Thanks. -----הודעה מקורית----- מאת: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] בשם J.P. Delport נשלח: Monday, September 08, 2008 12:16 PM אל: OpenSceneGraph Users נושא: Re: [osg-users] GL_LINEAR
Hi, AFAIK sampling in OpenGL occurs at pixel centers. That would explain your "quarter" effect. As for the inconsistency in the center of the output, I can only speculate. Things I would try: Use TextureRectangle instead of normal texture (coordinates are then closer to pixel values) Try various output sizes to see if it is a sampling/math problem in the card implementation. Use a shader to do the sampling to see what is going wrong where. jp Guy wrote: > Hello, > > I have a problem with GL_LINEAR filtering of a float texture. > > > > I created a 2D float image with the values > > > > 100 100 > > 200 200 > > > > I stretched this image over 300x300 float buffer. > > > > The results are defiantly not a linear interpolation of these values. > > > > 1. The upper and lower quarters of the image are constants. The > constant value is the value that should have been only in the > upper most and lower most rows. It seems the interpolation of a > pixel with 0.001 coordinates for example, takes into consideration > values with negative texture coordinates. (I can't find any other > explanation). > 2. Between these quarters, the image SEEMS to be linearly > interpolated, but it is not. I would expect the differences > between two sequential pixels to be constant, but the differences > are not the same. > > > > > > I had this problem both with OSG1.2 and OSG2.0. I don't believe it has > anything to do with the OSG code, but with the hardware implementation. > > > > I used the following code to create the texture: > > > > image->setImage( width, > > height, > > 1, > > GL_RGBA16F_ARB, > > GL_RGBA, > > GL_FLOAT, > > (unsigned char*)(new > float[4*width*height]), > > osg::Image::USE_NEW_DELETE); > > > > > > osg::Texture2D* rtexture = new osg::Texture2D; > > > //------------------------------------------------------------------------ > > // make the texture float texture > > > //------------------------------------------------------------------------ > > rtexture->setInternalFormat(GL_RGBA16F_ARB); > > rtexture->setWrap(osg::Texture2D::WRAP_S, > osg::Texture2D::CLAMP_TO_EDGE); > > rtexture->setWrap(osg::Texture2D::WRAP_T, > osg::Texture2D::CLAMP_TO_EDGE); > > > > > rtexture->setFilter(osg::Texture2D::MIN_FILTER,osg::Texture2D::LINEAR); > > > rtexture->setFilter(osg::Texture2D::MAG_FILTER,osg::Texture2D::LINEAR); > > rtexture->setSourceFormat(GL_RGBA); > > rtexture->setSourceType(GL_FLOAT); > > > //======================================================================== > > rtexture->setImage(image); > > rtexture->setTextureSize(image->s(), image->t()); > > rtexture->setResizeNonPowerOfTwoHint(false); > > > > I also tried it with 32 bit float image. > > > > I'm using windows XP and nvidia 8800. > > > > Any ideas how to apply a true linear mapping for textures? > > > > Thanks, > > Guy. > > > > > ------------------------------------------------------------------------ > > _______________________________________________ > osg-users mailing list > [email protected] > http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org -- This message is subject to the CSIR's copyright terms and conditions, e-mail legal notice, and implemented Open Document Format (ODF) standard. The full disclaimer details can be found at http://www.csir.co.za/disclaimer.html. This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean. MailScanner thanks Transtec Computers for their support. _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org _______________________________________________ osg-users mailing list [email protected] http://lists.openscenegraph.org/listinfo.cgi/osg-users-openscenegraph.org
