POV-Ray : Newsgroups : povray.binaries.images : Crackle Server Time
30 Nov 2022 05:46:11 EST (-0500)
  Crackle (Message 1 to 10 of 13)  
Goto Latest 10 Messages Next 3 Messages >>>
From: Chris R
Subject: Crackle
Date: 11 Nov 2022 10:00:00
Message: <web.636e627393b68ffd7aaec48e5cc1b6e@news.povray.org>
I like to use the crackle pattern for creating stone pavers for floors, rough
stone walls, etc. I use the pattern to outline the stones in an isosurface, and
then apply a texture on it.

This all works well if I want the stones to be of a uniform type, but I haven't
found an effective way to do this when I want some variations in the types of
stones.  I do something similar with brick walls and floors, but since bricks
have a regular shape, I can use warp repeats to ensure that individual bricks
have a consistent texture, but are randomized between bricks.

Has anyone come up with a trick to do something similar with irregular patterns
like crackle?  I usually end up using some sort of random pigment pattern with
the different textures I want to apply, (see the image below), and then
scale/rotate/translate it to match the stones as best I can, but there is always
bleeding between them.

-- Chris R.


Post a reply to this message


Attachments:
Download 'cabin.png' (690 KB)

Preview of image 'cabin.png'
cabin.png


 

From: Alain Martel
Subject: Re: Crackle
Date: 11 Nov 2022 11:07:10
Message: <636e732e$1@news.povray.org>
Le 2022-11-11 à 09:55, Chris R a écrit :
> I like to use the crackle pattern for creating stone pavers for floors, rough
> stone walls, etc. I use the pattern to outline the stones in an isosurface, and
> then apply a texture on it.
> 
> This all works well if I want the stones to be of a uniform type, but I haven't
> found an effective way to do this when I want some variations in the types of
> stones.  I do something similar with brick walls and floors, but since bricks
> have a regular shape, I can use warp repeats to ensure that individual bricks
> have a consistent texture, but are randomized between bricks.
> 
> Has anyone come up with a trick to do something similar with irregular patterns
> like crackle?  I usually end up using some sort of random pigment pattern with
> the different textures I want to apply, (see the image below), and then
> scale/rotate/translate it to match the stones as best I can, but there is always
> bleeding between them.
> 
> -- Chris R.

Try using the same crackle, but the with solid modifier as the pigment.
Use a colour_map containing various orientations of a collection of 
patterns.
That way, you'll have a texture with a pattern matching that of the 
isosurface.


Post a reply to this message

From: Chris R
Subject: Re: Crackle
Date: 11 Nov 2022 12:30:00
Message: <web.636e8591302862a47aaec48e5cc1b6e@news.povray.org>
Alain Martel <kua### [at] videotronca> wrote:

> > I like to use the crackle pattern for creating stone pavers for floors, rough
> > stone walls, etc. I use the pattern to outline the stones in an isosurface, and
> > then apply a texture on it.
> >
> > This all works well if I want the stones to be of a uniform type, but I haven't
> > found an effective way to do this when I want some variations in the types of
> > stones.  I do something similar with brick walls and floors, but since bricks
> > have a regular shape, I can use warp repeats to ensure that individual bricks
> > have a consistent texture, but are randomized between bricks.
> >
> > Has anyone come up with a trick to do something similar with irregular patterns
> > like crackle?  I usually end up using some sort of random pigment pattern with
> > the different textures I want to apply, (see the image below), and then
> > scale/rotate/translate it to match the stones as best I can, but there is always
> > bleeding between them.
> >
> > -- Chris R.
>
> Try using the same crackle, but the with solid modifier as the pigment.
> Use a colour_map containing various orientations of a collection of
> patterns.
> That way, you'll have a texture with a pattern matching that of the
> isosurface.

That's brilliant!  I don't know how I missed that in the documentation, (or
maybe I just never understood what it was trying to say).

What controls the pigment value selected for the cell?  Is it just a random
number, or do proximate cells select from the same value range.  I'm finding the
more variation with smaller ranges in my pigment_map, the less "clumpy" the
cells become, but does it follow the normal ramp_wave or is it just a linear
random number?

-- Chris R.


