~ubuntu-branches/ubuntu/utopic/blender/utopic-proposed

/*

 * Copyright 2011-2013 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

 */

#ifdef __OSL__

#include "osl_shader.h"

#endif

#include "kernel_differential.h"

#include "kernel_montecarlo.h"

#include "kernel_projection.h"

#include "kernel_object.h"

#include "kernel_triangle.h"

#include "kernel_curve.h"

#include "kernel_primitive.h"

#include "kernel_projection.h"

#include "kernel_random.h"

#include "kernel_bvh.h"

#include "kernel_accumulate.h"

#include "kernel_camera.h"

#include "kernel_shader.h"

#include "kernel_light.h"

#include "kernel_emission.h"

#include "kernel_passes.h"

#include "kernel_path_state.h"

#ifdef __SUBSURFACE__

#include "kernel_subsurface.h"

#endif

CCL_NAMESPACE_BEGIN

__device_inline bool shadow_blocked(KernelGlobals *kg, PathState *state, Ray *ray, float3 *shadow)

{

	*shadow = make_float3(1.0f, 1.0f, 1.0f);

	if(ray->t == 0.0f)

		return false;

	Intersection isect;

#ifdef __HAIR__

	bool result = scene_intersect(kg, ray, PATH_RAY_SHADOW_OPAQUE, &isect, NULL, 0.0f, 0.0f);

#else

	bool result = scene_intersect(kg, ray, PATH_RAY_SHADOW_OPAQUE, &isect);

#endif

#ifdef __TRANSPARENT_SHADOWS__

	if(result && kernel_data.integrator.transparent_shadows) {

		/* transparent shadows work in such a way to try to minimize overhead

		 * in cases where we don't need them. after a regular shadow ray is

		 * cast we check if the hit primitive was potentially transparent, and

		 * only in that case start marching. this gives on extra ray cast for

		 * the cases were we do want transparency.

		 *

		 * also note that for this to work correct, multi close sampling must

		 * be used, since we don't pass a random number to shader_eval_surface */

		if(shader_transparent_shadow(kg, &isect)) {

			float3 throughput = make_float3(1.0f, 1.0f, 1.0f);

			float3 Pend = ray->P + ray->D*ray->t;

			int bounce = state->transparent_bounce;

			for(;;) {

				if(bounce >= kernel_data.integrator.transparent_max_bounce) {

					return true;

				}

				else if(bounce >= kernel_data.integrator.transparent_min_bounce) {

					/* todo: get random number somewhere for probabilistic terminate */

#if 0

					float probability = average(throughput);

					float terminate = 0.0f;

					if(terminate >= probability)

						return true;

					throughput /= probability;

#endif

				}

#ifdef __HAIR__

				if(!scene_intersect(kg, ray, PATH_RAY_SHADOW_TRANSPARENT, &isect, NULL, 0.0f, 0.0f)) {

#else

				if(!scene_intersect(kg, ray, PATH_RAY_SHADOW_TRANSPARENT, &isect)) {

#endif

					*shadow *= throughput;

					return false;

				}

				if(!shader_transparent_shadow(kg, &isect))

					return true;

				ShaderData sd;

				shader_setup_from_ray(kg, &sd, &isect, ray, state->bounce+1);

				shader_eval_surface(kg, &sd, 0.0f, PATH_RAY_SHADOW, SHADER_CONTEXT_SHADOW);

				throughput *= shader_bsdf_transparency(kg, &sd);

				ray->P = ray_offset(sd.P, -sd.Ng);

				if(ray->t != FLT_MAX)

					ray->D = normalize_len(Pend - ray->P, &ray->t);

				bounce++;

			}

		}

	}

#endif

	return result;

}

#if defined(__BRANCHED_PATH__) || defined(__SUBSURFACE__)

__device void kernel_path_indirect(KernelGlobals *kg, RNG *rng, int sample, Ray ray, __global float *buffer,

	float3 throughput, int num_samples, int num_total_samples,

	float min_ray_pdf, float ray_pdf, PathState state, int rng_offset, PathRadiance *L)

{

#ifdef __LAMP_MIS__

	float ray_t = 0.0f;

#endif

	/* path iteration */

	for(;; rng_offset += PRNG_BOUNCE_NUM) {

		/* intersect scene */

		Intersection isect;

		uint visibility = path_state_ray_visibility(kg, &state);

