The Density proportional to expression must be strictly positive.
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For Expression a single ray is released in the specified direction. Enter coordinates for the Ray direction vector L0 (dimensionless) based on space dimension.
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For Spherical a number of rays are released at each point, sampled from a spherical distribution in wave vector space. Enter the Number of rays in wave vector space Nw (dimensionless). The default is 50.
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For Hemispherical a number of rays are released at each point, sampled from a hemispherical distribution in wave vector space. Enter the Number of rays in wave vector space Nw (dimensionless). The default is 50. Then enter coordinates for the Hemisphere axis r based on space dimension.
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For Conical a number of rays are released at each point, sampled from a conical distribution in wave vector space. Enter the Number of rays in wave vector space Nw (dimensionless). The default is 50. Then enter coordinates for the Cone axis r based on space dimension. Then enter the Cone angle α (SI unit: rad). The default is π/3 radians.
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The Lambertian option is only available in 3D. A number of rays are released at each point, sampled from a hemisphere in wave vector space with probability density based on the cosine law. Enter the Number of rays in wave vector space Nw (dimensionless). The default is 50. Then enter coordinates for the Hemisphere axis r based on space dimension.
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For Uniform density rays are released with polar angles from 0 to the specified cone angle. The rays are distributed in wave vector space so that each ray subtends approximately the same solid angle.
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For Specify polar and azimuthal distributions specify the Number of polar angles Nθ (dimensionless) and the Number of azimuthal angles Nϕ (dimensionless). Rays are released at uniformly distributed polar angles from 0 to the specified cone angle. A single axial ray (θ = 0) is also released. For each value of the polar angle, rays are released at uniformly distributed azimuthal angles from 0 to 2π. Unlike other options for specifying the conical distribution, it is not necessary to directly specify the Number of rays in wave vector space Nw (dimensionless), which is instead derived from the relation Nw = Nθ × Nϕ + 1.
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For Hexapolar specify the Number of polar angles Nθ (dimensionless). In this distribution, for each release point, one ray will be released along the cone axis. Six rays are released at an angle α/Nθ from the cone axis, then 12 rays at an angle of 2α/Nθ, and so on. The total number of ray directions in the distribution is Nw = 3Nθ(Nθ + 1) + 1.
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For Marginal rays only the rays are all released at an angle α with respect to the cone axis. The rays are released at uniformly distributed azimuthal angles from 0 to 2π.
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For Marginal and axial rays only the rays are all released at an angle α with respect to the cone axis, except for one ray which is released along the cone axis. The marginal rays are released at uniformly distributed azimuthal angles from 0 to 2π.
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For With respect to fluid the initial wave vector is computed with respect to a coordinate system that moves at the background velocity, so the initial ray direction might not be parallel to the vector entered in the Ray direction vector text field if the medium is moving.
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For With respect to coordinate system the initial ray direction is parallel to the vector entered in the Ray direction vector text field as long as a ray could reasonably propagate in that direction. For example, rays cannot be released in certain directions if the background fluid is moving with a supersonic velocity.
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For an idealized plane wave the radii of curvature would be infinite. However, because the algorithm used to compute intensity requires finite values, when Plane wave is selected the initial radii of curvature are instead given an initial value that is 108 times greater than the characteristic size of the geometry.
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For an Ellipsoid, enter the Initial radius of curvature, 1 r1,0 (SI unit: m) and the Initial radius of curvature, 2 r2,0 (SI unit: m). Also enter the Initial principal curvature direction, 1 e1,0 (dimensionless).
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For spherical and cylindrical waves the Initial radius of curvature must be nonzero. To release a ray such that the initial wavefront radius of curvature is zero, instead select a different option such as Conical from the Ray direction vector list.
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It is also available when the ray power is solved for, and then any choice of Ray direction vector displays this section.
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