Post a reply to this message


Attachments:
Download 'cabin.png' (730 KB)

Preview of image 'cabin.png'
cabin.png


 

From: Bald Eagle
Subject: Re: Crackle
Date: 11 Nov 2022 14:10:00
Message: <web.636e9ce9302862a41f9dae3025979125@news.povray.org>
"Chris R" <car### [at] comcastnet> wrote:

> What controls the pigment value selected for the cell?  Is it just a random
> number, or do proximate cells select from the same value range.  I'm finding the
> more variation with smaller ranges in my pigment_map, the less "clumpy" the
> cells become, but does it follow the normal ramp_wave or is it just a linear
> random number?


From source/core/material/pattern.cpp

There's a few extra pre-main-pattern sections, and I've always wanted to
translate the source code algorithm into SDL so that people could vary the field
of random points, or otherwise modify the pattern to suit their needs.

The following may also interest you:

http://news.povray.org/povray.binaries.images/thread/%3C5acf08bc%241%40news.povray.org%3E/


* FUNCTION
*
*   crackle_pattern
*
* INPUT
*
*   EPoint -- The point in 3d space at which the pattern
*   is evaluated.
* OUTPUT
*
* RETURNS
*
*   DBL value in the range 0.0 to 1.0
*
* AUTHOR
*
*   Jim McElhiney
*
* DESCRIPTION
*
*   "crackle":
*
*   New colour function by Jim McElhiney,
*     CompuServe 71201,1326, aka mce### [at] acmorg
*
*   Large scale, without turbulence, makes a pretty good stone wall.
*   Small scale, without turbulence, makes a pretty good crackle ceramic glaze.
*   Highly turbulent (with moderate displacement) makes a good marble, solving
*   the problem of apparent parallel layers in Perlin's method.
*   2 octaves of full-displacement turbulence make a great "drizzled paint"
*   pattern, like a 1950's counter top.
*   Rule of thumb:  put a single colour transition near 0 in your colour map.
*
*   Mathematically, the set crackle(p)=0 is a 3D Voronoi diagram of a field of
*   semirandom points, and crackle(p)>0 is distance from set along shortest
path.
*   (A Voronoi diagram is the locus of points equidistant from their 2 nearest
*   neighbours from a set of disjoint points, like the membranes in suds are
*   to the centres of the bubbles).
*
*   The original "crackle" specific source code and examples are in the public
domain.
*
* CHANGES
*   Oct 1994    : adapted from pigment by [CY]
*   Other changes: enhanced by Ron Parker, Integer math by Nathan Kopp
*
******************************************************************************/
static int IntPickInCube(int tvx, int tvy, int tvz, Vector3d& p1);

DBL CracklePattern::EvaluateRaw(const Vector3d& EPoint, const Intersection
*pIsection, const Ray *pRay, TraceThreadData *pThread) const
{
    Vector3d tmpPoint = EPoint;
    DBL sum, minsum, minsum2, minsum3, tf;
    int minVecIdx = 0;
    Vector3d dv;

    int flox, floy, floz;

    bool UseSquare = ( crackleMetric == 2);
    bool UseUnity  = ( crackleMetric == 1);

    if (repeat.x())
        tmpPoint.x() = wrap(tmpPoint.x(), DBL(repeat.x()));
    if (repeat.y())
        tmpPoint.y() = wrap(tmpPoint.y(), DBL(repeat.y()));
    if (repeat.z())
        tmpPoint.z() = wrap(tmpPoint.z(), DBL(repeat.z()));

    /*
     * This uses floor() not FLOOR, so it will not be a mirror
     * image about zero in the range -1.0 to 1.0. The viewer
     * won't see an artefact around the origin.
     */

    flox = (int)floor(tmpPoint[X] - EPSILON);
    floy = (int)floor(tmpPoint[Y] - EPSILON);
    floz = (int)floor(tmpPoint[Z] - EPSILON);

    /*
     * Check to see if the input point is in the same unit cube as the last
     * call to this function, to use cache of cubelets for speed.
     */

    CrackleCellCoord ccoord(flox, floy, floz, repeat.x(), repeat.y(),
repeat.z());
    pThread->Stats()[CrackleCache_Tests]++;

    CrackleCacheEntry dummy_entry;
    CrackleCacheEntry* entry = &dummy_entry;

    if (pThread->mpCrackleCache->Lookup(entry, ccoord))
    {
        // Cache hit. `entry` now points to the cached entry.
        pThread->Stats()[CrackleCache_Tests_Succeeded]++;
    }
    else
    {
        // Cache miss. `entry` now points to a pristine entry set up in the
        // cache, or to `dummy_entry` if the cache is too crowded already.
        // In either case we need to fill in the blanks.

