My recent Qt3D/QML question collection

[Midori Yakumo]

I am learning OpenGL with http://learnopengl.com/ as well as Qt3D, the documnet of Qt3D is far from complete (especially the QML part), so I feel quite puzzled

1. https://github.com/MidoriYakumo/learnopengl-qt3d/blob/master/qml/hellotriangle.qml vs http://learnopengl.com/code_viewer.php?code=getting-started/hellotriangle
   Why render by default do face culling with normal array though there is no normal set in my code , without

renderStates: CullFace { mode: CullFace.NoCulling }

a reversed-ordered triangle vertices will not be drawn on screen.

2. The same example hellotriangle in https://github.com/MidoriYakumo/learnopengl-qt3d/blob/master/qml/Components/RenderSettings0.qml

	activeFrameGraph: ClearBuffers {
		buffers: ClearBuffers.ColorDepthBuffer // Why not ColorBuffer only???
		clearColor: Qt.rgba(0.2, 0.3, 0.3, 1.0)
		RenderSurfaceSelector {
		}
	}

vs

     glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
     glClear(GL_COLOR_BUFFER_BIT);

The triangle do not have z-depth information, however Qt3D will not draw any thing with buffers:ClearBuffers.ColorBuffer, why?

3. Will TextureImage and other resource type support resources from url scheme of http in the future? <= An example of lack of unity of QtQuick and Qt3D

4. https://github.com/MidoriYakumo/learnopengl-qt3d/blob/master/qml/transformations.qml vs http://learnopengl.com/code_viewer.php?code=getting-started/transformations-exercise2
   We can call glDrawElements twice for different parameters as two render pass, can I somehow assemble with Transform for first render pass and switch to another in the second pass？

5. https://github.com/MidoriYakumo/learnopengl-qt3d/blob/master/qml/coordinate_systems_multiple_objects.qml
   Old question, any good way to assmble Entities in scene dynamically?
   I have tried:
   a. ListElements of Entites

property list<Box0> boxes:[ Box0{ }, Box0{ }, Box0{ } ]

almost read-only, seems data cannot be binded in run-time
b. QtQuick.Repeater

QQ2.Repeater {
	id: repeater
	model: root.cubePositions
	delegate: Box0 {
		transform: Transform {
			translation: data
		}
	}
}

It doesn't work because that an Item is not an Entity [#QTBUG-27444]
c. QtQuick.OnCompleted + createComponent + createQmlObject (for binding)

QQ2.Component.onCompleted: {
	var component = Qt.createComponent("Components/Box0.qml")
	for (var i in cubePositions) {
		var box = component.createObject(root)
		var transform = Qt.createQmlObject("import Qt3D.Core 2.0;
			Transform {
				rotation: fromAxisAndAngle(Qt.vector3d(1, .3, 5), root.angle*%1)
			}".arg(i), box); // Dirty binding and namespace
		transform.translation = cubePositions[i]
		box.transform = transform
	}
}

It just works but I feel dirty
6. There is something interesting in above that I have to use createQmlObject, because

box.transform.rotation = Transform.fromAxisAndAngle(Qt.vector3d(1, .3, 5), root.angle) 

will not work, is there any workaround/trick for QtQuick method namespace restriction?

Thanks for your discussion!

[SGaist]

Hi,

Not a direct answer, Qt3D in it's current version is a tech preview thus the documentation is also a work in progress that will be improved.

For your current questions, you should bring them to the interest mailing list. You'll find there Qt3D's developers/maintainers. This forum is more user oriented.

[Midori Yakumo]

@SGaist thank you dude!