User:Phoenix/GSoc2012/Reports

Log

Community Bonding

• May 2
  • Downloaded the source code of the latest revision from svn checkout and got more familiar with subversion.
  • Compiled and built the source both in Ubuntu and Windows (Visual Studio 2010) successfully.
• May 13
  • Found and fixed a small bug in eto_brep (the rotation axis of eto is wrong), and submitted a patch on sourceforge.net.
• May 15
  • Modified the eto_brep patch with the test case provided by Cliff.
• May 16
  • Continued working on the conversion of eto.
  • Tested the brep conversion of hyp, but found the raytrace result of implicit CSG hyp quite strange.
• May 17
  • The raytrace of implicit hyp is wrong when H is not perpendicular to A.
  • Fixed the conversion to brep of hyp (havn't commited yet).
• May 18
  • My first SVN Commit: fixed the shearing direction of hyp.

Week 1

• May 21
  • Fixed the bug of wrong id & od for pipe b-rep, by changing some prevp to curp.
  • Dealt with duplicated points by deleting them from the linklist.
• May 22
  • Added some control to deal with special cases in pipe_brep.cpp and add a few comments.
• May 23
  • Read and tried to understood the code in revolve_brep.cpp, but got confused by the implicit definition.
  • Changed the revolution axis and origin of the sketch plane of revolve_brep.
• May 24
  • Changed the position of the sketch in extrude_brep according to the parameters.
  • Fixed the plane direction of circle arcs in sketch_brep as well as in revolve_brep.
• May 25
  • Dealt with non-full revolution of revolve_brep. It took a long time to get the expected result, but I got more familiar to NURBS/BREP during that procedure.

Week 2

• May 27
  • Tested and examined the implemented brep conversions. Checked the current status of my work.
• May 28
  • Added the implicit -> brep conversion to conversion.sh, so that massive testing will be more convenient.
• May 29
  • Tested the functionality of conversion.sh and brep conversions. Made a small change.
  • Modified brep.c in libged to check whether the conversion is successful.
• May 30
  • Read the code in clone.c, and began to implement the temporary unevaluated conversion of comb in the brep command in MGED.
• May 31
  • Extended the functionality of the brep command in MGED to deal with comb. Unevaluated breps are generated. More tests are needed.
• June 1
  • The unevaluated conversion for comb has been implemented. Changed conversion.sh accordingly. And the whole elasped time for each object is evaluated.
  • Handled some exceptions in brep_debug.cpp.
  • Freed memories and corrected the "name existed" output in brep.c in libged.
• June 2
  • Tested the brep conversion on ktank.g, m35.g, etc. with conversion.sh.
  • Modified brep_debug.cpp to deal with empty combs.

Week 3

• June 3
  • Fixed the wrong malloc size and freed tmpname before returning in brep_debug.cpp.
• June 4
  • Modified openNUBRS_ext.cpp to quell set-but-unused warnings.
  • Tested brep conversion of all /db/*.g files. Looked into the log to find out what to do next.
  • Found a bug in pipe_brep.cpp dealing with colinear points.
• June 5
  • Modified pipe_brep.cpp. It's much better now, but problems still remain.
• June 6
  • Fixed a concealed bug in pipe_brep.cpp. Now it works properly.
• June 7
  • Fixed the destruction failure in pipe_brep.cpp by duplicating the curves.
• June 8
  • Modified brep_debug.cpp to skip the conversion of half when converting a comb. The implicit primitive of half remains in the hierarchy.
  • Explored the usage of ON_BrepRegion to represent an infinite halfspace, but had no good luck.

Week 4

• June 11 - June 18
  • Final examination week in our school.

Week 5

• June 18
  • Final exams finished. Started to work!
  • Added pnts to the ignore list when converting a comb.
  • Modified the describe and ifree functions in pnts.c checking whether count==0 to avoid segmentation fault.
• June 19
  • Corrected the wrong comments in arb8_brep.cpp and arbn_brep.cpp.
  • Add a brep conversion function to ars, which first converts it to an nmg and then to b-rep.
• June 20
  • Use ft_brep functions for half and pnts, returning a NULL brep pointer, and check within brep_conversion() and brep_conversion_tree().
• June 21
  • Tried implementing rt_part_brep() for primitive part. Things get much closer now after much tests and modifications.
• June 22
  • Finished a raw version of brep conversion for part. Some special cases need to be considered later.
• June 23
  • Enhanced some special cases (sphere) in part_brep.cpp.

Week 6

• June 24
  • Fixed the wrong normal direction of the brep form of part.
• June 25
  • Studied the primitive metaball. Found it quite hard to get started.
• June 26
  • Studied the two papers Cliff provided on metaballs, but still cannot find the answer.
  • Copied the transformation matrix when converting the leaves in a tree. (Later adjusted to copying all data from the old tree first)
• June 27
  • Evaluated the results and uploaded the screenshots to the log page. (See "Test Results")
  • Modified dsp_brep.cpp, using the dsp_stom matrix to do the transformation, instead of using the magic numbers.
• June 28
  • Implemented a b-rep conversion function for superell.
• June 29
  • Tested the results of conversion of superell. (See below)
• June 30
  • Uploaded the raytracing results of superells with e or n > 2.

