/*
 * 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
 */

CCL_NAMESPACE_BEGIN

#ifdef __VOLUME__

ccl_device void kernel_path_volume_connect_light(KernelGlobals *kg, RNG *rng,
	ShaderData *sd, float3 throughput, PathState *state, PathRadiance *L,
	float num_samples_adjust)
{
#ifdef __EMISSION__
	if(!kernel_data.integrator.use_direct_light)
		return;

	/* sample illumination from lights to find path contribution */
	float light_t = path_state_rng_1D(kg, rng, state, PRNG_LIGHT);
	float light_u, light_v;
	path_state_rng_2D(kg, rng, state, PRNG_LIGHT_U, &light_u, &light_v);

	Ray light_ray;
	BsdfEval L_light;
	LightSample ls;
	bool is_lamp;

	/* connect to light from given point where shader has been evaluated */
#ifdef __OBJECT_MOTION__
	light_ray.time = sd->time;
#endif

	if(!light_sample(kg, light_t, light_u, light_v, sd->time, sd->P, &ls, true))
		return;
	else if(ls.pdf == 0.0f)
		return;
	
	if(direct_emission(kg, sd, &ls, &light_ray, &L_light, &is_lamp, state->bounce, state->transparent_bounce)) {
		/* trace shadow ray */
		float3 shadow;

		if(!shadow_blocked(kg, state, &light_ray, &shadow)) {
			/* accumulate */
			path_radiance_accum_light(L, throughput * num_samples_adjust, &L_light, shadow, 1.0f, state->bounce, is_lamp);
		}
	}
#endif
}

ccl_device bool kernel_path_volume_bounce(KernelGlobals *kg, RNG *rng,
	ShaderData *sd, float3 *throughput, PathState *state, PathRadiance *L, Ray *ray,
	float num_samples_adjust)
{
	/* sample phase function */
	float phase_pdf;
	BsdfEval phase_eval;
	float3 phase_omega_in;
	differential3 phase_domega_in;
	float phase_u, phase_v;
	path_state_rng_2D(kg, rng, state, PRNG_PHASE_U, &phase_u, &phase_v);
	int label;

	label = shader_volume_phase_sample(kg, sd, phase_u, phase_v, &phase_eval,
		&phase_omega_in, &phase_domega_in, &phase_pdf);

	if(phase_pdf == 0.0f || bsdf_eval_is_zero(&phase_eval))
		return false;
	
	/* modify throughput */
	path_radiance_bsdf_bounce(L, throughput, &phase_eval, phase_pdf, state->bounce, label);

	/* set labels */
	state->ray_pdf = phase_pdf;
#ifdef __LAMP_MIS__
	state->ray_t = 0.0f;
#endif
	state->min_ray_pdf = fminf(phase_pdf, state->min_ray_pdf);

	/* update path state */
	path_state_next(kg, state, label);

	/* setup ray */
	ray->P = sd->P;
	ray->D = phase_omega_in;
	ray->t = FLT_MAX;

#ifdef __RAY_DIFFERENTIALS__
	ray->dP = sd->dP;
	ray->dD = phase_domega_in;
#endif

	return true;
}

#ifdef __KERNEL_CPU__

ccl_device void kernel_branched_path_volume_connect_light(KernelGlobals *kg, RNG *rng,
	ShaderData *sd, float3 throughput, PathState *state, PathRadiance *L,
	float num_samples_adjust, bool sample_all_lights, Ray *ray, const VolumeSegment *segment)
{
#ifdef __EMISSION__
	if(!kernel_data.integrator.use_direct_light)
		return;

	Ray light_ray;
	BsdfEval L_light;
	bool is_lamp;

#ifdef __OBJECT_MOTION__
	light_ray.time = sd->time;
#endif

	if(sample_all_lights) {
		/* lamp sampling */
		for(int i = 0; i < kernel_data.integrator.num_all_lights; i++) {
			int num_samples = ceil_to_int(num_samples_adjust*light_select_num_samples(kg, i));
			float num_samples_inv = num_samples_adjust/(num_samples*kernel_data.integrator.num_all_lights);
			RNG lamp_rng = cmj_hash(*rng, i);

			if(kernel_data.integrator.pdf_triangles != 0.0f)
				num_samples_inv *= 0.5f;

			for(int j = 0; j < num_samples; j++) {
				/* sample random position on given light */
				float light_u, light_v;
				path_branched_rng_2D(kg, &lamp_rng, state, j, num_samples, PRNG_LIGHT_U, &light_u, &light_v);

				LightSample ls;
				if(!light_select(kg, i, light_u, light_v, ray->P, &ls, true))
					continue;

				float3 tp = throughput;

				/* sample position on volume segment */
				if(segment) {
					float rphase = path_branched_rng_1D_for_decision(kg, rng, state, j, num_samples, PRNG_PHASE);
					float rscatter = path_branched_rng_1D_for_decision(kg, rng, state, j, num_samples, PRNG_SCATTER_DISTANCE);

