blender/intern/cycles/bvh/bvh_embree.cpp

/*
 * Copyright 2018, 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.
 */

/* This class implemens a ray accelerator for Cycles using Intel's Embree library.
 * It supports triangles, curves, object and deformation blur and instancing.
 * Not supported are thick line segments, those have no native equivalent in Embree.
 * They could be implemented using Embree's thick curves, at the expense of wasted memory.
 * User defined intersections for Embree could also be an option, but since Embree only uses aligned BVHs
 * for user geometry, this would come with reduced performance and/or higher memory usage.
 *
 * Since Embree allows object to be either curves or triangles but not both, Cycles object IDs are maapped
 * to Embree IDs by multiplying by two and adding one for curves.
 *
 * This implementation shares RTCDevices between Cycles instances. Eventually each instance should get
 * a separate RTCDevice to correctly keep track of memory usage.
 *
 * Vertex and index buffers are duplicated between Cycles device arrays and Embree. These could be merged,
 * which would requrie changes to intersection refinement, shader setup, mesh light sampling and a few
 * other places in Cycles where direct access to vertex data is required.
 */

#ifdef WITH_EMBREE

#include <pmmintrin.h>
#include <xmmintrin.h>
#include <embree3/rtcore_geometry.h>

#include "bvh/bvh_embree.h"

/* Kernel includes are necessary so that the filter function for Embree can access the packed BVH. */
#include "kernel/bvh/bvh_embree.h"
#include "kernel/kernel_compat_cpu.h"
#include "kernel/split/kernel_split_data_types.h"
#include "kernel/kernel_globals.h"
#include "kernel/kernel_random.h"

#include "render/mesh.h"
#include "render/object.h"
#include "util/util_foreach.h"
#include "util/util_logging.h"
#include "util/util_progress.h"

CCL_NAMESPACE_BEGIN

#define IS_HAIR(x) (x & 1)

/* This gets called by Embree at every valid ray/object intersection.
 * Things like recording subsurface or shadow hits for later evaluation
 * as well as filtering for volume objects happen here.
 * Cycles' own BVH does that directly inside the traversal calls.
 */
static void rtc_filter_func(const RTCFilterFunctionNArguments *args)
{
	/* Current implementation in Cycles assumes only single-ray intersection queries. */
	assert(args->N == 1);

	const RTCRay *ray = (RTCRay*)args->ray;
	const RTCHit *hit = (RTCHit*)args->hit;
	CCLIntersectContext *ctx = ((IntersectContext*)args->context)->userRayExt;
	KernelGlobals *kg = ctx->kg;

	/* Check if there is backfacing hair to ignore. */
	if(IS_HAIR(hit->geomID) && (kernel_data.curve.curveflags & CURVE_KN_INTERPOLATE)
	   && !(kernel_data.curve.curveflags & CURVE_KN_BACKFACING)
	   && !(kernel_data.curve.curveflags & CURVE_KN_RIBBONS)) {
		if(dot(make_float3(ray->dir_x, ray->dir_y, ray->dir_z), make_float3(hit->Ng_x, hit->Ng_y, hit->Ng_z)) > 0.0f) {
			*args->valid = 0;
			return;
		}
	}
}

static void rtc_filter_occluded_func(const RTCFilterFunctionNArguments* args)
{
	assert(args->N == 1);

	const RTCRay *ray = (RTCRay*)args->ray;
	RTCHit *hit = (RTCHit*)args->hit;
	CCLIntersectContext *ctx = ((IntersectContext*)args->context)->userRayExt;
	KernelGlobals *kg = ctx->kg;

	/* For all ray types: Check if there is backfacing hair to ignore */
	if(IS_HAIR(hit->geomID) && (kernel_data.curve.curveflags & CURVE_KN_INTERPOLATE)
	   && !(kernel_data.curve.curveflags & CURVE_KN_BACKFACING)
	   && !(kernel_data.curve.curveflags & CURVE_KN_RIBBONS)) {
		if(dot(make_float3(ray->dir_x, ray->dir_y, ray->dir_z), make_float3(hit->Ng_x, hit->Ng_y, hit->Ng_z)) > 0.0f) {
			*args->valid = 0;
			return;
		}
	}

