小笔记 - Houdini Vex

1, intersect

int  intersect(<geometry>geometry, vector orig, vector dir, vector &p, vector &uvw)

dir的距离表示最大的映射方向

2, 添加属性

1 addpointattrib(0, "tmp_dist", 0);
2 int allpoints[] = primpoints(0, 0);
3 int nps = npoints(0);
4 
5 for(int i=0;i<nps;i++){
6 vector tmp = point(0,"P",i+1)-point(0,"P",i);
7 setpointattrib(0, "tmp_dist", i, length(tmp), "set");
8 }

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3，让数字前生成0，比如45变成045　　

padzero(5, 126) = 00126 不是vex

 s@id = sprintf(\'%04d\', @ptnum);

 4，if else 缩略写法

1 if (int(ch("flip_green"))) @Cd.g = 1 - @Cd.g;
2 else @Cd.r = 1 - @Cd.r;

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 5，删除分叉

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 6，rotate by vector direction

1 vector up = set(0, 1, 0);
2 matrix m=dihedral(@N, up);
3 @P*=m;

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7，测量线的长度 arclen expression function - Returns the arc length of a curve between two U positions.

arclen(surface_node, prim_num, ustart, ustop)

8, Quaternion To Euler ?

 matrix m = qconvert(@orient);

v@geoRotation = cracktransform(0, 0, 1, {0,0,0}, m);

 

9，get transform

v@t = cracktransform(0, 0, 0, {0,0,0}, 4@xform);
v@r = cracktransform(0, 0, 1, {0,0,0}, 4@xform);
v@s = getbbox_size(1); 

10, 字符串替换

表达式

`strreplace(chs("root"), \'output\', \'cache\')`

vex
string path = "../shop/principled1";
s@path = re_replace("../shop/", "../shopnet1/", path);

11, 点蔓延

 1 if(@infect == 0){
 2     int spnts[] = nearpoints(0, @P, ch(\'search\'), ch(\'searchnum\'));
 3     foreach(int pt; spnts){
 4         if(point(0, \'infect\', pt)==1 ){
 5             vector pdir = normalize( @P - point(0, "P", pt) );
 6             float dotflow = dot(pdir, v@flowup);
 7             if( dotflow<chf("slope") ){
 8                 @infect = 1; 
 9                 @Cd = {1,0,0}; 
10                 @v = pdir;
11             }
12         } 
13     } 
14 } 

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 12，均匀点

 1 // Average Neighbouring Points
 2 int n[] = nearpoints(0, @P, chf("maxdist"));
 3 vector avgP = @P;
 4 
 5 // Loops over all elements of n, setting pt
 6 // to be the value of each element
 7 foreach (int pt; n)
 8 {
 9     avgP += point(0, "P", pt);
10 }
11 
12 // +1 because we included ourself.
13 avgP /= len(n)+1;
14 @P.y = avgP.y;

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 13, flat curve

 1 vector begin_position = point(0, "P", 0);
 2 float begin_height = begin_position.y;
 3 float last_height = begin_height;
 4 
 5 int i=0;
 6 for(i; i<npoints(0);i++){
 7     vector current_pos = point(0, "P", i);
 8     float current_height = current_pos.y;
 9     if(current_height > last_height){
10         current_pos = set(current_pos.x, last_height, current_pos.z);
11         setattrib(0, "point", "P", i, 0, current_pos, "set");
12     }
13     else{
14         last_height = current_height;
15     }             
16 }        

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