d8223ffa75
That year should bring the long-awaited OpenGL ES 3.0 compatible renderer
with state-of-the-art rendering techniques tuned to work as low as middle
end handheld devices - without compromising with the possibilities given
for higher end desktop games of course. Great times ahead for the Godot
community and the gamers that will play our games!
(cherry picked from commit c7bc44d5ad)
804 lines
19 KiB
C++
804 lines
19 KiB
C++
/*************************************************************************/
|
|
/* broad_phase_2d_hash_grid.cpp */
|
|
/*************************************************************************/
|
|
/* This file is part of: */
|
|
/* GODOT ENGINE */
|
|
/* http://www.godotengine.org */
|
|
/*************************************************************************/
|
|
/* Copyright (c) 2007-2017 Juan Linietsky, Ariel Manzur. */
|
|
/* */
|
|
/* Permission is hereby granted, free of charge, to any person obtaining */
|
|
/* a copy of this software and associated documentation files (the */
|
|
/* "Software"), to deal in the Software without restriction, including */
|
|
/* without limitation the rights to use, copy, modify, merge, publish, */
|
|
/* distribute, sublicense, and/or sell copies of the Software, and to */
|
|
/* permit persons to whom the Software is furnished to do so, subject to */
|
|
/* the following conditions: */
|
|
/* */
|
|
/* The above copyright notice and this permission notice shall be */
|
|
/* included in all copies or substantial portions of the Software. */
|
|
/* */
|
|
/* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, */
|
|
/* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF */
|
|
/* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
|
|
/* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY */
|
|
/* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, */
|
|
/* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE */
|
|
/* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. */
|
|
/*************************************************************************/
|
|
#include "broad_phase_2d_hash_grid.h"
|
|
#include "globals.h"
|
|
|
|
#define LARGE_ELEMENT_FI 1.01239812
|
|
|
|
void BroadPhase2DHashGrid::_pair_attempt(Element *p_elem, Element* p_with) {
|
|
|
|
Map<Element*,PairData*>::Element *E=p_elem->paired.find(p_with);
|
|
|
|
ERR_FAIL_COND(p_elem->_static && p_with->_static);
|
|
|
|
if (!E) {
|
|
|
|
PairData *pd = memnew( PairData );
|
|
p_elem->paired[p_with]=pd;
|
|
p_with->paired[p_elem]=pd;
|
|
} else {
|
|
E->get()->rc++;
|
|
}
|
|
|
|
}
|
|
|
|
void BroadPhase2DHashGrid::_unpair_attempt(Element *p_elem, Element* p_with) {
|
|
|
|
Map<Element*,PairData*>::Element *E=p_elem->paired.find(p_with);
|
|
|
|
ERR_FAIL_COND(!E); //this should really be paired..
|
|
|
|
E->get()->rc--;
|
|
|
|
if (E->get()->rc==0) {
|
|
|
|
if (E->get()->colliding) {
|
|
//uncollide
|
|
if (unpair_callback) {
|
|
unpair_callback(p_elem->owner,p_elem->subindex,p_with->owner,p_with->subindex,E->get()->ud,unpair_userdata);
|
|
}
|
|
|
|
|
|
}
|
|
|
|
memdelete(E->get());
|
|
p_elem->paired.erase(E);
|
|
p_with->paired.erase(p_elem);
|
|
}
|
|
|
|
|
|
}
|
|
|
|
void BroadPhase2DHashGrid::_check_motion(Element *p_elem) {
|
|
|
|
for (Map<Element*,PairData*>::Element *E=p_elem->paired.front();E;E=E->next()) {
|
|
|
|
bool pairing = p_elem->aabb.intersects( E->key()->aabb );
|
|
|
|
if (pairing!=E->get()->colliding) {
|
|
|
|
if (pairing) {
|
|
|
|
if (pair_callback) {
|
|
E->get()->ud=pair_callback(p_elem->owner,p_elem->subindex,E->key()->owner,E->key()->subindex,pair_userdata);
|
|
}
|
|
} else {
|
|
