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Fix persp. corr (ugly)
This commit is contained in:
Miloslav Číž
parent
a7237a2aee
commit
625d2436eb
2 changed files with 45 additions and 149 deletions
190
small3dlib.h
190
small3dlib.h
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@ -1077,106 +1077,6 @@ typedef struct
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#define S3L_stepFastLerp(state)\
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state.valueScaled += state.stepScaled
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typedef struct
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{
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S3L_ScreenCoord p0[2]; ///< 2D coordinates of the 1st point projection
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S3L_ScreenCoord p1[2]; ///< 2D coordinates of the 2nd point projection
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S3L_Unit a[3]; ///< 3D coordinates of the 1st projected point of the line
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S3L_Unit b[3]; ///< 3D coordinates of the 2nd projected point of the line
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S3L_Unit pointDifference[3]; ///< [bx - ax, by - ay, bz - cz]
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S3L_ScreenCoord c[2]; /**< helper point to for a plane for the intersection
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with line */
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S3L_Unit fcx; ///< precomputed helper product
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S3L_Unit fcy; ///< precomputed helper product
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S3L_Unit focalLength;
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} S3L_PerspectiveCorrectionState; ///< State for computing persp. correction.
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/**
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Initializes the state of perspective correction along a line. The correction
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itself is then done using S3L_correctPerspective function, using the state.
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*/
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void S3L_initPerspectiveCorrectionState(
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S3L_ScreenCoord x0,
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S3L_ScreenCoord y0,
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S3L_Unit depth0,
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S3L_ScreenCoord x1,
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S3L_ScreenCoord y1,
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S3L_Unit depth1,
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S3L_Unit focalLength,
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S3L_PerspectiveCorrectionState *state)
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{
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state->focalLength = focalLength;
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state->p0[0] = x0;
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state->p0[1] = y0;
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state->p1[0] = x1;
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state->p1[1] = y1;
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state->a[0] = (x0 * (depth0 + focalLength)) / focalLength;
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state->a[1] = (y0 * (depth0 + focalLength)) / focalLength;
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state->a[2] = depth0;
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state->b[0] = (x1 * (depth1 + focalLength)) / focalLength;
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state->b[1] = (y1 * (depth1 + focalLength)) / focalLength;
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state->b[2] = depth1;
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state->pointDifference[0] = state->b[0] - state->a[0];
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state->pointDifference[1] = state->b[1] - state->a[1];
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state->pointDifference[2] = state->b[2] - state->a[2];
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state->c[0] = x1 + y1 - y0;
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state->c[1] = y1 - x1 + x0;
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state->fcx = focalLength * state->c[0];
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state->fcy = focalLength * state->c[1];
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}
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S3L_Unit S3L_correctPerspective(
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S3L_Unit interpolationParameter, S3L_PerspectiveCorrectionState *state)
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{
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S3L_Unit p[2]; // lin. interpolated position between the projections
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// TODO: perhaps this could be interpolated faster by stepping?
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p[0] =
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S3L_interpolateByUnit(state->p0[0],state->p1[0],interpolationParameter);
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p[1] =
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S3L_interpolateByUnit(state->p0[1],state->p1[1],interpolationParameter);
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S3L_Unit a, b, c, d; // plane coeficients
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a = state->focalLength * p[1] - state->fcy;
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b = state->fcx - state->focalLength * p[0];
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c = p[0] * state->c[1] - p[1] * state->c[0];
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d = state->focalLength * c;
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a >>= 4; // TODO: this sometimes prevents overflow, but should be solved better!
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b >>= 4;
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c >>= 4;
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d >>= 4;
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S3L_Unit result =
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(
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- a * state->a[0] - b * state->a[1] - c * state->a[2] - d
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)
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/
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S3L_nonZero(
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(
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a * state->pointDifference[0] +
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b * state->pointDifference[1] +
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c * state->pointDifference[2]
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) / S3L_FRACTIONS_PER_UNIT
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);
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return result < 0 ? 0 :
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(result > S3L_FRACTIONS_PER_UNIT ? S3L_FRACTIONS_PER_UNIT : result);
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}
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static inline S3L_Unit S3L_interpolateBarycentric(
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S3L_Unit value0,
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S3L_Unit value1,
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@ -1475,22 +1375,23 @@ 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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#define initPC(f,t,pc)\
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S3L_initPerspectiveCorrectionState(\
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f##PointPP->x,\
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f##PointPP->y,\
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f##PointPP->z,\
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t##PointPP->x,\
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t##PointPP->y,\
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t##PointPP->z,\
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camera->focalLength,\
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&pc##PC);
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#if S3L_PERSPECTIVE_CORRECTION == S3L_PC_FULL
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S3L_PerspectiveCorrectionState lPC, rPC, rowPC;
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S3L_Unit tPointRecipZ, lPointRecipZ, rPointRecipZ,
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lRecip0, lRecip1, rRecip0, rRecip1;
