bvh_packet_traversal.cpp

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/*
 * This program source code file is part of KiCad, a free EDA CAD application.
 *
 * Copyright (C) 2015-2016 Mario Luzeiro <[email protected]>
 * Copyright (C) 2015-2020 KiCad Developers, see AUTHORS.txt for contributors.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, you may find one here:
 * http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
 * or you may search the http://www.gnu.org website for the version 2 license,
 * or you may write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
 */

#include "bvh_pbrt.h"


#define BVH_RANGED_TRAVERSAL
//#define BVH_PARTITION_TRAVERSAL


#define MAX_TODOS 64


struct StackNode
{
 int cell;
 unsigned int ia; // Index to the first alive ray
};


static inline unsigned int getFirstHit( const RAYPACKET& aRayPacket, const BBOX_3D& aBBox,
 unsigned int ia, HITINFO_PACKET* aHitInfoPacket )
{
 float hitT;

 if( aBBox.Intersect( aRayPacket.m_ray[ia], &hitT )
 && ( hitT < aHitInfoPacket[ia].m_HitInfo.m_tHit ) )
 return ia;

 if( !aRayPacket.m_Frustum.Intersect( aBBox ) )
 return RAYPACKET_RAYS_PER_PACKET;

 for( unsigned int i = ia + 1; i < RAYPACKET_RAYS_PER_PACKET; ++i )
 {
 if( aBBox.Intersect( aRayPacket.m_ray[i], &hitT )
 && ( hitT < aHitInfoPacket[i].m_HitInfo.m_tHit ) )
 return i;
 }

 return RAYPACKET_RAYS_PER_PACKET;
}


#ifdef BVH_RANGED_TRAVERSAL

static inline unsigned int getLastHit( const RAYPACKET& aRayPacket, const BBOX_3D& aBBox,
 unsigned int ia, HITINFO_PACKET* aHitInfoPacket )
{
 for( unsigned int ie = (RAYPACKET_RAYS_PER_PACKET - 1); ie > ia; --ie )
 {
 float hitT;

 if( aBBox.Intersect( aRayPacket.m_ray[ie], &hitT )
 && ( hitT < aHitInfoPacket[ie].m_HitInfo.m_tHit ) )
 return ie + 1;
 }

 return ia + 1;
}


// "Large Ray Packets for Real-time Whitted Ray Tracing"
// http://cseweb.ucsd.edu/~ravir/whitted.pdf

// Ranged Traversal
bool BVH_PBRT::Intersect( const RAYPACKET& aRayPacket, HITINFO_PACKET* aHitInfoPacket ) const
{
 if( m_nodes == nullptr )
 return false;

 if( &m_nodes[0] == nullptr )
 return false;

 bool anyHit = false;
 int todoOffset = 0, nodeNum = 0;
 StackNode todo[MAX_TODOS];

 unsigned int ia = 0;

 while( true )
 {
 const LinearBVHNode *curCell = &m_nodes[nodeNum];

 ia = getFirstHit( aRayPacket, curCell->bounds, ia, aHitInfoPacket );

 if( ia < RAYPACKET_RAYS_PER_PACKET )
 {
 if( curCell->nPrimitives == 0 )
 {
 StackNode& node = todo[todoOffset++];
 node.cell = curCell->secondChildOffset;
 node.ia = ia;
 nodeNum = nodeNum + 1;
 continue;
 }
 else
 {
 const unsigned int ie = getLastHit( aRayPacket, curCell->bounds, ia,
 aHitInfoPacket );

 for( int j = 0; j < curCell->nPrimitives; ++j )
 {
 const OBJECT_3D* obj = m_primitives[curCell->primitivesOffset + j];

 if( aRayPacket.m_Frustum.Intersect( obj->GetBBox() ) )
 {
 for( unsigned int i = ia; i < ie; ++i )
 {
 const bool hit = obj->Intersect( aRayPacket.m_ray[i],
 aHitInfoPacket[i].m_HitInfo );

 if( hit )
 {
 anyHit |= hit;
 aHitInfoPacket[i].m_hitresult |= hit;
 aHitInfoPacket[i].m_HitInfo.m_acc_node_info = nodeNum;
 }
 }
 }
 }
 }
 }

 if( todoOffset == 0 )
 break;

 const StackNode& node = todo[--todoOffset];

 nodeNum = node.cell;
 ia = node.ia;
 }

 return anyHit;

