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Start barycentric
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20ec0693a7
commit
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2 changed files with 77 additions and 13 deletions
79
s3l.h
79
s3l.h
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@ -51,6 +51,26 @@ static inline int16_t S3L_max(int16_t v1, int16_t v2)
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return v1 >= v2 ? v1 : v2;
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}
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/**
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Interpolated between two values, v1 and v2, in the same ratio as t is to
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tMax. Does NOT prevent zero division.
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*/
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static inline int16_t S3L_interpolate(int16_t v1, int16_t v2, int16_t t,
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int16_t tMax)
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{
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return v1 + ((v2 - v1) * t) / tMax;
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}
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/**
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Same as S3L_interpolate but with v1 = 0. Should be faster.
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*/
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static inline int16_t S3L_interpolateFrom0(int16_t v2, int16_t t, int16_t tMax)
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{
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return (v2 * t) / tMax;
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}
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void S3L_bresenhamInit(S3L_BresenhamState *state, int16_t x0, int16_t y0, int16_t x1, int16_t y1)
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{
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int16_t dx = x1 - x0;
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@ -165,9 +185,9 @@ void S3L_drawTriangle(int16_t x0, int16_t y0, int16_t x1, int16_t y1, int16_t x2
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#undef handleLR
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S3L_COORD splitY;
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S3L_COORD endY;
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int splitOnLeft;
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S3L_COORD splitY; // Y at which one side (L or R) changes
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S3L_COORD endY; // bottom Y of the whole triangle
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int splitOnLeft; // whether split happens on L or R
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if (rPointY <= lPointY)
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{
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@ -198,12 +218,23 @@ void S3L_drawTriangle(int16_t x0, int16_t y0, int16_t x1, int16_t y1, int16_t x2
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lErrAdd, rErrAdd, // error value to add in each Bresenham cycle
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lErrSub, rErrSub; // error value to substract when moving in x direction
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S3L_UNIT
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lSideUnitStep, rSideUnitStep,
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lSideUnitPos, rSideUnitPos;
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int16_t helperDxAbs;
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#define initSide(v,p1,p2)\
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#define initSide(v,p1,p2, down)\
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v##X = p1##PointX;\
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v##Dx = p2##PointX - p1##PointX;\
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v##Dy = p2##PointY - p1##PointY;\
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v##SideUnitStep = S3L_FRACTIONS_PER_UNIT / (v##Dy != 0 ? v##Dy : 1);\
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v##SideUnitPos = 0;\
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if (!down)\
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{\
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v##SideUnitPos = S3L_FRACTIONS_PER_UNIT;\
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v##SideUnitStep *= -1;\
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}\
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helperDxAbs = S3L_abs(v##Dx);\
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v##Inc = v##Dx >= 0 ? 1 : -1;\
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v##Err = 2 * helperDxAbs - v##Dy;\
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@ -220,8 +251,8 @@ void S3L_drawTriangle(int16_t x0, int16_t y0, int16_t x1, int16_t y1, int16_t x2
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}\
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s##Err += s##ErrAdd;
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initSide(r,t,r)
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initSide(l,t,l)
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initSide(r,t,r,1)
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initSide(l,t,l,1)
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S3L_PixelInfo p;
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@ -229,8 +260,9 @@ void S3L_drawTriangle(int16_t x0, int16_t y0, int16_t x1, int16_t y1, int16_t x2
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p.barycentricB = 0;
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p.barycentricC = 0;
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//lBarStep = S3L_FRACTIONS_PER_UNIT
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//rBarStep = S3L_FRACTIONS_PER_UNIT
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S3L_UNIT *barycentric1 = &p.barycentricA;
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S3L_UNIT *barycentric2 = &p.barycentricB;
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S3L_UNIT *barycentric3 = &p.barycentricC;
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while (currentY <= endY)
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{
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@ -238,11 +270,20 @@ void S3L_drawTriangle(int16_t x0, int16_t y0, int16_t x1, int16_t y1, int16_t x2
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{
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if (splitOnLeft)
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{
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initSide(l,l,r);
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initSide(l,l,r,0);
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barycentric1 = &p.barycentricC;
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barycentric2 = &p.barycentricB;
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barycentric3 = &p.barycentricA;
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rSideUnitPos = S3L_FRACTIONS_PER_UNIT - rSideUnitPos;
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rSideUnitStep *= -1;
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}
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else
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{
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initSide(r,r,l);
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initSide(r,r,l,0);
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// TODO
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}
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}
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@ -250,20 +291,36 @@ void S3L_drawTriangle(int16_t x0, int16_t y0, int16_t x1, int16_t y1, int16_t x2
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// draw the line
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S3L_UNIT tMax = rX - lX;
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tMax = tMax != 0 ? tMax : 1; // prevent division by zero
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S3L_UNIT t1 = 0;
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S3L_UNIT t2 = tMax;
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for (S3L_COORD x = lX; x <= rX; ++x)
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{
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*barycentric1 = S3L_interpolateFrom0(rSideUnitPos,t1,tMax);
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*barycentric2 = S3L_interpolateFrom0(lSideUnitPos,t2,tMax);
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*barycentric3 = S3L_FRACTIONS_PER_UNIT - *barycentric1 - *barycentric2;
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p.x = x;
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S3L_PIXEL_FUNCTION(&p);
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++t1;
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--t2;
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}
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stepSide(r)
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stepSide(l)
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lSideUnitPos += lSideUnitStep;
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rSideUnitPos += rSideUnitStep;
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++currentY;
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}
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#undef initSide
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#undef stepSide
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#undef stepSide
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}
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#endif
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11
testSDL.c
11
testSDL.c
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@ -34,7 +34,13 @@ static inline void setPixel(int x, int y, uint8_t red, uint8_t green, uint8_t bl
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void drawPixel(S3L_PixelInfo *p)
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{
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setPixel(p->x,p->y,255,255,255);
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setPixel(p->x,p->y,
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p->barycentricA / ((float) S3L_FRACTIONS_PER_UNIT) * 255,
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p->barycentricB / ((float) S3L_FRACTIONS_PER_UNIT) * 255,
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p->barycentricC / ((float) S3L_FRACTIONS_PER_UNIT) * 255);
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}
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const int16_t test_coords[] =
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@ -62,10 +68,11 @@ void draw()
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y2 = test_coords[6 * c + 5];
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S3L_drawTriangle(x0,y0,x1,y1,x2,y2);
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/*
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setPixel(x0,y0,255,0,0);
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setPixel(x1,y1,255,0,0);
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setPixel(x2,y2,255,0,0);
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*/
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}
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}
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