topic Re: Sketch circle is drawn very inaccurate in Fusion Support Forum

Sketch circle is drawn very inaccurate

adesk-tom34 — Sat, 13 Apr 2024 12:01:47 GMT

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

Re: Sketch circle is drawn very inaccurate

TheCADWhisperer — Sat, 13 Apr 2024 16:24:03 GMT

@adesk-tom34 wrote:
...gets very shaky when zoomed.

~~Why zoom to that extreme amount?~~

Re: Sketch circle is drawn very inaccurate

jeff_strater — Sat, 13 Apr 2024 22:08:06 GMT

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:

Re: Sketch circle is drawn very inaccurate

adesk-tom34 — Sat, 13 Apr 2024 22:33:57 GMT

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?

Re: Sketch circle is drawn very inaccurate

adesk-tom34 — Sat, 13 Apr 2024 22:42:10 GMT

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.

Re: Sketch circle is drawn very inaccurate

g-andresen — Sun, 14 Apr 2024 08:48:53 GMT

Hi,

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

günther

Re: Sketch circle is drawn very inaccurate

TrippyLighting — Sun, 14 Apr 2024 12:27:17 GMT

@adesk-tom34 wrote:

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

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 😉

Re: Sketch circle is drawn very inaccurate

adesk-tom34 — Sun, 14 Apr 2024 13:40:36 GMT

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.

Re: Sketch circle is drawn very inaccurate

TrippyLighting — Sun, 14 Apr 2024 13:58:39 GMT

@adesk-tom34 wrote:

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

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!

Re: Sketch circle is drawn very inaccurate

jeff_strater — Sun, 14 Apr 2024 16:30:39 GMT

"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.