}
#endif


// "Ray Tracing Deformable Scenes Using Dynamic Bounding Volume Hierarchies"
// http://www.cs.cmu.edu/afs/cs/academic/class/15869-f11/www/readings/wald07_packetbvh.pdf

#ifdef BVH_PARTITION_TRAVERSAL

static inline unsigned int getLastHit( const RAYPACKET& aRayPacket, const BBOX_3D& aBBox,
 unsigned int ia, const unsigned int* aRayIndex,
 HITINFO_PACKET* aHitInfoPacket )
{
 for( unsigned int ie = (RAYPACKET_RAYS_PER_PACKET - 1); ie > ia; --ie )
 {
 float hitT;

 if( aBBox.Intersect( aRayPacket.m_ray[ aRayIndex[ie] ], &hitT )
 && ( hitT < aHitInfoPacket[ aRayIndex[ie] ].m_HitInfo.m_tHit ) )
 return ie + 1;
 }

 return ia + 1;
}


static inline unsigned int partRays( const RAYPACKET& aRayPacket, const BBOX_3D& aBBox,
 unsigned int ia, unsigned int* aRayIndex,
 HITINFO_PACKET* aHitInfoPacket )
{

 if( !aRayPacket.m_Frustum.Intersect( aBBox ) )
 return RAYPACKET_RAYS_PER_PACKET;

 unsigned int ie = 0;

 for( unsigned int i = 0; i < ia; ++i )
 {
 float hitT;

 if( aBBox.Intersect( aRayPacket.m_ray[ aRayIndex[i] ], &hitT )
 && ( hitT < aHitInfoPacket[ aRayIndex[i] ].m_HitInfo.m_tHit ) )
 std::swap( aRayIndex[ie++], aRayIndex[i] );
 }

 return ie;
}


bool BVH_PBRT::Intersect( const RAYPACKET& aRayPacket, HITINFO_PACKET* aHitInfoPacket ) const
{
 bool anyHit = false;
 int todoOffset = 0, nodeNum = 0;
 StackNode todo[MAX_TODOS];

 unsigned int I[RAYPACKET_RAYS_PER_PACKET];

 memcpy( I, m_I, RAYPACKET_RAYS_PER_PACKET * sizeof( unsigned int ) );

 unsigned int ia = 0;

 while( true )
 {
 const LinearBVHNode *curCell = &m_nodes[nodeNum];

 ia = partRays( aRayPacket, curCell->bounds, ia, I, aHitInfoPacket );

 if( ia < RAYPACKET_RAYS_PER_PACKET )
 {
 if( curCell->nPrimitives == 0 )
 {
 StackNode& node = todo[todoOffset++];
 node.cell = curCell->secondChildOffset;
 node.ia = ia;
 nodeNum = nodeNum + 1;
 continue;
 }
 else
 {
 unsigned int ie = getLastHit( aRayPacket, curCell->bounds, ia, I,
 aHitInfoPacket );

 for( int j = 0; j < curCell->nPrimitives; ++j )
 {
 const OBJECT_3D* obj = m_primitives[curCell->primitivesOffset + j];

 if( aRayPacket.m_Frustum.Intersect( obj->GetBBox() ) )
 {
 for( unsigned int i = 0; i < ie; ++i )
 {
 unsigned int idx = I[i];

 bool hit = obj->Intersect( aRayPacket.m_ray[idx],
 aHitInfoPacket[idx].m_HitInfo );

 if( hit )
 {
  anyHit |= hit;
 aHitInfoPacket[idx].m_hitresult |= hit;
 aHitInfoPacket[idx].m_HitInfo.m_acc_node_info = nodeNum;
 }
 }
 }
 }
 }
 }

 if( todoOffset == 0 )
 break;

 const StackNode& node = todo[--todoOffset];

 nodeNum = node.cell;
 ia = node.ia;
 }

 return anyHit;
}
#endif