					VolumeIntegrateResult result = kernel_volume_decoupled_scatter(kg,
						state, ray, sd, &tp, rphase, rscatter, segment, (ls.t != FLT_MAX)? &ls.P: NULL, false);

					if(result != VOLUME_PATH_SCATTERED)
						continue;

					/* todo: split up light_sample so we don't have to call it again with new position */
					if(!light_select(kg, i, light_u, light_v, sd->P, &ls, true))
						continue;
				}

				if(ls.pdf == 0.0f)
					continue;

				if(direct_emission(kg, sd, &ls, &light_ray, &L_light, &is_lamp, state->bounce, state->transparent_bounce)) {
					/* trace shadow ray */
					float3 shadow;

					if(!shadow_blocked(kg, state, &light_ray, &shadow)) {
						/* accumulate */
						path_radiance_accum_light(L, tp*num_samples_inv, &L_light, shadow, num_samples_inv, state->bounce, is_lamp);
					}
				}
			}
		}

		/* mesh light sampling */
		if(kernel_data.integrator.pdf_triangles != 0.0f) {
			int num_samples = ceil_to_int(num_samples_adjust*kernel_data.integrator.mesh_light_samples);
			float num_samples_inv = num_samples_adjust/num_samples;

			if(kernel_data.integrator.num_all_lights)
				num_samples_inv *= 0.5f;

			for(int j = 0; j < num_samples; j++) {
				/* sample random position on random triangle */
				float light_t = path_branched_rng_1D_for_decision(kg, rng, state, j, num_samples, PRNG_LIGHT);
				float light_u, light_v;
				path_branched_rng_2D(kg, rng, state, j, num_samples, PRNG_LIGHT_U, &light_u, &light_v);

				/* only sample triangle lights */
				if(kernel_data.integrator.num_all_lights)
					light_t = 0.5f*light_t;

				LightSample ls;
				if(!light_sample(kg, light_t, light_u, light_v, sd->time, ray->P, &ls, true))
					continue;

				float3 tp = throughput;

				/* sample position on volume segment */
				if(segment) {
					float rphase = path_branched_rng_1D_for_decision(kg, rng, state, j, num_samples, PRNG_PHASE);
					float rscatter = path_branched_rng_1D_for_decision(kg, rng, state, j, num_samples, PRNG_SCATTER_DISTANCE);

					VolumeIntegrateResult result = kernel_volume_decoupled_scatter(kg,
						state, ray, sd, &tp, rphase, rscatter, segment, (ls.t != FLT_MAX)? &ls.P: NULL, false);

					if(result != VOLUME_PATH_SCATTERED)
						continue;

					/* todo: split up light_sample so we don't have to call it again with new position */
					if(!light_sample(kg, light_t, light_u, light_v, sd->time, sd->P, &ls, true))
						continue;
				}

				if(ls.pdf == 0.0f)
					continue;

				if(direct_emission(kg, sd, &ls, &light_ray, &L_light, &is_lamp, state->bounce, state->transparent_bounce)) {
					/* trace shadow ray */
					float3 shadow;

					if(!shadow_blocked(kg, state, &light_ray, &shadow)) {
						/* accumulate */
						path_radiance_accum_light(L, tp*num_samples_inv, &L_light, shadow, num_samples_inv, state->bounce, is_lamp);
					}
				}
			}
		}
	}
	else {
		/* sample random position on random light */
		float light_t = path_state_rng_1D(kg, rng, state, PRNG_LIGHT);
		float light_u, light_v;
		path_state_rng_2D(kg, rng, state, PRNG_LIGHT_U, &light_u, &light_v);

		LightSample ls;
		if(!light_sample(kg, light_t, light_u, light_v, sd->time, ray->P, &ls, true))
			return;

		float3 tp = throughput;

		/* sample position on volume segment */
		if(segment) {
			float rphase = path_state_rng_1D_for_decision(kg, rng, state, PRNG_PHASE);
			float rscatter = path_state_rng_1D_for_decision(kg, rng, state, PRNG_SCATTER_DISTANCE);

			VolumeIntegrateResult result = kernel_volume_decoupled_scatter(kg,
				state, ray, sd, &tp, rphase, rscatter, segment, (ls.t != FLT_MAX)? &ls.P: NULL, false);

			if(result != VOLUME_PATH_SCATTERED)
				return;

			/* todo: split up light_sample so we don't have to call it again with new position */
			if(!light_sample(kg, light_t, light_u, light_v, sd->time, sd->P, &ls, true))
				return;
		}

		if(ls.pdf == 0.0f)
			return;

		/* sample random light */
		if(direct_emission(kg, sd, &ls, &light_ray, &L_light, &is_lamp, state->bounce, state->transparent_bounce)) {
			/* trace shadow ray */
			float3 shadow;

			if(!shadow_blocked(kg, state, &light_ray, &shadow)) {
				/* accumulate */
				path_radiance_accum_light(L, tp, &L_light, shadow, 1.0f, state->bounce, is_lamp);
			}
		}
	}
#endif
}

#endif

#endif

CCL_NAMESPACE_END

