How can I transfer a color attribute from one geo to texture of another geo?

[Masoud]

Hello;

To create a very high-resolution footprint, I would like to transfer the color attribute from one geometry (from a box, or some sliding particles ) to another geometry ( a grid ),  based on a UV texture map (UV on second object).

This is something like creating a wet-map, and I don't want to scatter points on a surface to ... (I mean that I  know that workflow).

Actually I want to extract a very high-quality texture as output.

 

Any idea?

 

 

Thanks for helping.

 

 

Edited April 14, 2020 by Masoud

[Pazuzu]

16 minutes ago, Masoud said:

Hello;

To create a very high-resolution footprint, I would like to transfer the color attribute from one geometry (from a box, or some sliding particles ) to another geometry ( a grid ),  based on a UV texture map (UV on second object).

This is something like creating a wet-map, and I don't want to scatter points on a surface to ... (I mean that I  know that workflow).

Actually I want to extract a very high-quality texture as output.

 

Any idea?

 

 

Thanks for helping.

 

 

Here is a good way to deal with that. https://lesterbanks.com/2019/01/create-uv-based-wetmap-houdini/

[konstantin magnus]

Hi Masoud,

you can write attributes directly to a 2D volume inside a solver using a volume wrangle:

float radius = 0.02;

int prim;
vector uvw;
float dist = xyzdist(1, v@P, prim, uvw);
vector clr_sample = 0.0;
if(dist < radius){
    clr_sample = primuv(1, 'Cd', prim, uvw) * vector(0.2);
}
v@clr += clr_sample;

The example above is using the usual suspects for transferring attributes, xyzdist() and primuv(). Then the SOP import-node imports attribute values to COPs.

 

color_field.hipnc

[Librarian]

You have on Vimeo ..from Asia some Dude posted a huge library of files about everything on that Teman  .. I can't find the link  sorry.

 

Edited April 14, 2020 by Librarian

[Librarian]

I found him
here you gonna find Olaaa la nice stuff to investigate and have fun.

vimeo.com/zengchen

[Masoud]

20 hours ago, Pazuzu said:

Here is a good way to deal with that. https://lesterbanks.com/2019/01/create-uv-based-wetmap-houdini/

Hi " Alejandro ";

Thanks for the reply. I watched that tutorial and It uses points to transfer attributes, so the quality depends on the number of points...

[Masoud]

17 hours ago, konstantin magnus said:

Hi Masoud,

you can write attributes directly to a 2D volume inside a solver using a volume wrangle:

float radius = 0.02;

int prim;
vector uvw;
float dist = xyzdist(1, v@P, prim, uvw);
vector clr_sample = 0.0;
if(dist < radius){
    clr_sample = primuv(1, 'Cd', prim, uvw) * vector(0.2);
}
v@clr += clr_sample;

The example above is using the usual suspects for transferring attributes, xyzdist() and primuv(). Then the SOP import-node imports attribute values to COPs.

 

color_field.hipnc

Hi " Konstantin ";

Thanks for the reply. I don't want to use a 2D plane.
Actually I need to access a corresponding pixel in a UV texture when a point collides a primitive (surface).

[Masoud]

16 hours ago, Librarian said:

I found him
here you gonna find Olaaa la nice stuff to investigate and have fun.

vimeo.com/zengchen

Hi " Tesan ";

Thanks for the reply. I don't want to scatter extra points on a 2D surface, and I need to access a corresponding pixel in a UV texture when a point collides a primitive (surface).

[Librarian]

You constantly on every Post changing(editing) what you actually want ..its OK

You must define first on-grid some flow map make attributes also what your box do on-grid. Than learn this ..

new asset-SHOP SURFACE.  2 surface that you need somehow-to combine to get that effect I think.

//Read data
#pragma label       mult        "Multiplier"
#pragma label       spread      "Overall Spread"
#pragma label       DATA        "Data Points"
#pragma label       group       "Point Group"

surface
color_transfer
(   float   mult    = 0.5,
            spread  = 1;
    string  DATA    = "$HIP/../VEX/Reading-Data-Points/_datapoints.bgeo.sc",
            group   = "group0";)
{
    float d, Np, pFratt;
    vector _P, pP, pCd, pVratt, outColor;
    
