Proc. meshes code: get some figures in
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Chris Hodapp
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@ -13,24 +13,40 @@ draft: true
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# (TODO: pictures will make this post make a *lot* more sense, and it
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# may need a lot of them)
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Context Free is one of my favorite projects since I discovered it
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about 2010. It's one I've written about before (TODO: link to my
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posts), played around in (TODO: link to images), presented on, as well
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as re-implemented myself in different ways (see: [[https://github.com/hodapp87/contextual][Contextual]]). That is
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sometimes because I wanted to do something Context Free couldn't, such
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as make it realtime and interactive, and sometimes because
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implementing its system of recursive grammars and replacement rules
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can be an excellent way to learn things in a new language. (I think
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it's similar to [[https://en.wikipedia.org/wiki/L-system][L-systems]], but I haven't yet learned those very well.)
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{{< load-photoswipe >}}
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[[https://www.contextfreeart.org/][Context Free]] is one of my favorite projects since I discovered it
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about 2010. It's one I've [[../2011-08-29-context-free/][written about before]], played around in (see
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some of the images below), presented on, as well as re-implemented
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myself in different ways (see: [[https://github.com/hodapp87/contextual][Contextual]]). That is sometimes because
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I wanted to do something Context Free couldn't, such as make it
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realtime and interactive, and sometimes because implementing its
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system of recursive grammars and replacement rules can be an excellent
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way to learn things in a new language. (I think it's similar to
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[[https://en.wikipedia.org/wiki/L-system][L-systems]], but I haven't yet learned those very well.)
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# TODO: Set captions?
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{{< gallery >}}
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{{< figure page="images" resource="placeholder/dream20191115b.jpg" caption="Something">}}
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{{< figure page="images" resource="placeholder/2011-11-25-electron.jpg">}}
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{{< figure page="images" resource="portfolio/2011-11-04-crystal1.jpg">}}
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{{< figure page="images" resource="placeholder/2011-11-03-feather2.jpg">}}
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{{< figure page="images" resource="placeholder/2011-11-03-feather1.jpg">}}
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{{< figure page="images" resource="portfolio/2011-09-09-conch.jpg">}}
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{{< /gallery >}}
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I've also played around in 3D graphics, particularly raytracing, since
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about 1999 in PolyRay and POV-Ray. POV-Ray is probably what led me to
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about 1999 in PolyRay and POV-Ray... though my [[../../images/portfolio/1999-12-22-table.jpg][few surviving]] [[../../images/portfolio/1999-12-21-moo.jpg][renders
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from 1999]] are mostly garbage. POV-Ray is probably what led me to
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learn about things like implicit surfaces, parametric surfaces, and
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procedural geometry - its scene language is full of constructs for
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that. Naturally, this led me to wonder how I might extend Context
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Free's model to work more generally with 3D geometry, and let me use
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it to produce procedural geometry.
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# TODO: Link to some POV-Ray scenes here with implicit & parametric
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# surfaces?
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[[http://structuresynth.sourceforge.net/index.php][Structure Synth]] of course already exists, and is a straightforward
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generalization of Context Free's model to 3D (thank you to Mikael
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Hvidtfeldt Christensen's blog [[http://blog.hvidtfeldts.net/][Syntopia]], another of my favorite things
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@ -50,16 +66,16 @@ these, but I quickly ran into a problem: they were made for actual
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practical applications in CAD, not so much for my generative art, and
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they scaled quite poorly with the sort of recursion I was asking for.
