mirror of
https://git.coom.tech/drummyfish/small3dlib.git
synced 2024-11-21 20:39:57 +01:00
Create triangle suboutine
This commit is contained in:
Miloslav Číž
parent
d4872e6984
commit
9881fadb94
1 changed files with 243 additions and 234 deletions
477
s3l.h
477
s3l.h
|
|
@ -627,6 +627,248 @@ int S3L_bresenhamStep(S3L_BresenhamState *state)
|
|||
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(
|
||||
S3L_ScreenCoord x0, S3L_ScreenCoord y0,
|
||||
S3L_ScreenCoord x1, S3L_ScreenCoord y1,
|
||||
|
|
@ -650,240 +892,7 @@ void S3L_drawTriangle(
|
|||
|
||||
if (config.mode == S3L_MODE_TRIANGLES) // triangle mode
|
||||
{
|
||||
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
|
||||
_S3L_drawFilledTriangle(x0,y0,x1,y1,x2,y2,&p);
|
||||
}
|
||||
else if (config.mode == S3L_MODE_LINES) // line mode
|
||||
{
|
||||
|
|
|
|||
Loading…
Reference in a new issue