Houdini 17.0 VEX

VEX cookbook

Examples and suggestions for programming in VEX.

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VEX examples

To see the VEX implementation of a VEX-based operator:

  1. Add the operator to your network.

  2. Open the tile menu and choose Type Properties.

Other example VEX source code is available on the web.

Constant Color COP

You could write a "Constant Color COP" function this way:

cop
constant(vector clr=1; float alpha=1)
{
R = clr.r;
G = clr.g;
B = clr.b;
A = alpha;
}

However, you should use the high-efficiency assign function whenever possible.

cop
constant(vector clr=1; float alpha=1)
{
assign(R, G, B, clr);
A = alpha;
}

User noise functions

This example defines two user functions which generate normalized multiple octaves of Perlin noise.

float
myfperlin3d(vector pos; int octaves; float rough)
{
int    i;
float    nval;
vector    pp;
float    result, sum, scale;
// Because parameters are passed by reference, we don't really
// want to modify the parameters value.  Therefore, we copy it
// to a temporary variable.
pp = pos;
scale = 1;
sum = 0;
result = 0;
for (i = 0; i <= octaves; i++)
{
    result += noise(pp);
    sum += scale;
    pp *= 2;
    scale *= rough;
}
return result / sum;
}
float
myfperlin1d(float pos; int octaves; float rough)
{
int    i;
float    nval;
float    pp;
float    result, sum, scale;
// Because parameters are passed by reference, we don't really
// want to modify the parameters value.  Therefore, we copy it
// to a temporary variable.
pp = pos;
scale = 1;
sum = 0;
result = 0;
for (i = 0; i <= octaves; i++)
{
    result += noise(pp);
    sum += scale;
    pp *= 2;
    scale *= rough;
}
return result / sum;
}

It is possible to use #define macros to encode the contents of the function and simply call the macro to generate vector or other dimensions of noise.

VEX

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Reference