[HN Gopher] OpenSCAD 3D rendering just got an order of magnitude...
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       OpenSCAD 3D rendering just got an order of magnitude faster
        
       Author : voussoir
       Score  : 54 points
       Date   : 2022-02-09 19:38 UTC (3 hours ago)
        
 (HTM) web link (ochafik.com)
 (TXT) w3m dump (ochafik.com)
        
       | prideout wrote:
       | I'm surprised that OpenSCAD uses GMP. I would think that 64-bit
       | doubles would be good enough.
        
         | R0b0t1 wrote:
         | It's wise to pick a library that can act as a portable layer
         | over implementation details.
        
         | amelius wrote:
         | Perhaps they need it to ensure robustness of geometric
         | predicates, in edge cases.
         | 
         | E.g. if the determinant of some matrix becomes too close to
         | zero, switch to exact arithmetic.
        
         | ur-whale wrote:
         | > I would think that 64-bit doubles would be good enough.
         | 
         | Implementing _robust_ boolean operations on polyhedral geometry
         | is and has been known for quite a while to be _very_ hard if
         | you do not have arbitrary precision math, or at the very least
         | some sort of interval arithmetic that kind winds back a
         | calculation and increases the precision up to the point where
         | an unambiguous decision can be made about the sign of an
         | expression.
         | 
         | Here's an example: create a sphere, tesselate it to - say - a
         | million triangle (not much these days), make a rotated copy of
         | the original by 0.01 degrees and intersect with the original. I
         | guarantee you the resulting calculation will either crash your
         | floating point based implementation or it'll produce a model
         | that will be non manifold.
        
       | b33j0r wrote:
       | Best tool for boolean geometry I've personally used. I've had
       | many more successful 3D prints than any of the point-and-click
       | CAD tools in which I have also spent hundreds of hours.
       | 
       | But with ADHD tendencies, the rendering time of OpenSCAD often
       | had me getting distracted and forgetting to finish whatever I was
       | doing for a while.
       | 
       | This is very exciting! Great work, OpenSCAD team.
        
         | YaBomm wrote:
        
       | ur-whale wrote:
       | If true, this is fantastic news. OMW to try it right now on a
       | score of old models I have stashed around.
        
       | mrfusion wrote:
       | Wow I'm so happy people are working on this. I love the program
       | but Ive had to abandon several interesting ideas due to never
       | rendering.
        
       | IgorPartola wrote:
       | Sweet. I use OpenSCAD for my models and it's been really cool.
       | Wish I was better after designing more organic looking shapes but
       | lost times I need simple objects anyways so it doesn't matter as
       | much.
        
       | PennRobotics wrote:
       | Alternatively, now you can increase $fn an order of magnitude and
       | get imperceptibly smooth curved surfaces and complicated
       | minkowski sums.
        
       | bseidensticker wrote:
       | This is so incredible! I just tried this out with a few of my
       | models and I can vouch for the order of magnitude.
        
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       (page generated 2022-02-09 23:00 UTC)