|
|
if (unpair_callback) {
|
|
unpair_callback(p_elem->owner,p_elem->subindex,E->key()->owner,E->key()->subindex,E->get()->ud,unpair_userdata);
|
|
}
|
|
|
|
}
|
|
|
|
E->get()->colliding=pairing;
|
|
}
|
|
}
|
|
}
|
|
|
|
void BroadPhase2DHashGrid::_enter_grid( Element* p_elem, const Rect2& p_rect,bool p_static) {
|
|
|
|
|
|
|
|
Vector2 sz = (p_rect.size/cell_size*LARGE_ELEMENT_FI); //use magic number to avoid floating point issues
|
|
if (sz.width*sz.height > large_object_min_surface) {
|
|
//large object, do not use grid, must check against all elements
|
|
for (Map<ID,Element>::Element *E=element_map.front();E;E=E->next()) {
|
|
if (E->key()==p_elem->self)
|
|
continue; // do not pair against itself
|
|
if (E->get().owner == p_elem->owner)
|
|
continue;
|
|
if (E->get()._static && p_static)
|
|
continue;
|
|
|
|
_pair_attempt(p_elem,&E->get());
|
|
}
|
|
|
|
|
|
large_elements[p_elem].inc();
|
|
return;
|
|
}
|
|
|
|
Point2i from = (p_rect.pos/cell_size).floor();
|
|
Point2i to = ((p_rect.pos+p_rect.size)/cell_size).floor();
|
|
|
|
for(int i=from.x;i<=to.x;i++) {
|
|
|
|
|
|
for(int j=from.y;j<=to.y;j++) {
|
|
|
|
PosKey pk;
|
|
pk.x=i;
|
|
pk.y=j;
|
|
|
|
uint32_t idx = pk.hash() % hash_table_size;
|
|
PosBin *pb = hash_table[idx];
|
|
|
|
while (pb) {
|
|
|
|
if (pb->key == pk) {
|
|
break;
|
|
}
|
|
|
|
pb=pb->next;
|
|
}
|
|
|
|
|
|
bool entered=false;
|
|
|
|
if (!pb) {
|
|
//does not exist, create!
|
|
pb = memnew( PosBin );
|
|
pb->key=pk;
|
|
pb->next=hash_table[idx];
|
|
hash_table[idx]=pb;
|
|
}
|
|
|
|
|
|
|
|
if (p_static) {
|
|
if (pb->static_object_set[p_elem].inc()==1) {
|
|
entered=true;
|
|
}
|
|
} else {
|
|
if (pb->object_set[p_elem].inc()==1) {
|
|
|
|
entered=true;
|
|
}
|
|
}
|
|
|
|
if (entered) {
|
|
|
|
for(Map<Element*,RC>::Element *E=pb->object_set.front();E;E=E->next()) {
|
|
|
|
if (E->key()->owner==p_elem->owner)
|
|
continue;
|
|
_pair_attempt(p_elem,E->key());
|
|
}
|
|
|
|
if (!p_static) {
|
|
|
|
for(Map<Element*,RC>::Element *E=pb->static_object_set.front();E;E=E->next()) {
|
|
|
|
if (E->key()->owner==p_elem->owner)
|
|
continue;
|
|
_pair_attempt(p_elem,E->key());
|
|
}
|
|
}
|
|
}
|
|
|
|
}
|
|
|
|
}
|
|
|
|
//pair separatedly with large elements
|
|
|
|
for (Map<Element*,RC>::Element *E=large_elements.front();E;E=E->next()) {
|
|
|
|
if (E->key()==p_elem)
|
|
continue; // do not pair against itself
|
|
if (E->key()->owner == p_elem->owner)
|
|
continue;
|
|
if (E->key()->_static && p_static)
|
|
continue;
|
|
|
|
_pair_attempt(E->key(),p_elem);
|
|
}
|
|
|
|
}
|
|
|
|
|
|
void BroadPhase2DHashGrid::_exit_grid( Element* p_elem, const Rect2& p_rect,bool p_static) {
|
|
|
|
Vector2 sz = (p_rect.size/cell_size*LARGE_ELEMENT_FI);
|
|
if (sz.width*sz.height > large_object_min_surface) {
|
|
|
|
//unpair all elements, instead of checking all, just check what is already paired, so we at least save from checking static vs static
|
|
for (Map<Element*,PairData*>::Element *E=p_elem->paired.front();E;E=E->next()) {
|
|
|
|
_unpair_attempt(p_elem,E->key());
|
|
}
|
|
|
|
if (large_elements[p_elem].dec()==0) {
|
|
large_elements.erase(p_elem);
|
|
}
|
|
return;
|
|
}
|
|
|
|
|
|
Point2i from = (p_rect.pos/cell_size).floor();
|
|
Point2i to = ((p_rect.pos+p_rect.size)/cell_size).floor();
|
|
|
|
for(int i=from.x;i<=to.x;i++) {
|
|
|
|
for(int j=from.y;j<=to.y;j++) {
|
|
|
|
PosKey pk;
|
|
pk.x=i;
|
|
pk.y=j;
|
|
|
|
uint32_t idx = pk.hash() % hash_table_size;
|
|
PosBin *pb = hash_table[idx];
|
|
|
|
while (pb) {
|
|
|
|
if (pb->key == pk) {
|
|
break;
|
|
}
|
|
|
|
pb=pb->next;
|
|
}
|
|
|
|
ERR_CONTINUE(!pb); //should exist!!
