Sketch circle is drawn very inaccurate

[adesk-tom34]

Situation: most simple case of a square-rectangle and a circle (with exact same radius) on one edge.

While the (fill-)profile of the circle does visually match (touch) the rectangle, the circle drawing does NOT touch (see blue selection of the circle on my screenshot below)!
This only happens on the Y-up position, the X side is perfect (when zoomed-in).
I think its a optimization bug. IMHO at least at the 4 XY-positions a circle should be drawn perfectly; I tolerate some tiny deviation (due approximation) on the arc.

BTW any mouse interaction (snap/constrain) on the circle gets very shaky when zoomed. Not nice.
Thanks

[TheCADWhisperer]

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@adesk-tom34 wrote:

...gets very shaky when zoomed. 

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Why zoom to that extreme amount?

[jeff_strater]

There is no problem here.  You are just seeing graphics inaccuracies from zooming in too close.  As you can see by selecting profiles, the geometry is fine:

[adesk-tom34]

Thanks, but as I wrote, the profile (filled) circle is OK. But NOT the circle (draw). So can you explain why a different painting algorithm is used? (or the bad/optimized algorithm is using single-precision floating-point only?) Else I have to assume its another of the countless UI/usability issues/flaws in Fusion... don't you think it's about time to invest development time in this area?

[adesk-tom34]

this is NOT an extreme zoom. As you can see the shown reference line is 0.11 compared to circle radius 50. On todays system this is a joke of precision (double-float has 15 digits precision). Any way, the profile circle is correct, so the drawing (outline) is just a very badly optimized approximation.

[g-andresen]

Hi,

As long as the resulting bodies are correct, and they are, I ignore such minor details in the display.

günther

[TrippyLighting]

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@adesk-tom34 wrote:

...(or the bad/optimized algorithm is using single-precision floating-point only?) ...

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These sorts of artifacts appear in all CAD systems I have ever worked with, whether that's Catia, SolidWorks, ZW3D, or Fusion 360. 

If you are interested in how computer graphics work under the hood, even on the most modern graphics hardware, I can send you my copy of  Computer Graphics, Principles and Practice...

Actually, I'll take that back. My copy is from 1990 and I am not giving it away. You'll have to get your own 😉

[adesk-tom34]

Hi, note I'm a SW developer since before this book was written, I know almost everything about graphics/UI/GPUs.
AGAIN please explain why the profile-circle is perfect and the hairline-circle is NOT? 
Also note in many places in Fusion, the (3D) graphics paint while zooming is at first a coarse approximation only, but gets refreshed with a closer (much better) approximation within a sub-second time span. This is an acceptable solution to preserve performance.

[TrippyLighting]

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@adesk-tom34 wrote:

Hi, note I'm a SW developer since before this book was written, I know almost everything about graphics/UI/GPUs.

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Then your comments are truly puzzling!

Fusion 360 uses an object level adaptive LOD algorithm, at least for displaying 3D geometry.

I assume similar things are happening in the 2D sketch environment. Again, this is done in all CAD systems for known reasons!

Usually these effects only bother folks that are new to CAD and computer graphics. 

As has been explained, your geometry representation in computer memory is fine, as it is represented by analytic and NURBS geometry. 

Move on!

[jeff_strater]

"don't you think it's about time to invest development time in this area?"

Again, this is just graphics.  It is not geometry.  And, there will always be a tradeoff in graphics accuracy with speed vs accuracy.  It is just a visual representation.  Fusion is intended to be a geometry-authoring product, not a graphics-authoring product.  So, yes, there be these kinds of visual glitches that appear in some cases.  It is not really high priority at the moment, to be honest.