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-/*
- * Copyright 2011-2020 Blender Foundation
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- * http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#pragma once
-
-#include "kernel_light_common.h"
-
-CCL_NAMESPACE_BEGIN
-
-/* Background Light */
-
-#ifdef __BACKGROUND_MIS__
-
-ccl_device float3 background_map_sample(KernelGlobals kg,
- float randu,
- float randv,
- ccl_private float *pdf)
-{
- /* for the following, the CDF values are actually a pair of floats, with the
- * function value as X and the actual CDF as Y. The last entry's function
- * value is the CDF total. */
- int res_x = kernel_data.background.map_res_x;
- int res_y = kernel_data.background.map_res_y;
- int cdf_width = res_x + 1;
-
- /* This is basically std::lower_bound as used by PBRT. */
- int first = 0;
- int count = res_y;
-
- while (count > 0) {
- int step = count >> 1;
- int middle = first + step;
-
- if (kernel_tex_fetch(__light_background_marginal_cdf, middle).y < randv) {
- first = middle + 1;
- count -= step + 1;
- }
- else
- count = step;
- }
-
- int index_v = max(0, first - 1);
- kernel_assert(index_v >= 0 && index_v < res_y);
-
- float2 cdf_v = kernel_tex_fetch(__light_background_marginal_cdf, index_v);
- float2 cdf_next_v = kernel_tex_fetch(__light_background_marginal_cdf, index_v + 1);
- float2 cdf_last_v = kernel_tex_fetch(__light_background_marginal_cdf, res_y);
-
- /* importance-sampled V direction */
- float dv = inverse_lerp(cdf_v.y, cdf_next_v.y, randv);
- float v = (index_v + dv) / res_y;
-
- /* This is basically std::lower_bound as used by PBRT. */
- first = 0;
- count = res_x;
- while (count > 0) {
- int step = count >> 1;
- int middle = first + step;
-
- if (kernel_tex_fetch(__light_background_conditional_cdf, index_v * cdf_width + middle).y <
- randu) {
- first = middle + 1;
- count -= step + 1;
- }
- else
- count = step;
- }
-
- int index_u = max(0, first - 1);
- kernel_assert(index_u >= 0 && index_u < res_x);
-
- float2 cdf_u = kernel_tex_fetch(__light_background_conditional_cdf,
- index_v * cdf_width + index_u);
- float2 cdf_next_u = kernel_tex_fetch(__light_background_conditional_cdf,
- index_v * cdf_width + index_u + 1);
- float2 cdf_last_u = kernel_tex_fetch(__light_background_conditional_cdf,
- index_v * cdf_width + res_x);
-
- /* importance-sampled U direction */
- float du = inverse_lerp(cdf_u.y, cdf_next_u.y, randu);
- float u = (index_u + du) / res_x;
-
- /* compute pdf */
- float sin_theta = sinf(M_PI_F * v);
- float denom = (M_2PI_F * M_PI_F * sin_theta) * cdf_last_u.x * cdf_last_v.x;
-
- if (sin_theta == 0.0f || denom == 0.0f)
- *pdf = 0.0f;
- else
- *pdf = (cdf_u.x * cdf_v.x) / denom;
-
- /* compute direction */
- return equirectangular_to_direction(u, v);
-}
-
-/* TODO(sergey): Same as above, after the release we should consider using
- * 'noinline' for all devices.
