/*
 * Adapted from Open Shading Language with this license:
 *
 * Copyright (c) 2009-2010 Sony Pictures Imageworks Inc., et al.
 * All Rights Reserved.
 *
 * Modifications Copyright 2011, Blender Foundation.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 * * Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * * Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * * Neither the name of Sony Pictures Imageworks nor the names of its
 *   contributors may be used to endorse or promote products derived from
 *   this software without specific prior written permission.
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef __BSDF_TRANSPARENT_H__
#define __BSDF_TRANSPARENT_H__

CCL_NAMESPACE_BEGIN

ccl_device void bsdf_transparent_setup(ShaderData *sd, const float3 weight, int path_flag)
{
	/* Check cutoff weight. */
	float sample_weight = fabsf(average(weight));
	if(!(sample_weight >= CLOSURE_WEIGHT_CUTOFF)) {
		return;
	}

	if(sd->flag & SD_TRANSPARENT) {
		sd->closure_transparent_extinction += weight;

		/* Add weight to existing transparent BSDF. */
		for(int i = 0; i < sd->num_closure; i++) {
			ShaderClosure *sc = &sd->closure[i];

			if(sc->type == CLOSURE_BSDF_TRANSPARENT_ID) {
				sc->weight += weight;
				sc->sample_weight += sample_weight;
				break;
			}
		}
	}
	else {
		sd->flag |= SD_BSDF|SD_TRANSPARENT;
		sd->closure_transparent_extinction = weight;

		if(path_flag & PATH_RAY_TERMINATE) {
			/* In this case the number of closures is set to zero to disable
			 * all others, but we still want to get transparency so increase
			 * the number just for this. */
			sd->num_closure_left = 1;
		}

		/* Create new transparent BSDF. */
		ShaderClosure *bsdf = closure_alloc(sd, sizeof(ShaderClosure), CLOSURE_BSDF_TRANSPARENT_ID, weight);

		if(bsdf) {
			bsdf->sample_weight = sample_weight;
			bsdf->N = sd->N;
		}
		else if(path_flag & PATH_RAY_TERMINATE) {
			sd->num_closure_left = 0;
		}
	}
}

ccl_device float3 bsdf_transparent_eval_reflect(const ShaderClosure *sc, const float3 I, const float3 omega_in, float *pdf)
{
	return make_float3(0.0f, 0.0f, 0.0f);
}

ccl_device float3 bsdf_transparent_eval_transmit(const ShaderClosure *sc, const float3 I, const float3 omega_in, float *pdf)
{
	return make_float3(0.0f, 0.0f, 0.0f);
}

ccl_device int bsdf_transparent_sample(const ShaderClosure *sc, float3 Ng, float3 I, float3 dIdx, float3 dIdy, float randu, float randv, float3 *eval, float3 *omega_in, float3 *domega_in_dx, float3 *domega_in_dy, float *pdf)
{
	// only one direction is possible
	*omega_in = -I;
#ifdef __RAY_DIFFERENTIALS__
	*domega_in_dx = -dIdx;
	*domega_in_dy = -dIdy;
#endif
	*pdf = 1;
	*eval = make_float3(1, 1, 1);
	return LABEL_TRANSMIT|LABEL_TRANSPARENT;
}

CCL_NAMESPACE_END

#endif /* __BSDF_TRANSPARENT_H__ */