text: /*
   * 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__ */
  