#ifdef __HAIR__

		bool hit = scene_intersect(kg, &ray, visibility, &isect, NULL, 0.0f, 0.0f);

#else

		bool hit = scene_intersect(kg, &ray, visibility, &isect);

#endif

#ifdef __LAMP_MIS__

		if(kernel_data.integrator.use_lamp_mis && !(state.flag & PATH_RAY_CAMERA)) {

			/* ray starting from previous non-transparent bounce */

			Ray light_ray;

			light_ray.P = ray.P - ray_t*ray.D;

			ray_t += isect.t;

			light_ray.D = ray.D;

			light_ray.t = ray_t;

			light_ray.time = ray.time;

			light_ray.dD = ray.dD;

			light_ray.dP = ray.dP;

			/* intersect with lamp */

			float light_t = path_rng_1D(kg, rng, sample, num_total_samples, rng_offset + PRNG_LIGHT);

			float3 emission;

			if(indirect_lamp_emission(kg, &light_ray, state.flag, ray_pdf, light_t, &emission, state.bounce))

				path_radiance_accum_emission(L, throughput, emission, state.bounce);

		}

#endif

		if(!hit) {

#ifdef __BACKGROUND__

			/* sample background shader */

			float3 L_background = indirect_background(kg, &ray, state.flag, ray_pdf, state.bounce);

			path_radiance_accum_background(L, throughput, L_background, state.bounce);

#endif

			break;

		}

		/* setup shading */

		ShaderData sd;

		shader_setup_from_ray(kg, &sd, &isect, &ray, state.bounce);

		float rbsdf = path_rng_1D(kg, rng, sample, num_total_samples, rng_offset + PRNG_BSDF);

		shader_eval_surface(kg, &sd, rbsdf, state.flag, SHADER_CONTEXT_INDIRECT);

#ifdef __BRANCHED_PATH__

		shader_merge_closures(kg, &sd);

#endif

		/* blurring of bsdf after bounces, for rays that have a small likelihood

		 * of following this particular path (diffuse, rough glossy) */

		if(kernel_data.integrator.filter_glossy != FLT_MAX) {

			float blur_pdf = kernel_data.integrator.filter_glossy*min_ray_pdf;

			if(blur_pdf < 1.0f) {

				float blur_roughness = sqrtf(1.0f - blur_pdf)*0.5f;

				shader_bsdf_blur(kg, &sd, blur_roughness);

			}

		}

#ifdef __EMISSION__

		/* emission */

		if(sd.flag & SD_EMISSION) {

			float3 emission = indirect_primitive_emission(kg, &sd, isect.t, state.flag, ray_pdf);

			path_radiance_accum_emission(L, throughput, emission, state.bounce);

		}

#endif

		/* path termination. this is a strange place to put the termination, it's

		 * mainly due to the mixed in MIS that we use. gives too many unneeded

		 * shader evaluations, only need emission if we are going to terminate */

		float probability = path_state_terminate_probability(kg, &state, throughput*num_samples);

		if(probability == 0.0f) {

			break;

		}

		else if(probability != 1.0f) {

			float terminate = path_rng_1D(kg, rng, sample, num_total_samples, rng_offset + PRNG_TERMINATE);

			if(terminate >= probability)

				break;

			throughput /= probability;

		}

#ifdef __AO__

		/* ambient occlusion */

		if(kernel_data.integrator.use_ambient_occlusion || (sd.flag & SD_AO)) {

			float bsdf_u, bsdf_v;

			path_rng_2D(kg, rng, sample, num_total_samples, rng_offset + PRNG_BSDF_U, &bsdf_u, &bsdf_v);

			float ao_factor = kernel_data.background.ao_factor;

			float3 ao_N;

			float3 ao_bsdf = shader_bsdf_ao(kg, &sd, ao_factor, &ao_N);

			float3 ao_D;

			float ao_pdf;

			float3 ao_alpha = make_float3(0.0f, 0.0f, 0.0f);

			sample_cos_hemisphere(ao_N, bsdf_u, bsdf_v, &ao_D, &ao_pdf);

			if(dot(sd.Ng, ao_D) > 0.0f && ao_pdf != 0.0f) {

				Ray light_ray;

				float3 ao_shadow;

				light_ray.P = ray_offset(sd.P, sd.Ng);

				light_ray.D = ao_D;

				light_ray.t = kernel_data.background.ao_distance;

