[求助]：如何对变比例的块中的三维实体进行干涉检查

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如何对变比例的块中的三维实体进行干涉检查

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[B]如何对变比例的块中的三维实体进行干涉检查 [/B]

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2. 
   
3. [FONT=courier new]
   
4. 
   
5. Testing interference of solid in non-uniformly transformed block  
   
6. ID    2029  
   
7. Applies to:    AutoCAD 2000I
   
8. AutoCAD 2002
   
9. 
   
10. 
    
11. This document is part of    Coordinates and Transformations   Solids   Block Reference   Intersecting Entities     
    
12. 
    
13. 
    
14. Question
    
15. How can I test whether two solids interfere, if one is in a BLOCK, which has
    
16. a non-uniform transformation.
    
17. Answer
    
18. ACIS doesn't allow non-uniform transformations on the solids. Since its going
    
19. to be ACIS that does the interference detection, this will be a problem,
    
20. assuming that you want to interfere one solid which has the transformation
    
21. and one which does not. If you are testing two block references which both
    
22. have the same transformation, then one can simply test the contents of the
    
23. block without applying the transformation.
    
24. 
    
25. An alternative approach would be to facet the solids, transform the facets,
    
26. and test these. There are various techniques for extracting facets listed
    
27. elsewhere, for example using the ACRE functions, or calling the worldDraw
    
28. function of the solid. The disadvantage to this approach is that you have to write
    
29. the code to check the facet interference, and the result would only be to a
    
30. certain tolerance.
    
31. 
    
32. Testing whether two facets interfere is fairly straightforward, assuming the
    
33. facets are triangular. If the two triangles are coplanar, then just test
    
34. whether any of the line segments intersect, and if not, whether either
    
35. triangle lies wholly inside the other. If they are not coplanar, then take
    
36. each edge of the facet and calculate whether it intersects the plane of the
    
37. other triangle. If it does, check whether the intersection point lies within
    
38. the triangle.
    
39. 
    
40. Finally, if you know that the facetted models do not interfere, you'll need
    
41. to check whether one solid is contained entirely within the other. To do
    
42. this, take any point on one of the solids, transform this point with the
    
43. transform of its block references. Then transform the point with the inverse
    
44. of the transformation of the block references of the other solid ( to get it
    
45. back into the space of the other solid ). Then test whether it lies inside
    
46. the solid ( using the B-Rep API point containment function ). You'll have to
    
47. do this both ways round of course.
    
48. [/FONT]

<br /> [FONT=courier new]<br /> <br /> Testing interference of solid in non-uniformly transformed block  <br /> ID    2029  <br /> Applies to:    AutoCAD 2000I<br /> AutoCAD 2002<br /> <br /> <br /> This document is part of    Coordinates and Transformations   Solids   Block Reference   Intersecting Entities     <br /> <br /> <br /> Question <br /> How can I test whether two solids interfere, if one is in a BLOCK, which has<br /> a non-uniform transformation.<br /> Answer <br /> ACIS doesn't allow non-uniform transformations on the solids. Since its going<br /> to be ACIS that does the interference detection, this will be a problem,<br /> assuming that you want to interfere one solid which has the transformation<br /> and one which does not. If you are testing two block references which both<br /> have the same transformation, then one can simply test the contents of the<br /> block without applying the transformation.<br /> <br /> An alternative approach would be to facet the solids, transform the facets,<br /> and test these. There are various techniques for extracting facets listed<br /> elsewhere, for example using the ACRE functions, or calling the worldDraw<br /> function of the solid. The disadvantage to this approach is that you have to write<br /> the code to check the facet interference, and the result would only be to a <br /> certain tolerance.<br /> <br /> Testing whether two facets interfere is fairly straightforward, assuming the<br /> facets are triangular. If the two triangles are coplanar, then just test<br /> whether any of the line segments intersect, and if not, whether either<br /> triangle lies wholly inside the other. If they are not coplanar, then take<br /> each edge of the facet and calculate whether it intersects the plane of the<br /> other triangle. If it does, check whether the intersection point lies within<br /> the triangle.<br /> <br /> Finally, if you know that the facetted models do not interfere, you'll need<br /> to check whether one solid is contained entirely within the other. To do<br /> this, take any point on one of the solids, transform this point with the<br /> transform of its block references. Then transform the point with the inverse<br /> of the transformation of the block references of the other solid ( to get it<br /> back into the space of the other solid ). Then test whether it lies inside<br /> the solid ( using the B-Rep API point containment function ). You'll have to<br /> do this both ways round of course.<br /> [/FONT]

i_want_2

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