Hi Philip,
OpenGL has various clamping modes for textures that effect the way
texture coords are mapped into the associated textures. The OSG
supports all the modes that OpenGL provides so have a look at OpenGL
docs for explanation of the details. On the OSG side osg::Texture has
the following settings, note the direct OpenGL mapping used for
WrapMode.
enum WrapMode {
CLAMP = GL_CLAMP,
CLAMP_TO_EDGE = GL_CLAMP_TO_EDGE,
CLAMP_TO_BORDER = GL_CLAMP_TO_BORDER_ARB,
REPEAT = GL_REPEAT,
MIRROR = GL_MIRRORED_REPEAT_IBM
};
/** Sets the texture wrap mode. */
void setWrap(WrapParameter which, WrapMode wrap);
/** Gets the texture wrap mode. */
WrapMode getWrap(WrapParameter which) const;
Robert.
On 22 January 2013 13:18, Philip Woerner <[email protected]> wrote:
> Hi all,
>
> our problem is that different rendered osg:Textures are missing single row or
> column of the corresponding osg::Image. Each row or column can be missed. The
> missed rows or columns aren't only the outer but also the inner ones.
>
> It was noticed by an osg::Texture2D, whose image size is only 8 by 8 pixel.
> But it happens also by other Textures with a bigger size, where a missing
> row/column doesn't really interest.
>
> The lose of the row or column in the texture happens, if ...
>
> ... the view size (height,width) is changed.
> ... the content of the view is moved.
> ... the content of the view is zoomed with the mouse wheel.
>
> If you go back or moved further the missing row/column appears again.
>
> This is the code of the osg::Texture with the 8x8 Image:
>
>
> osg::Geode* osgGeode = new osg::Geode();
>
> osg::Geometry* osgGeometry = new osg::Geometry();
> osgGeode->addDrawable(osgGeometry);
>
> //create vertex array for graphics item
> osg::Vec3Array* vertices = new osg::Vec3Array;
> vertices->push_back(osg::Vec3(-(w/2) + 0.0f, - (h/2)
> -(h_texture - h) + 0.0f, 0.0)); // bottom left
> vertices->push_back(osg::Vec3(-(w/2) + pImageOSG->s(), - (h/2)
> -(h_texture - h) + 0.0f, 0.0)); // bottom right
> vertices->push_back(osg::Vec3(-(w/2) + pImageOSG->s(), - (h/2)
> -(h_texture - h) + pImageOSG->t(), 0.0)); // top right
> vertices->push_back(osg::Vec3(-(w/2) + 0.0f, - (h/2)
> -(h_texture - h) + pImageOSG->t(), 0.0)); // top left
> osgGeometry->setVertexArray(vertices);
>
> osg::Vec4Array* color = new osg::Vec4Array;
> color->push_back( osg::Vec4( 1., 1., 1., 1. ) );
> osgGeometry->setColorArray( color );
> osgGeometry->setColorBinding( osg::Geometry::BIND_OVERALL );
>
> // create primitive set drawable
> osg::DrawElementsUInt* polygon = new osg::DrawElementsUInt
> (osg::PrimitiveSet::TRIANGLE_STRIP, 0);
> polygon->push_back(0);
> polygon->push_back(1);
> polygon->push_back(3);
> polygon->push_back(2);
> osgGeometry->addPrimitiveSet(polygon);
>
> // create texture coordinates for graphics item
> osg::Vec2Array* texcoords = new osg::Vec2Array (4);
> (*texcoords)[0].set(0.0f, 0.0f); // tex coord for vertex 0
> (*texcoords)[1].set(1.0f, 0.0f); // tex coord for vertex 1
> (*texcoords)[2].set(1.0f, 1.0f); // ""
> (*texcoords)[3].set(0.0f, 1.0f); // ""
> osgGeometry->setTexCoordArray(0, texcoords);
>
> // create texture for graphics item
> osg::Texture2D* texture = new osg::Texture2D;
>
> texture->setDataVariance (osg::Object::DYNAMIC); // protect from being
> optimized away as static state
> texture->setFilter(osg::Texture2D::MIN_FILTER, osg::Texture2D::NEAREST);
> texture->setFilter(osg::Texture2D::MAG_FILTER, osg::Texture2D::NEAREST);
> texture->setImage(pImageOSG.get());
>
> You can see, that we use no filtering, because the image has only a 8x8 size
> and with a filter the 8x8 image is blured.
>
> A image file of the problem is attached. The Texture in the lower left corner
> is missing the second row from below, the Texture with same image in the
> upper right corner is well (8x8).
>
> Is there any hope for fixing this problem or is it as feared a precision
> problem of OpenGL, which can't be solved?
>
> Thank you!
>
> Cheers,
> Philip
>
> ------------------
> Read this topic online here:
> http://forum.openscenegraph.org/viewtopic.php?p=52067#52067
>
>
>
>
> Attachments:
> http://forum.openscenegraph.org//files/8x8problem_935.png
>
>
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