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Move triangle code to the top

This commit is contained in:
Miloslav Číž 2019-05-04 21:05:42 +02:00
parent cf7b6494f8
commit 55ebaef41c

479
s3l.h
View file

@ -634,28 +634,233 @@ void S3L_drawTriangle(
S3L_initPixelInfo(&p); S3L_initPixelInfo(&p);
p.triangleID = triangleID; p.triangleID = triangleID;
// point mode if (config.mode == S3L_MODE_TRIANGLES) // triangle mode
if (config.mode == S3L_MODE_POINTS)
{ {
p.x = x0; p.y = y0; p.barycentric0 = S3L_FRACTIONS_PER_UNIT; S3L_ScreenCoord
p.barycentric1 = 0; p.barycentric2 = 0; tPointX, tPointY, // top triangle point coords
S3L_PIXEL_FUNCTION(&p); lPointX, lPointY, // left triangle point coords
rPointX, rPointY; // right triangle point coords
p.x = x1; p.y = y1; p.barycentric0 = 0; S3L_Unit *barycentric0; // bar. coord that gets higher from L to R
p.barycentric1 = S3L_FRACTIONS_PER_UNIT; p.barycentric2 = 0; S3L_Unit *barycentric1; // bar. coord that gets higher from R to L
S3L_PIXEL_FUNCTION(&p); S3L_Unit *barycentric2; // bar. coord that gets higher from bottom up
p.x = x2; p.y = y2; p.barycentric0 = 0; // Sort the points.
p.barycentric1 = 0; p.barycentric2 = S3L_FRACTIONS_PER_UNIT;
S3L_PIXEL_FUNCTION(&p); #define handleLR(t,a,b)\
int16_t aDx = x##a - x##t;\
return; int16_t bDx = x##b - x##t;\
int16_t aDy = S3L_nonZero(y##a - y##t);\
int16_t bDy = S3L_nonZero(y##b - y##t);\
if ((aDx << 4) / aDy < (bDx << 4) / bDy)\
/*if (x##a <= x##b)*/\
{\
lPointX = x##a; lPointY = y##a;\
rPointX = x##b; rPointY = y##b;\
barycentric0 = &p.barycentric##b;\
barycentric1 = &p.barycentric##a;\
}\
else\
{\
lPointX = x##b; lPointY = y##b;\
rPointX = x##a; rPointY = y##a;\
barycentric0 = &p.barycentric##a;\
barycentric1 = &p.barycentric##b;\
}
if (y0 <= y1)
{
if (y0 <= y2)
{
tPointX = x0;
tPointY = y0;
barycentric2 = &p.barycentric0;
handleLR(0,1,2)
}
else
{
tPointX = x2;
tPointY = y2;
barycentric2 = &p.barycentric2;
handleLR(2,0,1)
}
}
else
{
if (y1 <= y2)
{
tPointX = x1;
tPointY = y1;
barycentric2 = &p.barycentric1;
handleLR(1,0,2)
}
else
{
tPointX = x2;
tPointY = y2;
barycentric2 = &p.barycentric2;
handleLR(2,0,1)
}
}
// Now draw the triangle line by line.
#undef handleLR
S3L_ScreenCoord splitY; // Y of the vertically middle point of the triangle
S3L_ScreenCoord endY; // bottom Y of the whole triangle
int splitOnLeft; // whether splitY happens on L or R side
if (rPointY <= lPointY)
{
splitY = rPointY;
splitOnLeft = 0;
endY = lPointY;
}
else
{
splitY = lPointY;
splitOnLeft = 1;
endY = rPointY;
}
S3L_ScreenCoord currentY = tPointY;
/* We'll be using an algorithm similar to Bresenham line algorithm. The
specifics of this algorithm are among others:
- drawing possibly a NON-CONTINUOUS line
- NOT tracing the line exactly, but rather rasterizing either on the
left or right side of it (depending on what's chosen), according to
the pixel CENTERS
The principle is this:
- Move vertically by pixels and accumulate the error (abs(dx/dy)).