Week 7

• July 2
  • Added conversion functions to cline. We first convert cline to an implicit pipe, and then convert the pipe to b-rep.
• July 3
  • Modified superell_brep.cpp to generate multiple surfaces for superells with e or n > 2.
  • Uploaded images with the modified b-rep conversion routine for superell.
• July 4
  • Uploaded images of the raytrace results of cline (both implicit and b-rep).
  • Fixed the wrong weight when the center (origin) is set to be control points (superell_brep.cpp).
• July 5
  • Some minor modifications on brep_debug.cpp, half_brep.cpp and pnts_brep.cpp.
  • Add a b-rep conversion function to grip, but it just returns a NULL ON_Brep pointer because grip is a pseudo solid and doesn't have its own shape.

Week 7

• July 2
  • Added conversion functions to cline. We first convert cline to an implicit pipe, and then convert the pipe to b-rep.
• July 3
  • Modified superell_brep.cpp to generate multiple surfaces for superells with e or n > 2.
  • Uploaded images with the modified b-rep conversion routine for superell.
• July 4
  • Uploaded images of the raytrace results of cline (both implicit and b-rep).
  • Fixed the wrong weight when the center (origin) is set to be control points (superell_brep.cpp).
• July 5
  • Some minor modifications on brep_debug.cpp, half_brep.cpp and pnts_brep.cpp.
  • Add a b-rep conversion function to grip, but it just returns a NULL ON_Brep pointer because grip is a pseudo solid and doesn't have its own shape.
• July 6
  • Implemented degree reduction to Bezier curves to simplify the representation of the dsp top surface. But still a long way to go. As I tested it with terra.dsp, the result made me very upset. There were great differences in the middle of the curves. For dsp with smaller xcnt & ycnt, the result quite accurate. But it's big xcnt & ycnt that counts, because this is introduced to shorten the raytrace time of dsp with large maps.
  • TODO: Calculate the accumulated deviation. A torelance value TOL might be used to decide whether the result is acceptable or not. Or replace it with a better algorithm. (e.g. The specific way for DSP Cliff mentioned in E-mail)

Test Results

The brep conversion has been tested on several db/*.g files. Below are the screenshots of the raytrace results.

• m35.g: component (left: implicit + csg, right: brep + csg)

• ktank.g: tank (left: implicit + csg, right: brep + csg)

• havoc.g: havoc (the raytrace of brep+csg takes a too long time, so the result hasn't been generated yet)

• A DSP primitive with a 30*30 map: (left: implicit, right: brep)

• Brep form of superell primitives with axes of the same magnitude: (left: n = 0.8, e = 0.2, right: n = 1.0, e = 2.0)
  • Reference page: http://paulbourke.net/geometry/superellipse/

• • There is still some problems when n > 2 or e > 2. (left: n = 0.2, e = 3.0, right: n = e = 3.0)

• • The problem above was fixed in r51405. (first: n = 0.2, e = 3.0, second: n = e = 3.0, third: n = 3.0, e = 0.2)

• A cline primitive raytraced in different views. You can see that it's a primitive whose raytrace is view-dependent. We use a pipe to represent it when it's converted to b-rep, whose raytrace is view-independent. The shape of the pipe is according to what we see when plotting a cline with the draw command in MGED. (Two different views, left: implicit, right: brep)

Original development timeline

• - May 21 (~4 weeks)
  • Study materials on NURBS/BREP etc
  • Read the codes in librt/primitives
  • Get familiar to OpenNURBS
  • Fix some bugs and make patches
  • Implement a method for convenient testing (finished)

• May 21 - June 10 (~3 weeks)
  • Modify implemented conversions if not finished
    • pipe
    • sph, ell, tor, hyp
    • eto, extrude, revolve, etc.

• June 11 - June 18 (~1 week)
  • Final examination week in our school

• June 19 - July 1 (~2 weeks)
  • Still work on existing conversions
  • Work on non-origin primitives
    • Deduce transformation matrices
    • Apply the transformation
    • Test the results and write documents

• July 1 - July 29 (~4 weeks)
  • Add new conversions to missing primitives
    • Test whether it works well
    • Write clear documents
    • From easy ones to hard ones
  • July 1 - July 8 (1 week)
    • rec
    • ars
    • half
    • ell1
  • July 8 - July 15 (1 week)
    • metaball
    • pnts
    • part
    • grip
  • July 15 - July 22 (1 week)
    • superell
    • cline
  • July 22 - July 29 (1 week)
    • hf
    • other missing primitives

• July 29 - August 13 (~2 week)
  • Write a convert for whole
    • Write a function to walk the tree
    • Add a command to MGED
    • Discussions and documents
  • Test the work and fix bugs

• August 13 - August 20 (~1 week)
  • Pencil down data
    • Improve documentation
    • Evaluations

• Post-GSoc
  • Further involvement with BRL-CAD :)