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Continue triangle

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This commit is contained in:
Miloslav Číž 2018-11-17 16:15:16 +01:00
parent ee0f4f0f2c
commit 15c28205ac
1 changed files with 63 additions and 12 deletions
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73
s3l.h
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@ -31,6 +31,16 @@ static inline int16_t S3L_abs(int16_t value)
return value >= 0 ? value : -1 * value;
}
static inline int16_t S3L_min(int16_t v1, int16_t v2)
{
return v1 >= v2 ? v2 : v1;
}
static inline int16_t S3L_max(int16_t v1, int16_t v2)
{
return v1 >= v2 ? v1 : v2;
}
void S3L_bresenhamInit(S3L_BresenhamState *state, int16_t x0, int16_t y0, int16_t x1, int16_t y1)
{
int16_t dx = x1 - x0;
@ -145,19 +155,47 @@ void S3L_drawTriangle(int16_t x0, int16_t y0, int16_t x1, int16_t y1, int16_t x2
#undef handleLR
S3L_COORD splitY;
S3L_COORD endY;
int splitOnLeft;
if (rPointY <= lPointY)
{
splitY = rPointY;
splitOnLeft = 0;
endY = lPointY;
}
else
{
splitY = lPointY;
splitOnLeft = 1;
endY = rPointY;
}
S3L_COORD currentY = tPointY;
/* We'll be using a slight modification of Bresenham line algorithm (a one
that draws a _non-continous_ line). */
#define initSide(s)\
int16_t s##X = tPointX;\
int16_t s##Dx = s##PointX - tPointX;\
int16_t s##Dy = s##PointY - tPointY;\
int16_t s##Inc = s##Dx >= 0 ? 1 : -1;\
int16_t s##Err = 2 * s##Dx - s##Dy;\
int16_t s##ErrAdd = 2 * S3L_abs(s##Dx);\
int16_t s##ErrSub = 2 * S3L_abs(s##Dy);
int16_t
/* triangle side:
left right */
lX, rX, // current x position
lDx, rDx, // dx (end point - start point)
lDy, rDy, // dy (end point - start point)
lInc, rInc, // direction in which to increment (1 or -1)
lErr, rErr, // current error (Bresenham)
lErrAdd, rErrAdd, // error value to add in each Bresenham cycle
lErrSub, rErrSub; // error value to substract when moving in x direction
#define initSide(v,p1,p2)\
v##X = p1##PointX;\
v##Dx = p2##PointX - p1##PointX;\
v##Dy = p2##PointY - p1##PointY;\
v##Inc = v##Dx >= 0 ? 1 : -1;\
v##Err = 2 * v##Dx - v##Dy;\
v##ErrAdd = 2 * S3L_abs(v##Dx);\
v##ErrSub = 2 * S3L_abs(v##Dy);
#define stepSide(s)\
while (s##Err > 0)\
@ -167,12 +205,12 @@ void S3L_drawTriangle(int16_t x0, int16_t y0, int16_t x1, int16_t y1, int16_t x2
}\
s##Err += s##ErrAdd;
initSide(r)
initSide(l)
initSide(r,t,r)
initSide(l,t,l)
S3L_PixelInfo p;
while (currentY <= rPointY)
while (currentY <= endY)
{
p.y = currentY;
@ -185,12 +223,25 @@ void S3L_drawTriangle(int16_t x0, int16_t y0, int16_t x1, int16_t y1, int16_t x2
stepSide(r)
stepSide(l)
if (currentY == splitY)
{
if (splitOnLeft)
{
initSide(l,l,r);
}
else
{
initSide(r,r,l);
}
}
++currentY;
}
#undef initSide
#undef stepSide
}
#endif