#ifdef __OBJECT_MOTION__

				light_ray.time = sd.time;

#endif

				light_ray.dP = sd.dP;

				light_ray.dD = differential3_zero();

				if(!shadow_blocked(kg, &state, &light_ray, &ao_shadow))

					path_radiance_accum_ao(L, throughput, ao_alpha, ao_bsdf, ao_shadow, state.bounce);

			}

		}

#endif

#ifdef __SUBSURFACE__

		/* bssrdf scatter to a different location on the same object, replacing

		 * the closures with a diffuse BSDF */

		if(sd.flag & SD_BSSRDF) {

			float bssrdf_probability;

			ShaderClosure *sc = subsurface_scatter_pick_closure(kg, &sd, &bssrdf_probability);

			/* modify throughput for picking bssrdf or bsdf */

			throughput *= bssrdf_probability;

			/* do bssrdf scatter step if we picked a bssrdf closure */

			if(sc) {

				uint lcg_state = lcg_init(*rng + rng_offset + sample*0x68bc21eb);

				if(old_subsurface_scatter_use(&sd)) {

					old_subsurface_scatter_step(kg, &sd, state.flag, sc, &lcg_state, false);

				}

				else {

					float bssrdf_u, bssrdf_v;

					path_rng_2D(kg, rng, sample, num_total_samples, rng_offset + PRNG_BSDF_U, &bssrdf_u, &bssrdf_v);

					subsurface_scatter_step(kg, &sd, state.flag, sc, &lcg_state, bssrdf_u, bssrdf_v, false);

				}

				state.flag |= PATH_RAY_BSSRDF_ANCESTOR;

			}

		}

#endif

#ifdef __EMISSION__

		if(kernel_data.integrator.use_direct_light) {

			/* sample illumination from lights to find path contribution */

			if(sd.flag & SD_BSDF_HAS_EVAL) {

				float light_t = path_rng_1D(kg, rng, sample, num_total_samples, rng_offset + PRNG_LIGHT);

#ifdef __MULTI_CLOSURE__

				float light_o = 0.0f;

#else

				float light_o = path_rng_1D(kg, rng, sample, num_total_samples, rng_offset + PRNG_LIGHT_F);

#endif

				float light_u, light_v;

				path_rng_2D(kg, rng, sample, num_total_samples, rng_offset + PRNG_LIGHT_U, &light_u, &light_v);

				Ray light_ray;

				BsdfEval L_light;

				bool is_lamp;

#ifdef __OBJECT_MOTION__

				light_ray.time = sd.time;

#endif

				/* sample random light */

				if(direct_emission(kg, &sd, -1, light_t, light_o, light_u, light_v, &light_ray, &L_light, &is_lamp, state.bounce)) {

					/* trace shadow ray */

					float3 shadow;

					if(!shadow_blocked(kg, &state, &light_ray, &shadow)) {

						/* accumulate */

						path_radiance_accum_light(L, throughput, &L_light, shadow, 1.0f, state.bounce, is_lamp);

					}

				}

			}

		}

#endif

		/* no BSDF? we can stop here */

		if(!(sd.flag & SD_BSDF))

			break;

		/* sample BSDF */

		float bsdf_pdf;

		BsdfEval bsdf_eval;

		float3 bsdf_omega_in;

		differential3 bsdf_domega_in;

		float bsdf_u, bsdf_v;

		path_rng_2D(kg, rng, sample, num_total_samples, rng_offset + PRNG_BSDF_U, &bsdf_u, &bsdf_v);

		int label;

		label = shader_bsdf_sample(kg, &sd, bsdf_u, bsdf_v, &bsdf_eval,

			&bsdf_omega_in, &bsdf_domega_in, &bsdf_pdf);

		if(bsdf_pdf == 0.0f || bsdf_eval_is_zero(&bsdf_eval))

			break;

		/* modify throughput */

		path_radiance_bsdf_bounce(L, &throughput, &bsdf_eval, bsdf_pdf, state.bounce, label);

		/* set labels */

		if(!(label & LABEL_TRANSPARENT)) {

			ray_pdf = bsdf_pdf;

#ifdef __LAMP_MIS__

			ray_t = 0.0f;