	switch(ctx->type) {
		case CCLIntersectContext::RAY_SHADOW_ALL: {
			/* Append the intersection to the end of the array. */
			if(ctx->num_hits < ctx->max_hits) {
				Intersection current_isect;
				kernel_embree_convert_hit(kg, ray, hit, &current_isect);
				for(size_t i = 0; i < ctx->max_hits; ++i) {
					if(current_isect.object == ctx->isect_s[i].object &&
					   current_isect.prim == ctx->isect_s[i].prim &&
					   current_isect.t == ctx->isect_s[i].t) {
						/* This intersection was already recorded, skip it. */
						*args->valid = 0;
						break;
					}
				}
				Intersection *isect = &ctx->isect_s[ctx->num_hits];
				++ctx->num_hits;
				*isect = current_isect;
				int prim = kernel_tex_fetch(__prim_index, isect->prim);
				int shader = 0;
				if(kernel_tex_fetch(__prim_type, isect->prim) & PRIMITIVE_ALL_TRIANGLE) {
					shader = kernel_tex_fetch(__tri_shader, prim);
				}
				else {
					float4 str = kernel_tex_fetch(__curves, prim);
					shader = __float_as_int(str.z);
				}
				int flag = kernel_tex_fetch(__shaders, shader & SHADER_MASK).flags;
				/* If no transparent shadows, all light is blocked. */
				if(flag & (SD_HAS_TRANSPARENT_SHADOW)) {
					/* This tells Embree to continue tracing. */
					*args->valid = 0;
				}
			}
			else {
				/* Increase the number of hits beyond ray.max_hits
				 * so that the caller can detect this as opaque. */
				++ctx->num_hits;
			}
			break;
		}
		case CCLIntersectContext::RAY_SSS: {
			/* No intersection information requested, just return a hit. */
			if(ctx->max_hits == 0) {
				break;
			}

			/* See triangle_intersect_subsurface() for the native equivalent. */
			for(int i = min(ctx->max_hits, ctx->ss_isect->num_hits) - 1; i >= 0; --i) {
				if(ctx->ss_isect->hits[i].t == ray->tfar) {
					/* This tells Embree to continue tracing. */
					*args->valid = 0;
					break;
				}
			}

			++ctx->ss_isect->num_hits;
			int hit_idx;

			if(ctx->ss_isect->num_hits <= ctx->max_hits) {
				hit_idx = ctx->ss_isect->num_hits - 1;
			}
			else {
				/* reservoir sampling: if we are at the maximum number of
				 * hits, randomly replace element or skip it */
				hit_idx = lcg_step_uint(ctx->lcg_state) % ctx->ss_isect->num_hits;

				if(hit_idx >= ctx->max_hits) {
					/* This tells Embree to continue tracing. */
					*args->valid = 0;
					break;
				}
			}
			/* record intersection */
			kernel_embree_convert_local_hit(kg, ray, hit, &ctx->ss_isect->hits[hit_idx], ctx->sss_object_id);
			ctx->ss_isect->Ng[hit_idx].x = hit->Ng_x;
			ctx->ss_isect->Ng[hit_idx].y = hit->Ng_y;
			ctx->ss_isect->Ng[hit_idx].z = hit->Ng_z;
			ctx->ss_isect->Ng[hit_idx] = normalize(ctx->ss_isect->Ng[hit_idx]);
			/* This tells Embree to continue tracing .*/
			*args->valid = 0;
			break;
		}
		case CCLIntersectContext::RAY_VOLUME_ALL: {
			/* Append the intersection to the end of the array. */
			if(ctx->num_hits < ctx->max_hits) {
				Intersection current_isect;
				kernel_embree_convert_hit(kg, ray, hit, &current_isect);
				for(size_t i = 0; i < ctx->max_hits; ++i) {
					if(current_isect.object == ctx->isect_s[i].object &&
					   current_isect.prim == ctx->isect_s[i].prim &&
					   current_isect.t == ctx->isect_s[i].t) {
						/* This intersection was already recorded, skip it. */
						*args->valid = 0;
						break;
					}
				}
				Intersection *isect = &ctx->isect_s[ctx->num_hits];
				++ctx->num_hits;
				*isect = current_isect;
				/* Only primitives from volume object. */
				uint tri_object = (isect->object == OBJECT_NONE) ?
								   kernel_tex_fetch(__prim_object, isect->prim) : isect->object;
				int object_flag = kernel_tex_fetch(__object_flag, tri_object);
				if((object_flag & SD_OBJECT_HAS_VOLUME) == 0) {
					--ctx->num_hits;
				}
				/* This tells Embree to continue tracing. */
				*args->valid = 0;
				break;
			}
		}
		case CCLIntersectContext::RAY_REGULAR:
		default:
			/* Nothing to do here. */
			break;
	}
}

static size_t unaccounted_mem = 0;

