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https://git.coom.tech/drummyfish/small3dlib.git
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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
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@ -627,6 +627,248 @@ int S3L_bresenhamStep(S3L_BresenhamState *state)
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return state->steps >= 0;
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}
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void _S3L_drawFilledTriangle(
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S3L_ScreenCoord x0, S3L_ScreenCoord y0,
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S3L_ScreenCoord x1, S3L_ScreenCoord y1,
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S3L_ScreenCoord x2, S3L_ScreenCoord y2,
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S3L_PixelInfo *p)
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{
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S3L_ScreenCoord
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tPointX, tPointY, // top triangle point coords
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lPointX, lPointY, // left triangle point coords
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rPointX, rPointY; // right triangle point coords
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S3L_Unit *barycentric0; // bar. coord that gets higher from L to R
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S3L_Unit *barycentric1; // bar. coord that gets higher from R to L
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S3L_Unit *barycentric2; // bar. coord that gets higher from bottom up
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// Sort the points.
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#define handleLR(t,a,b)\
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int16_t aDx = x##a - x##t;\
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int16_t bDx = x##b - x##t;\
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int16_t aDy = S3L_nonZero(y##a - y##t);\
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int16_t bDy = S3L_nonZero(y##b - y##t);\
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if ((aDx << 4) / aDy < (bDx << 4) / bDy)\
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/*if (x##a <= x##b)*/\
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{\
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lPointX = x##a; lPointY = y##a;\
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rPointX = x##b; rPointY = y##b;\
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barycentric0 = &(p->barycentric##b);\
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barycentric1 = &(p->barycentric##a);\
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}\
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else\
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{\
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lPointX = x##b; lPointY = y##b;\
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rPointX = x##a; rPointY = y##a;\
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barycentric0 = &(p->barycentric##a);\
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barycentric1 = &(p->barycentric##b);\
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}
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if (y0 <= y1)
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{
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if (y0 <= y2)
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{
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tPointX = x0;
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tPointY = y0;
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barycentric2 = &(p->barycentric0);
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handleLR(0,1,2)
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}
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else
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{
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tPointX = x2;
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tPointY = y2;
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barycentric2 = &(p->barycentric2);
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handleLR(2,0,1)
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}
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}
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else
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{
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if (y1 <= y2)
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{
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tPointX = x1;
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tPointY = y1;
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barycentric2 = &(p->barycentric1);
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handleLR(1,0,2)
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}
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else
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{
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tPointX = x2;
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tPointY = y2;
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barycentric2 = &(p->barycentric2);
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handleLR(2,0,1)
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}
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}
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// Now draw the triangle line by line.
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#undef handleLR
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S3L_ScreenCoord splitY; // Y of the vertically middle point of the triangle
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S3L_ScreenCoord endY; // bottom Y of the whole triangle
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int splitOnLeft; // whether splitY happens on L or R side
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if (rPointY <= lPointY)
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{
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splitY = rPointY;
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splitOnLeft = 0;
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endY = lPointY;
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}
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else
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{
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splitY = lPointY;
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splitOnLeft = 1;
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endY = rPointY;
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}
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S3L_ScreenCoord currentY = tPointY;
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/* We'll be using an algorithm similar to Bresenham line algorithm. The
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specifics of this algorithm are among others:
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- drawing possibly a NON-CONTINUOUS line
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- NOT tracing the line exactly, but rather rasterizing one the right
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side of it, according to the pixel CENTERS, INCLUDING the pixel
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centers
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The principle is this:
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- Move vertically by pixels and accumulate the error (abs(dx/dy)).
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- If the error is greater than one (crossed the next pixel center), keep
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moving horizontally and substracting 1 from the error until it is less
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than 1 again.
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- To make this INTEGER ONLY, scale the case so that distance between
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pixels is equal to dy (instead of 1). This way the error becomes
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dx/dy * dy == dx, and we're comparing the error to (and potentially
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substracting) 1 * dy == dy. */
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int16_t
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/* triangle side:
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left right */
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lX, rX, // current x position
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lDx, rDx, // dx (end point - start point)
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lDy, rDy, // dy (end point - start point)
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lInc, rInc, // direction in which to increment (1 or -1)
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lErr, rErr, // current error (Bresenham)
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lErrCmp, rErrCmp, // helper for deciding comparison (> vs >=)
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lErrAdd, rErrAdd, // error value to add in each Bresenham cycle
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lErrSub, rErrSub; // error value to substract when moving in x direction
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S3L_Unit
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lSideUnitStep, rSideUnitStep,
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lSideUnitPos, rSideUnitPos;
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/* init side for the algorithm, params:
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s - which side (l or r)
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p1 - point from (t, l or r)
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p2 - point to (t, l or r)
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down - whether the side coordinate goes top-down or vice versa
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*/
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#define initSide(s,p1,p2,down)\
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s##X = p1##PointX;\
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s##Dx = p2##PointX - p1##PointX;\
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s##Dy = p2##PointY - p1##PointY;\
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s##SideUnitStep = (S3L_FRACTIONS_PER_UNIT << S3L_LERP_QUALITY)\
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/ (s##Dy != 0 ? s##Dy : 1);\
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s##SideUnitPos = 0;\
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if (!down)\
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{\
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s##SideUnitPos = S3L_FRACTIONS_PER_UNIT << S3L_LERP_QUALITY;\
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s##SideUnitStep *= -1;\
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}\
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s##Inc = s##Dx >= 0 ? 1 : -1;\
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if (s##Dx < 0)\
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{s##Err = 0; s##ErrCmp = 0;}\
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else\
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{s##Err = s##Dy; s##ErrCmp = 1;}\
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s##ErrAdd = S3L_abs(s##Dx);\
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s##ErrSub = s##Dy != 0 ? s##Dy : 1; /* don't allow 0, could lead to an
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infinite substracting loop */
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#define stepSide(s)\
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while (s##Err - s##Dy >= s##ErrCmp)\
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{\
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s##X += s##Inc;\
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s##Err -= s##ErrSub;\
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}\
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s##Err += s##ErrAdd;
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initSide(r,t,r,1)
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initSide(l,t,l,1)
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while (currentY < endY) /* draw the triangle from top to bottom -- the
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bottom-most row is left out because, following
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from the rasterization rules (see top of the
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source), it is to never be rasterized. */
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{
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if (currentY == splitY) // reached a vertical split of the triangle?
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{ // then reinit one side
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if (splitOnLeft)
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{
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initSide(l,l,r,0);
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S3L_Unit *tmp = barycentric0;
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barycentric0 = barycentric2;
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barycentric2 = tmp;
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rSideUnitPos = (S3L_FRACTIONS_PER_UNIT << S3L_LERP_QUALITY)
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- rSideUnitPos;
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rSideUnitStep *= -1;
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}
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else
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{
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initSide(r,r,l,0);
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S3L_Unit *tmp = barycentric1;
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barycentric1 = barycentric2;
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barycentric2 = tmp;
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lSideUnitPos = (S3L_FRACTIONS_PER_UNIT << S3L_LERP_QUALITY)
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- lSideUnitPos;
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lSideUnitStep *= -1;
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}
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}
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stepSide(r)
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stepSide(l)
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p->y = currentY;
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// draw the horizontal line
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S3L_Unit rowLength = S3L_nonzero(rX - lX - 1); // prevent zero div
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S3L_Unit b0 = 0;
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S3L_Unit b1 = lSideUnitPos;
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S3L_Unit b0Step = rSideUnitPos / rowLength;
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S3L_Unit b1Step = lSideUnitPos / rowLength;
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for (S3L_ScreenCoord x = lX; x < rX; ++x)
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{
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*barycentric0 = b0 >> S3L_LERP_QUALITY;
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*barycentric1 = b1 >> S3L_LERP_QUALITY;
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*barycentric2 = S3L_FRACTIONS_PER_UNIT - *barycentric0 - *barycentric1;
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p->x = x;
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S3L_PIXEL_FUNCTION(p);
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b0 += b0Step;
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b1 -= b1Step;
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}
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lSideUnitPos += lSideUnitStep;
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rSideUnitPos += rSideUnitStep;
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++currentY;
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}
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#undef initSide
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#undef stepSide
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}
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void S3L_drawTriangle(
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S3L_ScreenCoord x0, S3L_ScreenCoord y0,
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S3L_ScreenCoord x1, S3L_ScreenCoord y1,
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@ -650,240 +892,7 @@ void S3L_drawTriangle(
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if (config.mode == S3L_MODE_TRIANGLES) // triangle mode
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{
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S3L_ScreenCoord
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tPointX, tPointY, // top triangle point coords
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lPointX, lPointY, // left triangle point coords
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rPointX, rPointY; // right triangle point coords
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S3L_Unit *barycentric0; // bar. coord that gets higher from L to R
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S3L_Unit *barycentric1; // bar. coord that gets higher from R to L
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S3L_Unit *barycentric2; // bar. coord that gets higher from bottom up
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// Sort the points.