- If the error is greater than one (crossed the next pixel center), keep
moving horizontally and substracting 1 from the error until it is less
than 1 again.
- To make this INTEGER ONLY, scale the case so that distance between
pixels is equal to dy (instead of 1). This way the error becomes
dx/dy * dy == dx, and we're comparing the error to (and potentially
substracting) 1 * dy == dy.
- The inital error is set to either 0 or dy (effectively shifting the
line) dependin on whether we want to rasterize on right or left. */
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
S3L_Unit
lSideUnitStep, rSideUnitStep,
lSideUnitPos, rSideUnitPos;
/* init side for the algorithm, params:
s - which side (l or r)
p1 - point from (t, l or r)
p2 - point to (t, l or r)
down - whether the side coordinate goes top-down or vice versa
left - whether to rasterize on left of the line or vice versa */
#define initSide(s,p1,p2,down,left)\
s##X = p1##PointX;\
s##Dx = p2##PointX - p1##PointX;\
s##Dy = p2##PointY - p1##PointY;\
s##SideUnitStep = S3L_FRACTIONS_PER_UNIT / (s##Dy != 0 ? s##Dy : 1);\
s##SideUnitPos = 0;\
if (!down)\
{\
s##SideUnitPos = S3L_FRACTIONS_PER_UNIT;\
s##SideUnitStep *= -1;\
}\
s##Inc = s##Dx >= 0 ? 1 : -1;\
s##Err = left != (s##Dx < 0) ? 0 : s##Dy;\
s##ErrAdd = S3L_abs(s##Dx);\
s##ErrSub = s##Dy != 0 ? s##Dy : 1; /* don't allow 0, could lead to an
infinite substracting loop */
#define stepSide(s)\
while (s##Err > s##Dy)\
{\
s##X += s##Inc;\
s##Err -= s##ErrSub;\
}\
s##Err += s##ErrAdd;
initSide(r,t,r,1,1)
initSide(l,t,l,1,0)
while (currentY <= endY) // draw the triangle from top to bottom
{
if (currentY == splitY) // reached a vertical split of the triangle?
{ // then reinit one side
if (splitOnLeft)
{
initSide(l,l,r,0,0);
S3L_Unit *tmp = barycentric0;
barycentric0 = barycentric2;
barycentric2 = tmp;
rSideUnitPos = S3L_FRACTIONS_PER_UNIT - rSideUnitPos;
rSideUnitStep *= -1;
}
else
{
initSide(r,r,l,0,1);
S3L_Unit *tmp = barycentric1;
barycentric1 = barycentric2;
barycentric2 = tmp;
lSideUnitPos = S3L_FRACTIONS_PER_UNIT - lSideUnitPos;
lSideUnitStep *= -1;
}
}
stepSide(r)
stepSide(l)
p.y = currentY;
// draw the horizontal line
S3L_Unit tMax = rX - lX;
tMax = S3L_NONZERO(tMax); // prevent division by zero
S3L_Unit t1 = 0;
S3L_Unit t2 = tMax;
for (S3L_ScreenCoord x = lX; x <= rX; ++x)
{
*barycentric0 = S3L_interpolateFrom0(rSideUnitPos,t1,tMax);
*barycentric1 = S3L_interpolateFrom0(lSideUnitPos,t2,tMax);
*barycentric2 = S3L_FRACTIONS_PER_UNIT - *barycentric0 - *barycentric1;
p.x = x;
S3L_PIXEL_FUNCTION(&p);
++t1;
--t2;
}
lSideUnitPos += lSideUnitStep;
rSideUnitPos += rSideUnitStep;
++currentY;
}
#undef initSide
#undef stepSide
} }
else if (config.mode == S3L_MODE_LINES) // line mode
// line mode
if (config.mode == S3L_MODE_LINES)
{ {
S3L_BresenhamState line; S3L_BresenhamState line;
S3L_Unit lineLen; S3L_Unit lineLen;
@ -680,235 +885,21 @@ void S3L_drawTriangle(
drawLine(1,2) drawLine(1,2)
#undef drawLine #undef drawLine
return;
} }
else // point mode
// triangle mode -- TODO: maybe move to the top as this is most common?
S3L_ScreenCoord
tPointX, tPointY, // top triangle point coords
lPointX, lPointY, // left triangle point coords
rPointX, rPointY; // right triangle point coords
S3L_Unit *barycentric0; // bar. coord that gets higher from L to R
S3L_Unit *barycentric1; // bar. coord that gets higher from R to L
S3L_Unit *barycentric2; // bar. coord that gets higher from bottom up
// Sort the points.
#define handleLR(t,a,b)\
int16_t aDx = x##a - x##t;\
int16_t bDx = x##b - x##t;\
int16_t aDy = S3L_nonZero(y##a - y##t);\
int16_t bDy = S3L_nonZero(y##b - y##t);\
if ((aDx << 4) / aDy < (bDx << 4) / bDy)\
/*if (x##a <= x##b)*/\
{\
lPointX = x##a; lPointY = y##a;\
rPointX = x##b; rPointY = y##b;\
barycentric0 = &p.barycentric##b;\
barycentric1 = &p.barycentric##a;\
}\
else\
{\
lPointX = x##b; lPointY = y##b;\
rPointX = x##a; rPointY = y##a;\
barycentric0 = &p.barycentric##a;\
barycentric1 = &p.barycentric##b;\
}
if (y0 <= y1)
{ {
if (y0 <= y2) p.x = x0; p.y = y0; p.barycentric0 = S3L_FRACTIONS_PER_UNIT;
{ p.barycentric1 = 0; p.barycentric2 = 0;
tPointX = x0; S3L_PIXEL_FUNCTION(&p);
tPointY = y0;
barycentric2 = &p.barycentric0; p.x = x1; p.y = y1; p.barycentric0 = 0;
handleLR(0,1,2) p.barycentric1 = S3L_FRACTIONS_PER_UNIT; p.barycentric2 = 0;
} S3L_PIXEL_FUNCTION(&p);
else
{ p.x = x2; p.y = y2; p.barycentric0 = 0;
tPointX = x2; p.barycentric1 = 0; p.barycentric2 = S3L_FRACTIONS_PER_UNIT;
tPointY = y2; S3L_PIXEL_FUNCTION(&p);
barycentric2 = &p.barycentric2;
handleLR(2,0,1)
}
} }
else
{
if (y1 <= y2)
{
tPointX = x1;
tPointY = y1;
barycentric2 = &p.barycentric1;
handleLR(1,0,2)
}
else
{
tPointX = x2;
tPointY = y2;
barycentric2 = &p.barycentric2;
handleLR(2,0,1)
}
}
// Now draw the triangle line by line.
#undef handleLR
S3L_ScreenCoord splitY; // Y of the vertically middle point of the triangle
S3L_ScreenCoord endY; // bottom Y of the whole triangle
int splitOnLeft; // whether splitY happens on L or R side
if (rPointY <= lPointY)
{
splitY = rPointY;
splitOnLeft = 0;
endY = lPointY;
}
else
{
splitY = lPointY;
splitOnLeft = 1;
endY = rPointY;
}
S3L_ScreenCoord currentY = tPointY;
/* We'll be using an algorithm similar to Bresenham line algorithm. The
specifics of this algorithm are among others:
- drawing possibly a NON-CONTINUOUS line
- NOT tracing the line exactly, but rather rasterizing either on the
left or right side of it (depending on what's chosen), according to
the pixel CENTERS
The principle is this:
- Move vertically by pixels and accumulate the error (abs(dx/dy)).
