> On May 13, 2016, at 12:39 PM, Bojian Wu <ustcb...@gmail.com> wrote:
>
> Hi, everyone, I am Bojian (IRC nickname: boj) and will be excited to
> participate in the Plate Mode NURBS ray tracing project in this year GSOC.
> And I have already created a wiki page for this project
> (http://brlcad.org/wiki/User:Bojian_ustc/GSoC2016/Project
> <http://brlcad.org/wiki/User:Bojian_ustc/GSoC2016/Project>), could someone
> give me some suggestions that do I need to make any changes to my proposal?
It looks pretty good to me. Good enough to get started.
> By the way, recently, I read the document and run some tests, then try to
> understand some basic ideas about plate mode implemented in BoT primitive.
> Here is my blog that maintains the recent
> activities(http://bojianwu.github.io/gsoc2016
> <http://bojianwu.github.io/gsoc2016>), and I am now trying to generate some
> B-rep models and using 'rtshot' to trace it and get some results. If I miss
> some important parts regarding to test and verification, please let me know,
> thanks.
The “rtshot” tool is rather low-level as it is a debugging tool intended for
developers, not users. If it’s not reporting two hits on a platemode box, you
may be needing to set/unset some option(s) or check your box parameters.
> 1. I use 'obj-g' to generate two cube models, one with thickness and the
> other one without thickness, when using 'rtshot' to ray trace the model, they
> will output same result, does that result mean, the 'plate mode' is only
> useful when the model is not a closed mesh(that is to say, the closed mesh
> can always be considered as solid model)?
If you run “nirt” or “rtweight” on both, you should see very different results.
If you shoot through the middle of your two boxes, nirt should hit the
platemode version twice and the solid version only once. The volume of the
solid version should be significantly bigger than the platemode one too.
> 2. I create a single open NURBS surface(not closed mesh), and use 'rtshot' to
> trace it, the result shows that the ray misses the object, could someone give
> me some information? By the way, I use 'brep-cobb' to generate the twisted
> cube model, then trace it, the result seems to be reasonable with a in hit
> and a out hit point.
Objects that fail a solidity check are currently ignored.
If you follow the ray tracing code for brep/nurbs, you’ll see that there is
already code for hitting objects that fail the IsSolid test, but that it’s
compile-time disabled. See src/librt/primitives/brep for starters to trace
what happens during prep and shot.
> 3. How to visualize the plate mode of BoT, I mean, how to show the
> *thickness* in MGED?
You can define a means for visualizing this in the wireframe by modifying
brep_plot or you can call the rt command to render the surface.
> Next, my arrangement is going to be following the 'rtshot' code, and try to
> understand the basic ray tracing principles?
Sounds like a good place to start. You’ll quickly see that dirbuild and
shootray are where most of the work happens — those respectively end up calling
brep_prep and brep_shot.
Cheers!
Sean
p.s. Read http://brlcad.org/wiki/BoT
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