|
|
|
|
bool exited=false;
|
|
|
|
|
|
if (p_static) {
|
|
if (pb->static_object_set[p_elem].dec()==0) {
|
|
|
|
pb->static_object_set.erase(p_elem);
|
|
exited=true;
|
|
|
|
}
|
|
} else {
|
|
if (pb->object_set[p_elem].dec()==0) {
|
|
|
|
pb->object_set.erase(p_elem);
|
|
exited=true;
|
|
|
|
}
|
|
}
|
|
|
|
if (exited) {
|
|
|
|
for(Map<Element*,RC>::Element *E=pb->object_set.front();E;E=E->next()) {
|
|
|
|
if (E->key()->owner==p_elem->owner)
|
|
continue;
|
|
_unpair_attempt(p_elem,E->key());
|
|
|
|
}
|
|
|
|
if (!p_static) {
|
|
|
|
for(Map<Element*,RC>::Element *E=pb->static_object_set.front();E;E=E->next()) {
|
|
|
|
if (E->key()->owner==p_elem->owner)
|
|
continue;
|
|
_unpair_attempt(p_elem,E->key());
|
|
}
|
|
}
|
|
}
|
|
|
|
if (pb->object_set.empty() && pb->static_object_set.empty()) {
|
|
|
|
if (hash_table[idx]==pb) {
|
|
hash_table[idx]=pb->next;
|
|
} else {
|
|
|
|
PosBin *px = hash_table[idx];
|
|
|
|
while (px) {
|
|
|
|
if (px->next==pb) {
|
|
px->next=pb->next;
|
|
break;
|
|
}
|
|
|
|
px=px->next;
|
|
}
|
|
|
|
ERR_CONTINUE(!px);
|
|
}
|
|
|
|
memdelete(pb);
|
|
|
|
}
|
|
}
|
|
|
|
}
|
|
|
|
|
|
for (Map<Element*,RC>::Element *E=large_elements.front();E;E=E->next()) {
|
|
if (E->key()==p_elem)
|
|
continue; // do not pair against itself
|
|
if (E->key()->owner == p_elem->owner)
|
|
continue;
|
|
if (E->key()->_static && p_static)
|
|
continue;
|
|
|
|
//unpair from large elements
|
|
_unpair_attempt(p_elem,E->key());
|
|
}
|
|
|
|
|
|
}
|
|
|
|
|
|
BroadPhase2DHashGrid::ID BroadPhase2DHashGrid::create(CollisionObject2DSW *p_object, int p_subindex) {
|
|
|
|
current++;
|
|
|
|
Element e;
|
|
e.owner=p_object;
|
|
e._static=false;
|
|
e.subindex=p_subindex;
|
|
e.self=current;
|
|
e.pass=0;
|
|
|
|
element_map[current]=e;
|
|
return current;
|
|
|
|
}
|
|
|
|
void BroadPhase2DHashGrid::move(ID p_id, const Rect2& p_aabb) {
|
|
|
|
|
|
Map<ID,Element>::Element *E=element_map.find(p_id);
|
|
ERR_FAIL_COND(!E);
|
|
|
|
Element &e=E->get();
|
|
|
|
if (p_aabb==e.aabb)
|
|
return;
|
|
|
|
|
|
if (p_aabb!=Rect2()) {
|
|
|
|
_enter_grid(&e,p_aabb,e._static);
|
|
}
|
|
|
|
if (e.aabb!=Rect2()) {
|
|
|
|
_exit_grid(&e,e.aabb,e._static);
|
|
}
|
|
|
|
e.aabb=p_aabb;
|
|
|
|
_check_motion(&e);
|
|
|
|
e.aabb=p_aabb;
|
|
|
|
}
|
|
void BroadPhase2DHashGrid::set_static(ID p_id, bool p_static) {
|
|
|
|
Map<ID,Element>::Element *E=element_map.find(p_id);
|
|
ERR_FAIL_COND(!E);
|
|
|
|
Element &e=E->get();
|
|
|
|
if (e._static==p_static)
|
|
return;
|
|
|
|
if (e.aabb!=Rect2())
|
|
_exit_grid(&e,e.aabb,e._static);
|
|
