diff options
Diffstat (limited to 'intern/sky')
| -rw-r--r-- | intern/sky/source/sky_nishita.cpp | 103 |
1 files changed, 52 insertions, 51 deletions
diff --git a/intern/sky/source/sky_nishita.cpp b/intern/sky/source/sky_nishita.cpp index eae95dc73fe..f36bfcc3d7b 100644 --- a/intern/sky/source/sky_nishita.cpp +++ b/intern/sky/source/sky_nishita.cpp @@ -18,20 +18,21 @@ #include "sky_model.h" /* Constants */ -static const float rayleigh_scale = 8000.0f; // Rayleigh scale height (m) -static const float mie_scale = 1200.0f; // Mie scale height (m) -static const float mie_coeff = 2e-5f; // Mie scattering coefficient -static const float mie_G = 0.76f; // aerosols anisotropy -static const float sqr_G = mie_G * mie_G; // squared aerosols anisotropy -static const float earth_radius = 6360000.0f; // radius of Earth (m) -static const float atmosphere_radius = 6420000.0f; // radius of atmosphere (m) -static const int steps = 32; // segments per primary ray -static const int steps_light = 16; // segments per sun connection ray -static const int num_wavelengths = 21; // number of wavelengths -static const int max_luminous_efficacy = 683; // maximum luminous efficacy -static const float step_lambda = (num_wavelengths - 1) * - 1e-9f; // step between each sampled wavelength -/* irradiance at top of atmosphere */ +static const float rayleigh_scale = 8e3f; // Rayleigh scale height (m) +static const float mie_scale = 1.2e3f; // Mie scale height (m) +static const float mie_coeff = 2e-5f; // Mie scattering coefficient (m^-1) +static const float mie_G = 0.76f; // aerosols anisotropy +static const float sqr_G = mie_G * mie_G; // squared aerosols anisotropy +static const float earth_radius = 6360e3f; // radius of Earth (m) +static const float atmosphere_radius = 6420e3f; // radius of atmosphere (m) +static const int steps = 32; // segments of primary ray +static const int steps_light = 16; // segments of sun connection ray +static const int num_wavelengths = 21; // number of wavelengths +static const int min_wavelength = 380; // lowest sampled wavelength (nm) +static const int max_wavelength = 780; // highest sampled wavelength (nm) +// step between each sampled wavelength (nm) +static const float step_lambda = (max_wavelength - min_wavelength) / (num_wavelengths - 1); +/* Sun irradiance on top of the atmosphere (W*m^-2*nm^-1) */ static const float irradiance[] = { 1.45756829855592995315f, 1.56596305559738380175f, 1.65148449067670455293f, 1.71496242737209314555f, 1.75797983805020541226f, 1.78256407885924539336f, @@ -40,7 +41,7 @@ static const float irradiance[] = { 1.61993437242451854274f, 1.57083597368892080581f, 1.51932335059305478886f, 1.46628494965214395407f, 1.41245852740172450623f, 1.35844961970384092709f, 1.30474913844739281998f, 1.25174963272610817455f, 1.19975998755420620867f}; -/* Rayleigh scattering coefficient */ +/* Rayleigh scattering coefficient (m^-1) */ static const float rayleigh_coeff[] = { 0.00005424820087636473f, 0.00004418549866505454f, 0.00003635151910165377f, 0.00003017929012024763f, 0.00002526320226989157f, 0.00002130859310621843f, @@ -49,7 +50,7 @@ static const float rayleigh_coeff[] = { 0.00000765513700977967f, 0.00000674217203751443f, 0.00000596134125832052f, 0.00000529034598065810f, 0.00000471115687557433f, 0.00000420910481110487f, 0.00000377218381260133f, 0.00000339051255477280f, 0.00000305591531679811f}; -/* Ozone absorption coefficient */ +/* Ozone absorption coefficient (m^-1) */ static const float ozone_coeff[] = { 0.00000000325126849861f, 0.00000000585395365047f, 0.00000001977191155085f, 0.00000007309568762914f, 0.00000020084561514287f, 0.00000040383958096161f, @@ -94,11 +95,10 @@ static float3 spec_to_xyz(float *spectrum) xyz.y += cmf_xyz[i][1] * spectrum[i]; xyz.z += cmf_xyz[i][2] * spectrum[i]; } - return xyz * step_lambda * max_luminous_efficacy; + return xyz * step_lambda; } /* Atmosphere volume models */ - static float density_rayleigh(float height) { return expf(-height / rayleigh_scale); @@ -135,11 +135,13 @@ static bool surface_intersection(float3 pos, float3 dir) { if (dir.z >= 0) return false; - float t = dot(dir, -pos) / len_squared(dir); - float D = pos.x * pos.x - 2.0f * (-pos.x) * dir.x * t + dir.x * t * dir.x * t + pos.y * pos.y - - 2.0f * (-pos.y) * dir.y * t + (dir.y * t) * (dir.y * t) + pos.z * pos.z - - 2.0f * (-pos.z) * dir.z * t + dir.z * t * dir.z * t; - return (D <= sqr(earth_radius)); + float b = -2.0f * dot(dir, -pos); + float c = len_squared(pos) - sqr(earth_radius); + float t = b * b - 4.0f * c; + if (t >= 0.0f) + return true; + else + return false; } static float3 atmosphere_intersection(float3 pos, float3 dir) @@ -152,41 +154,40 @@ static float3 atmosphere_intersection(float3 pos, float3 dir) static float3 ray_optical_depth(float3 ray_origin, float3 ray_dir) { - /* This code computes the optical depth along a ray through the atmosphere. */ + /* this code computes the optical depth along a ray through the atmosphere */ float3 ray_end = atmosphere_intersection(ray_origin, ray_dir); float ray_length = distance(ray_origin, ray_end); - /* To compute the optical depth, we step along the ray in segments and - * accumulate the optical depth along each segment. */ + /* to compute the optical depth, we step along the ray in segments and + * accumulate the optical depth along each segment */ float segment_length = ray_length / steps_light; float3 segment = segment_length * ray_dir; - /* Instead of tracking the transmission spectrum across all wavelengths directly, + /* instead of tracking the transmission spectrum across all wavelengths directly, * we use the fact that the density always has the same spectrum for each type of * scattering, so we split the density into a constant spectrum and a factor and - * only track the factors. */ + * only track the factors */ float3 optical_depth = make_float3(0.0f, 0.0f, 0.0f); - /* The density of each segment is evaluated at its middle. */ + /* the density of each segment is evaluated at its middle */ float3 P = ray_origin + 0.5f * segment; for (int i = 0; i < steps_light; i++) { - /* Compute height above sea level. */ + /* height above sea level */ float height = len(P) - earth_radius; - /* Accumulate optical depth of this segment (density is assumed to be constant along it). */ + /* accumulate optical depth of this segment (density is assumed to be constant along it) */ float3 density = make_float3( density_rayleigh(height), density_mie(height), density_ozone(height)); optical_depth += density; - /* Advance along ray. */ + /* advance along ray */ P += segment; } return optical_depth * segment_length; } -/* Single Scattering implementation */ static void single_scattering(float3 ray_dir, float3 sun_dir, float3 ray_origin, @@ -195,45 +196,45 @@ static void single_scattering(float3 ray_dir, float ozone_density, float *r_spectrum) { - /* This code computes single-inscattering along a ray through the atmosphere. */ + /* this code computes single-inscattering along a ray through the atmosphere */ float3 ray_end = atmosphere_intersection(ray_origin, ray_dir); float ray_length = distance(ray_origin, ray_end); - /* To compute the inscattering, we step along the ray in segments and accumulate - * the inscattering as well as the optical depth along each segment. */ + /* to compute the inscattering, we step along the ray in segments and accumulate + * the inscattering as well as the optical depth along each segment */ float segment_length = ray_length / steps; float3 segment = segment_length * ray_dir; - /* Instead of tracking the transmission spectrum across all wavelengths directly, + /* instead of tracking the