END OF AN ERA, FRACTALFORUMS.COM IS CONTINUED ON FRACTALFORUMS.ORG

I am wondering on this concept. Take the normal 3d space in ortho coords. A sphere lies inside...
(x-x0)**2+(y-y0)**2+(z-z0)**2<=1
okay. think about 2 spheres. r is the distance from each origin as explained
min(r1,r2)<=1
is the region where both spheres exist
max(r1,r2)<=1
gives the intersection
but i wanted to find an appropriate fun of r1 and r2 that
. far from the intersection works as min(r1,r2) or almost like
. near the intersection "melts" the spheres in some way
what should I use as f? wondering of an exp smoothing but how?
thanks

Have you seen http://www.iquilezles.org/www/articles/distfunctions/distfunctions.htm ?
Distance estimation oriented but why would you want it any other way 

Wooo!!!! GREAT find.  but:

Blend

float opBlend( vec3 p )
{
    float d1 = primitiveA(p);
    float d2 = primitiveB(p);
    floar dd = smoothcurve(d1-d2);
    return mix(d1,d2,dd);
}

He forgot to tell what is mix() and smoothcurve() 

Luca

mix(a, b, c): result =a when c <= 0 and =b when c >= 1 with a linear blend inbetween

I'm guessing smoothcurve is like the smoothstep function in OpenGL, which (from the spec):

Returns 0.0 if x <= edge0 and 1.0 if x >= edge1 and performs smooth Hermite interpolation between 0 and 1 when edge0 < x < edge1.  This is useful in cases where you would want a threshold function with a smooth transition.
This is equivalent to:
   t = clamp ((x – edge0) / (edge1 – edge0), 0, 1);
   return t * t * (3 – 2 * t);

I played around with this exact problem some weeks ago.

I never really understood Quilez's formula. If I use smoothcurve(d1-d2) = smoothstep(0,1,d1-d2), I get some very asymmetric objects, not very blobby (see the top of attached pictures).

Also, if you look at slide 42 in his 'Rendering Worlds...' (http://www.iquilezles.org/www/material/nvscene2008/rwwtt.pdf), he uses a different formula - here he uses a global distance to interpolate: smoothstep(length(p),0,1) - notice the order of arguments?. And if you look at the Slisesix demo code, it seems he just mixes linearly ("float a = clamp( r*3.0, 0.0, 1.0 ); return c*a + d*(1.0-a);").

I came up with the following formula, which mixes linearly based on the distance from the center of each object (I could not find a good formula based on the ratios of the distance estimates, even though I would have preferred it). Fragmentarium code:


This produces the lower image.

I also just tried fractowers formula, but it seems not very 'blobby' to me either - at least not if the r1 and r2 are distance estimates. It does, however, provide a nice controllable weighting if you mix the distance estimates by the distances to the center:

Fantastic ... Thanks for those replies

Anyway, reading the original blob article, I think that the accurate fmla shoul depend on a min and max radii.
under the min rad nothing should happen (so we can take safely min(r1,r2)
over it we can start mangling. I think that syntopia's approach is good, edventually fixed with an exponential function? To emulate the "thin bridge" effect (the plasticity should be adjusted with a max/minrad factor in the original blob method).
To see things clearly anyway I need more images and to test by myself. There is no hurry

Sure! Think about a blob-based folding or sphere inversion or decombine
For now decombines are "static" anyways