|
|
e._static=p_static;
|
|
|
|
if (e.aabb!=Rect2()) {
|
|
_enter_grid(&e,e.aabb,e._static);
|
|
_check_motion(&e);
|
|
}
|
|
|
|
}
|
|
void BroadPhase2DHashGrid::remove(ID p_id) {
|
|
|
|
Map<ID,Element>::Element *E=element_map.find(p_id);
|
|
ERR_FAIL_COND(!E);
|
|
|
|
Element &e=E->get();
|
|
|
|
if (e.aabb!=Rect2())
|
|
_exit_grid(&e,e.aabb,e._static);
|
|
|
|
element_map.erase(p_id);
|
|
|
|
}
|
|
|
|
CollisionObject2DSW *BroadPhase2DHashGrid::get_object(ID p_id) const {
|
|
|
|
const Map<ID,Element>::Element *E=element_map.find(p_id);
|
|
ERR_FAIL_COND_V(!E,NULL);
|
|
return E->get().owner;
|
|
|
|
}
|
|
bool BroadPhase2DHashGrid::is_static(ID p_id) const {
|
|
|
|
const Map<ID,Element>::Element *E=element_map.find(p_id);
|
|
ERR_FAIL_COND_V(!E,false);
|
|
return E->get()._static;
|
|
|
|
}
|
|
int BroadPhase2DHashGrid::get_subindex(ID p_id) const {
|
|
|
|
const Map<ID,Element>::Element *E=element_map.find(p_id);
|
|
ERR_FAIL_COND_V(!E,-1);
|
|
return E->get().subindex;
|
|
}
|
|
|
|
template<bool use_aabb,bool use_segment>
|
|
void BroadPhase2DHashGrid::_cull(const Point2i p_cell,const Rect2& p_aabb,const Point2& p_from, const Point2& p_to,CollisionObject2DSW** p_results,int p_max_results,int *p_result_indices,int &index) {
|
|
|
|
|
|
PosKey pk;
|
|
pk.x=p_cell.x;
|
|
pk.y=p_cell.y;
|
|
|
|
uint32_t idx = pk.hash() % hash_table_size;
|
|
PosBin *pb = hash_table[idx];
|
|
|
|
while (pb) {
|
|
|
|
if (pb->key == pk) {
|
|
break;
|
|
}
|
|
|
|
pb=pb->next;
|
|
}
|
|
|
|
if (!pb)
|
|
return;
|
|
|
|
|
|
|
|
for(Map<Element*,RC>::Element *E=pb->object_set.front();E;E=E->next()) {
|
|
|
|
|
|
if (index>=p_max_results)
|
|
break;
|
|
if (E->key()->pass==pass)
|
|
continue;
|
|
|
|
E->key()->pass=pass;
|
|
|
|
if (use_aabb && !p_aabb.intersects(E->key()->aabb))
|
|
continue;
|
|
|
|
if (use_segment && !E->key()->aabb.intersects_segment(p_from,p_to))
|
|
continue;
|
|
|
|
p_results[index]=E->key()->owner;
|
|
p_result_indices[index]=E->key()->subindex;
|
|
index++;
|
|
|
|
|
|
}
|
|
|
|
for(Map<Element*,RC>::Element *E=pb->static_object_set.front();E;E=E->next()) {
|
|
|
|
|
|
if (index>=p_max_results)
|
|
break;
|
|
if (E->key()->pass==pass)
|
|
continue;
|
|
|
|
if (use_aabb && !p_aabb.intersects(E->key()->aabb)) {
|
|
continue;
|
|
}
|
|
|
|
if (use_segment && !E->key()->aabb.intersects_segment(p_from,p_to))
|
|
continue;
|
|
|
|
E->key()->pass=pass;
|
|
p_results[index]=E->key()->owner;
|
|
p_result_indices[index]=E->key()->subindex;
|
|
index++;
|
|
|
|
}
|
|
}
|
|
|
|