static bool rtc_memory_monitor_func(void* userPtr, const ssize_t bytes, const bool)
{
	Stats *stats = (Stats*)userPtr;
	if(stats) {
		if(bytes > 0) {
			stats->mem_alloc(bytes);
		}
		else {
			stats->mem_free(-bytes);
		}
	}
	else {
		/* A stats pointer may not yet be available. Keep track of the memory usage for later. */
		if(bytes >= 0) {
			atomic_add_and_fetch_z(&unaccounted_mem, bytes);
		}
		else {
			atomic_sub_and_fetch_z(&unaccounted_mem, -bytes);
		}
	}
	return true;
}

static void rtc_error_func(void*, enum RTCError, const char* str)
{
	VLOG(1) << str;
}

static double progress_start_time = 0.0f;

static bool rtc_progress_func(void* user_ptr, const double n)
{
	Progress *progress = (Progress*)user_ptr;

	if(time_dt() - progress_start_time < 0.25) {
		return true;
	}

	string msg = string_printf("Building BVH %.0f%%", n * 100.0);
	progress->set_substatus(msg);
	progress_start_time = time_dt();

	return !progress->get_cancel();
}

/* This is to have a shared device between all BVH instances.
   It would be useful to actually to use a separte RTCDevice per Cycles instance. */
RTCDevice BVHEmbree::rtc_shared_device = NULL;
int BVHEmbree::rtc_shared_users = 0;
thread_mutex BVHEmbree::rtc_shared_mutex;

BVHEmbree::BVHEmbree(const BVHParams& params_, const vector<Object*>& objects_)
: BVH(params_, objects_), scene(NULL), mem_used(0), top_level(NULL), stats(NULL),
  curve_subdivisions(params.curve_subdivisions), build_quality(RTC_BUILD_QUALITY_REFIT),
  use_curves(params_.curve_flags & CURVE_KN_INTERPOLATE),
  use_ribbons(params.curve_flags & CURVE_KN_RIBBONS), dynamic_scene(true)
{
	_MM_SET_FLUSH_ZERO_MODE(_MM_FLUSH_ZERO_ON);
	_MM_SET_DENORMALS_ZERO_MODE(_MM_DENORMALS_ZERO_ON);
	thread_scoped_lock lock(rtc_shared_mutex);
	if(rtc_shared_users == 0) {
		rtc_shared_device = rtcNewDevice("verbose=0");
		/* Check here if Embree was built with the correct flags. */
		ssize_t ret = rtcGetDeviceProperty (rtc_shared_device,RTC_DEVICE_PROPERTY_RAY_MASK_SUPPORTED);
		if(ret != 1) {
			assert(0);
			VLOG(1) << "Embree is compiled without the RTC_DEVICE_PROPERTY_RAY_MASK_SUPPORTED flag."\
			           "Ray visiblity will not work.";
		}
		ret = rtcGetDeviceProperty (rtc_shared_device,RTC_DEVICE_PROPERTY_FILTER_FUNCTION_SUPPORTED);
		if(ret != 1) {
			assert(0);
			VLOG(1) << "Embree is compiled without the RTC_DEVICE_PROPERTY_FILTER_FUNCTION_SUPPORTED flag."\
			           "Renders may not look as expected.";
		}
		ret = rtcGetDeviceProperty (rtc_shared_device,RTC_DEVICE_PROPERTY_CURVE_GEOMETRY_SUPPORTED);
		if(ret != 1) {
			assert(0);
			VLOG(1) << "Embree is compiled without the RTC_DEVICE_PROPERTY_CURVE_GEOMETRY_SUPPORTED flag. "\
			           "Line primitives will not be rendered.";
		}
		ret = rtcGetDeviceProperty (rtc_shared_device,RTC_DEVICE_PROPERTY_TRIANGLE_GEOMETRY_SUPPORTED);
		if(ret != 1) {
			assert(0);
			VLOG(1) << "Embree is compiled without the RTC_DEVICE_PROPERTY_TRIANGLE_GEOMETRY_SUPPORTED flag. "\
			           "Triangle primitives will not be rendered.";
		}
		ret = rtcGetDeviceProperty (rtc_shared_device,RTC_DEVICE_PROPERTY_BACKFACE_CULLING_ENABLED);
		if(ret != 0) {
			assert(0);
			VLOG(1) << "Embree is compiled with the RTC_DEVICE_PROPERTY_BACKFACE_CULLING_ENABLED flag. "\
			           "Renders may not look as expected.";
		}
	}
	++rtc_shared_users;

	rtcSetDeviceErrorFunction(rtc_shared_device, rtc_error_func, NULL);