transmission spectrum across all wavelengths directly, * we use the fact that the density always has the same spectrum for each type of * scattering, so we split the density into a constant spectrum and a factor and - * only track the factors. */ + * only track the factors */ float3 optical_depth = make_float3(0.0f, 0.0f, 0.0f); - /* Zero out light accumulation. */ + /* zero out light accumulation */ for (int wl = 0; wl < num_wavelengths; wl++) { r_spectrum[wl] = 0.0f; } - /* Compute phase function for scattering and the density scale factor. */ + /* phase function for scattering and the density scale factor */ float mu = dot(ray_dir, sun_dir); float3 phase_function = make_float3(phase_rayleigh(mu), phase_mie(mu), 0.0f); float3 density_scale = make_float3(air_density, dust_density, ozone_density); - /* The density and in-scattering of each segment is evaluated at its middle. */ + /* the density and in-scattering of each segment is evaluated at its middle */ float3 P = ray_origin + 0.5f * segment; for (int i = 0; i < steps; i++) { - /* Compute height above sea level. */ + /* height above sea level */ float height = len(P) - earth_radius; - /* Evaluate and accumulate optical depth along the ray. */ + /* evaluate and accumulate optical depth along the ray */ float3 density = density_scale * make_float3(density_rayleigh(height), density_mie(height), density_ozone(height)); optical_depth += segment_length * density; - /* If the earth isn't in the way, evaluate inscattering from the sun. */ + /* if the Earth isn't in the way, evaluate inscattering from the sun */ if (!surface_intersection(P, sun_dir)) { float3 light_optical_depth = density_scale * ray_optical_depth(P, sun_dir); float3 total_optical_depth = optical_depth + light_optical_depth; @@ -247,7 +248,7 @@ static void single_scattering(float3 ray_dir, float3 scattering_density = density * make_float3(rayleigh_coeff[wl], mie_coeff, 0.0f); - /* The total inscattered radiance from one segment is: + /* the total inscattered radiance from one segment is: * Tr(A<->B) * Tr(B<->C) * sigma_s * phase * L * segment_length * * These terms are: @@ -258,19 +259,18 @@ static void single_scattering(float3 ray_dir, * length of the segment * * The code here is just that, with a bit of additional optimization to not store full - * spectra for the optical depth. + * spectra for the optical depth */ r_spectrum[wl] += attenuation * reduce_add(phase_function * scattering_density) * irradiance[wl] * segment_length; } } - /* Advance along ray. */ + /* advance along ray */ P += segment; } } -/* calculate texture array */ void SKY_nishita_skymodel_precompute_texture(float *pixels, int stride, int start_y, @@ -305,6 +305,7 @@ void SKY_nishita_skymodel_precompute_texture(float *pixels, single_scattering(dir, sun_dir, cam_pos, air_density, dust_density, ozone_density, spectrum); float3 xyz = spec_to_xyz(spectrum); + /* store pixels */ int pos_x = x * stride; pixel_row[pos_x] = xyz.x; pixel_row[pos_x + 1] = xyz.y; @@ -318,7 +319,7 @@ void SKY_nishita_skymodel_precompute_texture(float *pixels, } } -/* Sun disc */ +/*********** Sun ***********/ static void sun_radiation(float3 cam_dir, float altitude, float air_density, @@ -329,9 +330,9 @@ static void sun_radiation(float3 cam_dir, float3 cam_pos = make_float3(0, 0, earth_radius + altitude); float3 optical_depth = ray_optical_depth(cam_pos, cam_dir); - /* Compute final spectrum. */ + /* compute final spectrum */ for (int i = 0; i < num_wavelengths; i++) { - /* Combine spectra and the optical depth into transmittance. */ + /* combine spectra and the optical depth into transmittance */ float transmittance = rayleigh_coeff[i] * optical_depth.x * air_density + 1.11f * mie_coeff * optical_depth.y * dust_density; r_spectrum[i] = irradiance[i] * expf(-transmittance) / solid_angle; |