        // Calculate the random points for this new
        // cube and its 80 neighbours which differ in any axis by 1 or 2.
        // Why distance of 2?  If there is 1 point in each cube, located
        // randomly, it is possible for the closest random point to be in the
        // cube 2 over, or the one two over and one up.  It is NOT possible
        // for it to be two over and two up.  Picture a 3x3x3 cube with 9 more
        // cubes glued onto each face.

        // TODO - Note that we're currently re-computing each cell up to 81
        //        times - once as a main cell and 80 times as a neighbor -
        //        even in the best case scenario. Wouldn't it be more efficient
        //        to just cache the individual cells?

        int *pc = gaCrackleCubeTable;
        for (int i = 0; i < 81; i++, pc += 3)
        {
            Vector3d wrappingOffset(0.0);
            int cacheX = flox + pc[X];
            int cacheY = floy + pc[Y];
            int cacheZ = floz + pc[Z];
            if (repeat.x())
            {
                int wrapped = wrapInt(cacheX, repeat.x());
                wrappingOffset.x() += (cacheX - wrapped);
                cacheX = wrapped;
            }
            if (repeat.y())
            {
                int wrapped = wrapInt(cacheY, repeat.y());
                wrappingOffset.y() += (cacheY - wrapped);
                cacheY = wrapped;
            }
            if (repeat.z())
            {
                int wrapped = wrapInt(cacheZ, repeat.z());
                wrappingOffset.z() += (cacheZ - wrapped);
                cacheZ = wrapped;
            }
            IntPickInCube(cacheX, cacheY, cacheZ, entry->aCellNuclei[i]);
            entry->aCellNuclei[i] += wrappingOffset;
        }
    }

    // Find the 3 points with the 3 shortest distances from the input point.
    // Set up the loop so the invariant is true:  minsum <= minsum2 <= minsum3
    dv = entry->aCellNuclei[0] - tmpPoint;

    if(UseSquare)
    {
        minsum = dv.lengthSqr();

        dv = entry->aCellNuclei[1] - tmpPoint;
        minsum2 = dv.lengthSqr();

        dv = entry->aCellNuclei[2] - tmpPoint;
        minsum3  = dv.lengthSqr();
    }
    else if(UseUnity)
    {
        minsum = fabs(dv[X]) + fabs(dv[Y]) + fabs(dv[Z]);

        dv = entry->aCellNuclei[1] - tmpPoint;
        minsum2 = fabs(dv[X]) + fabs(dv[Y]) + fabs(dv[Z]);

        dv = entry->aCellNuclei[2] - tmpPoint;
        minsum3 = fabs(dv[X]) + fabs(dv[Y]) + fabs(dv[Z]);
    }
    else
    {
        minsum = pow(fabs(dv[X]), crackleMetric) +
                 pow(fabs(dv[Y]), crackleMetric) +
                 pow(fabs(dv[Z]), crackleMetric);

        dv = entry->aCellNuclei[1] - tmpPoint;
        minsum2 = pow(fabs(dv[X]), crackleMetric) +
                  pow(fabs(dv[Y]), crackleMetric) +
                  pow(fabs(dv[Z]), crackleMetric);

        dv = entry->aCellNuclei[2] - tmpPoint;
        minsum3 = pow(fabs(dv[X]), crackleMetric) +
                  pow(fabs(dv[Y]), crackleMetric) +
                  pow(fabs(dv[Z]), crackleMetric);
    }

    // sort the 3 computed sums
    if(minsum2 < minsum)
    {
        tf = minsum; minsum = minsum2; minsum2 = tf;
        minVecIdx = 1;
    }

    if(minsum3 < minsum)
    {
        tf = minsum; minsum = minsum3; minsum3 = tf;
        minVecIdx = 2;
    }

    if(minsum3 < minsum2)
    {
        tf = minsum2; minsum2 = minsum3; minsum3 = tf;
    }