	pack.root_index = -1;
}

BVHEmbree::~BVHEmbree()
{
	if(!params.top_level) {
		destroy(scene);
	}
}

void BVHEmbree::destroy(RTCScene scene)
{
	if(scene) {
		rtcReleaseScene(scene);
		scene = NULL;
	}
	thread_scoped_lock lock(rtc_shared_mutex);
	--rtc_shared_users;
	if(rtc_shared_users == 0) {
		rtcReleaseDevice (rtc_shared_device);
		rtc_shared_device = NULL;
	}
}

void BVHEmbree::delete_rtcScene()
{
	if(scene) {
		/* When this BVH is used as an instance in a top level BVH, don't delete now
		 * Let the top_level BVH know that it should delete it later. */
		if(top_level) {
			top_level->add_delayed_delete_scene(scene);
		}
		else {
			rtcReleaseScene(scene);
			if(delayed_delete_scenes.size()) {
				foreach(RTCScene s, delayed_delete_scenes) {
					rtcReleaseScene(s);
				}
			}
			delayed_delete_scenes.clear();
		}
		scene = NULL;
	}
}

void BVHEmbree::build(Progress& progress, Stats *stats_)
{
	assert(rtc_shared_device);
	stats = stats_;
	rtcSetDeviceMemoryMonitorFunction(rtc_shared_device, rtc_memory_monitor_func, stats);

	progress.set_substatus("Building BVH");

	if(scene) {
		rtcReleaseScene(scene);
		scene = NULL;
	}

	const bool dynamic = params.bvh_type == SceneParams::BVH_DYNAMIC;

	scene = rtcNewScene(rtc_shared_device);
	const RTCSceneFlags scene_flags = (dynamic ? RTC_SCENE_FLAG_DYNAMIC : RTC_SCENE_FLAG_NONE) |
	                                   RTC_SCENE_FLAG_COMPACT | RTC_SCENE_FLAG_ROBUST;
	rtcSetSceneFlags(scene, scene_flags);
	build_quality = dynamic ? RTC_BUILD_QUALITY_LOW :
	               (params.use_spatial_split ? RTC_BUILD_QUALITY_HIGH : RTC_BUILD_QUALITY_MEDIUM);
	rtcSetSceneBuildQuality(scene, build_quality);

	int i = 0;

	pack.object_node.clear();

	foreach(Object *ob, objects) {
		if(params.top_level) {
			if(!ob->is_traceable()) {
				++i;
				continue;
			}
			if(!ob->mesh->is_instanced()) {
				add_object(ob, i);
			}
			else {
				add_instance(ob, i);
			}
		}
		else {
			add_object(ob, i);
		}
		++i;
		if(progress.get_cancel()) return;
	}

	if(progress.get_cancel()) {
		delete_rtcScene();
		stats = NULL;
		return;
	}

	rtcSetSceneProgressMonitorFunction(scene, rtc_progress_func, &progress);
	rtcCommitScene(scene);

	pack_primitives();

	if(progress.get_cancel()) {
		delete_rtcScene();
		stats = NULL;
		return;
	}

	progress.set_substatus("Packing geometry");
	pack_nodes(NULL);

	stats = NULL;
}

void BVHEmbree::add_object(Object *ob, int i)
{
	Mesh *mesh = ob->mesh;
	if(params.primitive_mask & PRIMITIVE_ALL_TRIANGLE && mesh->num_triangles() > 0) {
		add_triangles(ob, i);
	}
	if(params.primitive_mask & PRIMITIVE_ALL_CURVE && mesh->num_curves() > 0) {
		add_curves(ob, i);
	}
}

void BVHEmbree::add_instance(Object *ob, int i)
{
	if(!ob || !ob->mesh) {
		assert(0);
		return;
	}
	BVHEmbree *instance_bvh = (BVHEmbree*)(ob->mesh->bvh);

	if(instance_bvh->top_level != this) {
		instance_bvh->top_level = this;
	}

	const size_t num_motion_steps = ob->use_motion() ? ob->motion.size() : 1;
	RTCGeometry geom_id = rtcNewGeometry(rtc_shared_device, RTC_GEOMETRY_TYPE_INSTANCE);
	rtcSetGeometryInstancedScene(geom_id, instance_bvh->scene);
	rtcSetGeometryTimeStepCount(geom_id, num_motion_steps);

	if(ob->use_motion()) {
		for(size_t step = 0; step < num_motion_steps; ++step) {
			rtcSetGeometryTransform(geom_id, step, RTC_FORMAT_FLOAT3X4_ROW_MAJOR, (const float*)&ob->motion[step]);
		}
	}
	else {
		rtcSetGeometryTransform(geom_id, 0, RTC_FORMAT_FLOAT3X4_ROW_MAJOR, (const float*)&ob->tfm);
	}

