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Implement approximate PC (ugly)
This commit is contained in:
Miloslav Číž
parent
d1b20675d3
commit
15d17a9c02
2 changed files with 88 additions and 14 deletions
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@ -11,7 +11,7 @@
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#define S3L_FLAT 0
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#define S3L_STRICT_NEAR_CULLING 0
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#define S3L_PERSPECTIVE_CORRECTION 1
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#define S3L_PERSPECTIVE_CORRECTION 2
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#define S3L_SORT 2
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#define S3L_STENCIL_BUFFER 1
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#define S3L_Z_BUFFER 0
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100
small3dlib.h
100
small3dlib.h
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@ -177,11 +177,16 @@ typedef uint16_t S3L_Index;
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is an expensive operation! Possible values:
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- 0: No perspective correction. Fastest, ugly.
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- 1: Per-pixel perspective correction, nice but very expensive.*/
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- 1: Per-pixel perspective correction, nice but very expensive.
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- 2: Approximation (computing only at every S3L_PC_APPROX_LENGTHth pixel). */
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#define S3L_PERSPECTIVE_CORRECTION 0
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#endif
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#ifndef S3L_PC_APPROX_LENGTH
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#define S3L_PC_APPROX_LENGTH 32
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#endif
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#if S3L_PERSPECTIVE_CORRECTION
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#define S3L_COMPUTE_DEPTH 1 // PC inevitably computes depth, so enable it
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#endif
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@ -695,7 +700,7 @@ static inline int8_t S3L_stencilTest(
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#endif
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#define S3L_COMPUTE_LERP_DEPTH\
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(S3L_COMPUTE_DEPTH && (S3L_PERSPECTIVE_CORRECTION != 1))
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(S3L_COMPUTE_DEPTH && (S3L_PERSPECTIVE_CORRECTION == 0))
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#define S3L_SIN_TABLE_LENGTH 128
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@ -1758,7 +1763,7 @@ void S3L_drawTriangle(
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initSide(r,t,r,1)
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initSide(l,t,l,1)
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#if S3L_PERSPECTIVE_CORRECTION == 1
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#if S3L_PERSPECTIVE_CORRECTION != 0
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/* PC is done by linearly interpolating reciprocals from which the corrected
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velues can be computed. See
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http://www.lysator.liu.se/~mikaelk/doc/perspectivetexture/ */
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@ -1842,7 +1847,7 @@ void S3L_drawTriangle(
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#if !S3L_FLAT
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S3L_Unit rowLength = S3L_nonZero(rX - lX - 1); // prevent zero div
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#if S3L_PERSPECTIVE_CORRECTION == 1
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#if S3L_PERSPECTIVE_CORRECTION != 0
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S3L_Unit lOverZ, lRecipZ, rOverZ, rRecipZ, lT, rT;
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lT = S3L_getFastLerpValue(lSideFLS);
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@ -1869,6 +1874,7 @@ void S3L_drawTriangle(
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b0FLS.stepScaled = rSideFLS.valueScaled / rowLength;
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b1FLS.stepScaled = -1 * lSideFLS.valueScaled / rowLength;
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#endif
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#endif
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@ -1881,7 +1887,7 @@ void S3L_drawTriangle(
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{
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lXClipped = 0;
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#if S3L_PERSPECTIVE_CORRECTION != 1 && !S3L_FLAT
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#if S3L_PERSPECTIVE_CORRECTION == 0 && !S3L_FLAT
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b0FLS.valueScaled -= lX * b0FLS.stepScaled;
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b1FLS.valueScaled -= lX * b1FLS.stepScaled;
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@ -1891,7 +1897,7 @@ void S3L_drawTriangle(
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#endif
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}
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#if S3L_PERSPECTIVE_CORRECTION == 1
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#if S3L_PERSPECTIVE_CORRECTION != 0
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S3L_ScreenCoord i = lXClipped - lX; /* helper var to save one
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substraction in the inner
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loop */
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@ -1912,6 +1918,29 @@ void S3L_drawTriangle(
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// draw the row -- inner loop:
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#if S3L_PERSPECTIVE_CORRECTION == 2
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S3L_FastLerpState depthPC, b0PC, b1PC;
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depthPC.valueScaled =
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((S3L_FRACTIONS_PER_UNIT * S3L_FRACTIONS_PER_UNIT) /
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S3L_nonZero(S3L_interpolate(lRecipZ,rRecipZ,i,rowLength)))
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<< S3L_FAST_LERP_QUALITY;
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b0PC.valueScaled =
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(
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S3L_interpolateFrom0(rOverZ,i,rowLength)
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* depthPC.valueScaled
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) / S3L_FRACTIONS_PER_UNIT;
