[Soc-2017-dev] Weekly Report #09 - Silhouette Operator

[Sebastian Witt]

**


  *Weekly Report #09 - Silhouette Operator*

*

The second evaluation is now done. That means only one month left to 
finish the Silhouette Operator! Judging by the rate of progress I will 
not be able to implement all the features and ideas I had within the 
Gsoc timeframe. Nevertheless achieving the number one goal: “Giving the 
sculptor the freedom to add new geometry contrary to just shaping the 
existing” is definitely within reach.


What has been done this week?

This week i started to finish the geometry generation by adding code to 
generate backsides as well. Now generating a silhouette creates a 
waterproof shape with the configured settings. I created a small video 
to demonstrate the impact of the different settings. You can find it 
here for now: 
https://www.dropbox.com/s/x12a62zf2ynevum/Basic_002_fs.mp4?dl=0

In the second half of the week I started with the next big step: 
Connecting new silhouettes to existing geometry.

This poses a challenge for multiple reasons:

  *

    The intersection of both, the silhouette and the old geometry needs
    to be calculated. Depending on the geometry complexity this is
    really computational heavy.

  *

    The transition between the two shapes can be rather complex because
    minimal assumptions can be made about both shapes.

  *

    The topology of the transition is not trivial. Depending on the
    existing topology many different factors need to be taken into
    account. Vertex density, edge/loop flow orientation and varying face
    sizes or even ngons.


For the transition between the two shapes i decided to go with a more 
practical than precise approach. CAD-style precision is not the goal of 
the tool. Moreso the tool is supposed to give the artist the option to 
get a quick basemesh to start sculpting on. -Not a perfect shape.


I was able to get a good start tackling the first challenging factor. I 
reduced the intersection problem to a 2D-Polygon point intersection 
task. It is fast but gives inaccurate results if the shape in the z-axis 
is not primitive as is the case if smoothness is close to 1. But in 
practice this is a reasonable drawback to take. If the smoothness factor 
is high, the transition between the silhouette and old geometry is 
supposed to be blurred and smooth anyways. I finished detecting interior 
vertices and I am currently in the process to find the necessary edges 
and loops which will later be deleted and/or connected.


Looking forward to the next week,


Sebastian Witt

*

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