- */
-ccl_device float background_map_pdf(KernelGlobals kg, float3 direction)
-{
- float2 uv = direction_to_equirectangular(direction);
- int res_x = kernel_data.background.map_res_x;
- int res_y = kernel_data.background.map_res_y;
- int cdf_width = res_x + 1;
-
- float sin_theta = sinf(uv.y * M_PI_F);
-
- if (sin_theta == 0.0f)
- return 0.0f;
-
- int index_u = clamp(float_to_int(uv.x * res_x), 0, res_x - 1);
- int index_v = clamp(float_to_int(uv.y * res_y), 0, res_y - 1);
-
- /* pdfs in V direction */
- float2 cdf_last_u = kernel_tex_fetch(__light_background_conditional_cdf,
- index_v * cdf_width + res_x);
- float2 cdf_last_v = kernel_tex_fetch(__light_background_marginal_cdf, res_y);
-
- float denom = (M_2PI_F * M_PI_F * sin_theta) * cdf_last_u.x * cdf_last_v.x;
-
- if (denom == 0.0f)
- return 0.0f;
-
- /* pdfs in U direction */
- float2 cdf_u = kernel_tex_fetch(__light_background_conditional_cdf,
- index_v * cdf_width + index_u);
- float2 cdf_v = kernel_tex_fetch(__light_background_marginal_cdf, index_v);
-
- return (cdf_u.x * cdf_v.x) / denom;
-}
-
-ccl_device_inline bool background_portal_data_fetch_and_check_side(
- KernelGlobals kg, float3 P, int index, ccl_private float3 *lightpos, ccl_private float3 *dir)
-{
- int portal = kernel_data.background.portal_offset + index;
- const ccl_global KernelLight *klight = &kernel_tex_fetch(__lights, portal);
-
- *lightpos = make_float3(klight->co[0], klight->co[1], klight->co[2]);
- *dir = make_float3(klight->area.dir[0], klight->area.dir[1], klight->area.dir[2]);
-
- /* Check whether portal is on the right side. */
- if (dot(*dir, P - *lightpos) > 1e-4f)
- return true;
-
- return false;
-}
-
-ccl_device_inline float background_portal_pdf(
- KernelGlobals kg, float3 P, float3 direction, int ignore_portal, ccl_private bool *is_possible)
-{
- float portal_pdf = 0.0f;
-
- int num_possible = 0;
- for (int p = 0; p < kernel_data.background.num_portals; p++) {
- if (p == ignore_portal)
- continue;
-
- float3 lightpos, dir;
- if (!background_portal_data_fetch_and_check_side(kg, P, p, &lightpos, &dir))
- continue;
-
- /* There's a portal that could be sampled from this position. */
- if (is_possible) {
- *is_possible = true;
- }
- num_possible++;
-
- int portal = kernel_data.background.portal_offset + p;
- const ccl_global KernelLight *klight = &kernel_tex_fetch(__lights, portal);
- float3 axisu = make_float3(
- klight->area.axisu[0], klight->area.axisu[1], klight->area.axisu[2]);
- float3 axisv = make_float3(
- klight->area.axisv[0], klight->area.axisv[1], klight->area.axisv[2]);
- bool is_round = (klight->area.invarea < 0.0f);
-
- if (!ray_quad_intersect(P,
- direction,
- 1e-4f,
- FLT_MAX,
- lightpos,
- axisu,
- axisv,
- dir,
- NULL,
- NULL,
- NULL,
- NULL,
- is_round))
- continue;
-
- if (is_round) {
- float t;
- float3 D = normalize_len(lightpos - P, &t);
- portal_pdf += fabsf(klight->area.invarea) * lamp_light_pdf(kg, dir, -D, t);
- }
- else {
- portal_pdf += rect_light_sample(P, &lightpos, axisu, axisv, 0.0f, 0.0f, false);
- }
- }
-
- if (ignore_portal >= 0) {
- /* We have skipped a portal that could be sampled as well. */
- num_possible++;
- }
-
- return (num_possible > 0) ? portal_pdf / num_possible : 0.0f;
-}
-
-ccl_device int background_num_possible_portals(KernelGlobals kg, float3 P)
-{
- int num_possible_portals = 0;
- for (int p = 0; p < kernel_data.background.num_portals; p++) {
- float3 lightpos, dir;
- if (background_portal_data_fetch_and_check_side(kg, P, p, &lightpos, &dir))
- num_possible_portals++;
- }
- return num_possible_portals;
-}
-
-ccl_device float3 background_portal_sample(KernelGlobals kg,
- float3 P,
- float randu,
- float randv,
- int num_possible,
- ccl_private int *sampled_portal,
- ccl_private float *pdf)
-{
- /* Pick a portal, then re-normalize randv. */
- randv *= num_possible;
- int portal = (int)randv;
- randv -= portal;
-
- /* TODO(sergey): Some smarter way of finding portal to sample
- * is welcome.