    // Loop for the 81 cubelets to find closest and 2nd closest.
    for(int i = 3; i < 81; i++)
    {
        dv = entry->aCellNuclei[i] - tmpPoint;

        if(UseSquare)
            sum = dv.lengthSqr();
        else if(UseUnity)
            sum = fabs(dv[X]) + fabs(dv[Y]) + fabs(dv[Z]);
        else
            sum = pow(fabs(dv[X]), crackleMetric) +
                  pow(fabs(dv[Y]), crackleMetric) +
                  pow(fabs(dv[Z]), crackleMetric);

        if(sum < minsum)
        {
            minsum3 = minsum2;
            minsum2 = minsum;
            minsum = sum;
            minVecIdx = i;
        }
        else if(sum < minsum2)
        {
            minsum3 = minsum2;
            minsum2 = sum;
        }
        else if( sum < minsum3 )
        {
            minsum3 = sum;
        }
    }

    if (crackleOffset)
    {
        if(UseSquare)
        {
            minsum += crackleOffset*crackleOffset;
            minsum2 += crackleOffset*crackleOffset;
            minsum3 += crackleOffset*crackleOffset;
        }
        else if (UseUnity)
        {
            minsum += crackleOffset;
            minsum2 += crackleOffset;
            minsum3 += crackleOffset;
        }
        else
        {
            minsum += pow( crackleOffset, crackleMetric );
            minsum2 += pow( crackleOffset, crackleMetric );
            minsum3 += pow( crackleOffset, crackleMetric );
        }
    }

    if(crackleIsSolid)
    {
        tf = Noise( entry->aCellNuclei[minVecIdx], GetNoiseGen(pThread) );
    }
    else if(UseSquare)
    {
        tf = crackleForm[X]*sqrt(minsum) +
             crackleForm[Y]*sqrt(minsum2) +
             crackleForm[Z]*sqrt(minsum3);
    }
    else if(UseUnity)
    {
        tf = crackleForm[X]*minsum +
             crackleForm[Y]*minsum2 +
             crackleForm[Z]*minsum3;
    }
    else
    {
        tf = crackleForm[X]*pow(minsum, 1.0/crackleMetric) +
             crackleForm[Y]*pow(minsum2, 1.0/crackleMetric) +
             crackleForm[Z]*pow(minsum3, 1.0/crackleMetric);
    }

    return max(min(tf, 1.), 0.);
}


Post a reply to this message

From: Chris R
Subject: Re: Crackle
Date: 14 Nov 2022 11:00:00
Message: <web.637265f9302862a47aaec48e5cc1b6e@news.povray.org>
"Bald Eagle" <cre### [at] netscapenet> wrote:
> "Chris R" <car### [at] comcastnet> wrote:
>
> > What controls the pigment value selected for the cell?  Is it just a random
> > number, or do proximate cells select from the same value range.  I'm finding the
> > more variation with smaller ranges in my pigment_map, the less "clumpy" the
> > cells become, but does it follow the normal ramp_wave or is it just a linear
> > random number?
>
>
> From source/core/material/pattern.cpp
>
> There's a few extra pre-main-pattern sections, and I've always wanted to
> translate the source code algorithm into SDL so that people could vary the field
> of random points, or otherwise modify the pattern to suit their needs.
>
> The following may also interest you:
>
>
http://news.povray.org/povray.binaries.images/thread/%3C5acf08bc%241%40news.povray.org%3E/
>
> ...

Thanks, that's very helpful.  I should probably spend some time looking over the
source code more often.  My C++ is a little rusty from disuse, though.

So, the _map entry based on the node point of the cell, and uses the noise
generator chosen in your global options for the scene.  It doesn't appear there
is a way to separately scale the node points for the call to the noise
generator, so creating more randomness across neighboring cells is a matter of
having fine-grained _maps to choose from.

-- Chris R.


Post a reply to this message

From: Bald Eagle
Subject: Re: Crackle
Date: 14 Nov 2022 16:55:00
Message: <web.6372b903302862a41f9dae3025979125@news.povray.org>
"Chris R" <car### [at] comcastnet> wrote:

> Thanks, that's very helpful.

Well, I'm glad it's of _some_ use.  ;)

> I should probably spend some time looking over the
> source code more often.  My C++ is a little rusty from disuse, though.

