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author
mhugent
committedJan 27, 2011
Use 'fast clip' line clipping algorithm for long lines. Huge improvement for wms benchmark performance (long contour lines)
git-svn-id: http://svn.osgeo.org/qgis/trunk/qgis@15090 c8812cc2-4d05-0410-92ff-de0c093fc19c
·
final-1_7_1final-1_7_0
1 parent 9e12afe commit c0b6f68

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3 files changed

+666
-13
lines changed

3 files changed

+666
-13
lines changed
 

‎src/core/qgsclipper.cpp

Lines changed: 168 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -35,3 +35,171 @@ const double QgsClipper::MAX_Y = 16000;
3535
const double QgsClipper::MIN_Y = -16000;
3636

3737
const double QgsClipper::SMALL_NUM = 1e-12;
38+
39+
unsigned char* QgsClipper::clippedLineWKB( unsigned char* wkb, const QgsRectangle& clipExtent, QPolygonF& line )
40+
{
41+
wkb++; // jump over endian info
42+
unsigned int wkbType = *(( int* ) wkb );
43+
wkb += sizeof( unsigned int );
44+
unsigned int nPoints = *(( int* ) wkb );
45+
wkb += sizeof( unsigned int );
46+
47+
bool hasZValue = ( wkbType == QGis::WKBLineString25D );
48+
49+
double p0x, p0y, p1x, p1y; //original coordinates
50+
double p1x_c, p1y_c; //clipped end coordinates
51+
double lastClipX, lastClipY; //last successfully clipped coords
52+
53+
line.reserve( nPoints + 1 );
54+
line.clear();
55+
56+
for ( unsigned int i = 0; i < nPoints; ++i )
57+
{
58+
if ( i == 0 )
59+
{
60+
memcpy( &p1x, wkb, sizeof( double ) );
61+
wkb += sizeof( double );
62+
memcpy( &p1y, wkb, sizeof( double ) );
63+
wkb += sizeof( double );
64+
if ( hasZValue ) // ignore Z value
65+
{
66+
wkb += sizeof( double );
67+
}
68+
continue;
69+
}
70+
else
71+
{
72+
p0x = p1x;
73+
p0y = p1y;
74+
75+
memcpy( &p1x, wkb, sizeof( double ) );
76+
wkb += sizeof( double );
77+
memcpy( &p1y, wkb, sizeof( double ) );
78+
wkb += sizeof( double );
79+
if ( hasZValue ) // ignore Z value
80+
{
81+
wkb += sizeof( double );
82+
}
83+
84+
p1x_c = p1x; p1y_c = p1y;
85+
if ( clipLineSegment( clipExtent.xMinimum(), clipExtent.xMaximum(), clipExtent.yMinimum(), clipExtent.yMaximum(),
86+
p0x, p0y, p1x_c, p1y_c ) )
87+
{
88+
bool newLine = line.size() > 0 && ( p1x_c != lastClipX || p1y_c != lastClipY );
89+
if ( newLine )
90+
{
91+
//add edge points to connect old and new line
92+
connectSeparatedLines( lastClipX, lastClipY, p0x, p0y, clipExtent, line );
93+
}
94+
if ( line.size() < 1 || newLine )
95+
{
96+
//add first point
97+
line << QPointF( p0x, p0y );
98+
}
99+
100+
//add second point
101+
lastClipX = p1x_c; lastClipY = p1y_c;
102+
line << QPointF( p1x_c, p1y_c );
103+
}
104+
}
105+
}
106+
return wkb;
107+
}
108+
109+
void QgsClipper::connectSeparatedLines( double x0, double y0, double x1, double y1,
110+
const QgsRectangle& clipRect, QPolygonF& pts )
111+
{
112+
//test the different edge combinations...
113+
if ( doubleNear( x0, clipRect.xMinimum() ) )
114+
{
115+
if ( doubleNear( x1, clipRect.xMinimum() ) )
116+
{
117+
return;
118+
}
119+
else if ( doubleNear( y1, clipRect.yMaximum() ) )
120+
{
121+
pts << QPointF( clipRect.xMinimum(), clipRect.yMaximum() );
122+
return;
123+
}
124+
else if ( doubleNear( x1, clipRect.xMaximum() ) )
125+
{
126+
pts << QPointF( clipRect.xMinimum(), clipRect.yMaximum() );
127+
pts << QPointF( clipRect.xMaximum(), clipRect.yMaximum() );
128+
return;
129+
}
130+
else if ( doubleNear( y1, clipRect.yMinimum() ) )
131+
{
132+
pts << QPointF( clipRect.xMinimum(), clipRect.yMinimum() );
133+
return;
134+
}
135+
}
136+
else if ( doubleNear( y0, clipRect.yMaximum() ) )
137+
{
138+
if ( doubleNear( y1, clipRect.yMaximum() ) )
139+
{
140+
return;
141+
}
142+
else if ( doubleNear( x1, clipRect.xMaximum() ) )
143+
{
144+
pts << QPointF( clipRect.xMaximum(), clipRect.yMaximum() );
145+
return;
146+
}
147+
else if ( doubleNear( y1, clipRect.yMinimum() ) )
148+
{
149+
pts << QPointF( clipRect.xMaximum(), clipRect.yMaximum() );
150+
pts << QPointF( clipRect.xMaximum(), clipRect.yMinimum() );
151+
return;
152+
}
153+
else if ( doubleNear( x1, clipRect.xMinimum() ) )
154+
{
155+
pts << QPointF( clipRect.xMinimum(), clipRect.yMaximum() );
156+
return;
157+
}
158+
}
159+
else if ( doubleNear( x0, clipRect.xMaximum() ) )
160+
{
161+
if ( doubleNear( x1, clipRect.xMaximum() ) )
162+
{
163+
return;
164+
}
165+
else if ( doubleNear( y1, clipRect.yMinimum() ) )
166+
{
167+
pts << QPointF( clipRect.xMaximum(), clipRect.yMinimum() );
168+
return;
169+
}
170+
else if ( doubleNear( x1, clipRect.xMinimum() ) )
171+
{
172+
pts << QPointF( clipRect.xMaximum(), clipRect.yMinimum() );
173+
pts << QPointF( clipRect.xMinimum(), clipRect.yMinimum() );
174+
return;
175+
}
176+
else if ( doubleNear( y1, clipRect.yMaximum() ) )
177+
{
178+
pts << QPointF( clipRect.xMaximum(), clipRect.yMaximum() );
179+
return;
180+
}
181+
}
182+
else if ( doubleNear( y0, clipRect.yMinimum() ) )
183+
{
184+
if ( doubleNear( y1, clipRect.yMinimum() ) )
185+
{
186+
return;
187+
}
188+
else if ( doubleNear( x1, clipRect.xMinimum() ) )
189+
{
190+
pts << QPointF( clipRect.xMinimum(), clipRect.yMinimum() );
191+
return;
192+
}
193+
else if ( doubleNear( y1, clipRect.yMaximum() ) )
194+
{
195+
pts << QPointF( clipRect.xMinimum(), clipRect.yMinimum() );
196+
pts << QPointF( clipRect.xMinimum(), clipRect.yMaximum() );
197+
return;
198+
}
199+
else if ( doubleNear( x1, clipRect.xMaximum() ) )
200+
{
201+
pts << QPointF( clipRect.xMaximum(), clipRect.yMinimum() );
202+
return;
203+
}
204+
}
205+
}

‎src/core/qgsclipper.h

Lines changed: 470 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -22,10 +22,13 @@
2222

2323
#include "qgis.h"
2424
#include "qgspoint.h"
25+
#include "qgsrectangle.h"
2526

2627
#include <vector>
2728
#include <utility>
2829

30+
#include <QPolygonF>
31+
2932
/** \ingroup core
3033
* A class to trim lines and polygons to within a rectangular region.
3134
* The functions in this class are likely to be called from within a
@@ -76,6 +79,12 @@ class CORE_EXPORT QgsClipper
7679
std::vector<double>& y,
7780
bool shapeOpen );
7881

82+
/**Reads a polyline from WKB and clips it to clipExtent
83+
@param wkb pointer to the start of the line wkb
84+
@param clipExtent clipping bounds
85+
@param line out: clipped line coordinates*/
86+
static unsigned char* clippedLineWKB( unsigned char* wkb, const QgsRectangle& clipExtent, QPolygonF& line );
87+
7988
private:
8089

8190
// Used when testing for equivalance to 0.0
@@ -98,6 +107,30 @@ class CORE_EXPORT QgsClipper
98107
static QgsPoint intersect( const double x1, const double y1,
99108
const double x2, const double y2,
100109
Boundary b );
110+
111+
//Implementation of 'Fast clipping' algorithm (Sobkow et al. 1987, Computers & Graphics Vol.11, 4, p.459-467)
112+
static bool clipLineSegment( double xLeft, double xRight, double yBottom, double yTop, double& x0, double& y0, double& x1, double& y1 );
113+
114+
/**Connects two lines splitted by the clip (by inserting points on the clip border)
115+
@param x0 x-coordinate of the first line end
116+
@param y0 y-coordinate of the first line end
117+
@param x1 x-coordinate of the second line start
118+
@param y1 y-coordinate of the second line start
119+
@param clipRect clip rectangle
120+
@param pts: in/out array of clipped points
121+
@param writePtr in/out: writing poisiton in the wkb array*/
122+
static void connectSeparatedLines( double x0, double y0, double x1, double y1,
123+
const QgsRectangle& clipRect, QPolygonF& pts );
124+
125+
//low level clip methods for fast clip algorithm
126+
static void clipStartTop( double& x0, double& y0, const double& x1, const double& y1, double yMax );
127+
static void clipStartBottom( double& x0, double& y0, const double& x1, const double& y1, double yMin );
128+
static void clipStartRight( double& x0, double& y0, const double& x1, const double& y1, double xMax );
129+
static void clipStartLeft( double& x0, double& y0, const double& x1, const double& y1, double xMin );
130+
static void clipEndTop( const double& x0, const double& y0, double& x1, double& y1, double yMax );
131+
static void clipEndBottom( const double& x0, const double& y0, double& x1, double& y1, double yMin );
132+
static void clipEndRight( const double& x0, const double& y0, double& x1, double& y1, double xMax );
133+
static void clipEndLeft( const double& x0, const double& y0, double& x1, double& y1, double xMin );
101134
};
102135

103136
// The inline functions
@@ -283,5 +316,442 @@ inline QgsPoint QgsClipper::intersect( const double x1, const double y1,
283316
return p;
284317
}
285318

