[Interest] Qt3D. Drawing a single 3d lines ability

[Sean Harmer]

Hi,

On 08/11/2016 09:34, MASTER OF ORION wrote:
> Dear developers, please add the ability for drawing 3D lines to Qt3D!
> Many developers of 3D CAD systems realy need it. We need ability to
> draw continuous, dotted, dashed (and so on) lines width given thickness
> and color. Alse we need to draw textured lines (like Sword of the Jedi
> :-) ), i think, this is Fake Volume technique...
> Also, these lines should draw over models, because usually they lie
> directly on the edges or planes models (i think, here is POLIGON OFFSET
> sheuld be)
> It is desirable to be able to change the line style, if it lies in the
> invisible zone, for example to change a continuous line to dotted style.

Yes, such conveniences are something we are considering adding to 
Qt3DExtras. However, as you already alluded to, there are many 
techniques for drawing even something as simple as a line and there is 
no one true method that fits for all occasions.

* Lines along edges of triangles (or a subset thereof)
** polygon mode + polygon offset
** GL_LINES + polygon offset
** Single pass drawing as per the wireframe example (requires geometry 
shader so not suitable for ES 2 or ES 3.0/3.1 (iirc) but doesn't suffer 
from z-fighting like polygon offset

* Wide lines
** Extrude in geometry and/or tessellation shaders + texture
** Extrude on CPU and texture

* Volumetric lines
** Extrude in geometry and/or tessellation shaders + texture/solid color
** Extrude on CPU and texture/solid colour

I'm sure there are plenty of others too. All of these are possible to 
implement now but we don't provide them out of the box yet. If you would 
like to contribute something in this area then you would be more than 
welcome to do so.

Cheers,

Sean


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Dr Sean Harmer | sean.harmer at kdab.com | Managing Director UK
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