dpdv),
o2w(dndu), o2w(dndv), u, v, this);
// Update _tHit_ for quadric intersection
*tHit = thit;
// Compute _rayEpsilon_ for quadric intersection
*rayEpsilon = 5e-4f * *tHit;
return true;
}
bool Sphere::Intersect( Ray const &ray, float *tHit, float *epsilon, DifferentialGeometry *geom ) const {
Transform tf = Tform();
Ray r = ray * Inverse( tf );
float t;
if( !Intersect( ray, &t ) )
return false;
// compute differential geometry
Vec4 p = ray.Point( t );
float x = p.X();
float y = p.Y();
float z = p.Z();
if( x == 0.0f && z == 0.0f ) {
// can't have both atan2 arguments be zero
z = kEpsilon * m_radius;
}
float theta = atan2( p.X(), p.Z() );
if( theta < 0.0f ) {
// remap theta to [0, 2pi] to match sphere's definition
theta += k2Pi;
}
float phi = Acos( Clamp( z / m_radius, -1.0f, 1.0f ) );
// parameterize sphere hit
float u = theta * kInv2Pi;
float v = phi * kInvPi;
float sTheta, cTheta;
float sPhi, cPhi;
SinCos( theta, &sTheta, &cTheta );
SinCos( phi, &sPhi, &cPhi );
Vec4 dpdu( k2Pi * z, 0.0f, -k2Pi * x, 0.0f );
Vec4 dpdv( kPi * y * sTheta, -kPi * m_radius * sPhi, kPi * y * cTheta, 0.0f );
Vec4 d2pdu2( -k2Pi * k2Pi * x, 0.0f, -k2Pi * k2Pi * z, 0.0f );
Vec4 d2pduv( k2Pi * kPi * y * cTheta, 0.0f, -k2Pi * kPi * y * sTheta, 0.0f );
Vec4 d2pdv2( -kPi * kPi * x, -kPi * kPi * y, -kPi * kPi * z, 0.0f );
// change in normal is computed using Weingarten equations
Scalar E = Dot( dpdu, dpdu );
Scalar F = Dot( dpdu, dpdv );
Scalar G = Dot( dpdv, dpdv );
Vec4 N = Normalize( Cross( dpdu, dpdv ) );
Scalar e = Dot( N, d2pdu2 );
Scalar f = Dot( N, d2pduv );
Scalar g = Dot( N, d2pdv2 );
Scalar h = 1.0f / ( E * G - F * F );
Vec4 dndu = ( f * F - e * G ) * h * dpdu + ( e * F - f * E ) * h * dpdv;
Vec4 dndv = ( g * F - f * G ) * h * dpdu + ( f * F - g * E ) * h * dpdv;
*tHit = t;
*epsilon = 5e-4f * t;
// return world space differential geometry
*geom = DifferentialGeometry( Handle(), p * tf, dpdu * tf, dpdv * tf, Normal( dndu ) * tf, Normal( dndv ) * tf, u, v );
return true;
}
NormalVector ShapeParabolicRectangle::GetNormal( double u, double v ) const
{
Vector3D dpdu( widthX.getValue(), ( (-0.5 + u) * widthX.getValue() * widthX.getValue() )/(2 * focusLength.getValue()), 0 );
Vector3D dpdv( 0.0, (( -0.5 + v) * widthZ.getValue() * widthZ.getValue() ) /( 2 * focusLength.getValue() ), widthZ.getValue() );
return Normalize( NormalVector( CrossProduct( dpdu, dpdv ) ) );
}
bool ShapeParabolicRectangle::Intersect(const Ray& objectRay, double *tHit, DifferentialGeometry *dg) const
{
double focus = focusLength.getValue();
double wX = widthX.getValue();
double wZ = widthZ.getValue();
// Compute quadratic coefficients
double A = objectRay.direction().x * objectRay.direction().x + objectRay.direction().z * objectRay.direction().z;
double B = 2.0 * ( objectRay.direction().x * objectRay.origin.x + objectRay.direction().z * objectRay.origin.z - 2 * focus * objectRay.direction().y );
