[osg-users] text appearing flipped and backwards

James Dickson james.dickson at gmail.com
Fri Jul 18 13:49:31 PDT 2008


 Hi,

I am having an issue with osgText::Text in that the text appears flipped and
backwards relative to the other geometry in the scene. (Please see
screenshot for what I mean)
In the attached screen shot I have written on the coords. of the billboard
geometry so hopefully the following code will make some sense:


// Go through data and plot lines.

for (_i = _testTimeLine.begin(); _i != _testTimeLine.end(); ++_i)

{

std::stringstream _caption;

_caption << *_j;

int _y = static_cast<int>(((*_j) + _minY) *

((
_height - 20) / (_maxY - _minY)));

int _x = static_cast<int>(((*_i) + _minX) *

((
_width - 20) / (_maxX - _minX)));

_x = _x + 10;

_y = _y + 10;

// If not at the beginning of the vector, draw a line, otherwise

// colour a pixel.

if (_i != _testTimeLine.begin())

{

m_graphImage->DrawLine(osg::Vec2(_prevx, _prevy),

osg::Vec2(_x, _y),

osg::Vec4(0.0f, 0.0f, 1.0f, 1.0f));

}

else

{

m_graphImage->SetPixel(osg::Vec2(_x, _y),

osg::Vec3(0.0f, 0.0f, 1.0f));

}

_prevx = _x;

_prevy = _y;

// Convert texture coordinates to uv's to use as offsets.

float _u = ((float)_x) / ((float)_width);

float _v = ((float)_y) / ((float)_height);

osg::Vec3 _xoffset(_u, 0.0f, 0.0f);

osg::Vec3 _zoffset(0.0f, 0.0f, _v);

// Use offsets to create world space coordinates.

osg::Vec3 _pos = m_corner + _xoffset + _yoffset

+
_zoffset;

// Create and position text displaying data point value.

osgText::Text * _text = new osgText::Text;

_text->setFont(_font);

_text->setCharacterSize(characterSize);

_text->setPosition(_pos);

_text->setAxisAlignment(osgText::Text::XZ_PLANE);

_text->setText(_caption.str());

_captions->addDrawable(_text);

++
_j;

}
I have managed to fix it by changing the alignment setting to
REVERSE_XZ_PLANE and switching the sign of the offset coords. However I feel
this is a slight hack and wondered if there is some other 'proper' setting?

Many thanks,

James
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