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Add triangle clipping

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This commit is contained in:
Miloslav Číž 2019-05-11 17:19:41 +02:00
parent 78fe74caf3
commit 229c3f465a
2 changed files with 79 additions and 51 deletions
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126
s3l.h
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@ -1022,6 +1022,13 @@ void _S3L_drawFilledTriangle(
initPC(t,r,r)
#endif
// clip to the screen in y dimension:
endY = S3L_min(endY,S3L_RESOLUTION_Y);
/* Clipping above the screen (y < 0) can't be easily done here, will be
handled inside the loop. */
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
@ -1062,64 +1069,85 @@ void _S3L_drawFilledTriangle(
stepSide(r)
stepSide(l)
p->y = currentY;
// draw the horizontal line
S3L_Unit rowLength = S3L_nonZero(rX - lX - 1); // prevent zero div
#if S3L_PERSPECTIVE_CORRECTION == 1
S3L_Unit
lDepth, rDepth,
lT, rT; // perspective-corrected position along either side
lT = S3L_correctPerspective(lSideUnitPosScaled >> S3L_LERP_QUALITY,&lPC);
rT = S3L_correctPerspective(rSideUnitPosScaled >> S3L_LERP_QUALITY,&rPC);
lDepth = S3L_interpolateByUnit(lPC.a[2],lPC.b[2],lT);
rDepth = S3L_interpolateByUnit(rPC.a[2],rPC.b[2],rT);
S3L_initPerspectiveCorrectionState(
S3L_interpolateByUnit(lPC.a[0],lPC.b[0],lT),
S3L_interpolateByUnit(lPC.a[1],lPC.b[1],lT),
lDepth,
S3L_interpolateByUnit(rPC.a[0],rPC.b[0],rT),
S3L_interpolateByUnit(rPC.a[1],rPC.b[1],rT),
rDepth,
camera->focalLength,
&rowPC
);
#else
S3L_Unit b0 = 0;
S3L_Unit b1 = lSideUnitPosScaled;
S3L_Unit b0Step = rSideUnitPosScaled / rowLength;
S3L_Unit b1Step = lSideUnitPosScaled / rowLength;
#endif
for (S3L_ScreenCoord x = lX; x < rX; ++x)
if (currentY >= 0) /* clipping of pixels whose y < 0 (can't be easily done
outside the loop) */
{
p->y = currentY;
// draw the horizontal line
S3L_Unit rowLength = S3L_nonZero(rX - lX - 1); // prevent zero div
#if S3L_PERSPECTIVE_CORRECTION == 1
S3L_Unit rowT =
S3L_correctPerspective(S3L_interpolateFrom0(S3L_FRACTIONS_PER_UNIT,
x - lX,rowLength),&rowPC);
S3L_Unit
lDepth, rDepth,
lT, rT; // perspective-corrected position along either side
*barycentric0 = S3L_interpolateByUnitFrom0(rT,rowT);
*barycentric1 = S3L_interpolateByUnit(lT,0,rowT);
lT = S3L_correctPerspective(lSideUnitPosScaled >> S3L_LERP_QUALITY,&lPC);
rT = S3L_correctPerspective(rSideUnitPosScaled >> S3L_LERP_QUALITY,&rPC);
lDepth = S3L_interpolateByUnit(lPC.a[2],lPC.b[2],lT);
rDepth = S3L_interpolateByUnit(rPC.a[2],rPC.b[2],rT);
S3L_initPerspectiveCorrectionState(
S3L_interpolateByUnit(lPC.a[0],lPC.b[0],lT),
S3L_interpolateByUnit(lPC.a[1],lPC.b[1],lT),
lDepth,
S3L_interpolateByUnit(rPC.a[0],rPC.b[0],rT),
S3L_interpolateByUnit(rPC.a[1],rPC.b[1],rT),
rDepth,
camera->focalLength,
&rowPC
);
#else
*barycentric0 = b0 >> S3L_LERP_QUALITY;
*barycentric1 = b1 >> S3L_LERP_QUALITY;
S3L_Unit b0 = 0;
S3L_Unit b1 = lSideUnitPosScaled;
b0 += b0Step;
b1 -= b1Step;
S3L_Unit b0Step = rSideUnitPosScaled / rowLength;
S3L_Unit b1Step = lSideUnitPosScaled / rowLength;
#endif
*barycentric2 = S3L_FRACTIONS_PER_UNIT - *barycentric0 - *barycentric1;
// clip to the screen in x dimension:
p->x = x;
S3L_PIXEL_FUNCTION(p);
}
S3L_ScreenCoord rXClipped = S3L_min(rX,S3L_RESOLUTION_X),
lXClipped = lX;
if (lXClipped < 0)
{
lXClipped = 0;
#if S3L_PERSPECTIVE_CORRECTION != 1
b0 -= lX * b0Step;
b1 += lX * b1Step;
#endif
}
// draw the row:
for (S3L_ScreenCoord x = lXClipped; x < rXClipped; ++x)
{
#if S3L_PERSPECTIVE_CORRECTION == 1
S3L_Unit rowT =
S3L_correctPerspective(S3L_interpolateFrom0(S3L_FRACTIONS_PER_UNIT,
x - lX,rowLength),&rowPC);
*barycentric0 = S3L_interpolateByUnitFrom0(rT,rowT);
*barycentric1 = S3L_interpolateByUnit(lT,0,rowT);
#else
*barycentric0 = b0 >> S3L_LERP_QUALITY;
*barycentric1 = b1 >> S3L_LERP_QUALITY;
b0 += b0Step;
b1 -= b1Step;
#endif
*barycentric2 = S3L_FRACTIONS_PER_UNIT - *barycentric0 - *barycentric1;
p->x = x;
S3L_PIXEL_FUNCTION(p);
}
} // y clipping
lSideUnitPosScaled += lSideStep;
rSideUnitPosScaled += rSideStep;

4
testSDL.c
View file

@ -132,8 +132,8 @@ void draw()
modelTransform.rotation.z = frame * 0.1;
modelTransform.rotation.x = frame * 0.3;
// modelTransform.translation.x = sin(frame >> 3) * 700;
// modelTransform.translation.y = sin(frame >> 4) * 600;
modelTransform.translation.x = sin(frame >> 7) * 700;
modelTransform.translation.y = sin(frame >> 8) * 600;
S3L_drawModelIndexed(ver,tri,12,modelTransform,&camera,&conf);