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Use stepping lerp

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This commit is contained in:
Miloslav Číž 2019-05-06 19:02:58 +02:00
parent 5849cc6f17
commit d4872e6984
2 changed files with 23 additions and 20 deletions
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38
s3l.h
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@ -121,12 +121,15 @@ typedef int32_t S3L_Unit; /**< Units of measurement in 3D space. There is
it will overflow. Also other things
may overflow, so rather don't do it. */
#define S3L_LERP_QUALITY 3 /**< Quality (scaling) of SOME linear interpolations.
0 will most likely be faster, but artifacts can
occur, while higher values can fix this -- in
theory all higher values will have the same
speed (it is a shift value), but it mustn't be
too high to prevent overflow (3 seems okay). */
#ifndef S3L_LERP_QUALITY
#define S3L_LERP_QUALITY 8 /**< Quality (scaling) of SOME linear
interpolations. 0 will most likely be faster,
but artifacts can occur for bigger tris,
while higher values can fix this -- in theory
all higher values will have the same speed
(it is a shift value), but it mustn't be too
high to prevent overflow. */
#endif
#define S3L_nonzero(value) ((value) != 0 ? (value) : 1) /**< prevents division
by zero */
@ -852,26 +855,25 @@ void S3L_drawTriangle(
// draw the horizontal line
S3L_Unit tMax = S3L_nonzero(rX - lX - 1); // prevent division by zero
S3L_Unit t1 = 0;
S3L_Unit t2 = tMax;
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)
{
// TODO: try to do this with stepping and S3L_LERP_QUALITY
*barycentric0 =
S3L_interpolateFrom0(rSideUnitPos >> S3L_LERP_QUALITY,t1,tMax);
*barycentric1 =
S3L_interpolateFrom0(lSideUnitPos >> S3L_LERP_QUALITY,t2,tMax);
*barycentric0 = b0 >> S3L_LERP_QUALITY;
*barycentric1 = b1 >> S3L_LERP_QUALITY;
*barycentric2 = S3L_FRACTIONS_PER_UNIT - *barycentric0 - *barycentric1;
p.x = x;
S3L_PIXEL_FUNCTION(&p);
++t1;
--t2;
b0 += b0Step;
b1 -= b1Step;
}
lSideUnitPos += lSideUnitStep;

5
testSDL.c
View file

@ -76,12 +76,13 @@ void drawPixel(S3L_PixelInfo *p)
uint8_t col = texturePixel(u,v);
// setPixel(p->x,p->y,col * 120,20,(2 - col) * 120);
setPixel(p->x,p->y,col * 120,20,(2 - col) * 120);
/*
setPixel(p->x,p->y,
p->barycentric0 / ((float) S3L_FRACTIONS_PER_UNIT) * 255,
p->barycentric1 / ((float) S3L_FRACTIONS_PER_UNIT) * 255,
p->barycentric2 / ((float) S3L_FRACTIONS_PER_UNIT) * 255);
*/
}
const int16_t test_coords[] =