[Bf-committers] Floating point compares

Kester Maddock bf-committers@blender.org
Thu, 30 Oct 2003 00:25:11 +1300

Hi guys,

I've just noticed that there are a lot of floating point compares in the 
code, ie:
        if(tex->cropxmin==0.0) ret++;
        if(tex->cropymin==0.0) ret++;
        if(tex->cropxmax==1.0) ret++;
        if(tex->cropymax==1.0) ret++;

Isn't this bad? (because of the finite floating point precision.)

#define FPRECISION 1e-10
static inline int fzero(float x)
    return fabs(x) < FPRECISION;

static inline int fequal(float x, float y)
    return fzero(x - y);

        if(fzero(tex->cropxmin)) ret++;
        if(fzero(tex->cropymin)) ret++;
        if(fequal(tex->cropxmax, 1.0)) ret++;
        if(fequal(tex->cropymax, 1.0)) ret++;

GCC will catch this with -Wfloat-equal.

Should I start fixing this or is there a valid reason to do it this way?