	pack.prim_index.push_back_slow(-1);
	pack.prim_object.push_back_slow(i);
	pack.prim_type.push_back_slow(PRIMITIVE_NONE);
	pack.prim_tri_index.push_back_slow(-1);

	rtcSetGeometryUserData(geom_id, (void*) instance_bvh->scene);
	rtcSetGeometryMask(geom_id, ob->visibility);

	rtcCommitGeometry(geom_id);
	rtcAttachGeometryByID(scene, geom_id, i*2);
	rtcReleaseGeometry(geom_id);
}

void BVHEmbree::add_triangles(Object *ob, int i)
{
	size_t prim_offset = pack.prim_index.size();
	Mesh *mesh = ob->mesh;
	const Attribute *attr_mP = NULL;
	size_t num_motion_steps = 1;
	if(mesh->has_motion_blur()) {
		attr_mP = mesh->attributes.find(ATTR_STD_MOTION_VERTEX_POSITION);
		if(attr_mP) {
			num_motion_steps = mesh->motion_steps;
			if(num_motion_steps > RTC_MAX_TIME_STEP_COUNT) {
				assert(0);
				num_motion_steps = RTC_MAX_TIME_STEP_COUNT;
			}
		}
	}

	const size_t num_triangles = mesh->num_triangles();
	RTCGeometry geom_id = rtcNewGeometry(rtc_shared_device, RTC_GEOMETRY_TYPE_TRIANGLE);
	rtcSetGeometryBuildQuality(geom_id, build_quality);
	rtcSetGeometryTimeStepCount(geom_id, num_motion_steps);

	unsigned *rtc_indices = (unsigned*)rtcSetNewGeometryBuffer(geom_id, RTC_BUFFER_TYPE_INDEX, 0,
	                                                           RTC_FORMAT_UINT3, sizeof (int) * 3, num_triangles);
	assert(rtc_indices);
	if(!rtc_indices) {
		VLOG(1) << "Embree could not create new geometry buffer for mesh " << mesh->name.c_str() << ".\n";
		return;
	}
	for(size_t j = 0; j < num_triangles; ++j) {
		Mesh::Triangle t = mesh->get_triangle(j);
		rtc_indices[j*3] = t.v[0];
		rtc_indices[j*3+1] = t.v[1];
		rtc_indices[j*3+2] = t.v[2];
	}

	update_tri_vertex_buffer(geom_id, mesh);

	pack.prim_object.reserve(pack.prim_object.size() + num_triangles);
	pack.prim_type.reserve(pack.prim_type.size() + num_triangles);
	pack.prim_index.reserve(pack.prim_index.size() + num_triangles);
	pack.prim_tri_index.reserve(pack.prim_index.size() + num_triangles);
	for(size_t j = 0; j < num_triangles; ++j) {
		pack.prim_object.push_back_reserved(i);
		pack.prim_type.push_back_reserved(num_motion_steps > 1 ? PRIMITIVE_MOTION_TRIANGLE : PRIMITIVE_TRIANGLE);
		pack.prim_index.push_back_reserved(j);
		pack.prim_tri_index.push_back_reserved(j);
	}

	rtcSetGeometryUserData(geom_id, (void*) prim_offset);
	rtcSetGeometryIntersectFilterFunction(geom_id, rtc_filter_func);
	rtcSetGeometryOccludedFilterFunction(geom_id, rtc_filter_occluded_func);
	rtcSetGeometryMask(geom_id, ob->visibility);

	rtcCommitGeometry(geom_id);
	rtcAttachGeometryByID(scene, geom_id, i*2);
	rtcReleaseGeometry(geom_id);
}

void BVHEmbree::update_tri_vertex_buffer(RTCGeometry geom_id, const Mesh* mesh)
{
	const Attribute *attr_mP = NULL;
	size_t num_motion_steps = 1;
	int t_mid = 0;
	if(mesh->has_motion_blur()) {
		attr_mP = mesh->attributes.find(ATTR_STD_MOTION_VERTEX_POSITION);
		if(attr_mP) {
			num_motion_steps = mesh->motion_steps;
			t_mid = (num_motion_steps - 1) / 2;
			if(num_motion_steps > RTC_MAX_TIME_STEP_COUNT) {
				assert(0);
				num_motion_steps = RTC_MAX_TIME_STEP_COUNT;
			}
		}
	}
	const size_t num_verts = mesh->verts.size();

	for(int t = 0; t < num_motion_steps; ++t) {
		const float3 *verts;
		if(t == t_mid) {
			verts = &mesh->verts[0];
		}
		else {
			int t_ = (t > t_mid) ? (t - 1) : t;
			verts = &attr_mP->data_float3()[t_ * num_verts];
		}