- */
- for (int p = 0; p < kernel_data.background.num_portals; p++) {
- /* Search for the sampled portal. */
- float3 lightpos, dir;
- if (!background_portal_data_fetch_and_check_side(kg, P, p, &lightpos, &dir))
- continue;
-
- if (portal == 0) {
- /* p is the portal to be sampled. */
- int portal = kernel_data.background.portal_offset + p;
- const ccl_global KernelLight *klight = &kernel_tex_fetch(__lights, portal);
- float3 axisu = make_float3(
- klight->area.axisu[0], klight->area.axisu[1], klight->area.axisu[2]);
- float3 axisv = make_float3(
- klight->area.axisv[0], klight->area.axisv[1], klight->area.axisv[2]);
- bool is_round = (klight->area.invarea < 0.0f);
-
- float3 D;
- if (is_round) {
- lightpos += ellipse_sample(axisu * 0.5f, axisv * 0.5f, randu, randv);
- float t;
- D = normalize_len(lightpos - P, &t);
- *pdf = fabsf(klight->area.invarea) * lamp_light_pdf(kg, dir, -D, t);
- }
- else {
- *pdf = rect_light_sample(P, &lightpos, axisu, axisv, randu, randv, true);
- D = normalize(lightpos - P);
- }
-
- *pdf /= num_possible;
- *sampled_portal = p;
- return D;
- }
-
- portal--;
- }
-
- return zero_float3();
-}
-
-ccl_device_inline float3 background_sun_sample(KernelGlobals kg,
- float randu,
- float randv,
- ccl_private float *pdf)
-{
- float3 D;
- const float3 N = float4_to_float3(kernel_data.background.sun);
- const float angle = kernel_data.background.sun.w;
- sample_uniform_cone(N, angle, randu, randv, &D, pdf);
- return D;
-}
-
-ccl_device_inline float background_sun_pdf(KernelGlobals kg, float3 D)
-{
- const float3 N = float4_to_float3(kernel_data.background.sun);
- const float angle = kernel_data.background.sun.w;
- return pdf_uniform_cone(N, D, angle);
-}
-
-ccl_device_inline float3 background_light_sample(
- KernelGlobals kg, float3 P, float randu, float randv, ccl_private float *pdf)
-{
- float portal_method_pdf = kernel_data.background.portal_weight;
- float sun_method_pdf = kernel_data.background.sun_weight;
- float map_method_pdf = kernel_data.background.map_weight;
-
- int num_portals = 0;
- if (portal_method_pdf > 0.0f) {
- /* Check if there are portals in the scene which we can sample. */
- num_portals = background_num_possible_portals(kg, P);
- if (num_portals == 0) {
- portal_method_pdf = 0.0f;
- }
- }
-
- float pdf_fac = (portal_method_pdf + sun_method_pdf + map_method_pdf);
- if (pdf_fac == 0.0f) {
- /* Use uniform as a fallback if we can't use any strategy. */
- *pdf = 1.0f / M_4PI_F;
- return sample_uniform_sphere(randu, randv);
- }
-
- pdf_fac = 1.0f / pdf_fac;
- portal_method_pdf *= pdf_fac;
- sun_method_pdf *= pdf_fac;
- map_method_pdf *= pdf_fac;
-
- /* We have 100% in total and split it between the three categories.
