[Interest] Quick3D mapping of png textures onto Item 3D

Thu Sep 20 14:15:13 CEST 2012

The example which you have sent is working only till the animation
completes.

When I use QtQuick2.0 in the example shared without any animation, the
blending doesnot works and the total .png is black in color.

Could you please let me know how to fix this issue in QtQuick3D.

Br,

Satya

From: Satya Praveen Ganapathi 
Sent: Thursday, September 20, 2012 4:20 PM
To: Thomas Senyk
Cc: Ramakanthreddy_Kesireddy; interest at qt-project.org
Subject: RE: [Interest] Quick3D mapping of png textures onto Item 3D

Hi,

Thanks for the reply.

Actually we donot have mesh for the png files..so we need to use 3D
Items predefined(like Quad,Cylnder etc).

I suppose there is no inbuilt 3D rectangle item.

Can I use 2.0 instead of 1.0 in the cube example that you shared?

import QtQuick 1.0
import Qt3D 1.0
import Qt3D.Shapes 1.0

Regards,

Satya

________________________________

From: Thomas Senyk [mailto:thomas.senyk at pelagicore.com]
Sent: Thu 9/20/2012 2:52 PM
To: Satya Praveen Ganapathi
Cc: Ramakanthreddy_Kesireddy; interest at qt-project.org
Subject: Re: [Interest] Quick3D mapping of png textures onto Item 3D

It's working for me.
I did a fresh build from source and used an old example and it's
working.
I just use the qmlviewer (don't forget the -opengl argument)

One important thing to know:
Doing blending in a generic way for a library is a quite tricky task.
To do it properly one would need to sort all surfaces by there position
in the
3D-space (and even that is not the end solution if you want to be
perfect)
which is in most cases not really necessary and would consume a lot of
cpu.
So I assume that's why this is not done in QtQuick3D and therefor the
blending
isn't "optically correct".
But one should definitely see the blending! (adding a blue Rectangle as
background helps "seeing it" ;) )

On Thu, September 20, 2012 02:40:13 PM Satya Praveen Ganapathi wrote:
> Hi,
>
> I tried with the below code to resolve the transparent area of png
shown
> as black shaded:-
>
> ViewPort
> {
> Width:parent.width
> Height:parent.height
> blending:true
>
> Quad{
> effect:Effect{
> texture:"img.png"
> }
> }
>
> However, it still shows the transparent area of png file as black
> shaded.
>
> Please let me know the solution or this is a known issue in Quick3D.
>
> Best Regards,
> Satya
>
> -----Original Message-----
> From: interest-bounces+praveen.s=hmie.co.in at qt-project.org
> [mailto:interest-bounces+praveen.s=hmie.co.in at qt-project.org] On
Behalf
> Of Ramakanthreddy_Kesireddy
> Sent: Thursday, September 20, 2012 10:25 AM
> To: Thomas Senyk; interest at qt-project.org
> Subject: Re: [Interest] Quick3D mapping of png textures onto Item 3D
>
> Hi,
>
> We tried with below blending property in Effect but transparent area
of
> the png file is
> still shown as black shaded.
>
>
> Quad{
>
> Effect{
> texture:"img.png"
> blending:true
> }
> }
>
> Could you please let us know if we are mssing anything in this regard.
>
> Br,
> Ramakanth
> ________________________________________
> From:
>
interest-bounces+ramakanthreddy_kesireddy=mahindrasatyam.com at qt-project.
> org
>
[interest-bounces+ramakanthreddy_kesireddy=mahindrasatyam.com at qt-project
> .org] on behalf of Thomas Senyk [thomas.senyk at pelagicore.com]
> Sent: Wednesday, September 19, 2012 5:13 PM
> To: interest at qt-project.org
> Subject: Re: [Interest] Quick3D mapping of png textures onto Item 3D
>
> As he is using QtQuick3D, the answer is simpler:
>
http://doc.qt.digia.com/qt-quick3d-snapshot/qml-effect.html#blending-pro
> p
>
> :)
>
> Greets
> Thomas
>
> On Tue, September 18, 2012 08:57:55 AM Till Oliver Knoll wrote:
> > 2012/9/18 Satya Praveen Ganapathi <praveen.s at hmie.co.in>:
> > > ...
> > > However, the png image is not getting displayed properly in 3D
space
>
> i.e.
>
> > > transparent area of the png file is
> > > shown as black shaded.
> >
> > Most probably you simply need to enable "alpha blending": In OpenGL
> > terms that usually means
> >
> > a) Turn blending on: glEnable(GL_BLEND)
> > b) Define a blend function, e.g.: glBlendFunc(GL_SRC_ALPHA,
> > GL_ONE_MINUS_SRC_ALPHA)
> >
> > Note: "Premultiplied alpha" textures (refer to Wikipedia or the Qt
> > docs about the same topic) are to be preferred, in which case you
> > would say glBlendFunc(GL_ONE, GL_ONE_MINUS_SRC_ALPHA)
> >
> > Here is a guy who is trying /exactly/ the same thing as you:
> >   http://galfar.vevb.net/imaging/smf/index.php?topic=296.0
> >
> > Depending on what you are trying to achieve the function glTexEnv()
> > with argument GL_BLEND might be useful too (if you want to apply
alpha
> > blending at the moment when applying the texture - and if you want
> > that the underlying surface colour shines through). Refer to the
>
> > (possibly outdated) FAQ:
>
http://www.opengl.org/archives/resources/faq/technical/transparency.htm
>
> > How you apply all this to Qt 3D I don't know - but I'm sure there
must
> > be this big "Enable blending" switch somewhere, too - refer to the
> > docs (and if not, to my little understanding you can still mix in
your
> > own "raw OpenGL" code as above, no?).
> >
> > Cheers, Oliver
> > _______________________________________________
> > Interest mailing list
> > Interest at qt-project.org
> > http://lists.qt-project.org/mailman/listinfo/interest
>
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