How to set color of the entity from the script in Amazon Sumerian?

Question

I am learning Amazon Sumerian for Web VR development. I am trying to change the color property from the script of that entity in the update() method. The code looks like this:

function update(args, ctx) {
    ctx.entity.transformComponent.setTranslation(0.6, 166, distance);
    distance += 10;
    if (distance > 1500) {
        distance = -10;
        ctx.entityData.color = "blue";
    }
}

I have tried setting the color property by ctx.entity.color and ctx.entity.setAttribute('color', 'blue') too but that also doesn't work. I also couldn't find any documentation on their official site for setting color. I think there is a simple catch that I am missing.

What is the correct way to update color of an entity from a script?

Answer 1

The following approach is undocumented. That could just be a symptom of incomplete Sumerian documentation or it could indicate that the approach is not officially supported and therefore may be subject to change in the future. But for now, you can use the following approach to accomplish what you want.

function update(args, ctx) {

    ctx.entity.transformComponent.setTranslation(0.6, 166, distance);
    distance += 10;

    if (distance > 1500) {

        distance = -10;

        // Color is a 4 component array in the order: red, green, blue, alpha
        const blueColor = [0, 0, 1, 1];
        ctx.entity.setDiffuse(blueColor);
    }
}

Answer 2

Answer below is for the Preview/new version of the Sumerian API. Answer for the Legacy version of the Sumerian API can be found above in Kris Schultz' answer.

Just wanted to contribute an answer to this question.

In this case, I am trying to change the shirt color of a host entity. For example, I would like to change the shirt color of the Cristine Polo entity to red dynamically using a script.

The answer can be obtained from the Amazon Sumerian scripting API's official documentation, which I recommend to everyone starting out: https://content.sumerian.amazonaws.com/engine/latest/doc/#content://sumerian-common/Guide/Quick%20Start

import * as s from 'module://sumerian-common/api';

export default function RotatorAction(ctx) {
  ctx.start( EnabledAction );
}

function EnabledAction(ctx) {
  ctx.start(
    [ s.material.SetMaterialColorAction, { color: s.color.Red } ]
  );
}

I ended up using Legacy API. Furthermore, with the Legacy API, I noticed that it's possible to just use three RGB values [r, g, b] without the alpha value. Also, that the RGB values that setDiffuse() takes are between 0-1, which needs conversion from the 0-255 scale usually found.