- If the error is greater than one (crossed the next pixel center), keep
moving horizontally and substracting 1 from the error until it is less
than 1 again.
- To make this INTEGER ONLY, scale the case so that distance between
pixels is equal to dy (instead of 1). This way the error becomes
dx/dy * dy == dx, and we're comparing the error to (and potentially
substracting) 1 * dy == dy.
- The inital error is set to either 0 or dy (effectively shifting the
line) dependin on whether we want to rasterize on right or left. */
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
S3L_Unit
lSideUnitStep, rSideUnitStep,
lSideUnitPos, rSideUnitPos;
/* init side for the algorithm, params:
s - which side (l or r)
p1 - point from (t, l or r)
p2 - point to (t, l or r)
down - whether the side coordinate goes top-down or vice versa
left - whether to rasterize on left of the line or vice versa */
#define initSide(s,p1,p2,down,left)\
s##X = p1##PointX;\
s##Dx = p2##PointX - p1##PointX;\
s##Dy = p2##PointY - p1##PointY;\
s##SideUnitStep = S3L_FRACTIONS_PER_UNIT / (s##Dy != 0 ? s##Dy : 1);\
s##SideUnitPos = 0;\
if (!down)\
{\
s##SideUnitPos = S3L_FRACTIONS_PER_UNIT;\
s##SideUnitStep *= -1;\
}\
s##Inc = s##Dx >= 0 ? 1 : -1;\
s##Err = left != (s##Dx < 0) ? 0 : s##Dy;\
s##ErrAdd = S3L_abs(s##Dx);\
s##ErrSub = s##Dy != 0 ? s##Dy : 1; /* don't allow 0, could lead to an
infinite substracting loop */
#define stepSide(s)\
while (s##Err > s##Dy)\
{\
s##X += s##Inc;\
s##Err -= s##ErrSub;\
}\
s##Err += s##ErrAdd;
initSide(r,t,r,1,1)
initSide(l,t,l,1,0)
while (currentY <= endY) // draw the triangle from top to bottom
{
if (currentY == splitY) // reached a vertical split of the triangle?
{ // then reinit one side
if (splitOnLeft)
{
initSide(l,l,r,0,0);
S3L_Unit *tmp = barycentric0;
barycentric0 = barycentric2;
barycentric2 = tmp;
rSideUnitPos = S3L_FRACTIONS_PER_UNIT - rSideUnitPos;
rSideUnitStep *= -1;
}
else
{
initSide(r,r,l,0,1);
S3L_Unit *tmp = barycentric1;
barycentric1 = barycentric2;
barycentric2 = tmp;
lSideUnitPos = S3L_FRACTIONS_PER_UNIT - lSideUnitPos;
lSideUnitStep *= -1;
}
}
stepSide(r)
stepSide(l)
p.y = currentY;
// draw the horizontal line
S3L_Unit tMax = rX - lX;
tMax = S3L_NONZERO(tMax); // prevent division by zero
S3L_Unit t1 = 0;
S3L_Unit t2 = tMax;
for (S3L_ScreenCoord x = lX; x <= rX; ++x)
{
*barycentric0 = S3L_interpolateFrom0(rSideUnitPos,t1,tMax);
*barycentric1 = S3L_interpolateFrom0(lSideUnitPos,t2,tMax);
*barycentric2 = S3L_FRACTIONS_PER_UNIT - *barycentric0 - *barycentric1;
p.x = x;
S3L_PIXEL_FUNCTION(&p);
++t1;
--t2;
}
lSideUnitPos += lSideUnitStep;
rSideUnitPos += rSideUnitStep;
++currentY;
}
#undef initSide
#undef stepSide
} }
static inline void S3L_rotate2DPoint(S3L_Unit *x, S3L_Unit *y, S3L_Unit angle) static inline void S3L_rotate2DPoint(S3L_Unit *x, S3L_Unit *y, S3L_Unit angle)