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Implement approximate PC (ugly)

This commit is contained in:
Miloslav Číž 2019-06-09 23:22:57 +02:00
parent d1b20675d3
commit 15d17a9c02
2 changed files with 88 additions and 14 deletions

View file

@ -11,7 +11,7 @@
#define S3L_FLAT 0
#define S3L_STRICT_NEAR_CULLING 0
#define S3L_PERSPECTIVE_CORRECTION 1
#define S3L_PERSPECTIVE_CORRECTION 2
#define S3L_SORT 2
#define S3L_STENCIL_BUFFER 1
#define S3L_Z_BUFFER 0

View file

@ -177,11 +177,16 @@ typedef uint16_t S3L_Index;
is an expensive operation! Possible values:
- 0: No perspective correction. Fastest, ugly.
- 1: Per-pixel perspective correction, nice but very expensive.*/
- 1: Per-pixel perspective correction, nice but very expensive.
- 2: Approximation (computing only at every S3L_PC_APPROX_LENGTHth pixel). */
#define S3L_PERSPECTIVE_CORRECTION 0
#endif
#ifndef S3L_PC_APPROX_LENGTH
#define S3L_PC_APPROX_LENGTH 32
#endif
#if S3L_PERSPECTIVE_CORRECTION
#define S3L_COMPUTE_DEPTH 1 // PC inevitably computes depth, so enable it
#endif
@ -695,7 +700,7 @@ static inline int8_t S3L_stencilTest(
#endif
#define S3L_COMPUTE_LERP_DEPTH\
(S3L_COMPUTE_DEPTH && (S3L_PERSPECTIVE_CORRECTION != 1))
(S3L_COMPUTE_DEPTH && (S3L_PERSPECTIVE_CORRECTION == 0))
#define S3L_SIN_TABLE_LENGTH 128
@ -1758,7 +1763,7 @@ void S3L_drawTriangle(
initSide(r,t,r,1)
initSide(l,t,l,1)
#if S3L_PERSPECTIVE_CORRECTION == 1
#if S3L_PERSPECTIVE_CORRECTION != 0
/* PC is done by linearly interpolating reciprocals from which the corrected
velues can be computed. See
http://www.lysator.liu.se/~mikaelk/doc/perspectivetexture/ */
@ -1842,7 +1847,7 @@ void S3L_drawTriangle(
#if !S3L_FLAT
S3L_Unit rowLength = S3L_nonZero(rX - lX - 1); // prevent zero div
#if S3L_PERSPECTIVE_CORRECTION == 1
#if S3L_PERSPECTIVE_CORRECTION != 0
S3L_Unit lOverZ, lRecipZ, rOverZ, rRecipZ, lT, rT;
lT = S3L_getFastLerpValue(lSideFLS);
@ -1869,6 +1874,7 @@ void S3L_drawTriangle(
b0FLS.stepScaled = rSideFLS.valueScaled / rowLength;
b1FLS.stepScaled = -1 * lSideFLS.valueScaled / rowLength;
#endif
#endif
@ -1881,7 +1887,7 @@ void S3L_drawTriangle(
{
lXClipped = 0;
#if S3L_PERSPECTIVE_CORRECTION != 1 && !S3L_FLAT
#if S3L_PERSPECTIVE_CORRECTION == 0 && !S3L_FLAT
b0FLS.valueScaled -= lX * b0FLS.stepScaled;
b1FLS.valueScaled -= lX * b1FLS.stepScaled;
@ -1891,7 +1897,7 @@ void S3L_drawTriangle(
#endif
}
#if S3L_PERSPECTIVE_CORRECTION == 1
#if S3L_PERSPECTIVE_CORRECTION != 0
S3L_ScreenCoord i = lXClipped - lX; /* helper var to save one
substraction in the inner
loop */
@ -1912,6 +1918,29 @@ void S3L_drawTriangle(
// draw the row -- inner loop:
#if S3L_PERSPECTIVE_CORRECTION == 2
S3L_FastLerpState depthPC, b0PC, b1PC;