#endif

			min_ray_pdf = fminf(bsdf_pdf, min_ray_pdf);

		}

		/* update path state */

		path_state_next(kg, &state, label);

		/* setup ray */

		ray.P = ray_offset(sd.P, (label & LABEL_TRANSMIT)? -sd.Ng: sd.Ng);

		ray.D = bsdf_omega_in;

		ray.t = FLT_MAX;

#ifdef __RAY_DIFFERENTIALS__

		ray.dP = sd.dP;

		ray.dD = bsdf_domega_in;

#endif

	}

}

#endif

#ifdef __SUBSURFACE__

__device_inline bool kernel_path_integrate_lighting(KernelGlobals *kg, RNG *rng,

	int sample, int num_samples,

	ShaderData *sd, float3 *throughput,

	float *min_ray_pdf, float *ray_pdf, PathState *state,

	int rng_offset, PathRadiance *L, Ray *ray, float *ray_t)

{

#ifdef __EMISSION__

	if(kernel_data.integrator.use_direct_light) {

		/* sample illumination from lights to find path contribution */

		if(sd->flag & SD_BSDF_HAS_EVAL) {

			float light_t = path_rng_1D(kg, rng, sample, num_samples, rng_offset + PRNG_LIGHT);

#ifdef __MULTI_CLOSURE__

			float light_o = 0.0f;

#else

			float light_o = path_rng_1D(kg, rng, sample, num_samples, rng_offset + PRNG_LIGHT_F);

#endif

			float light_u, light_v;

			path_rng_2D(kg, rng, sample, num_samples, rng_offset + PRNG_LIGHT_U, &light_u, &light_v);

			Ray light_ray;

			BsdfEval L_light;

			bool is_lamp;

#ifdef __OBJECT_MOTION__

			light_ray.time = sd->time;

#endif

			if(direct_emission(kg, sd, -1, light_t, light_o, light_u, light_v, &light_ray, &L_light, &is_lamp, state->bounce)) {

				/* trace shadow ray */

				float3 shadow;

				if(!shadow_blocked(kg, state, &light_ray, &shadow)) {

					/* accumulate */

					path_radiance_accum_light(L, *throughput, &L_light, shadow, 1.0f, state->bounce, is_lamp);

				}

			}

		}

	}

#endif

	/* no BSDF? we can stop here */

	if(!(sd->flag & SD_BSDF))

		return false;

	/* sample BSDF */

	float bsdf_pdf;

	BsdfEval bsdf_eval;

	float3 bsdf_omega_in;

	differential3 bsdf_domega_in;

	float bsdf_u, bsdf_v;

	path_rng_2D(kg, rng, sample, num_samples, rng_offset + PRNG_BSDF_U, &bsdf_u, &bsdf_v);

	int label;

	label = shader_bsdf_sample(kg, sd, bsdf_u, bsdf_v, &bsdf_eval,

		&bsdf_omega_in, &bsdf_domega_in, &bsdf_pdf);

	if(bsdf_pdf == 0.0f || bsdf_eval_is_zero(&bsdf_eval))

		return false;

	/* modify throughput */

	path_radiance_bsdf_bounce(L, throughput, &bsdf_eval, bsdf_pdf, state->bounce, label);

	/* set labels */

	if(!(label & LABEL_TRANSPARENT)) {

		*ray_pdf = bsdf_pdf;

#ifdef __LAMP_MIS__

		*ray_t = 0.0f;

#endif

		*min_ray_pdf = fminf(bsdf_pdf, *min_ray_pdf);

	}

	/* update path state */

	path_state_next(kg, state, label);

	/* setup ray */

	ray->P = ray_offset(sd->P, (label & LABEL_TRANSMIT)? -sd->Ng: sd->Ng);

	ray->D = bsdf_omega_in;

	if(state->bounce == 0)

		ray->t -= sd->ray_length; /* clipping works through transparent */

	else

		ray->t = FLT_MAX;

#ifdef __RAY_DIFFERENTIALS__

	ray->dP = sd->dP;

	ray->dD = bsdf_domega_in;

#endif

	return true;

}

#endif

__device float4 kernel_path_integrate(KernelGlobals *kg, RNG *rng, int sample, Ray ray, __global float *buffer)

{

	/* initialize */

	PathRadiance L;

	float3 throughput = make_float3(1.0f, 1.0f, 1.0f);

	float L_transparent = 0.0f;

	path_radiance_init(&L, kernel_data.film.use_light_pass);

	float min_ray_pdf = FLT_MAX;

	float ray_pdf = 0.0f;

