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Create triangle suboutine

This commit is contained in:
Miloslav Číž 2019-05-06 19:19:24 +02:00
parent d4872e6984
commit 9881fadb94

477
s3l.h
View file

@ -627,6 +627,248 @@ int S3L_bresenhamStep(S3L_BresenhamState *state)
return state->steps >= 0; return state->steps >= 0;
} }
void _S3L_drawFilledTriangle(
S3L_ScreenCoord x0, S3L_ScreenCoord y0,
S3L_ScreenCoord x1, S3L_ScreenCoord y1,
S3L_ScreenCoord x2, S3L_ScreenCoord y2,
S3L_PixelInfo *p)
{
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)
{
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 one the right
side of it, according to the pixel CENTERS, INCLUDING 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. */
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)
lErrCmp, rErrCmp, // helper for deciding comparison (> vs >=)
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
*/
#define initSide(s,p1,p2,down)\
s##X = p1##PointX;\
s##Dx = p2##PointX - p1##PointX;\
s##Dy = p2##PointY - p1##PointY;\
s##SideUnitStep = (S3L_FRACTIONS_PER_UNIT << S3L_LERP_QUALITY)\
/ (s##Dy != 0 ? s##Dy : 1);\
s##SideUnitPos = 0;\
if (!down)\
{\
s##SideUnitPos = S3L_FRACTIONS_PER_UNIT << S3L_LERP_QUALITY;\
s##SideUnitStep *= -1;\
}\
s##Inc = s##Dx >= 0 ? 1 : -1;\
if (s##Dx < 0)\
{s##Err = 0; s##ErrCmp = 0;}\
else\
{s##Err = s##Dy; s##ErrCmp = 1;}\
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##ErrCmp)\
{\
s##X += s##Inc;\
s##Err -= s##ErrSub;\
}\
s##Err += s##ErrAdd;
initSide(r,t,r,1)
initSide(l,t,l,1)
while (currentY < endY) /* draw the triangle from top to bottom -- the
bottom-most row is left out because, following
from the rasterization rules (see top of the
source), it is to never be rasterized. */
{
if (currentY == splitY) // reached a vertical split of the triangle?
{ // then reinit one side
if (splitOnLeft)
{
initSide(l,l,r,0);
S3L_Unit *tmp = barycentric0;
barycentric0 = barycentric2;
barycentric2 = tmp;
rSideUnitPos = (S3L_FRACTIONS_PER_UNIT << S3L_LERP_QUALITY)
- rSideUnitPos;
rSideUnitStep *= -1;
}
else
{
initSide(r,r,l,0);
S3L_Unit *tmp = barycentric1;
barycentric1 = barycentric2;
barycentric2 = tmp;
lSideUnitPos = (S3L_FRACTIONS_PER_UNIT << S3L_LERP_QUALITY)
- lSideUnitPos;
lSideUnitStep *= -1;
}
}
stepSide(r)
stepSide(l)
p->y = currentY;
// draw the horizontal line
S3L_Unit rowLength = S3L_nonzero(rX - lX - 1); // prevent zero div
S3L_Unit b0 = 0;
S3L_Unit b1 = lSideUnitPos;
S3L_Unit b0Step = rSideUnitPos / rowLength;
S3L_Unit b1Step = lSideUnitPos / rowLength;
for (S3L_ScreenCoord x = lX; x < rX; ++x)
{
*barycentric0 = b0 >> S3L_LERP_QUALITY;
*barycentric1 = b1 >> S3L_LERP_QUALITY;
*barycentric2 = S3L_FRACTIONS_PER_UNIT - *barycentric0 - *barycentric1;
p->x = x;
S3L_PIXEL_FUNCTION(p);
b0 += b0Step;
b1 -= b1Step;
}
lSideUnitPos += lSideUnitStep;
rSideUnitPos += rSideUnitStep;
++currentY;
}
#undef initSide
#undef stepSide
}