- * Therefore, we pick portals if randu is between 0 and portal_method_pdf,
- * sun if randu is between portal_method_pdf and (portal_method_pdf + sun_method_pdf)
- * and map if randu is between (portal_method_pdf + sun_method_pdf) and 1. */
- float sun_method_cdf = portal_method_pdf + sun_method_pdf;
-
- int method = 0;
- float3 D;
- if (randu < portal_method_pdf) {
- method = 0;
- /* Rescale randu. */
- if (portal_method_pdf != 1.0f) {
- randu /= portal_method_pdf;
- }
-
- /* Sample a portal. */
- int portal;
- D = background_portal_sample(kg, P, randu, randv, num_portals, &portal, pdf);
- if (num_portals > 1) {
- /* Ignore the chosen portal, its pdf is already included. */
- *pdf += background_portal_pdf(kg, P, D, portal, NULL);
- }
-
- /* Skip MIS if this is the only method. */
- if (portal_method_pdf == 1.0f) {
- return D;
- }
- *pdf *= portal_method_pdf;
- }
- else if (randu < sun_method_cdf) {
- method = 1;
- /* Rescale randu. */
- if (sun_method_pdf != 1.0f) {
- randu = (randu - portal_method_pdf) / sun_method_pdf;
- }
-
- D = background_sun_sample(kg, randu, randv, pdf);
-
- /* Skip MIS if this is the only method. */
- if (sun_method_pdf == 1.0f) {
- return D;
- }
- *pdf *= sun_method_pdf;
- }
- else {
- method = 2;
- /* Rescale randu. */
- if (map_method_pdf != 1.0f) {
- randu = (randu - sun_method_cdf) / map_method_pdf;
- }
-
- D = background_map_sample(kg, randu, randv, pdf);
-
- /* Skip MIS if this is the only method. */
- if (map_method_pdf == 1.0f) {
- return D;
- }
- *pdf *= map_method_pdf;
- }
-
- /* MIS weighting. */
- if (method != 0 && portal_method_pdf != 0.0f) {
- *pdf += portal_method_pdf * background_portal_pdf(kg, P, D, -1, NULL);
- }
- if (method != 1 && sun_method_pdf != 0.0f) {
- *pdf += sun_method_pdf * background_sun_pdf(kg, D);
- }
- if (method != 2 && map_method_pdf != 0.0f) {
- *pdf += map_method_pdf * background_map_pdf(kg, D);
- }
- return D;
-}
-
-ccl_device float background_light_pdf(KernelGlobals kg, float3 P, float3 direction)
-{
- float portal_method_pdf = kernel_data.background.portal_weight;
- float sun_method_pdf = kernel_data.background.sun_weight;
- float map_method_pdf = kernel_data.background.map_weight;
-
- float portal_pdf = 0.0f;
- /* Portals are a special case here since we need to compute their pdf in order
- * to find out if we can sample them. */
- if (portal_method_pdf > 0.0f) {
- /* Evaluate PDF of sampling this direction by portal sampling. */
- bool is_possible = false;
- portal_pdf = background_portal_pdf(kg, P, direction, -1, &is_possible);
- if (!is_possible) {
- /* Portal sampling is not possible here because all portals point to the wrong side.
- * If other methods can be used instead, do so, otherwise uniform sampling is used as a
- * fallback. */
- portal_method_pdf = 0.0f;
- }
- }
-
- float pdf_fac = (portal_method_pdf + sun_method_pdf + map_method_pdf);
- if (pdf_fac == 0.0f) {
- /* Use uniform as a fallback if we can't use any strategy. */
- return kernel_data.integrator.pdf_lights / M_4PI_F;
- }
-
- pdf_fac = 1.0f / pdf_fac;
- portal_method_pdf *= pdf_fac;
- sun_method_pdf *= pdf_fac;
- map_method_pdf *= pdf_fac;
-
- float pdf = portal_pdf * portal_method_pdf;
- if (sun_method_pdf != 0.0f) {
- pdf += background_sun_pdf(kg, direction) * sun_method_pdf;
- }
- if (map_method_pdf != 0.0f) {
- pdf += background_map_pdf(kg, direction) * map_method_pdf;
- }
-
- return pdf * kernel_data.integrator.pdf_lights;
-}
-
-#endif
-
-CCL_NAMESPACE_END
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