FreeCADView Issue Details
| ID | Project | Category | View Status | Date Submitted | Last Update |
|---|---|---|---|---|---|
| 0000960 | FreeCAD | Bug | public | 2013-01-16 08:16 | 2013-01-16 12:43 |
| Reporter | nicolasriglet | Assigned To | |||
| Priority | normal | Severity | crash | Reproducibility | always |
| Status | closed | Resolution | no change required | ||
| Product Version | 0.12 | ||||
| Fixed in Version | 0.13 | ||||
| Summary | 0000960: Distance error after rotation | ||||
| Description | It seems to have inversion between sin and cos to compute distance after rotating a block. I create two blocks with height of 3855mm. I rotate them of 40° to make something like a roof. Normally, the distance beetween these two blocks should be equal to : cos(40°)*3855 * 2 = 5906mm but it is equal to 4956mm. It is very strange because 4956 equal to sin(40°)*3855*2 which is the height multiple by 2 and not the total width. I hope I have been clairly... See the attachment file. | ||||
| Tags | No tags attached. | ||||
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2013-01-16 08:16
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Some comments: when computing the distance between two points P1=(x1,y1,z1) and P2=(x2,y2,z2) we neither need sin nor cos. The distance is just: d=sqrt((x1-x2)*(x1-x2) + (y1-y2)*(y1-y2) + (z1-z2)*(z1-z2)) The angle shown on the image is clearly >>40 deg, maybe 80 deg. Let's say A,B,C are the angles in the triangle and a,b,c the lengths of the opposing sides. Then we know from math that: (sin A)/a = (sin B)/b = (sin C)/c So, in this case A=80 deg and thus B=C=50 deg (due to symmetry) and b=c=3855 We want the value of a which is a=b*(sin A)/(sin B) => a = 3855*(sin 80 deg)/(sin 50 deg) = 4955.89 ~ 4956 So, everything makes pretty much sense and I don't see any bugs. |
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Btw, you can also get the distance with 2*B*(sin 40 deg) as you wrote above. It is sin, not cos. |
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Ok. I am really sorry. I understand my mistake. Finally by rotating my blocks to 40° degree, I create a angle of 50° and not 40°. So, there is not error, that give the good result cos(50°)*3855 * 2 = 4956mm Thank you wmayer, you was true. The angle was bigger than 40°. YOU COULD CLOSE THE ISSUE.... |
| Date Modified | Username | Field | Change |
|---|---|---|---|
| 2013-01-16 08:16 | nicolasriglet | New Issue | |
| 2013-01-16 08:16 | nicolasriglet | File Added: error_distance_after_rotation.PNG | |
| 2013-01-16 10:49 | wmayer | Note Added: 0002852 | |
| 2013-01-16 11:07 | wmayer | Note Added: 0002853 | |
| 2013-01-16 12:00 | nicolasriglet | Note Added: 0002854 | |
| 2013-01-16 12:37 | nicolasriglet | Note Edited: 0002854 | |
| 2013-01-16 12:43 | wmayer | Status | new => closed |
| 2013-01-16 12:43 | wmayer | Resolution | open => no change required |
| 2013-01-16 12:43 | wmayer | Fixed in Version | => 0.13 |