int BroadPhase2DHashGrid::cull_segment(const Vector2& p_from, const Vector2& p_to,CollisionObject2DSW** p_results,int p_max_results,int *p_result_indices) {
|
|
|
|
pass++;
|
|
|
|
Vector2 dir = (p_to-p_from);
|
|
if (dir==Vector2())
|
|
return 0;
|
|
//avoid divisions by zero
|
|
dir.normalize();
|
|
if (dir.x==0.0)
|
|
dir.x=0.000001;
|
|
if (dir.y==0.0)
|
|
dir.y=0.000001;
|
|
Vector2 delta = dir.abs();
|
|
|
|
delta.x=cell_size/delta.x;
|
|
delta.y=cell_size/delta.y;
|
|
|
|
Point2i pos = (p_from/cell_size).floor();
|
|
Point2i end = (p_to/cell_size).floor();
|
|
|
|
Point2i step = Vector2( SGN(dir.x), SGN(dir.y) );
|
|
|
|
Vector2 max;
|
|
|
|
if (dir.x<0)
|
|
max.x= (Math::floor(pos.x)*cell_size - p_from.x) / dir.x;
|
|
else
|
|
max.x= (Math::floor(pos.x + 1)*cell_size - p_from.x) / dir.x;
|
|
|
|
if (dir.y<0)
|
|
max.y= (Math::floor(pos.y)*cell_size - p_from.y) / dir.y;
|
|
else
|
|
max.y= (Math::floor(pos.y + 1)*cell_size - p_from.y) / dir.y;
|
|
|
|
int cullcount=0;
|
|
_cull<false,true>(pos,Rect2(),p_from,p_to,p_results,p_max_results,p_result_indices,cullcount);
|
|
|
|
bool reached_x=false;
|
|
bool reached_y=false;
|
|
|
|
while(true) {
|
|
|
|
if (max.x < max.y) {
|
|
|
|
max.x+=delta.x;
|
|
pos.x+=step.x;
|
|
} else {
|
|
|
|
max.y+=delta.y;
|
|
pos.y+=step.y;
|
|
|
|
}
|
|
|
|
if (step.x>0) {
|
|
if (pos.x>=end.x)
|
|
reached_x=true;
|
|
} else if (pos.x<=end.x) {
|
|
|
|
reached_x=true;
|
|
}
|
|
|
|
if (step.y>0) {
|
|
if (pos.y>=end.y)
|
|
reached_y=true;
|
|
} else if (pos.y<=end.y) {
|
|
|
|
reached_y=true;
|
|
}
|
|
|
|
_cull<false,true>(pos,Rect2(),p_from,p_to,p_results,p_max_results,p_result_indices,cullcount);
|
|
|
|
if (reached_x && reached_y)
|
|
break;
|
|
|
|
}
|
|
|
|
for (Map<Element*,RC>::Element *E=large_elements.front();E;E=E->next()) {
|
|
|
|
if (cullcount>=p_max_results)
|
|
break;
|
|
if (E->key()->pass==pass)
|
|
continue;
|
|
|
|
E->key()->pass=pass;
|
|
|
|
// if (use_aabb && !p_aabb.intersects(E->key()->aabb))
|
|
// continue;
|
|
|
|
if (!E->key()->aabb.intersects_segment(p_from,p_to))
|
|
continue;
|
|
|
|
p_results[cullcount]=E->key()->owner;
|
|
p_result_indices[cullcount]=E->key()->subindex;
|
|
cullcount++;
|
|
|
|
|
|
}
|
|
|
|
return cullcount;
|
|
}
|
|
|
|
|
|
int BroadPhase2DHashGrid::cull_aabb(const Rect2& p_aabb,CollisionObject2DSW** p_results,int p_max_results,int *p_result_indices) {
|
|
|
|
pass++;
|
|
|
|
Point2i from = (p_aabb.pos/cell_size).floor();
|
|
Point2i to = ((p_aabb.pos+p_aabb.size)/cell_size).floor();
|
|
int cullcount=0;
|
|
|
|
for(int i=from.x;i<=to.x;i++) {
|
|
|
|
for(int j=from.y;j<=to.y;j++) {
|
|
|
|
