GLSL and Instances

Curl Noise Functions for Instances

While Perlin and Simplex noise are great functions, Curl noise is an excellent contender for organic looking motion. In this example we’ll leverage the ability to utilize #include statements in TouchDesigner, along with an adapted outside noise function from Cabbibo on Github.

First off — an #include statement allows us to put some of our GLSL functions in another part of the TouchDesigner network, and then point to that code for use in another shader. In Python we might use the import keyword, and with GLSL we can instead use #include. We can see this in action in our vertex shader on line 11:

#include <text_curl_noise>

This gives us access to all of the functions in our text DAT text_curl_noise, and helps us keep our vertex shader tidy. In the curl noise function on Cabbibo’s Github there is a simplex noise function. Since TouchDesigner has a built-in noise function, I’ve adapted this code block to instead use the TD noise functions.

vec3 snoiseVec3( vec3 x ){
    x       += u_transform;
    float s  = TDSimplexNoise(vec3( x ));
    float s1 = TDSimplexNoise(vec3( x.y - 19.1 , x.z + 33.4 , x.x + 47.2 ));
    float s2 = TDSimplexNoise(vec3( x.z + 74.2 , x.x - 124.5 , x.y + 99.4 ));
    vec3 c = vec3( s , s1 , s2 );
    return c;
}

We can then see in our vertex shader on lines 23-25 where we’re using the curl noise fucntion:

vec3 inst_for_noise = (TDInstanceMat()[3].xyz + u_transform.xyz) * u_noise_scale;

vec3 scale      = curlNoise(inst_for_noise);  

Like in other examples, we retrieve the xyz position of our instance with the TDInstanceMat() function, and then use that value to seed our curlNoise() function. I’d encourage you to play with the network in this example to better understand what’s happening. Especially pay attention to the custom uniform u_noise_scale and u_transform. Noise scale will allow you to adjust the scale of the noise in x, y, and z.

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Tested in TouchDesigner099 2020.23680

Updated 06.03.20
Matthew Ragan
Zoe Sandoval