---
title: "Light Randomization"
canonical: "https://rmanwiki-27.pixar.com/space/RU/592019497/Light%20Randomization"
format: markdown
---
Above is the Solaris scene graph for the randomization of all the lights in our scene.
All the magic happens inside *attributewrangle* nodes that control the lighting randomization of each letter in our sign. I have one wrangle for each of the letters in the scene, as I want to have control over each letter individually.
Let’s take a look at the meshlight Neon tubes first:
---
**Letters - D - M - O - Neon Tubes**
Create a *attributewrangle *node and under Primitives, we’re selecting the neon tube meshlights we want this node to control.
Below is the VEX code used to set up the parameters
```
int off = chi("off");
int on = chi("on");
int transition = chi("transition");
int A = off;
int B = off + transition;
int C = off + transition + on;
int D = off + 2 * transition + on;
float val = 0;
int frame = int(@Frame - $FSTART + chi("frameOffset") * @elemnum) % (D + 1);
if(frame < A)
val = 0;
else if (frame >= A && frame < B)
val = 1 - (B - frame) / float(B - A);
else if(frame >= B && frame < C)
val = 1;
else if (frame >= C && frame < D)
val = (D - frame) / float(D - C);
val *= ch("intensity");
@inputs:defaultFloat = val;
//@inputs:intensity = val;
```
We now have a set of parameters that will allow us to control the randomisation of the prims.
**OFF**
The number of frames that the neons are switched off.
**ON**
The number of frames that the neons are switched on.
**Transition**
The number of frames to transition between OFF and ON states
**FrameOffset**:
**Intensity**
Sets and overrides the intensity of the lights
---
**Letter - E - Globe Bulbs**
This wrangler allows us to control the value of the two primvars we set up in the Globe bulb USD asset.
Remember, these were called Bulb_COL and Bulb_INT
Here is the code
```
float randomFloat(float min; float max; string primpath) {
return fit01(rand(random_shash(primpath), chi("seed")),min, max);
}
//@inputs:intensity = fit01(rand(random_shash(@primpath), chi("seed")), ch('min'),ch('max'));
@inputs:defaultFloat = randomFloat(ch('min'),ch('max'), @primpath);
float randomHue = randomFloat(ch('Hue'), ch('Hue'), @primpath + "hue");
float randomSat = randomFloat(ch('minSat'), ch('maxSat'), @primpath + "sat");
float randomVal = randomFloat(ch('minVal'), ch('maxVal'), @primpath + "val");
v@inputs:defaultColor = hsvtorgb(randomHue,randomSat,randomVal);
```
which creates this set of parameters
**Intensity Min + Max**
The min and max intensity values that will be randomly created for the bulb's intensity (Bulb_INT)
**Bulb Hue**
How much to randomize the hue of each bulb (Bulb_COL)
**Saturation Min + Max **
The minimum and maximum random saturation values of the bulb color (Bulb_COL)
**Value Min + Max**
The minimum and maximum random values of the bulb color (Bulb_COL)
**Seed**
Allows you to control the speed of the flashing of the bulbs.
If left to a single frame, the bulbs will not animate. However, using the $FF expression causes the seed to change every frame, thereby animating the bulbs.
**Facing Ratio**
Allows you to control the facing ratio of the bulbs.
---
**Letter - S - Fairground Bulbs**
This wrangler allows us to control the intensity and color values of the tiny sphere light inside of the glass fairground bulbs.
```
float randomFloat(float min; float max; string primpath) {
return fit01(rand(random_shash(primpath), chi("seed")),min, max);
}
//@inputs:intensity = fit01(rand(random_shash(@primpath), chi("seed")), ch('min'),ch('max'));
@inputs:intensity = randomFloat(ch('min'),ch('max'), @primpath);
float randomHue = randomFloat(ch('Hue'), ch('Hue'), @primpath + "hue");
float randomSat = randomFloat(ch('minSat'), ch('maxSat'), @primpath + "sat");
float randomVal = randomFloat(ch('minVal'), ch('maxVal'), @primpath + "val");
v@inputs:color = hsvtorgb(randomHue,randomSat,randomVal);
```
Again, creating this set of parameters
---
**Summary**
So … to summarize.
With this set of wrangles, we can randomly flash and control meshlights, the Glow intensity, and color of a PxrSurface and analytic USD lights.
Feel free to use these code snippets in your scenes where you need to create randomisation of lights and shaders.