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b1PC.valueScaled =
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(
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(lOverZ - S3L_interpolateFrom0(lOverZ,i,rowLength))
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* depthPC.valueScaled
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) / S3L_FRACTIONS_PER_UNIT;
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int8_t rowCount = S3L_PC_APPROX_LENGTH;
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#endif
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for (S3L_ScreenCoord x = lXClipped; x < rXClipped; ++x)
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{
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int8_t testsPassed = 1;
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@ -1926,6 +1955,42 @@ void S3L_drawTriangle(
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#if S3L_PERSPECTIVE_CORRECTION == 1
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p.depth = (S3L_FRACTIONS_PER_UNIT * S3L_FRACTIONS_PER_UNIT) /
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S3L_nonZero(S3L_interpolate(lRecipZ,rRecipZ,i,rowLength));
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#elif S3L_PERSPECTIVE_CORRECTION == 2
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if (rowCount >= S3L_PC_APPROX_LENGTH)
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{
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rowCount = 0;
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S3L_Unit nextI = i + S3L_PC_APPROX_LENGTH;
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S3L_Unit nextDepth =
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(
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(S3L_FRACTIONS_PER_UNIT * S3L_FRACTIONS_PER_UNIT) /
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S3L_nonZero(S3L_interpolate(lRecipZ,rRecipZ,nextI,rowLength))
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) << S3L_FAST_LERP_QUALITY;
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depthPC.stepScaled =
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(nextDepth - depthPC.valueScaled) / S3L_PC_APPROX_LENGTH;
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S3L_Unit nextValue =
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(
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S3L_interpolateFrom0(rOverZ,nextI,rowLength)
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* nextDepth
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) / S3L_FRACTIONS_PER_UNIT;
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b0PC.stepScaled =
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(nextValue - b0PC.valueScaled) / S3L_PC_APPROX_LENGTH;
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nextValue =
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(
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(lOverZ - S3L_interpolateFrom0(lOverZ,nextI,rowLength))
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* nextDepth
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) / S3L_FRACTIONS_PER_UNIT;
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b1PC.stepScaled =
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(nextValue - b1PC.valueScaled) / S3L_PC_APPROX_LENGTH;
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}
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p.depth = S3L_getFastLerpValue(depthPC);
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#else
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p.depth = S3L_getFastLerpValue(depthFLS);
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S3L_stepFastLerp(depthFLS);
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@ -1942,7 +2007,10 @@ void S3L_drawTriangle(
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if (testsPassed)
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{
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#if !S3L_FLAT
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#if S3L_PERSPECTIVE_CORRECTION == 1
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#if S3L_PERSPECTIVE_CORRECTION == 0
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*barycentric0 = S3L_getFastLerpValue(b0FLS);
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*barycentric1 = S3L_getFastLerpValue(b1FLS);
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#elif S3L_PERSPECTIVE_CORRECTION == 1
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*barycentric0 =
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(
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S3L_interpolateFrom0(rOverZ,i,rowLength)
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@ -1954,21 +2022,27 @@ void S3L_drawTriangle(
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(lOverZ - S3L_interpolateFrom0(lOverZ,i,rowLength))
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* p.depth
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) / S3L_FRACTIONS_PER_UNIT;
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#else
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*barycentric0 = S3L_getFastLerpValue(b0FLS);
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*barycentric1 = S3L_getFastLerpValue(b1FLS);
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#elif S3L_PERSPECTIVE_CORRECTION == 2
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*barycentric0 = S3L_getFastLerpValue(b0PC);
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*barycentric1 = S3L_getFastLerpValue(b1PC);
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#endif
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*barycentric2 =
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S3L_FRACTIONS_PER_UNIT - *barycentric0 - *barycentric1;
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#endif
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S3L_PIXEL_FUNCTION(&p);
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}
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#if !S3L_FLAT
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#if S3L_PERSPECTIVE_CORRECTION == 1
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i++;
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#if S3L_PERSPECTIVE_CORRECTION != 0
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i++;
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#if S3L_PERSPECTIVE_CORRECTION == 2
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rowCount++;
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S3L_stepFastLerp(depthPC);
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S3L_stepFastLerp(b0PC);
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S3L_stepFastLerp(b1PC);
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#endif
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#else
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S3L_stepFastLerp(b0FLS);
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S3L_stepFastLerp(b1FLS);
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