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initPC(t,l,l)
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initPC(t,r,r)
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tPointRecipZ = (S3L_FRACTIONS_PER_UNIT * S3L_FRACTIONS_PER_UNIT)
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/ S3L_nonZero(tPointPP->z);
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lPointRecipZ = (S3L_FRACTIONS_PER_UNIT * S3L_FRACTIONS_PER_UNIT)
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/ S3L_nonZero(lPointPP->z);
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rPointRecipZ = (S3L_FRACTIONS_PER_UNIT * S3L_FRACTIONS_PER_UNIT)
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/ S3L_nonZero(rPointPP->z);
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lRecip0 = tPointRecipZ;
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lRecip1 = lPointRecipZ;
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rRecip0 = tPointRecipZ;
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rRecip1 = rPointRecipZ;
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#endif
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// clip to the screen in y dimension:
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@ -1519,20 +1420,22 @@ void S3L_drawTriangle(
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{
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initSide(l,l,r,0);
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manageSplit(0,2,r)
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#if S3L_PERSPECTIVE_CORRECTION == S3L_PC_FULL
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initPC(r,l,l)
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initPC(r,t,r)
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lRecip0 = rPointRecipZ;
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lRecip1 = lPointRecipZ;
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rRecip0 = rPointRecipZ;
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rRecip1 = tPointRecipZ ;
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#endif
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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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manageSplit(1,2,l)
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#if S3L_PERSPECTIVE_CORRECTION == S3L_PC_FULL
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initPC(l,r,r)
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initPC(l,t,l)
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rRecip0 = lPointRecipZ;
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rRecip1 = rPointRecipZ;
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lRecip0 = lPointRecipZ;
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lRecip1 = tPointRecipZ;
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#endif
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}
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}
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@ -1552,26 +1455,16 @@ void S3L_drawTriangle(
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S3L_Unit rowLength = S3L_nonZero(rX - lX - 1); // prevent zero div
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#if S3L_PERSPECTIVE_CORRECTION == S3L_PC_FULL
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S3L_Unit
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lDepth, rDepth,
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lT, rT; // perspective-corrected position along either side
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S3L_Unit lOverZ, lRecipZ, rOverZ, rRecipZ, lT, rT;
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lT = S3L_correctPerspective(S3L_getFastLerpValue(lSideFLS),&lPC);
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rT = S3L_correctPerspective(S3L_getFastLerpValue(rSideFLS),&rPC);
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lT = S3L_getFastLerpValue(lSideFLS);
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rT = S3L_getFastLerpValue(rSideFLS);
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lDepth = S3L_interpolateByUnit(lPC.a[2],lPC.b[2],lT);
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rDepth = S3L_interpolateByUnit(rPC.a[2],rPC.b[2],rT);
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lOverZ = S3L_interpolateByUnitFrom0(lRecip1,lT);
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lRecipZ = S3L_interpolateByUnit(lRecip0,lRecip1,lT);
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S3L_initPerspectiveCorrectionState(
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S3L_interpolateByUnit(lPC.a[0],lPC.b[0],lT),
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S3L_interpolateByUnit(lPC.a[1],lPC.b[1],lT),
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lDepth,
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S3L_interpolateByUnit(rPC.a[0],rPC.b[0],rT),
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S3L_interpolateByUnit(rPC.a[1],rPC.b[1],rT),
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rDepth,
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camera->focalLength,
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&rowPC
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);
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rOverZ = S3L_interpolateByUnitFrom0(rRecip1,rT);
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rRecipZ = S3L_interpolateByUnit(rRecip0,rRecip1,rT);
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#else
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S3L_FastLerpState b0FLS, b1FLS;
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@ -1619,16 +1512,8 @@ void S3L_drawTriangle(
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#endif
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p.x = x;
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#if S3L_PERSPECTIVE_CORRECTION == S3L_PC_FULL
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S3L_Unit rowT =
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S3L_correctPerspective(S3L_interpolateFrom0(S3L_FRACTIONS_PER_UNIT,
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x - lX,rowLength),&rowPC);
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#endif
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#if S3L_COMPUTE_DEPTH
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#if S3L_PERSPECTIVE_CORRECTION == S3L_PC_FULL
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p.depth = S3L_interpolateByUnit(lDepth,rDepth,rowT);
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#else
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#if S3L_PERSPECTIVE_CORRECTION != S3L_PC_FULL
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p.depth = S3L_getFastLerpValue(depthFLS);
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S3L_stepFastLerp(depthFLS);
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#endif
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@ -1645,11 +1530,20 @@ void S3L_drawTriangle(
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#endif
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#if S3L_PERSPECTIVE_CORRECTION == S3L_PC_FULL
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p.depth = (S3L_FRACTIONS_PER_UNIT * S3L_FRACTIONS_PER_UNIT) /
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S3L_nonZero(S3L_interpolate(lRecipZ,rRecipZ,x - lX,rX - lX));
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*barycentric0 =
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S3L_interpolateByUnitFrom0(rT,rowT);
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(
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S3L_interpolate(0,rOverZ,x - lX,rX - lX)
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* p.depth
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) / S3L_FRACTIONS_PER_UNIT;
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*barycentric1 =
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S3L_interpolateByUnitFrom0(lT,S3L_FRACTIONS_PER_UNIT - rowT);
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(
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S3L_interpolate(lOverZ,0,x - lX,rX - lX)
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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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@ -7,7 +7,9 @@
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#include <stdio.h>
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#include <math.h>
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#define S3L_PRESET_HIGHEST_QUALITY
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//#define S3L_PRESET_HIGHEST_QUALITY
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#define S3L_PERSPECTIVE_CORRECTION 1
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#define S3L_PIXEL_FUNCTION drawPixel
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