319+
inline void QgsClipper::clipStartTop( double& x0, double& y0, const double& x1, const double& y1, double yMax )
320+
{
321+
x0 += ( x1 - x0 ) * ( yMax - y0 ) / ( y1 - y0 );
322+
y0 = yMax;
323+
}
324+
325+
inline void QgsClipper::clipStartBottom( double& x0, double& y0, const double& x1, const double& y1, double yMin )
326+
{
327+
x0 += ( x1 - x0 ) * ( yMin - y0 ) / ( y1 - y0 );
328+
y0 = yMin;
329+
}
330+
331+
inline void QgsClipper::clipStartRight( double& x0, double& y0, const double& x1, const double& y1, double xMax )
332+
{
333+
y0 += ( y1 - y0 ) * ( xMax - x0 ) / ( x1 - x0 );
334+
x0 = xMax;
335+
}
336+
337+
inline void QgsClipper::clipStartLeft( double& x0, double& y0, const double& x1, const double& y1, double xMin )
338+
{
339+
y0 += ( y1 - y0 ) * ( xMin - x0 ) / ( x1 - x0 );
340+
x0 = xMin;
341+
}
342+
343+
inline void QgsClipper::clipEndTop( const double& x0, const double& y0, double& x1, double& y1, double yMax )
344+
{
345+
x1 += ( x1 - x0 ) * ( yMax - y1 ) / ( y1 - y0 );
346+
y1 = yMax;
347+
}
348+
349+
inline void QgsClipper::clipEndBottom( const double& x0, const double& y0, double& x1, double& y1, double yMin )
350+
{
351+
x1 += ( x1 - x0 ) * ( yMin - y1 ) / ( y1 - y0 );
352+
y1 = yMin;
353+
}
354+
355+
inline void QgsClipper::clipEndRight( const double& x0, const double& y0, double& x1, double& y1, double xMax )
356+
{
357+
y1 += ( y1 - y0 ) * ( xMax - x1 ) / ( x1 - x0 );
358+
x1 = xMax;
359+
}
360+
361+
inline void QgsClipper::clipEndLeft( const double& x0, const double& y0, double& x1, double& y1, double xMin )
362+
{
363+
y1 += ( y1 - y0 ) * ( xMin - x1 ) / ( x1 - x0 );
364+
x1 = xMin;
365+
}
366+
367+
//'Fast clipping' algorithm (Sobkow et al. 1987, Computers & Graphics Vol.11, 4, p.459-467)
368+
inline bool QgsClipper::clipLineSegment( double xLeft, double xRight, double yBottom, double yTop, double& x0, double& y0, double& x1, double& y1 )
369+
{
370+
int lineCode = 0;
371+
372+
if ( y1 < yBottom )
373+
lineCode |= 4;
374+
else if ( y1 > yTop )
375+
lineCode |= 8;
376+
377+
if ( x1 > xRight )
378+
lineCode |= 2;
379+
else if ( x1 < xLeft )
380+
lineCode |= 1;
381+
382+
if ( y0 < yBottom )
383+
lineCode |= 64;
384+
else if ( y0 > yTop )
385+
lineCode |= 128;
386+
387+
if ( x0 > xRight )
388+
lineCode |= 32;
389+
else if ( x0 < xLeft )
390+
lineCode |= 16;
391+
392+
switch ( lineCode )
393+
{
394+
case 0: //completely inside
395+
return true;
396+
397+
case 1:
398+
clipEndLeft( x0, y0, x1, y1, xLeft );
399+
return true;
400+
401+
case 2:
402+
clipEndRight( x0, y0, x1, y1, xRight );
403+
return true;
404+
405+
case 4:
406+
clipEndBottom( x0, y0, x1, y1, yBottom );
407+
return true;
408+
409+
case 5:
410+
clipEndLeft( x0, y0, x1, y1, xLeft );
411+
if ( y1 < yBottom )
412+
clipEndBottom( x0, y0, x1, y1, yBottom );
413+
return true;
414+
415+
case 6:
416+
clipEndRight( x0, y0, x1, y1, xRight );