void S3L_drawTriangle( void S3L_drawTriangle(
S3L_ScreenCoord x0, S3L_ScreenCoord y0, S3L_ScreenCoord x0, S3L_ScreenCoord y0,
S3L_ScreenCoord x1, S3L_ScreenCoord y1, S3L_ScreenCoord x1, S3L_ScreenCoord y1,
@ -650,240 +892,7 @@ void S3L_drawTriangle(
if (config.mode == S3L_MODE_TRIANGLES) // triangle mode if (config.mode == S3L_MODE_TRIANGLES) // triangle mode
{ {
S3L_ScreenCoord _S3L_drawFilledTriangle(x0,y0,x1,y1,x2,y2,&p);
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)
{
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 one the right
side of it, according to the pixel CENTERS, INCLUDING 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. */
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)
lErrCmp, rErrCmp, // helper for deciding comparison (> vs >=)
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
*/
#define initSide(s,p1,p2,down)\
s##X = p1##PointX;\
s##Dx = p2##PointX - p1##PointX;\
s##Dy = p2##PointY - p1##PointY;\
s##SideUnitStep = (S3L_FRACTIONS_PER_UNIT << S3L_LERP_QUALITY)\
/ (s##Dy != 0 ? s##Dy : 1);\
s##SideUnitPos = 0;\
if (!down)\
{\
s##SideUnitPos = S3L_FRACTIONS_PER_UNIT << S3L_LERP_QUALITY;\
s##SideUnitStep *= -1;\
}\
s##Inc = s##Dx >= 0 ? 1 : -1;\
if (s##Dx < 0)\
{s##Err = 0; s##ErrCmp = 0;}\
else\
{s##Err = s##Dy; s##ErrCmp = 1;}\
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##ErrCmp)\
{\
s##X += s##Inc;\
s##Err -= s##ErrSub;\
}\
s##Err += s##ErrAdd;
initSide(r,t,r,1)
initSide(l,t,l,1)
while (currentY < endY) /* draw the triangle from top to bottom -- the
bottom-most row is left out because, following
from the rasterization rules (see top of the
source), it is to never be rasterized. */
{
if (currentY == splitY) // reached a vertical split of the triangle?
{ // then reinit one side
if (splitOnLeft)
{
initSide(l,l,r,0);
S3L_Unit *tmp = barycentric0;
barycentric0 = barycentric2;
barycentric2 = tmp;
rSideUnitPos = (S3L_FRACTIONS_PER_UNIT << S3L_LERP_QUALITY)
- rSideUnitPos;
rSideUnitStep *= -1;
}
else
{
initSide(r,r,l,0);
S3L_Unit *tmp = barycentric1;
barycentric1 = barycentric2;
barycentric2 = tmp;
lSideUnitPos = (S3L_FRACTIONS_PER_UNIT << S3L_LERP_QUALITY)
- lSideUnitPos;
lSideUnitStep *= -1;
}
}
stepSide(r)
stepSide(l)
p.y = currentY;
// draw the horizontal line
S3L_Unit rowLength = S3L_nonzero(rX - lX - 1); // prevent zero div
S3L_Unit b0 = 0;
S3L_Unit b1 = lSideUnitPos;
S3L_Unit b0Step = rSideUnitPos / rowLength;
S3L_Unit b1Step = lSideUnitPos / rowLength;
for (S3L_ScreenCoord x = lX; x < rX; ++x)
{
*barycentric0 = b0 >> S3L_LERP_QUALITY;
*barycentric1 = b1 >> S3L_LERP_QUALITY;
*barycentric2 = S3L_FRACTIONS_PER_UNIT - *barycentric0 - *barycentric1;
p.x = x;
S3L_PIXEL_FUNCTION(&p);
b0 += b0Step;
b1 -= b1Step;
}
lSideUnitPos += lSideUnitStep;
rSideUnitPos += rSideUnitStep;
++currentY;
}
#undef initSide
#undef stepSide
} }
else if (config.mode == S3L_MODE_LINES) // line mode else if (config.mode == S3L_MODE_LINES) // line mode
{ {