depthPC.valueScaled =
((S3L_FRACTIONS_PER_UNIT * S3L_FRACTIONS_PER_UNIT) /
S3L_nonZero(S3L_interpolate(lRecipZ,rRecipZ,i,rowLength)))
<< S3L_FAST_LERP_QUALITY;
b0PC.valueScaled =
(
S3L_interpolateFrom0(rOverZ,i,rowLength)
* depthPC.valueScaled
) / S3L_FRACTIONS_PER_UNIT;
b1PC.valueScaled =
(
(lOverZ - S3L_interpolateFrom0(lOverZ,i,rowLength))
* depthPC.valueScaled
) / S3L_FRACTIONS_PER_UNIT;
int8_t rowCount = S3L_PC_APPROX_LENGTH;
#endif
for (S3L_ScreenCoord x = lXClipped; x < rXClipped; ++x)
{
int8_t testsPassed = 1;
@ -1926,6 +1955,42 @@ void S3L_drawTriangle(
#if S3L_PERSPECTIVE_CORRECTION == 1
p.depth = (S3L_FRACTIONS_PER_UNIT * S3L_FRACTIONS_PER_UNIT) /
S3L_nonZero(S3L_interpolate(lRecipZ,rRecipZ,i,rowLength));
#elif S3L_PERSPECTIVE_CORRECTION == 2
if (rowCount >= S3L_PC_APPROX_LENGTH)
{
rowCount = 0;
S3L_Unit nextI = i + S3L_PC_APPROX_LENGTH;
S3L_Unit nextDepth =
(
(S3L_FRACTIONS_PER_UNIT * S3L_FRACTIONS_PER_UNIT) /
S3L_nonZero(S3L_interpolate(lRecipZ,rRecipZ,nextI,rowLength))
) << S3L_FAST_LERP_QUALITY;
depthPC.stepScaled =
(nextDepth - depthPC.valueScaled) / S3L_PC_APPROX_LENGTH;
S3L_Unit nextValue =
(
S3L_interpolateFrom0(rOverZ,nextI,rowLength)
* nextDepth
) / S3L_FRACTIONS_PER_UNIT;
b0PC.stepScaled =
(nextValue - b0PC.valueScaled) / S3L_PC_APPROX_LENGTH;
nextValue =
(
(lOverZ - S3L_interpolateFrom0(lOverZ,nextI,rowLength))
* nextDepth
) / S3L_FRACTIONS_PER_UNIT;
b1PC.stepScaled =
(nextValue - b1PC.valueScaled) / S3L_PC_APPROX_LENGTH;
}
p.depth = S3L_getFastLerpValue(depthPC);
#else
p.depth = S3L_getFastLerpValue(depthFLS);
S3L_stepFastLerp(depthFLS);
@ -1942,7 +2007,10 @@ void S3L_drawTriangle(
if (testsPassed)
{
#if !S3L_FLAT
#if S3L_PERSPECTIVE_CORRECTION == 1
#if S3L_PERSPECTIVE_CORRECTION == 0
*barycentric0 = S3L_getFastLerpValue(b0FLS);
*barycentric1 = S3L_getFastLerpValue(b1FLS);
#elif S3L_PERSPECTIVE_CORRECTION == 1
*barycentric0 =
(
S3L_interpolateFrom0(rOverZ,i,rowLength)
@ -1954,21 +2022,27 @@ void S3L_drawTriangle(
(lOverZ - S3L_interpolateFrom0(lOverZ,i,rowLength))
* p.depth
) / S3L_FRACTIONS_PER_UNIT;
#else
*barycentric0 = S3L_getFastLerpValue(b0FLS);
*barycentric1 = S3L_getFastLerpValue(b1FLS);
#elif S3L_PERSPECTIVE_CORRECTION == 2
*barycentric0 = S3L_getFastLerpValue(b0PC);
*barycentric1 = S3L_getFastLerpValue(b1PC);
#endif
*barycentric2 =
S3L_FRACTIONS_PER_UNIT - *barycentric0 - *barycentric1;
#endif
S3L_PIXEL_FUNCTION(&p);
}
#if !S3L_FLAT
#if S3L_PERSPECTIVE_CORRECTION == 1
#if S3L_PERSPECTIVE_CORRECTION != 0
i++;
#if S3L_PERSPECTIVE_CORRECTION == 2
rowCount++;
S3L_stepFastLerp(depthPC);
S3L_stepFastLerp(b0PC);
S3L_stepFastLerp(b1PC);
#endif
#else
S3L_stepFastLerp(b0FLS);
S3L_stepFastLerp(b1FLS);