I've learned a lot from reading through the source code, even though my cpp
knowledge is mostly acquired through hunt (online) and code, or writing Arduino
sketches.

> So, the _map entry based on the node point of the cell, and uses the noise
> generator chosen in your global options for the scene.  It doesn't appear there
> is a way to separately scale the node points for the call to the noise
> generator, so creating more randomness across neighboring cells is a matter of
> having fine-grained _maps to choose from.

There isn't any way (to my knowledge) to affect the distribution of random
points, which is why so many people have expressed interest over the years in
having an SDL version of the voronoi pattern.

I've had a lot of success (not 100%) with adapting ShaderToy code to SDL, so
maybe at some point I can figure out how to make a voronoi pattern in SDL based
on some of the scripts.

Maybe some of that will be clearer / of more use to you.

https://iquilezles.org/articles/voronoilines/
https://iquilezles.org/articles/smoothvoronoi/
https://iquilezles.org/articles/voronoise/

https://www.shadertoy.com/results?query=voronoi


Post a reply to this message

From: Bald Eagle
Subject: Re: Crackle
Date: 14 Nov 2022 19:40:00
Message: <web.6372dfa5302862a41f9dae3025979125@news.povray.org>
"Bald Eagle" <cre### [at] netscapenet> wrote:

> I've had a lot of success (not 100%) with adapting ShaderToy code to SDL, so
> maybe at some point I can figure out how to make a voronoi pattern in SDL based
> on some of the scripts.


Y'know - like this:
I'm not sure when I make all the squares or spheres fill up everything that it
turns black, with a few colored spots.  My POV-Ray suckage, likely.
But it's proof of concept, so here we go.

Next stage would be to code it using only functions, and then it could be used
as a pigment pattern.



#version 3.8;
global_settings {assumed_gamma 1.0}

#include "colors.inc"
//#include "BezierInclude.inc"
#include "math.inc"
#declare E = 0.0000001;

#declare Camera_Orthographic = true;
#declare Camera_Position = <0.5, 0.5, -100> ;  // front view
#declare Camera_Look_At  = <0.5, 0.5,  0> ;
#declare Fraction = 450;     // functions as a zoom for the orthographic view: 4
zooms in 4x, 8 zooms in 8x, etc.

// ###########################################
camera {
 #if (Camera_Orthographic = true)
  orthographic
  right     x*image_width/(Fraction)
  up   y*image_height/(Fraction)
 #else
  right     x*image_width/image_height
  up y
 #end
 location  Camera_Position
 look_at   Camera_Look_At}
// ###########################################

sky_sphere {pigment {rgb <1, 1, 1>}}
#declare LS = <0, 0, -20>;
light_source {LS rgb 1}
#declare Line = 0.5/image_width; // line thickness


// DOT product
#declare SFn_vdot = function (ax, ay, az, bx, by, bz) {ax*bx + ay*by + az*bz}

// Length or Norm
#declare SFn_vlength = function (ax, ay, az) {sqrt(ax*ax + ay*ay + az*az)}

#declare Clip = function (_Val, _Min, _Max) {min(_Max, max(_Val, _Min))}
#declare Window = function (_Val, _Eq, _Min, _Max, _E) {select (_Val-_Min, _Val,
select(_Max-_Val, _Val, _Eq))}
#declare LimitReps = function (Element, Period, Min, Max) {Element - Period *
Clip (Element/Period, Min, Max)}

#declare Smoothstep0 = function (_Val, _From, _To) {Clip ((_Val - _From) / (_To
- _From), 0.0, 1.0)}
#declare Smoothstep = function (_Val, _From, _To) {Smoothstep0 (_Val, _From,
_To) * Smoothstep0 (_Val, _From, _To) * (3.0 - 2.0 * Smoothstep0 (_Val, _From,
_To))}




#macro Clamp (N, minVal, maxVal)
 #local Val = min (max (N, minVal), maxVal);

 Val
#end

#macro hash (p)
 // input: 2D vector
 // output: 2D vector

    //p = mod(p, 4.0); // tile
    #local PX = vdot (p, <127.1, 311.7>);
    #local PY = vdot (p, <269.5, 183.3>);

