Hi Laurens.

Thank you for your patience regarding my issue.


I was not familiar with the "writing out .osg files and view them with 
osgviewer" method, but it is indeed a helpful hint!
I was able to view my quads/images in the osgviewer, and, to my surprise, they 
didn't seem to have any transparency issues!
So I must be doing something wrong within my program itself.


I'll try and keep digging for my issue, and report any interesting findings. 
And I'll keep your suggestions in mind.

Thank you for all the help!

________________________________
From: osg-users <osg-users-boun...@lists.openscenegraph.org> on behalf of L. 
Voerman <l.voer...@rug.nl>
Sent: Tuesday, July 3, 2018 9:04 AM
To: OpenSceneGraph Users
Subject: Re: [osg-users] Drawing a partially transparent image in a quad

Hi ,
I can't see what you are doing wrong, other guesses:
- you moved all quads into the transparent bin, and render them all at the same 
depth
- you compress the images to textures without transparency
- you are looking at a mipmap where the alpha values are interpolated as well.

for testing you could add
osg::AlphaFunc *alphaTest = new osg::AlphaFunc(osg::AlphaFunc::GREATER, 0.5f);
qss.setAttributeAndModes(alphaTest);
to discard (not blend) the fragments with an alpha value below 0.5

as you seem to have problems in your data, I would strongly recommend to write 
out the data to file (.osgt will do) and look at it in the osgviewer.
Laurens.

On Mon, Jul 2, 2018 at 6:25 PM Jose Pedro Canilho 
<jpc_...@hotmail.com<mailto:jpc_...@hotmail.com>> wrote:

Hi Laurens.
Thank you for your reply!

I've actually already had a black background color set in my camera 
("setClearColor( 0,0,0,1 )").

I've tried your rendering hint solution, but unfortunately it didn't solve my 
problem. Do I need to call any state set updating function after setting the 
rendering hint?

I've also double checked for the correct format in pretty much any place I can 
think of. I've checked that my raw images are indeed 8bit RGBA. When I 
construct my osg::image, I use the following:


osg::ref_ptr<osg::Image> img = new osg::Image();
img->setImage(width,height,1,GL_RGBA8,GL_RGBA,GL_UNSIGNED_BYTE,dataPtr,osg::Image::NO_DELETE);


I believe these format options are correct, since I'm able to create other RGBA 
images correctly.


Thanks once again.

José

________________________________
From: osg-users 
<osg-users-boun...@lists.openscenegraph.org<mailto:osg-users-boun...@lists.openscenegraph.org>>
 on behalf of L. Voerman <l.voer...@rug.nl<mailto:l.voer...@rug.nl>>
Sent: Monday, July 2, 2018 3:13 PM
To: OpenSceneGraph Users
Subject: Re: [osg-users] Drawing a partially transparent image in a quad


Hi Jose,
You may have a black background, with the blending actually (partly) working, 
change
getCamera()->setClearColor( osg::Vec4(r,g,b,a) );
to see if that's the case.
the stuff that needs blending needs to be rendered after the background, 
normally done with:
stateset->setRenderingHint(osg::StateSet::TRANSPARENT_BIN);

If it's not blending at all I would recommend you to check if your image did 
not end up as an RGB image instead of RGBA.
Regards, Laurens.




On Mon, Jul 2, 2018 at 11:28 AM Jose Pedro Canilho 
<jpc_...@hotmail.com<mailto:jpc_...@hotmail.com>> wrote:

Hi everyone!

I've been battling with this issue for a couple of days and could really use 
some assistance. I'm fairly new to OSG (and 3D rendering in general) so I might 
be doing some rookie mistake.


In my program, I draw several quads, each containing a RGBA squared image.

At one point, I'm required to draw a new image on top of the existent images. 
This new image is also squared, but it is partially transparent (i.e., several 
pixels have the RGBA value of 0,0,0,0). At the moment, these pixels are being 
rendered black instead of transparent, and thus are mistakenly covering some 
regions of the background images/quads.

After quite a few searches online, I was pointed in the direction of the 
GL_BLEND macro and blend functions. I tried to enable blending for the new 
image/quad:

auto qss = quad->getOrCreateStateSet();
qss->setMode(GL_BLEND, osg::StateAttribute::ON)


but to no avail.

I also tried to attach a blend function to the quad, like such:

osg::BlendFunc* blendFunc = new osg::BlendFunc(osg::BlendFunc::SRC_ALPHA, 
osg::BlendFunc::ONE_MINUS_SRC_ALPHA );
qss->setAttributeAndModes(blendFunc);


but that didn't work either.


Are there any other issues that I might be overlooking here?


Thanks in advance.

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