		float *rtc_verts = (float*) rtcSetNewGeometryBuffer(geom_id, RTC_BUFFER_TYPE_VERTEX, t,
		                                                    RTC_FORMAT_FLOAT3, sizeof(float) * 3, num_verts + 1);
		assert(rtc_verts);
		if(rtc_verts) {
			for(size_t j = 0; j < num_verts; ++j) {
				rtc_verts[0] = verts[j].x;
				rtc_verts[1] = verts[j].y;
				rtc_verts[2] = verts[j].z;
				rtc_verts += 3;
			}
		}
	}
}

void BVHEmbree::update_curve_vertex_buffer(RTCGeometry geom_id, const Mesh* mesh)
{
	const Attribute *attr_mP = NULL;
	size_t num_motion_steps = 1;
	if(mesh->has_motion_blur()) {
		attr_mP = mesh->curve_attributes.find(ATTR_STD_MOTION_VERTEX_POSITION);
		if(attr_mP) {
			num_motion_steps = mesh->motion_steps;
		}
	}
	
	const size_t num_curves = mesh->num_curves();
	size_t num_keys = 0;
	for(size_t j = 0; j < num_curves; ++j) {
		const Mesh::Curve c = mesh->get_curve(j);
		num_keys += c.num_keys;
	}

	/* Copy the CV data to Embree */
	const int t_mid = (num_motion_steps - 1) / 2;
	const float *curve_radius = &mesh->curve_radius[0];
	for(int t = 0; t < num_motion_steps; ++t) {
		const float3 *verts;
		if(t == t_mid || attr_mP == NULL) {
			verts = &mesh->curve_keys[0];
		}
		else {
			int t_ = (t > t_mid) ? (t - 1) : t;
			verts = &attr_mP->data_float3()[t_ * num_keys];
		}

		float4 *rtc_verts = (float4*)rtcSetNewGeometryBuffer(geom_id, RTC_BUFFER_TYPE_VERTEX, t,
		                                                     RTC_FORMAT_FLOAT4, sizeof (float) * 4, num_keys);
		float4 *rtc_tangents = NULL;
		if(use_curves) {
			rtc_tangents = (float4*)rtcSetNewGeometryBuffer(geom_id, RTC_BUFFER_TYPE_TANGENT, t,
																RTC_FORMAT_FLOAT4, sizeof (float) * 4, num_keys);
			assert(rtc_tangents);
		}
		assert(rtc_verts);
		if(rtc_verts) {
			if(use_curves && rtc_tangents) {
				const size_t num_curves = mesh->num_curves();
				for(size_t j = 0; j < num_curves; ++j) {
					Mesh::Curve c = mesh->get_curve(j);
					int fk = c.first_key;
					rtc_verts[0] = float3_to_float4(verts[fk]);
					rtc_verts[0].w = curve_radius[fk];
					rtc_tangents[0] = float3_to_float4(verts[fk + 1] - verts[fk]);
					rtc_tangents[0].w = curve_radius[fk + 1] - curve_radius[fk];
					++fk;
					int k = 1;
					for(;k < c.num_segments(); ++k, ++fk) {
						rtc_verts[k] = float3_to_float4(verts[fk]);
						rtc_verts[k].w = curve_radius[fk];
						rtc_tangents[k] = float3_to_float4((verts[fk + 1] - verts[fk - 1]) * 0.5f);
						rtc_tangents[k].w = (curve_radius[fk + 1] - curve_radius[fk - 1]) * 0.5f;
					}
					rtc_verts[k] = float3_to_float4(verts[fk]);
					rtc_verts[k].w = curve_radius[fk];
					rtc_tangents[k] = float3_to_float4(verts[fk] - verts[fk - 1]);
					rtc_tangents[k].w = curve_radius[fk] - curve_radius[fk - 1];
					rtc_verts += c.num_keys;
					rtc_tangents += c.num_keys;
				}
			}
			else {
				for(size_t j = 0; j < num_keys; ++j) {
					rtc_verts[j] = float3_to_float4(verts[j]);
					rtc_verts[j].w = curve_radius[j];
				}
			}
		}
	}
}

void BVHEmbree::add_curves(Object *ob, int i)
{
	size_t prim_offset = pack.prim_index.size();
	const Mesh *mesh = ob->mesh;
	const Attribute *attr_mP = NULL;
	size_t num_motion_steps = 1;
	if(mesh->has_motion_blur()) {
		attr_mP = mesh->curve_attributes.find(ATTR_STD_MOTION_VERTEX_POSITION);
		if(attr_mP) {
			num_motion_steps = mesh->motion_steps;
		}
	}

	const size_t num_curves = mesh->num_curves();
	size_t num_segments = 0;
	for(size_t j = 0; j < num_curves; ++j) {
		Mesh::Curve c = mesh->get_curve(j);
		assert(c.num_segments() > 0);
		num_segments += c.num_segments();
	}