double C = objectRay.origin.x * objectRay.origin.x + objectRay.origin.z * objectRay.origin.z - 4 * focus * objectRay.origin.y;
// Solve quadratic equation for _t_ values
double t0, t1;
if( !gf::Quadratic( A, B, C, &t0, &t1 ) ) return false;
// Compute intersection distance along ray
if( t0 > objectRay.maxt || t1 < objectRay.mint ) return false;
double thit = ( t0 > objectRay.mint )? t0 : t1 ;
if( thit > objectRay.maxt ) return false;
//Evaluate Tolerance
double tol = 0.00001;
//Compute possible hit position
Point3D hitPoint = objectRay( thit );
// Test intersection against clipping parameters
if( (thit - objectRay.mint) < tol || hitPoint.x < ( - wX / 2 ) || hitPoint.x > ( wX / 2 ) ||
hitPoint.z < ( - wZ / 2 ) || hitPoint.z > ( wZ / 2 ) )
{
if ( thit == t1 ) return false;
if ( t1 > objectRay.maxt ) return false;
thit = t1;
hitPoint = objectRay( thit );
if( (thit - objectRay.mint) < tol || hitPoint.x < ( - wX / 2 ) || hitPoint.x > ( wX / 2 ) ||
hitPoint.z < ( - wZ / 2 ) || hitPoint.z > ( wZ / 2 ) ) return false;
}
// Now check if the function is being called from IntersectP,
// in which case the pointers tHit and dg are 0
if( ( tHit == 0 ) && ( dg == 0 ) ) return true;
else if( ( tHit == 0 ) || ( dg == 0 ) ) gf::SevereError( "Function ParabolicCyl::Intersect(...) called with null pointers" );
///////////////////////////////////////////////////////////////////////////////////////
// Compute possible parabola hit position
// Find parametric representation of paraboloid hit
double u = ( hitPoint.x / wX ) + 0.5;
double v = ( hitPoint.z / wZ ) + 0.5;
Vector3D dpdu( wX, ( (-0.5 + u) * wX * wX ) / ( 2 * focus ), 0 );
Vector3D dpdv( 0.0, (( -0.5 + v) * wZ * wZ ) /( 2 * focus ), wZ );
// Compute parabaloid \dndu and \dndv
Vector3D d2Pduu( 0.0, (wX * wX ) /( 2 * focus ), 0.0 );
Vector3D d2Pduv( 0.0, 0.0, 0.0 );
Vector3D d2Pdvv( 0.0, (wZ * wZ ) /( 2 * focus ), 0.0 );
// Compute coefficients for fundamental forms
double E = DotProduct(dpdu, dpdu);
double F = DotProduct(dpdu, dpdv);
double G = DotProduct(dpdv, dpdv);
NormalVector N = Normalize( NormalVector( CrossProduct( dpdu, dpdv ) ) );
double e = DotProduct(N, d2Pduu);
double f = DotProduct(N, d2Pduv);
double g = DotProduct(N, d2Pdvv);
// Compute \dndu and \dndv from fundamental form coefficients
double invEGF2 = 1.0 / (E*G - F*F);
Vector3D dndu = (f*F - e*G) * invEGF2 * dpdu +
(e*F - f*E) * invEGF2 * dpdv;
Vector3D dndv = (g*F - f*G) * invEGF2 * dpdu +
(f*F - g*E) * invEGF2 * dpdv;
// Initialize _DifferentialGeometry_ from parametric information
*dg = DifferentialGeometry(hitPoint,
dpdu,
dpdv,
dndu,
dndv,
u, v, this);
dg->shapeFrontSide = ( DotProduct( N, objectRay.direction() ) > 0 ) ? false : true;
///////////////////////////////////////////////////////////////////////////////////////
// Update _tHit_ for quadric intersection
*tHit = thit;
return true;
}