    _P = ptransform("space:camera", "space:world", P);
    
    outColor = 0;
    
    int p[] = expandpointgroup(DATA, group);
    Np = len(p);
    for(int i = 0; i < Np; i++){
        pP = point(DATA, "P", p[i]);
        pCd = point(DATA, "Cd", p[i]);
        pFratt = point(DATA, "fratt", p[i]);
        d = distance2(pP, _P);
        d = exp(-d*d/(pFratt*spread));
        outColor += pCd*mult*d;
    }

    Cf = outColor;
}
---------------------------
SMUDGE

#define PI          3.1415926535897931
#pragma label       Theta       "Maximum Theta"
#pragma label       spread      "Overall Spread"
#pragma label       DATA        "Data Points"
#pragma label       kd          "Diffuse"
#pragma label       ks          "Specular"
#pragma label       bump        "Bump"

surface
qrotation_field
(   float   Theta   = 2.0,
            spread  = 3,
            kd      = 1,
            ks      = 0.5,
            bump    = 0.1;
    string  DATA    = "$HIP/../VEX/Reading-Data-Points/_datapoints.bgeo.sc")
{
    float d, Np, theta, pFratt, factor, pspread;
    vector _P, pP, axis, pVratt;
    vector4 Q;
    string group;
    
    _P = ptransform("space:camera", "space:world", P);

    theta = snoise(_P + 0.9, 1, 0.75, 1)*4.5;
    axis = snoise(_P + 0.05, 1, 0.05, 1);
    Q = quaternion(theta, axis);
    _P = qrotate(Q, _P);
    
    for(int g = 0; g < 2; g++){
        group = concat("group", itoa(g));
        int p[] = expandpointgroup(DATA, group);
        Np = len(p);
        factor = g + 1;
        for (int i = 0; i < Np; i++){
            pP = point(DATA, "P", p[i]);
            axis = point(DATA, "N", p[i]);
            pFratt = point(DATA, "fratt", p[i]);
            pVratt = point(DATA, "vratt", p[i]);
            pspread = pFratt*spread/factor;
            d = distance2(pP, _P);
            d = exp(-d*d/pspread);
            theta = 2*PI*(pFratt*2 - 1)*d*Theta/factor;
            Q = quaternion(theta, axis);
            _P = qrotate(Q, _P - pP) + pP;
        }
    }

    vector outColor = snoise(_P*0.25, 1, 0.25, 1);

    vector Nn = normalize(computenormal(P + min(outColor)*bump, N, Ng));
    
    vector diff = diffuse(Nn)*outColor*dot(normalize(-I), N);

    vector spec = specular(Nn, normalize(-I), fit01(min(outColor), 0.5, 0.1))*0.1;
    spec += specular(N, normalize(-I), 0.05);

    Cf = diff*kd + spec*ks;
}
------------------------------------------------------------------
CONST TEXTURE
#pragma label       mode    "Mode"
#pragma choice      mode    "uv"    "UV :: Geometry coordinates"
#pragma choice      mode    "st"    "ST :: Primitive coordinates"

#pragma label       text    "Texture map"
#pragma hint        text    image

#pragma label       mult    "Color multiplier"
#pragma hint        mult    color

#pragma label       opac    "Opacity"
#pragma hint        opac    color

#pragma label       uv      ""
#pragma hint        uv      invisible

#pragma label       repeat  "Repeat coordinates"
#pragma hint        repeat  uv

#pragma label       offset  "Offset"
#pragma hint        offset  uv

surface
constant_texture
(   string  mode    =   "uv",
            text    =   "Mandril.pic";
    vector  mult    =   {1, 1, 1},
            opac    =   {1, 1, 1},
            uv      =   {0, 0, 0};
    vector2 repeat  =   {1, 1},
            offset  =   {0, 0})
{
    vector  _coord2d, _texture, _color, _repeat, _offset;
    if(mode == "st"){
        _coord2d = set(s, t, 0);
    }
    else{
        _coord2d = uv;
    }
    _repeat = repeat;
    setcomp(_repeat, 1, 2);
    _offset = offset;
    setcomp(_offset, 1, 2);
    _coord2d = _coord2d*_repeat + _offset;
    _texture = texture(text, _coord2d.x, _coord2d.y);
    _color = _texture*mult;
    Cf = _color*opac;
    Of = opac;
}

I hope IT Helps .....and maybe someone can clarify

 

 

Edited April 15, 2020 by Librarian

[konstantin magnus]

3 hours ago, Masoud said:

I need to access a corresponding pixel in a UV texture when a point collides a primitive

I see. I have broken down all kinds of geometry-to-texture transfers here: