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Streamline shadowcasting implementation
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@kevingranade
kevingranade committed Sep 26, 2020
1 parent 7132d06 commit 5f1f318
Showing 1 changed file with 34 additions and 59 deletions.
93 changes: 34 additions & 59 deletions src/shadowcasting.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2,12 +2,12 @@

#include <list>

#include "cached_options.h"
#include "cuboid_rectangle.h"
#include "enums.h"
#include "fragment_cloud.h" // IWYU pragma: keep
#include "line.h"

extern int fov_3d_z_range;

struct slope {
slope( int_least8_t rise, int_least8_t run ) {
// Ensure run is always positive for the inequality operators
Expand All @@ -25,32 +25,20 @@ struct slope {
int_least8_t run;
};

inline bool operator<( const slope &lhs, const slope &rhs )
static bool operator<( const slope &lhs, const slope &rhs )
{
// a/b < c/d <=> a*d < c*b if b and d have the same sign.
return lhs.rise * rhs.run < rhs.rise * lhs.run;
}
inline bool operator>( const slope &lhs, const slope &rhs )
static bool operator>( const slope &lhs, const slope &rhs )
{
return rhs < lhs;
}
inline bool operator<=( const slope &lhs, const slope &rhs )
{
return !( lhs > rhs );
}
inline bool operator>=( const slope &lhs, const slope &rhs )
{
return !( lhs < rhs );
}
inline bool operator==( const slope &lhs, const slope &rhs )
static bool operator==( const slope &lhs, const slope &rhs )
{
// a/b == c/d <=> a*d == c*b
return lhs.rise * rhs.run == rhs.rise * lhs.run;
}
inline bool operator!=( const slope &lhs, const slope &rhs )
{
return !( lhs == rhs );
}

template<typename T>
struct span {
Expand Down Expand Up @@ -169,8 +157,8 @@ void cast_horizontal_zlight_segment(
slope new_start_minor( 1, 1 );

T last_intensity = 0.0;
tripoint delta( 0, 0, 0 );
tripoint current( 0, 0, 0 );
tripoint delta;
tripoint current;

// We start out with one span covering the entire horizontal and vertical space
// we are interested in. Then as changes in transparency are encountered, we truncate
Expand All @@ -192,6 +180,22 @@ void cast_horizontal_zlight_segment(
bool started_block = false;
// TODO: Precalculate min/max delta.z based on start/end and distance
for( delta.z = 0; delta.z <= distance; delta.z++ ) {
// Shadowcasting sweeps from the cardinal to the most extreme edge of the octant
// XXXX
// --->
// XXX
// -->
// XX
// ->
// X
// @
//
// Trailing edge -> +-
// |+| <- Center of tile
// -+ <- Leading Edge
// Direction of sweep --->
// Use corners of given tile as above to determine angles of
// leading and trailing edges being considered.
const slope trailing_edge_major( delta.z * 2 - 1, delta.y * 2 + 1 );
const slope leading_edge_major( delta.z * 2 + 1, delta.y * 2 - 1 );
current.z = offset.z + delta.z * z_transform;
Expand Down Expand Up @@ -222,27 +226,12 @@ void cast_horizontal_zlight_segment(
for( delta.x = 0; delta.x <= distance; delta.x++ ) {
current.x = offset.x + delta.x * xx_transform + delta.y * xy_transform;
current.y = offset.y + delta.x * yx_transform + delta.y * yy_transform;
// Shadowcasting sweeps from the cardinal to the most extreme edge of the octant
// XXXX
// --->
// XXX
// -->
// XX
// ->
// X
// @
//
// Trailing edge -> +-
// |+| <- Center of tile
// -+ <- Leading Edge
// Direction of sweep --->
// Use corners of given tile as above to determine angles of
// leading and trailing edges being considered.
// See definition of trailing_edge_major and leading_edge_major for clarification.
const slope trailing_edge_minor( delta.x * 2 - 1, delta.y * 2 + 1 );
const slope leading_edge_minor( delta.x * 2 + 1, delta.y * 2 - 1 );
static half_open_rectangle<point> bounds( point_zero, point( MAPSIZE_X, MAPSIZE_Y ) );

if( current.x < 0 || current.x >= MAPSIZE_X ||
current.y < 0 || current.y >= MAPSIZE_Y ) {
if( !bounds.contains( current.xy() ) ) {
// Current tile is out of bounds, advance to the next tile.
continue;
} else if( this_span->start_minor > leading_edge_minor ) {
Expand All @@ -257,10 +246,11 @@ void cast_horizontal_zlight_segment(

// If we're looking at a tile with floor or roof from the floor/roof side,
// that tile is actually invisible to us.
// TODO: Revisit this logic and differentiate between "can see bottom of tile"
// and "can see majority of tile".
bool floor_block = false;
if( current.z < offset.z ) {
if( z_index < ( OVERMAP_LAYERS - 1 ) &&
( *floor_caches[z_index + 1] )[current.x][current.y] ) {
if( ( *floor_caches[z_index + 1] )[current.x][current.y] ) {
floor_block = true;
new_transparency = LIGHT_TRANSPARENCY_SOLID;
}
Expand Down Expand Up @@ -351,8 +341,8 @@ void cast_vertical_zlight_segment(

T last_intensity = 0.0;
static constexpr tripoint origin( 0, 0, 0 );
tripoint delta( 0, 0, 0 );
tripoint current( 0, 0, 0 );
tripoint delta;
tripoint current;

// We start out with one span covering the entire horizontal and vertical space
// we are interested in. Then as changes in transparency are encountered, we truncate
Expand All @@ -373,6 +363,7 @@ void cast_vertical_zlight_segment(
for( auto this_span = spans.begin(); this_span != spans.end(); ) {
bool started_block = false;
for( delta.y = 0; delta.y <= distance; delta.y++ ) {
// See comment above trailing_edge_major and leading_edge_major in above function.
const slope trailing_edge_major( delta.y * 2 - 1, delta.z * 2 + 1 );
const slope leading_edge_major( delta.y * 2 + 1, delta.z * 2 - 1 );
current.y = offset.y + delta.y * y_transform;
Expand Down Expand Up @@ -402,22 +393,7 @@ void cast_vertical_zlight_segment(
for( delta.x = 0; delta.x <= distance; delta.x++ ) {
current.x = offset.x + delta.x * x_transform;
current.z = offset.z + delta.z * z_transform;
// Shadowcasting sweeps from the cardinal to the most extreme edge of the octant
// XXXX
// --->
// XXX
// -->
// XX
// ->
// X
// @
//
// Trailing edge -> +-
// |+| <- Center of tile
// -+ <- Leading Edge
// Direction of sweep --->
// Use corners of given tile as above to determine angles of
// leading and trailing edges being considered.
// See comment above trailing_edge_major and leading_edge_major in above function.
const slope trailing_edge_minor( delta.x * 2 - 1, delta.z * 2 + 1 );
const slope leading_edge_minor( delta.x * 2 + 1, delta.z * 2 - 1 );

Expand All @@ -441,8 +417,7 @@ void cast_vertical_zlight_segment(
// that tile is actually invisible to us.
bool floor_block = false;
if( current.z < offset.z ) {
if( z_index < ( OVERMAP_LAYERS - 1 ) &&
( *floor_caches[z_index + 1] )[current.x][current.y] ) {
if( ( *floor_caches[z_index + 1] )[current.x][current.y] ) {
floor_block = true;
new_transparency = LIGHT_TRANSPARENCY_SOLID;
}
Expand Down

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