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Sections and cutaways

Sections and cutaways. Why we need an improved Boolean Processor John Allison University of Manchester. DAWNCUT. DAWNCUT is available as ever Make a .prim file with DAWNFILE, then invoke dawncut , then view with dawn Make a section by successive application

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Sections and cutaways

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  1. Sections and cutaways Why we need an improved Boolean Processor John Allison University of Manchester John Allison Geant4 Workshop Lisbon October 2006

  2. DAWNCUT • DAWNCUT is available as ever • Make a .prim file with DAWNFILE, then invoke dawncut, then view with dawn • Make a section by successive application • dawncut 0 1 0 1 g4_00.prim g4_00_0.primdawncut 0 -1 0 1 g4_00_0.prim g4_00_1.primdawn g4_00_1.prim • Produces closed shapes • (but sometimes nice to see inside in surface mode) John Allison Geant4 Workshop Lisbon October 2006

  3. Sections (DCUT) • /vis/viewer/set/sectionPlane only ever worked on OpenGL (Mesa) • Bad news: it doesn’t work on today’s OpenGL (at least Mac and Linux; OK on Windows) • OpenGL’s clip plane clips too much Single clip plane Back-to-back clip planes Mesa, Windows eye Mac, Linux John Allison Geant4 Workshop Lisbon October 2006

  4. Cutaways • DAWNCUT is available as ever • but cannot see inside in surface mode • Good news: the aforementioned change of behaviour means • we can implement “see-inside” cutaways in OpenGL (Mac and Linux) John Allison Geant4 Workshop Lisbon October 2006

  5. New commands • New commands control up to 3 cutaway planes • /vis/viewer/addCutawayPlane/vis/viewer/changeCutawayPlane/vis/viewer/clearCutawayPlanes/vis/viewer/set/cutawayMode union|intersection • Implemented only by OpenGL driver at present John Allison Geant4 Workshop Lisbon October 2006

  6. Union of three cutaways OpenGL immediate and stored mode. Fast interaction in stored Xm mode. Can animate — see commands on next slide John Allison Geant4 Workshop Lisbon October 2006

  7. Animation commands /control/verbose 2 /vis/verbose confirmations /run/initialize /vis/open OGLSX 600x600-0+0 /vis/drawVolume tube_phys /vis/viewer/set/viewpointThetaPhi 30 30 /vis/viewer/set/style surface /vis/geometry/set/visibility tube_L ! true /vis/geometry/set/visibility divided_tube_L ! false /vis/geometry/set/visibility sub_divided_tube_L ! false /vis/geometry/set/colour daughter_box_L ! blue /vis/viewer/addCutawayPlane -220 0 0 cm -1 0 0 /vis/viewer/addCutawayPlane 0 -24 0 cm 0 -1 0 /vis/viewer/addCutawayPlane 0 0 -1 cm 0 0 -1 #/vis/oglx/set/printEPS true /control/verbose 0 /vis/verbose quiet /control/loop cutaway.loop x -150 -250 -0.1 where cutaway.loop is /vis/viewer/changeCutawayPlane 0 {x} 0 0 cm -1 0 0 /vis/viewer/zoom 1.001 /vis/viewer/update John Allison Geant4 Workshop Lisbon October 2006

  8. Cutaway movie (/vis/oglx/set/printEPS true) Shown here: mpeg4 movie G4OpenGL_cutaway.mp4.mpg or G4OpenGL_cutaway.mpg See parallel session presentation: Making a movie John Allison Geant4 Workshop Lisbon October 2006

  9. (Another new command)/vis/viewer/set/explodeFactor G4OpenGL_explode.mp4.mpg or G4OpenGL_explode.mpg Animation: /control/loop explode.loop f 1 2 0.001 where explode.loop is /vis/viewer/set/ explodeFactor {f} -200 0 0 cm John Allison Geant4 Workshop Lisbon October 2006

  10. Boolean Processor • Proposal: use to implement generic sections and cutaways • Extend to all drivers • Insulate from OpenGL ambiguities • Operates on G4Polyhedron objects available in principle for each Geant4 shape • Currently doesn’t do cutaways • Not all shapes implemented • Other problems… John Allison Geant4 Workshop Lisbon October 2006

  11. Current problems • Pathological cases cause failure and/or incorrect polyhedron objects • Subtraction of polyhedra with coincident or nearly coincident faces • Cascaded operations (Booleans of Booleans) • Continuing user problem reports • Signs of user fatigue • Sections and cutaways particularly troublesome • Prototype use code disabled John Allison Geant4 Workshop Lisbon October 2006

  12. Proposal • G4Polyhedron Discussion Document • John Allison and Evgueni Tchernaiev • October 2005!! • Needs your support • Proposal • Reimplement existing functionality, including • Improved robustness • Caching of normals (for speed) • Offer the option of user-supplied normals (for space saving and speed) • Add a new Boolean operation – cut – that creates open polyhedra for cutaway views • Complete the implementation of polyhedron representations of all Geant4 shapes John Allison Geant4 Workshop Lisbon October 2006

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