Bank of lights not lighting up in the right order

Plugin Development
1

I’m trying to bring a module from vcvrack over to metamodule, and am running into an odd issue. I have a bank of 128 SmallLight<RedGreenBlueLight> objects, and when I try to cycle through them one at a time, some of them get skipped over, and some of them light up with the wrong color at the wrong time. See here for a simplified version of the module, to highlight the issue.

The relevant code is as follows:
in the module struct we have

	enum LightId {
/* all the other lights... */
        ENUMS(STATE_LIGHT, 384), // 32 * 4 * 3
		LIGHTS_LEN
	};

Which are turned on one at a time like so:

        for (int i = 0; i < 32 * 4; ++i) {
            if (step == i) {
                // white
                lights[STATE_LIGHT + i * 3 + 0].setBrightnessSmooth(1.f, args.sampleTime);
                lights[STATE_LIGHT + i * 3 + 1].setBrightnessSmooth(1.f, args.sampleTime);
                lights[STATE_LIGHT + i * 3 + 2].setBrightnessSmooth(1.f, args.sampleTime);
            } else {
                lights[STATE_LIGHT + i * 3 + 0].setBrightnessSmooth(0.f, args.sampleTime);
                lights[STATE_LIGHT + i * 3 + 1].setBrightnessSmooth(0.f, args.sampleTime);
                lights[STATE_LIGHT + i * 3 + 2].setBrightnessSmooth(0.f, args.sampleTime);
            }
        }

In the modulewidget constructor, I create the lights like so:

        for (int i = 0; i < 4 * 32; ++i) {
            auto row = i % 32;
            auto col = i / 32;
            auto x = stateX + lightAreaMargin + col * xStep;
            auto y = stateY + lightAreaMargin + row * yStep;
            auto lightIndex = Pascal::STATE_LIGHT + i * 3;
            addChild(createLightCentered<SmallLight<RedGreenBlueLight>>(mm2px(Vec(x, y)), module, lightIndex));
        }

The module compiles fine, and runs as expected in vcvrack. But I’ve tried it on both metamodule 1.6.9 and 2.0.0 and it has this bug.

2

Sorry for missing this post last week.

So there is an (undocumented) limit of 255 lights, which explains what’s happening.

I tried building your plugin for both api-1.6 and also the v2.0-dev api, and it’s similar for both. One light tracks well (white), but offset by a fixed amount is a red and a blue light. This is because the light value is stored in a uint8_t at some point, so it wraps around (and 256 % 3 is not zero, so the RGB of the white light is spread across two lights).

So, I suppose I will need to raise that limit!

3

Gotcha. Thanks for looking into it, I wondered if it might be something like that. I’ll switch them to solid color lights instead or rgb in the meantime, that should bring me under the limit.