417+
if ( y1 < yBottom )
418+
clipEndBottom( x0, y0, x1, y1, yBottom );
419+
return true;
420+
421+
case 8:
422+
clipEndTop( x0, y0, x1, y1, yTop );
423+
return true;
424+
425+
case 9:
426+
clipEndLeft( x0, y0, x1, y1, xLeft );
427+
if ( y1 > yTop )
428+
clipEndTop( x0, y0, x1, y1, yTop );
429+
return true;
430+
431+
case 10:
432+
clipEndRight( x0, y0, x1, y1, xRight );
433+
if ( y1 > yTop )
434+
clipEndTop( x0, y0, x1, y1, yTop );
435+
return true;
436+
437+
case 16:
438+
clipStartLeft( x0, y0, x1, y1, xLeft );
439+
return true;
440+
441+
case 18:
442+
clipStartLeft( x0, y0, x1, y1, xLeft );
443+
clipEndRight( x0, y0, x1, y1, xRight );
444+
return true;
445+
446+
case 20:
447+
clipStartLeft( x0, y0, x1, y1, xLeft );
448+
if ( y0 < yBottom )
449+
return false;
450+
clipEndBottom( x0, y0, x1, y1, yBottom );
451+
return true;
452+
453+
case 22:
454+
clipStartLeft( x0, y0, x1, y1, xLeft );
455+
if ( y0 < yBottom )
456+
return false;
457+
clipEndBottom( x0, y0, x1, y1, yBottom );
458+
if ( x1 > xRight )
459+
clipEndRight( x0, y0, x1, y1, xRight );
460+
return true;
461+
462+
case 24:
463+
clipStartLeft( x0, y0, x1, y1, xLeft );
464+
if ( y0 > yTop )
465+
return false;
466+
clipEndTop( x0, y0, x1, y1, yTop );
467+
return true;
468+
469+
case 26:
470+
clipStartLeft( x0, y0, x1, y1, xLeft );
471+
if ( y0 > yTop )
472+
return false;
473+
clipEndTop( x0, y0, x1, y1, yTop );
474+
if ( x1 > xRight )
475+
clipEndRight( x0, y0, x1, y1, xRight );
476+
return true;
477+
478+
case 32:
479+
clipStartRight( x0, y0, x1, y1, xRight );
480+
return true;
481+
482+
case 33:
483+
clipStartRight( x0, y0, x1, y1, xRight );
484+
clipEndLeft( x0, y0, x1, y1, xLeft );
485+
return true;
486+
487+
case 36:
488+
clipStartRight( x0, y0, x1, y1, xRight );
489+
if ( y0 < yBottom )
490+
return false;
491+
clipEndBottom( x0, y0, x1, y1, yBottom );
492+
return true;
493+
494+
case 37:
495+
clipStartRight( x0, y0, x1, y1, xRight );
496+
if ( y0 < yBottom )
497+
return false;
498+
clipEndBottom( x0, y0, x1, y1, yBottom );
499+
if ( x1 < xLeft )
500+
clipEndLeft( x0, y0, x1, y1, xLeft );
501+
return true;
502+
503+
case 40:
504+
clipStartRight( x0, y0, x1, y1, xRight );
505+
if ( y0 > yTop )
506+
return false;
507+
clipEndTop( x0, y0, x1, y1, yTop );
508+
return true;
509+
510+
case 41:
511+
clipStartRight( x0, y0, x1, y1, xRight );
512+
if ( y0 > yTop )
513+
return false;
514+
clipEndTop( x0, y0, x1, y1, yTop );
515+
if ( x1 < xLeft )
516+
clipEndLeft( x0, y0, x1, y1, xLeft );
517+
return true;
518+
519+
case 64:
520+
clipStartBottom( x0, y0, x1, y1, yBottom );
521+
return true;
522+
523+
case 65:
524+
clipStartBottom( x0, y0, x1, y1, yBottom );
525+
if ( x0 < xLeft )
526+
return false;
527+
clipEndLeft( x0, y0, x1, y1, xLeft );
528+
if ( y1 < yBottom )
529+
clipEndBottom( x0, y0, x1, y1, yBottom );
530+
return true;
531+
532+
case 66:
533+
