Thread: Gouraud Shading problem

I removed the code fragment

I found the errors in the code fragment above, the most serious of which was that I forgot to call sqrt() for the left and right edges.

I've posted this a million times here but....

Code:

//No assembly
double BI(double v1,double v2,double v3,double v4,double f1,double f2)
{
  double val1=v1+f1*(v2-v1);
  double val2=v3+f1*(v4-v3);
  return (val1+f2*(val2-val1));
}

//Inline assembly
double BI(double v1,double v2,double v3,double v4,double f1,double f2)
}
  double val1=0.0,val2=0.0,rval=0.0;
  asm {
    
    fld     [v2]
    fsub  [v1]
    fmul  [f1]
    fadd  [v1]
    fstp   [val1]

    fld     [v4]
    fsub  [v3]
    fmul  [f1]
    fadd  [v3]
    fstp   [val2]

    fld     [val2]
    fsub  [val1]
    fmul  [f2]
    fadd  [val1]
    fstp   [rval]
   }
  return rval;
}

But to do what you want only requires 2 separate linear interpolations rather than one bilinear. Essentially you are doing a bilinear interpolation but its easier to do two singles which is:

interpolated_value=v1+f1*(v2-v1);

where f1 is the interpolant.

Code:

//Scan conversion
double m=(x2-x1)/(y2-y1);
double cm=(c2-c1)/y2-y1);
int x=x1;
int c=c1;

for (double y=y1;y<y2;y+=1.0)
{
  edge[(int)y].x=x;
  edge[(int)y].c=c;
  x+=m;
  c+=cm;
}


//Drawing from left edge to right edge
double x1=(double)left_edge[y].x;
double x2=(double)right_edge[y].x;
double c1=(double)left_edge[y].c;
double c2=(double)right_edge[y].c;

cm=(c2-c1)/(x2-x1);

double c=(double)c1;

for (double x=x1;x<x2;x++)
{
  putpixel((int)x,(int)y,(int)c);
  c+=cm;
}

So it is a type of bilinear interpolation since you first interpolate on y and then x. The data type conversions might be wrong in my examples but I'm sure you can get it right. Using < and > with doubles is not a good idea.

Apologies for the delay Silvercord. I tried to fix a few problems with the module. It's not error free but it works fine for triangles with flat bottom or top. Where shall I send the code?

Stop bumping threads...see rules in the link on my sig