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#define handleLR(t,a,b)\
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int16_t aDx = x##a - x##t;\
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int16_t bDx = x##b - x##t;\
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int16_t aDy = S3L_nonZero(y##a - y##t);\
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int16_t bDy = S3L_nonZero(y##b - y##t);\
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if ((aDx << 4) / aDy < (bDx << 4) / bDy)\
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/*if (x##a <= x##b)*/\
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{\
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lPointX = x##a; lPointY = y##a;\
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rPointX = x##b; rPointY = y##b;\
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barycentric0 = &p.barycentric##b;\
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barycentric1 = &p.barycentric##a;\
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}\
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else\
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{\
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lPointX = x##b; lPointY = y##b;\
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rPointX = x##a; rPointY = y##a;\
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barycentric0 = &p.barycentric##a;\
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barycentric1 = &p.barycentric##b;\
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}
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if (y0 <= y1)
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{
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if (y0 <= y2)
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{
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tPointX = x0;
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tPointY = y0;
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barycentric2 = &p.barycentric0;
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handleLR(0,1,2)
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}
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else
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{
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tPointX = x2;
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tPointY = y2;
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barycentric2 = &p.barycentric2;
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handleLR(2,0,1)
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}
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}
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else
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{
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if (y1 <= y2)
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{
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tPointX = x1;
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tPointY = y1;
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barycentric2 = &p.barycentric1;
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handleLR(1,0,2)
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}
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else
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{
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tPointX = x2;
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tPointY = y2;
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barycentric2 = &p.barycentric2;
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handleLR(2,0,1)
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}
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}
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// Now draw the triangle line by line.
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#undef handleLR
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S3L_ScreenCoord splitY; // Y of the vertically middle point of the triangle
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S3L_ScreenCoord endY; // bottom Y of the whole triangle
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int splitOnLeft; // whether splitY happens on L or R side
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if (rPointY <= lPointY)
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{
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splitY = rPointY;
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splitOnLeft = 0;
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endY = lPointY;
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}
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else
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{
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splitY = lPointY;
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splitOnLeft = 1;
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endY = rPointY;
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}
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S3L_ScreenCoord currentY = tPointY;
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/* We'll be using an algorithm similar to Bresenham line algorithm. The
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specifics of this algorithm are among others:
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- drawing possibly a NON-CONTINUOUS line
|
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- NOT tracing the line exactly, but rather rasterizing one the right
|
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side of it, according to the pixel CENTERS, INCLUDING the pixel
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centers
|
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|
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The principle is this:
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- Move vertically by pixels and accumulate the error (abs(dx/dy)).