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Implicit surfaces (or one of the many
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equivalent-except-for-when-it's-not names for this, e.g. F-Reps or
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distance bounds or SDFs or isosurfaces) handle almost all of this
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well! They express CSG (TODO: link to CSG) operations, they can be
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rendered directly on the GPU via shaders, operations like blending
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Implicit surfaces (or one of the many related-but-not-identical things
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around this, e.g. [[https://en.wikipedia.org/wiki/Function_representation][F-Reps]] or distance bounds or [[https://en.wikipedia.org/wiki/Signed_distance_function][SDFs]] or isosurfaces)
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handle almost all of this well! They express [[https://en.wikipedia.org/wiki/Constructive_solid_geometry][CSG]] operations, they can
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be rendered directly on the GPU via shaders, operations like blending
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shapes or twisting them are easy... for more on this, see [[http://blog.hvidtfeldts.net/][Syntopia]]
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again, or nearly anything by [[https://iquilezles.org/][Inigo Quilez]], or look up raymarching and
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sphere tracing, or see [[https://ntopology.com/][nTopology]], or Matt Keeter's work with [[https://www.libfive.com/][libfive]]
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and [[https://www.mattkeeter.com/research/mpr/][MPR]]. They're pure magic, they're wonderfully elegant, and I'll
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probably have many other posts on them.
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probably have many other posts on them. (TODO: Link to my CS6460
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stuff)
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However, there is one big issue: turning implicit surfaces to good
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meshes for rendering /is a huge pain/, and while many renderers can
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@ -79,8 +95,8 @@ self-intersection, no high-degree vertices, no triangles of extreme
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angles) - rather than attempting to patch up the mesh after its
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creation, or subdividing it to the necessary detail level. For
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something similar to what I mean (though I didn't have this in mind at
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the start), consider the [[https://en.wikipedia.org/wiki/Marching_squares][marching squares]] algorithm, which is
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guaranteed to produce closed, manifold meshes.
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the start), consider the [[https://en.wikipedia.org/wiki/Marching_cubes][marching cubes]] algorithm, which is guaranteed
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to produce closed, manifold meshes.
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(TODO: Illustrate this somehow)
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@ -90,29 +106,30 @@ them at least) by way of inductive steps.
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My meandering path to implementing it went something like this:
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- Write some very ad-hoc Python to generate a mesh of a parametric
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- Wrote some very ad-hoc Python to generate a mesh of a parametric
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conversion of my annoying spiral isosurface from 2005 by breaking it
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into planar "slices" or "frames", which move along the geometry and
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then are connected together at corresponding vertices. (TODO: Add
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link to the automata_scratch repo, whatever it's renamed to)
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- Explore [[https://github.com/thi-ng/geom][thi.ng/geom]] and pretty quickly give up - but in the process,
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discover [[https://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.42.8103][Parallel Transport Approach to Curve Framing]].
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- Implement that paper in Python, reusing the basic model from my
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- Explored [[https://github.com/thi-ng/geom][thi.ng/geom]] and pretty quickly gave up - but in the
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process, discovered [[https://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.42.8103][Parallel Transport Approach to Curve Framing]].
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- Implemented that paper in Python, reusing the basic model from my
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prior code. (See [[https://github.com/Hodapp87/parallel_transport][parallel_transport]])
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- Again continue with this model, allowing more arbitrary operations
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- Again continued with this model, allowing more arbitrary operations
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than parallel frame transport, eventually integrating most of what I
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wanted with the recursive grammars. (See
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[[https://github.com/Hodapp87/automata_scratch/tree/master/python_extrude_meshgen][automata_scratch/python_extrude_meshgen]])
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- Keep running into limitations in python_extrude_meshgen, and start
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- Kept running into limitations in python_extrude_meshgen, and start
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[[https://github.com/Hodapp87/prosha][Prosha]] in Rust - partly as a redesign/rewrite to avoid these
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limitations, and partly because I just wanted to learn Rust.
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- Realize that Rust is the wrong tool for the job, and rewrite *again*
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in Python but with a rather different design and mindset.
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- Realized that Rust is the wrong tool for the job, and rewrote
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*again* in Python but with a rather different design and mindset.
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(this is, of course, ignoring many other tangents with things like
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shaders)
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(TODO: Maybe split these off into sections for each one?)
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(TODO: Maybe split these off into sections for each one? That'd make
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explanations/pictures easier.)
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I put some serious effort into [[https://github.com/Hodapp87/prosha][Prosha]] and was conflicted on shelving
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the project indefinitely, but the issues didn't look easily solvable.
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