> On 10 Jan 2019, at 13:24, Vlad Stelmahovsky <vladstelmahov...@gmail.com> > wrote: > > Qwt is nice but supports only QWidgets, right? > > so any mobile or Desktop/QML is not supported. Probably this is one of the > reasons > > and its not HW accelerated
Last I checked (which was a couple years ago), Charts started out widget-oriented, and QtQuick support was added without changing how the rendering is done… so it’s not like how the rest of Qt Quick is implemented, more like use QPainter to render into an image, then make a texture out of that, and then oh yeah you can composite it into the scene as a final step. One exception is if you want to draw a simple line chart with GL_LINES, then the GPU can do it (but that way there is no built-in antialiasing). Writing highly efficient code (efficient even on low-end GPUs) for arbitrary 2D graphics _with_ AA is hard, unless you can afford multi-sampling (to do basic low-quality AA on anything that was jaggy), or can afford crazy fragment shaders (shadertoys.com approach). I got as close as I could to the “right way” a few years ago for line charts only: making a few extra vertices, and having the vertex shader calculate their positions and alphas, so that all the strokes have “feathered” edges and reasonably nice corners… it’s very efficient, but the shader is complex, and still imperfect, so quality of sharp corners especially is not as good as doing it with QPainter. (Writing it really tested my math skills. And debugging shaders is very hard too.) But maybe I’ll find a way eventually. It’s one of my back-burner research projects. QtQuick Shapes don’t have AA. (Unless you use multi-sampling, or NV_path_rendering) But if we had figured out a good generic solution for vertex AA for those (QTriangulator with AA), then the way I'd implement Lottie would be to allocate all the vertices for the whole shape at the beginning, then use two uniforms for each animated segment, to tell the vertex shader to collapse a range of the array (from a cut-off point to the end cap) and relocate the end cap. But it has to be possible for uniforms to be animated. The next problem is how to use custom shaders and adjustable uniforms without breaking batching in the scene graph; today, the number of draw calls goes up if you do that. This is the reason we don’t have GPU-calculated AA line charts, and it’s also the reason we don’t have the nice Ellipse that I wrote for Qt Quick. Every custom shader runs in a separate batch (that’s unavoidable). Shaders can’t have dynamically adjusted uniforms (for animation, or for limiting the scope of rendering of a vertex array), or even uniforms that vary between instances, without breaking batching, and that’s a terrible limitation that I would like to see solved somehow in a future scene graph implementation, if there’s any way. https://github.com/kbroulik/lottie-qml looks like a JS/canvas thing? I’m guessing that both of the Lottie implementations make QPainter work pretty hard? _______________________________________________ Development mailing list Development@qt-project.org https://lists.qt-project.org/listinfo/development