clipStartBottom( x0, y0, x1, y1, yBottom );
534+
if ( x0 > xRight )
535+
return false;
536+
clipEndRight( x0, y0, x1, y1, xRight );
537+
return true;
538+
539+
case 72:
540+
clipStartBottom( x0, y0, x1, y1, yBottom );
541+
clipEndTop( x0, y0, x1, y1, yTop );
542+
return true;
543+
544+
case 73:
545+
clipStartBottom( x0, y0, x1, y1, yBottom );
546+
if ( x0 < xLeft )
547+
return false;
548+
clipEndLeft( x0, y0, x1, y1, xLeft );
549+
if ( y1 > yTop )
550+
clipEndTop( x0, y0, x1, y1, yTop );
551+
return true;
552+
553+
case 74:
554+
clipStartBottom( x0, y0, x1, y1, yBottom );
555+
if ( x0 > xRight )
556+
return false;
557+
clipEndRight( x0, y0, x1, y1, xRight );
558+
if ( y1 > yTop )
559+
clipEndTop( x0, y0, x1, y1, yTop );
560+
return true;
561+
562+
case 80:
563+
clipStartLeft( x0, y0, x1, y1, xLeft );
564+
if ( y0 < yBottom )
565+
clipStartBottom( x0, y0, x1, y1, yBottom );
566+
return true;
567+
568+
case 82:
569+
clipEndRight( x0, y0, x1, y1, xRight );
570+
if ( y1 < yBottom )
571+
return false;
572+
clipStartBottom( x0, y0, x1, y1, yBottom );
573+
if ( x0 < xLeft )
574+
clipStartLeft( x0, y0, x1, y1, xLeft );
575+
return true;
576+
577+
case 88:
578+
clipEndTop( x0, y0, x1, y1, yTop );
579+
if ( x1 < xLeft )
580+
return false;
581+
clipStartBottom( x0, y0, x1, y1, yBottom );
582+
if ( x0 < xLeft )
583+
clipStartLeft( x0, y0, x1, y1, xLeft );
584+
return true;
585+
586+
case 90:
587+
clipStartLeft( x0, y0, x1, y1, xLeft );
588+
if ( y0 > yTop )
589+
return false;
590+
clipEndRight( x0, y0, x1, y1, xRight );
591+
if ( y1 < yBottom )
592+
return false;
593+
if ( y0 < yBottom )
594+
clipStartBottom( x0, y0, x1, y1, yBottom );
595+
if ( y1 > yTop )
596+
clipEndTop( x0, y0, x1, y1, yTop );
597+
return true;
598+
599+
case 96:
600+
clipStartRight( x0, y0, x1, y1, xRight );
601+
if ( y0 < yBottom )
602+
clipStartBottom( x0, y0, x1, y1, yBottom );
603+
return true;
604+
605+
case 97:
606+
clipEndLeft( x0, y0, x1, y1, xLeft );
607+
if ( y1 < yBottom )
608+
return false;
609+
clipStartBottom( x0, y0, x1, y1, yBottom );
610+
if ( x0 > xRight )
611+
clipStartRight( x0, y0, x1, y1, xRight );
612+
return true;
613+
614+
case 104:
615+
clipEndTop( x0, y0, x1, y1, yTop );
616+
if ( x1 > xRight )
617+
return false;
618+
clipStartRight( x0, y0, x1, y1, xRight );
619+
if ( y0 < yBottom )
620+
clipStartBottom( x0, y0, x1, y1, yBottom );
621+
return true;
622+
623+
case 105:
624+
clipEndLeft( x0, y0, x1, y1, xLeft );
625+
if ( y1 < yBottom )
626+
return false;
627+
clipStartRight( x0, y0, x1, y1, xRight );
628+
if ( y0 > yTop )
629+
return false;
630+
if ( y1 > yTop )
631+
clipEndTop( x0, y0, x1, y1, yTop );
632+
if ( y0 < yBottom )
633+
clipStartBottom( x0, y0, x1, y1, yBottom );
634+
return true;
635+
636+
case 128:
637+
clipStartTop( x0, y0, x1, y1, yTop );
638+
return true;
639+
640+
case 129:
641+
clipStartTop( x0, y0, x1, y1, yTop );
642+