	/* Make room for Cycles specific data. */
	pack.prim_object.reserve(pack.prim_object.size() + num_segments);
	pack.prim_type.reserve(pack.prim_type.size() + num_segments);
	pack.prim_index.reserve(pack.prim_index.size() + num_segments);
	pack.prim_tri_index.reserve(pack.prim_index.size() + num_segments);

	enum RTCGeometryType type = (!use_curves) ? RTC_GEOMETRY_TYPE_FLAT_LINEAR_CURVE :
	                            (use_ribbons ? RTC_GEOMETRY_TYPE_FLAT_HERMITE_CURVE :
	                                           RTC_GEOMETRY_TYPE_ROUND_HERMITE_CURVE);

	RTCGeometry geom_id = rtcNewGeometry(rtc_shared_device, type);
	rtcSetGeometryTessellationRate(geom_id, curve_subdivisions);
	unsigned *rtc_indices = (unsigned*) rtcSetNewGeometryBuffer(geom_id, RTC_BUFFER_TYPE_INDEX, 0,
																RTC_FORMAT_UINT, sizeof (int), num_segments);
	size_t rtc_index = 0;
	for(size_t j = 0; j < num_curves; ++j) {
		Mesh::Curve c = mesh->get_curve(j);
		for(size_t k = 0; k < c.num_segments(); ++k) {
			rtc_indices[rtc_index] = c.first_key + k;
			/* Cycles specific data. */
			pack.prim_object.push_back_reserved(i);
			pack.prim_type.push_back_reserved(PRIMITIVE_PACK_SEGMENT(num_motion_steps > 1 ?
																	 PRIMITIVE_MOTION_CURVE : PRIMITIVE_CURVE, k));
			pack.prim_index.push_back_reserved(j);
			pack.prim_tri_index.push_back_reserved(rtc_index);

			++rtc_index;
		}
	}

	rtcSetGeometryBuildQuality(geom_id, build_quality);
	rtcSetGeometryTimeStepCount(geom_id, num_motion_steps);

	update_curve_vertex_buffer(geom_id, mesh);

	rtcSetGeometryUserData(geom_id, (void*) prim_offset);
	rtcSetGeometryIntersectFilterFunction(geom_id, rtc_filter_func);
	rtcSetGeometryOccludedFilterFunction(geom_id, rtc_filter_occluded_func);
	rtcSetGeometryMask(geom_id, ob->visibility);

	rtcCommitGeometry(geom_id);
	rtcAttachGeometryByID(scene, geom_id, i * 2 + 1);
	rtcReleaseGeometry(geom_id);
}

void BVHEmbree::pack_nodes(const BVHNode *)
{
	/* Quite a bit of this code is for compatibility with Cycles' native BVH. */
	if(!params.top_level) {
		return;
	}

	for(size_t i = 0; i < pack.prim_index.size(); ++i) {
		if(pack.prim_index[i] != -1) {
			if(pack.prim_type[i] & PRIMITIVE_ALL_CURVE)
				pack.prim_index[i] += objects[pack.prim_object[i]]->mesh->curve_offset;
			else
				pack.prim_index[i] += objects[pack.prim_object[i]]->mesh->tri_offset;
		}
	}

	size_t prim_offset = pack.prim_index.size();

	/* reserve */
	size_t prim_index_size = pack.prim_index.size();
	size_t prim_tri_verts_size = pack.prim_tri_verts.size();

	size_t pack_prim_index_offset = prim_index_size;
	size_t pack_prim_tri_verts_offset = prim_tri_verts_size;
	size_t object_offset = 0;

	map<Mesh*, int> mesh_map;

	foreach(Object *ob, objects) {
		Mesh *mesh = ob->mesh;
		BVH *bvh = mesh->bvh;

		if(mesh->need_build_bvh()) {
			if(mesh_map.find(mesh) == mesh_map.end()) {
				prim_index_size += bvh->pack.prim_index.size();
				prim_tri_verts_size += bvh->pack.prim_tri_verts.size();
				mesh_map[mesh] = 1;
			}
		}
	}

	mesh_map.clear();

	pack.prim_index.resize(prim_index_size);
	pack.prim_type.resize(prim_index_size);
	pack.prim_object.resize(prim_index_size);
	pack.prim_visibility.clear();
	pack.prim_tri_verts.resize(prim_tri_verts_size);
	pack.prim_tri_index.resize(prim_index_size);
	pack.object_node.resize(objects.size());

	int *pack_prim_index = (pack.prim_index.size())? &pack.prim_index[0]: NULL;
	int *pack_prim_type = (pack.prim_type.size())? &pack.prim_type[0]: NULL;
	int *pack_prim_object = (pack.prim_object.size())? &pack.prim_object[0]: NULL;
	float4 *pack_prim_tri_verts = (pack.prim_tri_verts.size())? &pack.prim_tri_verts[0]: NULL;
	uint *pack_prim_tri_index = (pack.prim_tri_index.size())? &pack.prim_tri_index[0]: NULL;

