HI Robert,
I replaced the program from coin to osg and I don't know why osg display
the image from the same volume data is different from coin. I think the
problem is on texture format since I changed to use different parameter of
texture format such as GL_RGBA, GL_RGB16F_ARB, GL_RGBA8. The display images
are different. When GL_RGB16F_ARB is used, the colour is closer to I expected,
but I have no idea why the volume body is empty (1st attached file). When
GL_RGBA is used, the body of volume is filled, but the colour is not sharp
enough. I don't know how to set to use the right texture parameter. Sorry for
my worse explanation. Hope this time better. Thanks.
Regards,
Clement
________________________________________
From: osg-users-boun...@lists.openscenegraph.org
[osg-users-boun...@lists.openscenegraph.org] On Behalf Of Robert Osfield
[robert.osfi...@gmail.com]
Sent: Thursday, 19 January 2012 4:15 AM
To: OpenSceneGraph Users
Subject: Re: [osg-users] osgvolume opacity settings
Hi Clement,
I can't work out specifically what you are expecting to happen. What
coin does is something I have no experience with so can't comment on
how you might try to obtain a similar image.
Robert.
On 18 January 2012 15:14, <clement....@csiro.au> wrote:
> Hi Robert,
>
> Thanks for your reply. I found the problem may relate to the texture
> format when called setImage. I attached three images to describe my problem.
> The image texture_GL_RGBA.jpg is used GL_RGBA for the 4th parameter in
> setImage.
>
> eg. osgImage->setImage(nx, ny, nz, GL_RGBA, GL_RGBA, GL_UNSIGNED_BYTE,
> (uint8*)pdisp), osg::Image::NO_DELETE);
>
>
> The image texture_GL_RGB16F_ARB.jpg is used GL_RGB16F_ARB parameter. The
> colour of this image is I expected, but the problem is that this image is no
> body (only surface have colour). If I used GL_RGBA, it can fill in the whole
> volume, but the colour is very light and blur. The last attachment is
> captured from coin3d library and it is my original render library. Now I
> have replaced with osg, so I expect the osg can display the same result as
> coin3d.
>
> From the first two images, do you know which texture format parameter I
> should use? Thanks.
>
>
> Regards,
> Clement
>
> ________________________________________
> From: osg-users-boun...@lists.openscenegraph.org
> [osg-users-boun...@lists.openscenegraph.org] On Behalf Of Robert Osfield
> [robert.osfi...@gmail.com]
> Sent: Monday, 16 January 2012 8:21 PM
> To: OpenSceneGraph Users
> Subject: Re: [osg-users] osgvolume opacity settings
>
> Hi Clement,
>
> On 16 January 2012 06:21, <clement....@csiro.au> wrote:
>> My application is using osgvolume to display CT data. There is class
>> called CompositeProperty and there are three property classes
>> (AlphaFuncProperty, SampleDensityProperty and TransparencyProperty) as well.
>> I would like to know more details of those classes and how to apply on
>> osgvolume. I did to follow the example to use those classes, but when I
>> changed the value of SampleDensityProperty from 0.05 to 0.5. Some CT data
>> are disappear, so I would like to know more how to control property values.
>> Many thanks.
>
> AlphaFuncProperty is equivalent to glAlphaFunc and sets the alpha
> value below which fragments will be discarded
>
> TransparencyProperty is an alpha value multiplier that you can use to
> make your volume more transparent.
>
> SampleDensityProperty controls the size of the step during the ray
> tracing through the volume, the lower the value
> the more samples, the higher the value the less the samples. If you
> use a value of 0.5 you'll only get 3 samples which clearly won't be
> enough!
>
> Robert.
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