QSGGeometry / scenegraph: how to reuse data from QSGGeometry

t.verstraete

Hi,

I am using scenegraph to generate a chart and so each x ms I get a new data sample from the input module. Now I regenerate the data constantly using a for loop:
@
QSGGeometry* geometryNewLine = mNodeNewLine->geometry();
geometryNewLine->allocate(mLoopVertices->newLineVertices.count());
QSGGeometry::ColoredPoint2D *verticesNewLine = geometryNewLine->vertexDataAsColoredPoint2D();

    for (int i=0; i<mLoopVertices->newLineVertices.count(); i++)
    {
        color = mLoopVertices->newLineVertices.at(i).second ? colorInspiration : colorExpiration;
        verticesNewLine[i].set(//adapt vertice
                               mLoopVertices->newLineVertices.at(i).first.x, mLoopVertices->newLineVertices.at(i).first.y,
                               //adapt color
                               color.red(), color.green(), color.blue(), color.alpha()
                               );
    }

@
But this is taking quite some time and performance of course ... now I do not seem to see in the documentation a method for updating this with one new sample at the time? Do I always need to copy everything?

A immediate easy update could be using a QVector in code outside of the updatePaintNode and then get the data as an array out of it and doing a memcopy or some sort (std::copy).

Still I wonder if there is not an easier way of updating part of the data through QSGGeometry instead of always copying everything,

thanks in advance,

kind regards,

Tim

[edit, code tags added, koahnig]

koahnig

Please check out the "code wrapping section":http://qt-project.org/wiki/ForumHelp#e3f82045ad0f480d3fb9e0ac2d58fb01 in the forum help. This helps to make your code more readable in the forum.