_cull<true,false>(Point2i(i,j),p_aabb,Point2(),Point2(),p_results,p_max_results,p_result_indices,cullcount);
|
|
}
|
|
|
|
}
|
|
|
|
for (Map<Element*,RC>::Element *E=large_elements.front();E;E=E->next()) {
|
|
|
|
if (cullcount>=p_max_results)
|
|
break;
|
|
if (E->key()->pass==pass)
|
|
continue;
|
|
|
|
E->key()->pass=pass;
|
|
|
|
if (!p_aabb.intersects(E->key()->aabb))
|
|
continue;
|
|
|
|
// if (!E->key()->aabb.intersects_segment(p_from,p_to))
|
|
// continue;
|
|
|
|
p_results[cullcount]=E->key()->owner;
|
|
p_result_indices[cullcount]=E->key()->subindex;
|
|
cullcount++;
|
|
|
|
|
|
}
|
|
return cullcount;
|
|
}
|
|
|
|
void BroadPhase2DHashGrid::set_pair_callback(PairCallback p_pair_callback,void *p_userdata) {
|
|
|
|
pair_callback=p_pair_callback;
|
|
pair_userdata=p_userdata;
|
|
|
|
}
|
|
void BroadPhase2DHashGrid::set_unpair_callback(UnpairCallback p_unpair_callback,void *p_userdata) {
|
|
|
|
unpair_callback=p_unpair_callback;
|
|
unpair_userdata=p_userdata;
|
|
|
|
}
|
|
|
|
void BroadPhase2DHashGrid::update() {
|
|
|
|
|
|
}
|
|
|
|
BroadPhase2DSW *BroadPhase2DHashGrid::_create() {
|
|
|
|
return memnew( BroadPhase2DHashGrid );
|
|
}
|
|
|
|
|
|
BroadPhase2DHashGrid::BroadPhase2DHashGrid() {
|
|
|
|
hash_table_size = GLOBAL_DEF("physics_2d/bp_hash_table_size",4096);
|
|
hash_table_size = Math::larger_prime(hash_table_size);
|
|
hash_table = memnew_arr( PosBin*, hash_table_size);
|
|
|
|
cell_size = GLOBAL_DEF("physics_2d/cell_size",128);
|
|
large_object_min_surface = GLOBAL_DEF("physics_2d/large_object_surface_treshold_in_cells",512);
|
|
|
|
for(int i=0;i<hash_table_size;i++)
|
|
hash_table[i]=NULL;
|
|
pass=1;
|
|
|
|
current=0;
|
|
}
|
|
|
|
BroadPhase2DHashGrid::~BroadPhase2DHashGrid() {
|
|
|
|
for(int i=0;i<hash_table_size;i++) {
|
|
while(hash_table[i]) {
|
|
PosBin *pb=hash_table[i];
|
|
hash_table[i]=pb->next;
|
|
memdelete(pb);
|
|
}
|
|
}
|
|
|
|
memdelete_arr( hash_table );
|
|
|
|
|
|
}
|
|
|
|
|
|
|
|
/* 3D version of voxel traversal:
|
|
|
|
public IEnumerable<Point3D> GetCellsOnRay(Ray ray, int maxDepth)
|
|
{
|
|
// Implementation is based on:
|
|
// "A Fast Voxel Traversal Algorithm for Ray Tracing"
|
|
// John Amanatides, Andrew Woo
|
|
// http://www.cse.yorku.ca/~amana/research/grid.pdf
|
|
// http://www.devmaster.net/articles/raytracing_series/A%20faster%20voxel%20traversal%20algorithm%20for%20ray%20tracing.pdf
|
|
|
|
// NOTES:
|
|
// * This code assumes that the ray's position and direction are in 'cell coordinates', which means
|
|
// that one unit equals one cell in all directions.