if ( x0 < xLeft )
643+
return false;
644+
clipEndLeft( x0, y0, x1, y1, xLeft );
645+
return true;
646+
647+
case 130:
648+
clipStartTop( x0, y0, x1, y1, yTop );
649+
if ( x0 > xRight )
650+
return false;
651+
clipEndRight( x0, y0, x1, y1, xRight );
652+
return true;
653+
654+
case 132:
655+
clipStartTop( x0, y0, x1, y1, yTop );
656+
clipEndBottom( x0, y0, x1, y1, yBottom );
657+
return true;
658+
659+
case 133:
660+
clipStartTop( x0, y0, x1, y1, yTop );
661+
if ( x0 < xLeft )
662+
return false;
663+
clipEndLeft( x0, y0, x1, y1, xLeft );
664+
if ( y1 < yBottom )
665+
clipEndBottom( x0, y0, x1, y1, yBottom );
666+
return true;
667+
668+
case 134:
669+
clipStartTop( x0, y0, x1, y1, yTop );
670+
if ( x0 > xRight )
671+
return false;
672+
clipEndRight( x0, y0, x1, y1, xRight );
673+
if ( y1 < yBottom )
674+
clipEndBottom( x0, y0, x1, y1, yBottom );
675+
return true;
676+
677+
case 144:
678+
clipStartLeft( x0, y0, x1, y1, xLeft );
679+
if ( y0 > yTop )
680+
clipStartTop( x0, y0, x1, y1, yTop );
681+
return true;
682+
683+
case 146:
684+
clipEndRight( x0, y0, x1, y1, xRight );
685+
if ( y1 > yTop )
686+
return false;
687+
clipStartTop( x0, y0, x1, y1, yTop );
688+
if ( x0 < xLeft )
689+
clipStartLeft( x0, y0, x1, y1, xLeft );
690+
return true;
691+
692+
case 148:
693+
clipEndBottom( x0, y0, x1, y1, yBottom );
694+
if ( x1 < xLeft )
695+
return false;
696+
clipStartLeft( x0, y0, x1, y1, xLeft );
697+
if ( y0 > yTop )
698+
clipStartTop( x0, y0, x1, y1, yTop );
699+
return true;
700+
701+
case 150:
702+
clipStartLeft( x0, y0, x1, y1, xLeft );
703+
if ( y0 < yBottom )
704+
return false;
705+
clipEndRight( x0, y0, x1, y1, xRight );
706+
if ( y1 > yTop )
707+
return false;
708+
if ( y0 > yTop )
709+
clipStartTop( x0, y0, x1, y1, yTop );
710+
if ( y1 < yBottom )
711+
clipEndBottom( x0, y0, x1, y1, yBottom );
712+
return true;
713+
714+
case 160:
715+
clipStartRight( x0, y0, x1, y1, xRight );
716+
if ( y0 > yTop )
717+
clipStartTop( x0, y0, x1, y1, yTop );
718+
return true;
719+
720+
case 161:
721+
clipEndLeft( x0, y0, x1, y1, xLeft );
722+
if ( y1 > yTop )
723+
return false;
724+
clipStartTop( x0, y0, x1, y1, yTop );
725+
if ( x0 > xRight )
726+
clipStartRight( x0, y0, x1, y1, xRight );
727+
return true;
728+
729+
case 164:
730+
clipEndBottom( x0, y0, x1, y1, yBottom );
731+
if ( x1 > xRight )
732+
return false;
733+
clipStartRight( x0, y0, x1, y1, xRight );
734+
if ( y0 > yTop )
735+
clipStartTop( x0, y0, x1, y1, yTop );
736+
return true;
737+
738+
case 165:
739+
clipEndLeft( x0, y0, x1, y1, xLeft );
740+
if ( y1 > yTop )
741+
return false;
742+
clipStartRight( x0, y0, x1, y1, xRight );
743+
if ( y0 < yBottom )
744+
return false;
745+
if ( y1 < yBottom )
746+
clipEndBottom( x0, y0, x1, y1, yBottom );
747+
if ( y0 > yTop )
748+
clipStartTop( x0, y0, x1, y1, yTop );
749+
return true;
750+
}
751+
752+
return false;
753+
754+
}
755+
286756

