math: project point on a poly
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THE POST BELOW IS MORE THAN 5 YEARS OLD. RELATED SUPPORT INFORMATION MIGHT BE OUTDATED OR DEPRECATED
On 10/06/2004 at 10:07, xxxxxxxx wrote:
User Information:
Cinema 4D Version: 8.100
Platform: Windows ;
Language(s) : C++ ;---------
Hi all,
i need to find the closest point p1 in a poly
to point p2 outside of the poly.It should be possible to get p1 by projecting p2 along the normal of the poly, but unfortunately i dont know how to do it! (cos im quite bad at maths)
Is there maybe a function in the sdk that can
project a point on a plane along the planes normal?thanks,
devel -
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On 11/06/2004 at 09:43, xxxxxxxx wrote:
the solution of your problem is very difficult:
it is ease to do this with a Plain and a Point, because a plane has infinite extension. but in your case you have to check the bounds (edges) of your poly. Another problem is that that a poly can also be nonplanar, so you have to do this with triangles, they are always planar!btw: I don´t know any function in the sdk that does your thing!
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THE POST BELOW IS MORE THAN 5 YEARS OLD. RELATED SUPPORT INFORMATION MIGHT BE OUTDATED OR DEPRECATED
On 11/06/2004 at 10:34, xxxxxxxx wrote:
well,thanks for your answer..
your probably right, especially about the poly vs triangle thing..
..didnt think of that before x-|what i am actually trying to do with my plugin
is make a multispline stick to a deformable mesh..like when i make a spline-beard around a poly selection
and then make some facial expression morphing with the head, the beard stays attached to the poly-selection..well maybe there's another solution somewhere..
or somebody else already did it!thanks anyway,
and have a good time all,devel
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THE POST BELOW IS MORE THAN 5 YEARS OLD. RELATED SUPPORT INFORMATION MIGHT BE OUTDATED OR DEPRECATED
On 11/06/2004 at 11:24, xxxxxxxx wrote:
Don't 100% understand the question, but maybe you could use the GeRayCollider class.
Its a class used to check if a ray has intersected a polygon, and it returns a whole great deal of information, the point of intersection, the polygons normal, etc
The xpresso ray collider node is very useful to experiment with -
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On 11/06/2004 at 12:03, xxxxxxxx wrote:
thanks ill read it up in the manual and play around some,
but it looks like it can only check collision between ray(line) and object and i need to check collision ray/poly..--edit---
..should have read the manual BEFORE posting...
looks like the node can return the poly that was hit by the ray...
so thanks again, looks like this might work!
cheers,
devel -
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On 11/06/2004 at 12:18, xxxxxxxx wrote:
Yes its for object, but objects are made out of polygons right?
Its also not that hard to check if a point is inside a polygon, there are many ways to do it.
http://www.gametutorials.com/Tutorials/opengl/OpenGL_Pg3.htm
I learn't all I know about polygon detection from that site
1. Line Segment and Plane Collision
2. Line Segment and Polygon Collision
The source code contains a very good explaination on what is happening. Its easy to convert into c4d too, because sdk already has great vector operations
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On 11/06/2004 at 14:00, xxxxxxxx wrote:
thanks, i'll check it out..
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On 12/06/2004 at 01:57, xxxxxxxx wrote:
Quote: Originally posted by devel on 11 June 2004
>
> * * *
>
> what i am actually trying to do with my plugin
> is make a multispline stick to a deformable mesh..
>
> like when i make a spline-beard around a poly selection
> and then make some facial expression morphing with the head, the beard stays attached to the poly-selection..
>
>
> * * *what i understood is that you need something that always stays at the same place on top of a (deformable) surface, right? In my opinion you should do this with the uv-coordinates of the poly. else you are getting problems with the right position when the shape of the poly is changing! I don´t know if there is any function in the sdk that extracts you the 3d-coordinates with the input of a poly and the uv-coordinates!
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On 12/06/2004 at 02:07, xxxxxxxx wrote:
hmm, sounds like a good idea..
i'm not quite sure how to do it right now,
but im im just gonna play around with uv now, might
turn out to be easier than what i had in mind first..thanks for the hint,
devel -
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On 12/06/2004 at 02:46, xxxxxxxx wrote:
bad idea. This would require the object to always have accurate UV coords which is not always the case (some don´t even have any UVs assigned)
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On 12/06/2004 at 02:55, xxxxxxxx wrote:
yeah thats right,
but i actually need this plugin for my fully textured head (with complete uvw's), so that shouldnt be a problem..on the other hand, that wouldnt make it very handy in terms of general usefulness (e.g. for other people) i guess...
well, so how'd you do it?
the problem is indeed to get the right coordinate on the poly, when the mesh has deformed..
greetings,
devel -
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On 12/06/2004 at 03:05, xxxxxxxx wrote:
Well, actually I already did this ;o) I am using this for my own plugin DPInstantTree (for it now has hair support) and so I wrote such a plugin some days ago. I am triangulating the object and then calculate the initial position on the triangle (as written a tri is always planar) and stick it to this position. Actually not that complicated. Do a google search for the position in a triangle. It´s more than easy.
Good luck -
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On 12/06/2004 at 03:06, xxxxxxxx wrote:
when deforming the barrycentric coords of the poly do change too (maybe maxx meant these coords by uv coords) so it works here too.
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THE POST BELOW IS MORE THAN 5 YEARS OLD. RELATED SUPPORT INFORMATION MIGHT BE OUTDATED OR DEPRECATED
On 12/06/2004 at 03:21, xxxxxxxx wrote:
alright thanks Samir,
gonna check it out..greetings,
devel