On 10 December 2014 at 15:08, umesh ramesh <[email protected]> wrote:
> Hi Robert, > > OSG supports and displays RGB, RGB8 etc correctly, agreed. But whether it > is "packing" the RGB components properly, I need to analyze There is *nothing* to analyse, the OSG passes along to OpenGL what data is osg::Image according to your settings. You are wasting your time. > I think now we are deviating from my simple question that I asked > initially. I again give a short description: > I had originally 32 Bit textures. I wrote the geometry with the texture > data to IVE file. The IVE file size was 26 MB. Then I realized that I do > not need true color textures, so I converted my images to 8 Bit images > (RGBA8) reducing my image size from 4 mb to 1 mb (This can be easily done > using Paint.Net Free App). Then I again wrote the data to IVE file > expecting that now the IVE file size shall be far less as the image data > has reduced. But the file size is same 26 MB. > Thus I guess OSG stores the texture data in RGB or RGBA format only and > not in the original file format (that is RGB8 or RGBA8 unsigned byte in my > case). > The OSG stores data in whatever format you tell it to store, or what data it loads from. > > If I set RGBA8 in image->setInternalTextureFormat does not affect size or > view. But if I set RGB in image->setPixelFormat instead of RGBA, I see 1 MB > less size in the IVE file (now 25 MB). Maybe because now alpha componenet > is not written. > InternalTextureFormat is the hint to OepnGL what format to store the data in on the GPU. > > My final objective is if my texture sizes are less I should have more > texture memory available in graphics memory to load additional textures. > And i am trying to verify whether OSG loads OpenGL with actual texture size > (in my case RGBA8) or uses always RGB/RGBA format only. The display anyway > will not be affected but unnecessary texture memory will be allocated I > guess. The discussion above is on OSG with OpenGL & not OSG with OpenGL ES. > I am using OSG for our Simulation research & I do not doubt its > capabilities. But since I am neither a novice nor a full expert in OSG I > came across above doubts that someone in forum can answer/reply. If you want to minimize the texture object size on the GPU then you should use OpenGL compressed textures. Robert.
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