	/* merge */
	foreach(Object *ob, objects) {
		Mesh *mesh = ob->mesh;

		/* We assume that if mesh doesn't need own BVH it was already included
		 * into a top-level BVH and no packing here is needed.
		 */
		if(!mesh->need_build_bvh()) {
			pack.object_node[object_offset++] = prim_offset;
			continue;
		}

		/* if mesh already added once, don't add it again, but used set
		 * node offset for this object */
		map<Mesh*, int>::iterator it = mesh_map.find(mesh);

		if(mesh_map.find(mesh) != mesh_map.end()) {
			int noffset = it->second;
			pack.object_node[object_offset++] = noffset;
			continue;
		}

		BVHEmbree *bvh = (BVHEmbree*)mesh->bvh;

		rtc_memory_monitor_func(stats, unaccounted_mem, true);
		unaccounted_mem = 0;

		int mesh_tri_offset = mesh->tri_offset;
		int mesh_curve_offset = mesh->curve_offset;

		/* fill in node indexes for instances */
		pack.object_node[object_offset++] = prim_offset;

		mesh_map[mesh] = pack.object_node[object_offset-1];

		/* merge primitive, object and triangle indexes */
		if(bvh->pack.prim_index.size()) {
			size_t bvh_prim_index_size = bvh->pack.prim_index.size();
			int *bvh_prim_index = &bvh->pack.prim_index[0];
			int *bvh_prim_type = &bvh->pack.prim_type[0];
			uint *bvh_prim_tri_index = &bvh->pack.prim_tri_index[0];

			for(size_t i = 0; i < bvh_prim_index_size; ++i) {
				if(bvh->pack.prim_type[i] & PRIMITIVE_ALL_CURVE) {
					pack_prim_index[pack_prim_index_offset] = bvh_prim_index[i] + mesh_curve_offset;
					pack_prim_tri_index[pack_prim_index_offset] = -1;
				}
				else {
					pack_prim_index[pack_prim_index_offset] = bvh_prim_index[i] + mesh_tri_offset;
					pack_prim_tri_index[pack_prim_index_offset] =
					bvh_prim_tri_index[i] + pack_prim_tri_verts_offset;
				}

				pack_prim_type[pack_prim_index_offset] = bvh_prim_type[i];
				pack_prim_object[pack_prim_index_offset] = 0;

				++pack_prim_index_offset;
			}
		}

		/* Merge triangle vertices data. */
		if(bvh->pack.prim_tri_verts.size()) {
			const size_t prim_tri_size = bvh->pack.prim_tri_verts.size();
			memcpy(pack_prim_tri_verts + pack_prim_tri_verts_offset,
				   &bvh->pack.prim_tri_verts[0],
				   prim_tri_size*sizeof(float4));
			pack_prim_tri_verts_offset += prim_tri_size;
		}

		prim_offset += bvh->pack.prim_index.size();
	}
}

void BVHEmbree::refit_nodes()
{
	/* Update all vertex buffers, then tell Embree to rebuild/-fit the BVHs. */
	unsigned geom_id = 0;
	foreach(Object *ob, objects) {
		if(!params.top_level || (ob->is_traceable() && !ob->mesh->is_instanced())) {
			if(params.primitive_mask & PRIMITIVE_ALL_TRIANGLE && ob->mesh->num_triangles() > 0) {
				update_tri_vertex_buffer(rtcGetGeometry(scene, geom_id), ob->mesh);
				rtcCommitGeometry(rtcGetGeometry(scene,geom_id));
			}

			if(params.primitive_mask & PRIMITIVE_ALL_CURVE && ob->mesh->num_curves() > 0) {
				update_curve_vertex_buffer(rtcGetGeometry(scene, geom_id+1), ob->mesh);
				rtcCommitGeometry(rtcGetGeometry(scene,geom_id+1));
			}
		}
		geom_id += 2;
	}
	rtcCommitScene(scene);
}
CCL_NAMESPACE_END

#endif  /* WITH_EMBREE */