|
|
// * When the ray doesn't start within the voxel grid, calculate the first position at which the
|
|
// ray could enter the grid. If it never enters the grid, there is nothing more to do here.
|
|
// * Also, it is important to test when the ray exits the voxel grid when the grid isn't infinite.
|
|
// * The Point3D structure is a simple structure having three integer fields (X, Y and Z).
|
|
|
|
// The cell in which the ray starts.
|
|
Point3D start = GetCellAt(ray.Position); // Rounds the position's X, Y and Z down to the nearest integer values.
|
|
int x = start.X;
|
|
int y = start.Y;
|
|
int z = start.Z;
|
|
|
|
// Determine which way we go.
|
|
int stepX = Math.Sign(ray.Direction.X);
|
|
int stepY = Math.Sign(ray.Direction.Y);
|
|
int stepZ = Math.Sign(ray.Direction.Z);
|
|
|
|
// Calculate cell boundaries. When the step (i.e. direction sign) is positive,
|
|
// the next boundary is AFTER our current position, meaning that we have to add 1.
|
|
// Otherwise, it is BEFORE our current position, in which case we add nothing.
|
|
Point3D cellBoundary = new Point3D(
|
|
x + (stepX > 0 ? 1 : 0),
|
|
y + (stepY > 0 ? 1 : 0),
|
|
z + (stepZ > 0 ? 1 : 0));
|
|
|
|
// NOTE: For the following calculations, the result will be Single.PositiveInfinity
|
|
// when ray.Direction.X, Y or Z equals zero, which is OK. However, when the left-hand
|
|
// value of the division also equals zero, the result is Single.NaN, which is not OK.
|
|
|
|
// Determine how far we can travel along the ray before we hit a voxel boundary.
|
|
Vector3 tMax = new Vector3(
|
|
(cellBoundary.X - ray.Position.X) / ray.Direction.X, // Boundary is a plane on the YZ axis.
|
|
(cellBoundary.Y - ray.Position.Y) / ray.Direction.Y, // Boundary is a plane on the XZ axis.
|
|
(cellBoundary.Z - ray.Position.Z) / ray.Direction.Z); // Boundary is a plane on the XY axis.
|
|
if (Single.IsNaN(tMax.X)) tMax.X = Single.PositiveInfinity;
|
|
if (Single.IsNaN(tMax.Y)) tMax.Y = Single.PositiveInfinity;
|
|
if (Single.IsNaN(tMax.Z)) tMax.Z = Single.PositiveInfinity;
|
|
|
|
// Determine how far we must travel along the ray before we have crossed a gridcell.
|
|
Vector3 tDelta = new Vector3(
|
|
stepX / ray.Direction.X, // Crossing the width of a cell.
|
|
stepY / ray.Direction.Y, // Crossing the height of a cell.
|
|
stepZ / ray.Direction.Z); // Crossing the depth of a cell.
|
|
if (Single.IsNaN(tDelta.X)) tDelta.X = Single.PositiveInfinity;
|
|
if (Single.IsNaN(tDelta.Y)) tDelta.Y = Single.PositiveInfinity;
|
|
if (Single.IsNaN(tDelta.Z)) tDelta.Z = Single.PositiveInfinity;
|
|
|
|
// For each step, determine which distance to the next voxel boundary is lowest (i.e.
|
|
// which voxel boundary is nearest) and walk that way.
|
|
for (int i = 0; i < maxDepth; i++)
|
|
{
|
|
// Return it.
|
|
yield return new Point3D(x, y, z);
|
|
|
|
// Do the next step.
|
|
if (tMax.X < tMax.Y && tMax.X < tMax.Z)
|
|
{
|
|
// tMax.X is the lowest, an YZ cell boundary plane is nearest.
|
|
x += stepX;
|
|
tMax.X += tDelta.X;
|
|
}
|
|
else if (tMax.Y < tMax.Z)
|
|
{
|
|
// tMax.Y is the lowest, an XZ cell boundary plane is nearest.
|
|
y += stepY;
|
|
tMax.Y += tDelta.Y;
|
|
}
|
|
else
|
|
{
|
|
// tMax.Z is the lowest, an XY cell boundary plane is nearest.
|
|
z += stepZ;
|
|
tMax.Z += tDelta.Z;
|
|
}
|
|
}
|
|
|
|
*/
|