    #local PXr = mod (sin (PX)*18.5453, 1);
    #local PXy = mod (sin (PY)*18.5453, 1);

    <PXr, PXy>

#end


// return distance, and cell id
#macro voronoi (P)
 // input: 2D vector
 // output: 2D vector

 #local nx = floor (P.x);
 #local ny = floor (P.y);
 #local n  = <nx, ny>;

 #local fx = mod (P.x, 1);
 #local fy = mod (P.y, 1);

 #local m = <8, 8, 8>;

 #for (j, -1, 1)
  #for (i, -1, 1)
   #local g = <i, j>;
   #local o = hash (n + g);
        // #local r = g - f + o;
   #local rx = g.x - fx + (0.5 + 0.5*sin(clock + 6.2831*o.x));
   #local ry = g.y - fy + (0.5 + 0.5*sin(clock + 6.2831*o.y));
   #local r = <rx, ry>;

   #local d = vdot (r, r);
   #if(d < m.x)
    #local m = <d, o.x, o.y>; // m = vec3 (d, o);
   #end
  #end
 #end

 <sqrt (m.x), m.y + m.z>;

#end

#local M = max(image_width,image_height);
#local D = 1.75;

#macro mainImage (X, Y)


   #local PX = X / M;
   #local PY = Y / M;

   // computer voronoi pattern
   #local C = voronoi ( <(14.0 + 6.0 * sin (0.2*clock)) * PX,  (14.0 + 6.0 * sin
(0.2*clock)) * PY>);

   // colorize

   #local ColorR = 0.5 + 0.5 * cos (C.y*6.2831 + 0);
   #local ColorG = 0.5 + 0.5 * cos (C.y*6.2831 + 1);
   #local ColorB = 0.5 + 0.5 * cos (C.y*6.2831 + 2);

   #local C1 = Clamp (1.0 - 0.4*C.x*C.x, 0.0, 1.0);

   #local ColorR = ColorR * C1;
   #local ColorG = ColorG * C1;
   #local ColorB = ColorB * C1;

   #local C2 = (1.0 - Smoothstep (0.08, 0.09, C.x));

   #local ColorR = ColorR - C2;
   #local ColorG = ColorG - C2;
   #local ColorB = ColorB - C2;

   #local fragColor = <ColorR, ColorG, ColorB>;

   //sphere {<PX, PY>, Line*2 texture {pigment {rgb fragColor} finish {diffuse
1}} }
   //sphere {<PX, PY>, Line*2 pigment {rgb fragColor} }
   box {<PX-Line*D, PY-Line*D, 0>, <PX+Line*D, PY+Line*D, Line> pigment {rgb
fragColor} }

#end


#declare Step = 2;
 #for (Y, 0, image_width, Step)
  #debug concat("Y = ", str(Y, 0, 0), "\n")
  #for (X, 0, image_width, Step)
   mainImage (X, Y)
  #end
 #end

/*
vec2 hash( vec2 p )
{
    //p = mod(p, 4.0); // tile
    p = vec2(dot(p,vec2(127.1,311.7)),
             dot(p,vec2(269.5,183.3)));
    return fract(sin(p)*18.5453);
}

// return distance, and cell id
vec2 voronoi( in vec2 x )
{
    vec2 n = floor( x );
    vec2 f = fract( x );

 vec3 m = vec3( 8.0 );
    for( int j=-1; j<=1; j++ )
    for( int i=-1; i<=1; i++ )
    {
        vec2  g = vec2( float(i), float(j) );
        vec2  o = hash( n + g );
      //vec2  r = g - f + o;
     vec2  r = g - f + (0.5+0.5*sin(iTime+6.2831*o));
  float d = dot( r, r );
        if( d<m.x )
            m = vec3( d, o );
    }

    return vec2( sqrt(m.x), m.y+m.z );
}

void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
    vec2 p = fragCoord.xy/max(iResolution.x,iResolution.y);

    // computer voronoi patterm
    vec2 c = voronoi( (14.0+6.0*sin(0.2*iTime))*p );

    // colorize
    vec3 col = 0.5 + 0.5*cos( c.y*6.2831 + vec3(0.0,1.0,2.0) );
    col *= clamp(1.0 - 0.4*c.x*c.x,0.0,1.0);
    col -= (1.0-smoothstep( 0.08, 0.09, c.x));

    fragColor = vec4( col, 1.0 );
}
*/


Post a reply to this message


Attachments:
Download 'new_iq_voronoipattern.png' (416 KB)

Preview of image 'new_iq_voronoipattern.png'
new_iq_voronoipattern.png


 

From: Bald Eagle
Subject: Re: Crackle
Date: 15 Nov 2022 13:50:00
Message: <web.6373df27302862a41f9dae3025979125@news.povray.org>
"Bald Eagle" <cre### [at] netscapenet> wrote:

> Next stage would be to code it using only functions, and then it could be used
> as a pigment pattern.

