You can’t convert 2d coordinates to a 3d position because you are missing the z
coordinate. It is similar problem like with picking objects in a 3D scene - you
can unproject a 2d screen coordinate to a vector/ray in your 3d scene and then
do a ray casting to see what you hit but that’s about it.
If you just want to render a 3D object at a specific location on a screen you
can do so via rendering to an offscreen target and then displaying it like a
regular 2d image but that will look and act like an overlay image rather than
being composed into your scene.
Sent from my iPad
> On Mar 16, 2021, at 10:52 AM, Alex john <blackbriar...@gmail.com> wrote:
>
>
>
>
> I did the following changes to the wireframe example (Trefoilknot.qml file
> translation property of transform) but still unable to get the modelView
> Matrix, and also not sure whether the following changes to translation are
> right If anyone can confirm and let me know
>
> property var mainCam // got the mainCamera ID from main.qml (wireframe
> example)
> property var forwardRenderer //forwardRendered id from main.qml (wireframe
> example)
>
> Transform {
> id: trefoilMeshTransform
> translation:Qt.vector3d(Qt.vector2D(4, 4)).unproject( *modelView*
> ,mainCam.projectionMatrix, forwardRenderer.viewportRect)
> property real theta: 0.0
> property real phi: 0.0
> property real roll: 0.0
> rotation: fromEulerAngles(theta, phi, roll)
> scale: root.scale
> }
> /*
> translation : Qt.vector2D(100, 100) is where I intend to give window 2d
> coordinates(here its x:100, y:100)and I assume that unproject api will
> convert the 2d points to 3d and renders the 3d object exactly at 100, 100
> pixel 2d location
> */
>
> I got the projectionMatrix from camera, viewPortRect from ForwardRenderer in
> Rendering settings. I'm completely stuck for this step. If anyone can please
> confirm the changes and let me know the modelView matrix.
>
>
>> On Mon, Mar 15, 2021 at 5:14 PM Alex john <blackbriar...@gmail.com> wrote:
>> > Going the other way round (back-projection) can be done by e.g.
>> > QVector3D::unproject()
>>
>> Thanks, as I'm referring the the wireframe example I was able to get
>> the camera projection matrix from Camera Qml. However, I'm unsure how
>> to get the ModelView matrix and the viewport.
>>
>> As I have loaded my custom obj in wireframe example and using the same
>> geometry and camera settings as its for wireframe, therefore can you
>> please let me know how this can be done at QML side? I did try to find
>> this in the documentation but didn't find the usage.
>>
>>
>>
>>
>> > On Mon, Mar 15, 2021 at 11:03 AM Alex john <blackbriar...@gmail.com> wrote:
>> >>
>> >> Hello ,
>> >>
>> >> Im successessfully able to load the obj file in Scene3D, and by using
>> >> fromEulerAngles I'm able to get the required yaw, pitch and
>> >> roll.However, I'm not able to use the right translation to get the
>> >> object rendered. I get the x,y coordinates in pixels from the other
>> >> module and I need to render the 3d model exactly at that pixel
>> >> location. It turns out that the Transform type has translation and it
>> >> takes the input in 3d coordinates (not sure which unit) if I try to
>> >> assign the x,y coordinates to the 3d coordinates it renders somewhere
>> >> else. Seems like the x,y in the translation is not the pixel 2d
>> >> values, as even with a x=0.3 it deflects more than expected.
>> >>
>> >> Is there a way to assign the x,y 2d pixel values (as we do for
>> >> Rectangle {x: 100, y:100}) to the translation so that it is rendered
>> >> to the right place where it's desired.
>> >> _______________________________________________
>> >> Interest mailing list
>> >> Interest@qt-project.org
>> >> https://lists.qt-project.org/listinfo/interest
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