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- If the error is greater than one (crossed the next pixel center), keep
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moving horizontally and substracting 1 from the error until it is less
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than 1 again.
|
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- To make this INTEGER ONLY, scale the case so that distance between
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pixels is equal to dy (instead of 1). This way the error becomes
|
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dx/dy * dy == dx, and we're comparing the error to (and potentially
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substracting) 1 * dy == dy. */
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int16_t
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/* triangle side:
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left right */
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lX, rX, // current x position
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lDx, rDx, // dx (end point - start point)
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lDy, rDy, // dy (end point - start point)
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lInc, rInc, // direction in which to increment (1 or -1)
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lErr, rErr, // current error (Bresenham)
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lErrCmp, rErrCmp, // helper for deciding comparison (> vs >=)
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lErrAdd, rErrAdd, // error value to add in each Bresenham cycle
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lErrSub, rErrSub; // error value to substract when moving in x direction
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S3L_Unit
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lSideUnitStep, rSideUnitStep,
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lSideUnitPos, rSideUnitPos;
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/* init side for the algorithm, params:
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s - which side (l or r)
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p1 - point from (t, l or r)
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p2 - point to (t, l or r)
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down - whether the side coordinate goes top-down or vice versa
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*/
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#define initSide(s,p1,p2,down)\
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s##X = p1##PointX;\
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s##Dx = p2##PointX - p1##PointX;\
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s##Dy = p2##PointY - p1##PointY;\
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s##SideUnitStep = (S3L_FRACTIONS_PER_UNIT << S3L_LERP_QUALITY)\
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/ (s##Dy != 0 ? s##Dy : 1);\
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s##SideUnitPos = 0;\
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if (!down)\
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{\
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s##SideUnitPos = S3L_FRACTIONS_PER_UNIT << S3L_LERP_QUALITY;\
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s##SideUnitStep *= -1;\
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}\
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s##Inc = s##Dx >= 0 ? 1 : -1;\
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if (s##Dx < 0)\
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{s##Err = 0; s##ErrCmp = 0;}\
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else\
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{s##Err = s##Dy; s##ErrCmp = 1;}\
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s##ErrAdd = S3L_abs(s##Dx);\
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s##ErrSub = s##Dy != 0 ? s##Dy : 1; /* don't allow 0, could lead to an
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infinite substracting loop */
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#define stepSide(s)\
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while (s##Err - s##Dy >= s##ErrCmp)\
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{\
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s##X += s##Inc;\
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s##Err -= s##ErrSub;\
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}\
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s##Err += s##ErrAdd;
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initSide(r,t,r,1)
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initSide(l,t,l,1)
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while (currentY < endY) /* draw the triangle from top to bottom -- the
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bottom-most row is left out because, following
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from the rasterization rules (see top of the
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source), it is to never be rasterized. */
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{
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if (currentY == splitY) // reached a vertical split of the triangle?
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{ // then reinit one side
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if (splitOnLeft)
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{
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initSide(l,l,r,0);
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S3L_Unit *tmp = barycentric0;
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barycentric0 = barycentric2;
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barycentric2 = tmp;
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rSideUnitPos = (S3L_FRACTIONS_PER_UNIT << S3L_LERP_QUALITY)
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- rSideUnitPos;
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rSideUnitStep *= -1;
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}
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else
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{
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initSide(r,r,l,0);
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S3L_Unit *tmp = barycentric1;
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barycentric1 = barycentric2;
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barycentric2 = tmp;
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lSideUnitPos = (S3L_FRACTIONS_PER_UNIT << S3L_LERP_QUALITY)
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- lSideUnitPos;
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lSideUnitStep *= -1;
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}
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}
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stepSide(r)
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stepSide(l)
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p.y = currentY;
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// draw the horizontal line
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S3L_Unit rowLength = S3L_nonzero(rX - lX - 1); // prevent zero div
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S3L_Unit b0 = 0;
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S3L_Unit b1 = lSideUnitPos;
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S3L_Unit b0Step = rSideUnitPos / rowLength;
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S3L_Unit b1Step = lSideUnitPos / rowLength;
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for (S3L_ScreenCoord x = lX; x < rX; ++x)
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{
|
||||
*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