#ifdef __LAMP_MIS__

	float ray_t = 0.0f;

#endif

	PathState state;

	int rng_offset = PRNG_BASE_NUM;

#ifdef __CMJ__

	int num_samples = kernel_data.integrator.aa_samples;

#else

	int num_samples = 0;

#endif

	path_state_init(&state);

	/* path iteration */

	for(;; rng_offset += PRNG_BOUNCE_NUM) {

		/* intersect scene */

		Intersection isect;

		uint visibility = path_state_ray_visibility(kg, &state);

#ifdef __HAIR__

		float difl = 0.0f, extmax = 0.0f;

		uint lcg_state = 0;

		if(kernel_data.bvh.have_curves) {

			if((kernel_data.cam.resolution == 1) && (state.flag & PATH_RAY_CAMERA)) {	

				float3 pixdiff = ray.dD.dx + ray.dD.dy;

				/*pixdiff = pixdiff - dot(pixdiff, ray.D)*ray.D;*/

				difl = kernel_data.curve.minimum_width * len(pixdiff) * 0.5f;

			}

			extmax = kernel_data.curve.maximum_width;

			lcg_state = lcg_init(*rng + rng_offset + sample*0x51633e2d);

		}

		bool hit = scene_intersect(kg, &ray, visibility, &isect, &lcg_state, difl, extmax);

#else

		bool hit = scene_intersect(kg, &ray, visibility, &isect);

#endif

#ifdef __LAMP_MIS__

		if(kernel_data.integrator.use_lamp_mis && !(state.flag & PATH_RAY_CAMERA)) {

			/* ray starting from previous non-transparent bounce */

			Ray light_ray;

			light_ray.P = ray.P - ray_t*ray.D;

			ray_t += isect.t;

			light_ray.D = ray.D;

			light_ray.t = ray_t;

			light_ray.time = ray.time;

			light_ray.dD = ray.dD;

			light_ray.dP = ray.dP;

			/* intersect with lamp */

			float light_t = path_rng_1D(kg, rng, sample, num_samples, rng_offset + PRNG_LIGHT);

			float3 emission;

			if(indirect_lamp_emission(kg, &light_ray, state.flag, ray_pdf, light_t, &emission, state.bounce))

				path_radiance_accum_emission(&L, throughput, emission, state.bounce);

		}

#endif

		if(!hit) {

			/* eval background shader if nothing hit */

			if(kernel_data.background.transparent && (state.flag & PATH_RAY_CAMERA)) {

				L_transparent += average(throughput);

#ifdef __PASSES__

				if(!(kernel_data.film.pass_flag & PASS_BACKGROUND))

#endif

					break;

			}

#ifdef __BACKGROUND__

			/* sample background shader */

			float3 L_background = indirect_background(kg, &ray, state.flag, ray_pdf, state.bounce);

			path_radiance_accum_background(&L, throughput, L_background, state.bounce);

#endif

			break;

		}

		/* setup shading */

		ShaderData sd;

		shader_setup_from_ray(kg, &sd, &isect, &ray, state.bounce);

		float rbsdf = path_rng_1D(kg, rng, sample, num_samples, rng_offset + PRNG_BSDF);

		shader_eval_surface(kg, &sd, rbsdf, state.flag, SHADER_CONTEXT_MAIN);

		/* holdout */

#ifdef __HOLDOUT__

		if((sd.flag & (SD_HOLDOUT|SD_HOLDOUT_MASK)) && (state.flag & PATH_RAY_CAMERA)) {

			if(kernel_data.background.transparent) {

				float3 holdout_weight;

				if(sd.flag & SD_HOLDOUT_MASK)

					holdout_weight = make_float3(1.0f, 1.0f, 1.0f);

				else

					holdout_weight = shader_holdout_eval(kg, &sd);

				/* any throughput is ok, should all be identical here */

				L_transparent += average(holdout_weight*throughput);

			}

			if(sd.flag & SD_HOLDOUT_MASK)

				break;

		}

#endif

		/* holdout mask objects do not write data passes */

		kernel_write_data_passes(kg, buffer, &L, &sd, sample, state.flag, throughput);

