Engine exception if model has no graph node

[LeXXik]

The engine will throw, if a model that has no graph node is added to the entity. For example, the following will result in engine error:

    var entity = new pc.Entity();
    entity.addComponent('model', {});
    entity.model.model = new pc.Model();

The cause is in the model component:

engine/src/framework/components/model/component.js

Line 716 in d369b82

this.entity.addChild(this._model.graph);

which then tries to look for null's parent:

		addChild: function (node) {
			if (node._parent !== null)

[mvaligursky]

I'm not sure this is an actual problem. The model class is designed to contain a hierarchy (a single node would do), which is then connected to the entity when you add the component to it.

See the API docs:
https://developer.playcanvas.com/en/api/pc.Model.html
... It contains a hierarchy and any number of mesh instances.

[LeXXik]

I agree. Thought perhaps you wanted to put a guard for unhandled exception, hence the report. Feel free to ignore.

[mvaligursky]

We had a discussion and will at some point implement a larger system to handle this.
#2529

Thanks for bringing this to our attention.