Indeed.   If I knew how this all worked and could code it right.  <eyeroll>

Also, these things are SLOW.
I thought the function version would be faster, but this small render took 23.75
min.

My initial frustration with trying to make one of these things was the nested
loops, but I figured I could "unroll" that and just daisy chain the functions.
Which I did, and it works - sorta.
But it's 102 functions, and for some reason it looks like I got the color code
wrong too.

It also look like there are different methods for generating the Voronoi
pattern, and this one is (obviously) grid based, like POV-Ray's.   I'll have to
try my hand at one with a much more arbitrary data set.

Also: Chris R - are you aware that you can get a Voronoi pattern just using
overlapping cones?  Depending on what you're planning to do with it, that would
be both super easy and FAST.  And from what I understand, it's actually a
legitimate Voronoi result.

https://smathermather.com/2012/01/20/fast-calculation-of-voronoi-polygons-in-povray/


Post a reply to this message

From: Bald Eagle
Subject: Re: Crackle
Date: 15 Nov 2022 14:55:00
Message: <web.6373ed82302862a41f9dae3025979125@news.povray.org>
Maybe it would help if I attached the render.   :|


Post a reply to this message


Attachments:
Download 'new_iq_voronoifunction.png' (137 KB)

Preview of image 'new_iq_voronoifunction.png'
new_iq_voronoifunction.png


 

From: Chris R
Subject: Re: Crackle
Date: 16 Nov 2022 15:10:00
Message: <web.637542cb302862a47aaec48e5cc1b6e@news.povray.org>
"Bald Eagle" <cre### [at] netscapenet> wrote:
> "Bald Eagle" <cre### [at] netscapenet> wrote:
>
> > Next stage would be to code it using only functions, and then it could be used
> > as a pigment pattern.
>
> Indeed.   If I knew how this all worked and could code it right.  <eyeroll>
>
> Also, these things are SLOW.
> I thought the function version would be faster, but this small render took 23.75
> min.
>
> My initial frustration with trying to make one of these things was the nested
> loops, but I figured I could "unroll" that and just daisy chain the functions.
> Which I did, and it works - sorta.
> But it's 102 functions, and for some reason it looks like I got the color code
> wrong too.
>
> It also look like there are different methods for generating the Voronoi
> pattern, and this one is (obviously) grid based, like POV-Ray's.   I'll have to
> try my hand at one with a much more arbitrary data set.
>
> Also: Chris R - are you aware that you can get a Voronoi pattern just using
> overlapping cones?  Depending on what you're planning to do with it, that would
> be both super easy and FAST.  And from what I understand, it's actually a
> legitimate Voronoi result.
>
> https://smathermather.com/2012/01/20/fast-calculation-of-voronoi-polygons-in-povray/

Thanks for the pointers.  I'll check them out.

Most of my work is done with isosurfaces, especially for close-up views of
objects.  I end up coding the basic shape of the object I want as a function and
then apply perturbations using noise generators and pigment patterns to get the
"texture" I want on the surface of the object.  I then apply an SDL texture to
get the color and finish look to the object.

For the tiled floors, and some of my brick wall work, I have to find ways to
make the pigment pattern I use to generate the surface texture to match up with
the pigment pattern I use to generate the colors and finishes.  So, the crackle
pigment pattern works well that way, now that you have shown me how to get a
consistent texture to apply to the cells.  If I need more variability between
cells I'll just have to play with the texture maps and randomize them more.

-- Chris R.


Post a reply to this message

Goto Latest 10 Messages Next 3 Messages >>>

Copyright 2003-2021 Persistence of Vision Raytracer Pty. Ltd.