		/* blurring of bsdf after bounces, for rays that have a small likelihood

		 * of following this particular path (diffuse, rough glossy) */

		if(kernel_data.integrator.filter_glossy != FLT_MAX) {

			float blur_pdf = kernel_data.integrator.filter_glossy*min_ray_pdf;

			if(blur_pdf < 1.0f) {

				float blur_roughness = sqrtf(1.0f - blur_pdf)*0.5f;

				shader_bsdf_blur(kg, &sd, blur_roughness);

			}

		}

#ifdef __EMISSION__

		/* emission */

		if(sd.flag & SD_EMISSION) {

			/* todo: is isect.t wrong here for transparent surfaces? */

			float3 emission = indirect_primitive_emission(kg, &sd, isect.t, state.flag, ray_pdf);

			path_radiance_accum_emission(&L, throughput, emission, state.bounce);

		}

#endif

		/* path termination. this is a strange place to put the termination, it's

		 * mainly due to the mixed in MIS that we use. gives too many unneeded

		 * shader evaluations, only need emission if we are going to terminate */

		float probability = path_state_terminate_probability(kg, &state, throughput);

		if(probability == 0.0f) {

			break;

		}

		else if(probability != 1.0f) {

			float terminate = path_rng_1D(kg, rng, sample, num_samples, rng_offset + PRNG_TERMINATE);

			if(terminate >= probability)

				break;

			throughput /= probability;

		}

#ifdef __AO__

		/* ambient occlusion */

		if(kernel_data.integrator.use_ambient_occlusion || (sd.flag & SD_AO)) {

			/* todo: solve correlation */

			float bsdf_u, bsdf_v;

			path_rng_2D(kg, rng, sample, num_samples, rng_offset + PRNG_BSDF_U, &bsdf_u, &bsdf_v);

			float ao_factor = kernel_data.background.ao_factor;

			float3 ao_N;

			float3 ao_bsdf = shader_bsdf_ao(kg, &sd, ao_factor, &ao_N);

			float3 ao_D;

			float ao_pdf;

			float3 ao_alpha = shader_bsdf_alpha(kg, &sd);

			sample_cos_hemisphere(ao_N, bsdf_u, bsdf_v, &ao_D, &ao_pdf);

			if(dot(sd.Ng, ao_D) > 0.0f && ao_pdf != 0.0f) {

				Ray light_ray;

				float3 ao_shadow;

				light_ray.P = ray_offset(sd.P, sd.Ng);

				light_ray.D = ao_D;

				light_ray.t = kernel_data.background.ao_distance;

#ifdef __OBJECT_MOTION__

				light_ray.time = sd.time;

#endif

				light_ray.dP = sd.dP;

				light_ray.dD = differential3_zero();

				if(!shadow_blocked(kg, &state, &light_ray, &ao_shadow))

					path_radiance_accum_ao(&L, throughput, ao_alpha, ao_bsdf, ao_shadow, state.bounce);

			}

		}

#endif

#ifdef __SUBSURFACE__

		/* bssrdf scatter to a different location on the same object, replacing

		 * the closures with a diffuse BSDF */

		if(sd.flag & SD_BSSRDF) {

			float bssrdf_probability;

			ShaderClosure *sc = subsurface_scatter_pick_closure(kg, &sd, &bssrdf_probability);

			/* modify throughput for picking bssrdf or bsdf */

			throughput *= bssrdf_probability;

			/* do bssrdf scatter step if we picked a bssrdf closure */

			if(sc) {

				uint lcg_state = lcg_init(*rng + rng_offset + sample*0x68bc21eb);

				if(old_subsurface_scatter_use(&sd)) {

					old_subsurface_scatter_step(kg, &sd, state.flag, sc, &lcg_state, false);

				}

				else {

					ShaderData bssrdf_sd[BSSRDF_MAX_HITS];

					float bssrdf_u, bssrdf_v;

					path_rng_2D(kg, rng, sample, num_samples, rng_offset + PRNG_BSDF_U, &bssrdf_u, &bssrdf_v);

					int num_hits = subsurface_scatter_multi_step(kg, &sd, bssrdf_sd, state.flag, sc, &lcg_state, bssrdf_u, bssrdf_v, false);

					/* compute lighting with the BSDF closure */

					for(int hit = 0; hit < num_hits; hit++) {