forked from bartvdbraak/blender
23c276832b
This commit adds a new distribution to the Glossy, Anisotropic and Glass BSDFs that implements the multiple-scattering microfacet model described in the paper "Multiple-Scattering Microfacet BSDFs with the Smith Model". Essentially, the improvement is that unlike classical GGX, which only models single scattering and assumes the contribution of multiple bounces to be zero, this new model performs a random walk on the microsurface until the ray leaves it again, which ensures perfect energy conservation. In practise, this means that the "darkening problem" - GGX materials becoming darker with increasing roughness - is solved in a physically correct and efficient way. The downside of this model is that it has no (known) analytic expression for evalation. However, it can be evaluated stochastically, and although the correct PDF isn't known either, the properties of MIS and the balance heuristic guarantee an unbiased result at the cost of slightly higher noise. Reviewers: dingto, #cycles, brecht Reviewed By: dingto, #cycles, brecht Subscribers: bliblubli, ace_dragon, gregzaal, brecht, harvester, dingto, marcog, swerner, jtheninja, Blendify, nutel Differential Revision: https://developer.blender.org/D2002
71 lines
3.5 KiB
C
71 lines
3.5 KiB
C
/*
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* Copyright 2011-2015 Blender Foundation
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "kernel_split_common.h"
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/* Note on kernel_shader_eval kernel
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* This kernel is the 5th kernel in the ray tracing logic. This is
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* the 4rd kernel in path iteration. This kernel sets up the ShaderData
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* structure from the values computed by the previous kernels. It also identifies
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* the rays of state RAY_TO_REGENERATE and enqueues them in QUEUE_HITBG_BUFF_UPDATE_TOREGEN_RAYS queue.
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*
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* The input and output of the kernel is as follows,
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* rng_coop -------------------------------------------|--- kernel_shader_eval --|--- sd
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* Ray_coop -------------------------------------------| |--- Queue_data (QUEUE_HITBG_BUFF_UPDATE_TOREGEN_RAYS)
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* PathState_coop -------------------------------------| |--- Queue_index (QUEUE_HITBG_BUFF_UPDATE_TOREGEN_RAYS)
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* Intersection_coop ----------------------------------| |
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* Queue_data (QUEUE_ACTIVE_AND_REGENERATD_RAYS)-------| |
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* Queue_index(QUEUE_HITBG_BUFF_UPDATE_TOREGEN_RAYS)---| |
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* ray_state ------------------------------------------| |
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* kg (globals) ---------------------------------------| |
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* queuesize ------------------------------------------| |
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*
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* Note on Queues :
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* This kernel reads from the QUEUE_ACTIVE_AND_REGENERATED_RAYS queue and processes
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* only the rays of state RAY_ACTIVE;
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* State of queues when this kernel is called,
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* at entry,
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* QUEUE_ACTIVE_AND_REGENERATED_RAYS will be filled with RAY_ACTIVE and RAY_REGENERATED rays
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* QUEUE_HITBG_BUFF_UPDATE_TOREGEN_RAYS will be empty.
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* at exit,
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* QUEUE_ACTIVE_AND_REGENERATED_RAYS will be filled with RAY_ACTIVE and RAY_REGENERATED rays
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* QUEUE_HITBG_BUFF_UPDATE_TOREGEN_RAYS will be filled with RAY_TO_REGENERATE rays
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*/
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ccl_device void kernel_shader_eval(
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KernelGlobals *kg,
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ShaderData *sd, /* Output ShaderData structure to be filled */
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ccl_global uint *rng_coop, /* Required for rbsdf calculation */
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ccl_global Ray *Ray_coop, /* Required for setting up shader from ray */
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ccl_global PathState *PathState_coop, /* Required for all functions in this kernel */
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Intersection *Intersection_coop, /* Required for setting up shader from ray */
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ccl_global char *ray_state, /* Denotes the state of each ray */
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int ray_index)
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{
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if(IS_STATE(ray_state, ray_index, RAY_ACTIVE)) {
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Intersection *isect = &Intersection_coop[ray_index];
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ccl_global uint *rng = &rng_coop[ray_index];
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ccl_global PathState *state = &PathState_coop[ray_index];
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Ray ray = Ray_coop[ray_index];
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shader_setup_from_ray(kg,
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sd,
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isect,
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&ray);
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float rbsdf = path_state_rng_1D_for_decision(kg, rng, state, PRNG_BSDF);
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shader_eval_surface(kg, sd, rng, state, rbsdf, state->flag, SHADER_CONTEXT_MAIN);
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}
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}
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