287757
#endif

‎src/core/symbology-ng/qgsrendererv2.cpp

Lines changed: 28 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -8,6 +8,7 @@
88
#include "qgsrendererv2registry.h"
99

1010
#include "qgsrendercontext.h"
11+
#include "qgsclipper.h"
1112
#include "qgsgeometry.h"
1213
#include "qgsfeature.h"
1314
#include "qgslogger.h"
@@ -54,31 +55,45 @@ unsigned char* QgsFeatureRendererV2::_getLineString( QPolygonF& pts, QgsRenderCo
5455
bool hasZValue = ( wkbType == QGis::WKBLineString25D );
5556
double x, y;
5657

57-
pts.resize( nPoints );
58-
5958
const QgsCoordinateTransform* ct = context.coordinateTransform();
6059
const QgsMapToPixel& mtp = context.mapToPixel();
6160
double z = 0; // dummy variable for coordiante transform
6261

63-
for ( unsigned int i = 0; i < nPoints; ++i )
62+
//apply clipping for large lines to achieve a better rendering performance
63+
if ( nPoints > 100 )
6464
{
65-
x = *(( double * ) wkb );
66-
wkb += sizeof( double );
67-
y = *(( double * ) wkb );
68-
wkb += sizeof( double );
65+
const QgsRectangle& e = context.extent();
66+
double cw = e.width() / 10; double ch = e.height() / 10;
67+
QgsRectangle clipRect( e.xMinimum() - cw, e.yMinimum() - ch, e.xMaximum() + cw, e.yMaximum() + ch );
68+
wkb = QgsClipper::clippedLineWKB( wkb - ( 2 * sizeof( unsigned int ) + 1 ), clipRect, pts );
69+
}
70+
else
71+
{
72+
pts.resize( nPoints );
6973

70-
if ( hasZValue ) // ignore Z value
74+
for ( unsigned int i = 0; i < nPoints; ++i )
75+
{
76+
x = *(( double * ) wkb );
77+
wkb += sizeof( double );
78+
y = *(( double * ) wkb );
7179
wkb += sizeof( double );
7280

73-
// TODO: maybe to the transform at once (faster?)
74-
if ( ct )
75-
ct->transformInPlace( x, y, z );
76-
mtp.transformInPlace( x, y );
81+
if ( hasZValue ) // ignore Z value
82+
wkb += sizeof( double );
7783

78-
pts[i] = QPointF( x, y );
84+
pts[i] = QPointF( x, y );
85+
}
86+
}
7987

88+
//transform the QPolygonF to screen coordinates
89+
for ( unsigned int i = 0; i < pts.size(); ++i )
90+
{
91+
if ( ct )
92+
ct->transformInPlace( pts[i].rx(), pts[i].ry(), z );
93+
mtp.transformInPlace( pts[i].rx(), pts[i].ry() );
8094
}
8195

96+
8297
return wkb;
8398
}
8499

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