> On Thu, 11 Nov 2010 03:59:52 +0200, Alain <aze### [at] qwertyorg> wrote:
>

>>> Alain<aze### [at] qwertyorg> wrote:

>>>>> Hi there, I'd like to know if there is any way to extrude a mesh
>>>>> like this :
>>>>>
>>>>> mesh {
>>>>> triangle
>>>>> {<1,13.2146,-23.2146>,<3,14.286,-24.286>,<17,14.286,-24.286> }
>>>>> triangle
>>>>> {<17,14.286,-24.286>,<19,13.2146,-23.2146>,<1,13.2146,-23.2146> }
>>>>> triangle
>>>>> {<19,13.2146,-23.2146>,<17,14.286,-24.286>,<17,18.2146,-28.2146> }
>>>>> triangle
>>>>> {<17,18.2146,-28.2146>,<19,19.2861,-29.2861>,<19,13.2146,-23.2146> }
>>>>> triangle
>>>>> {<19,19.2861,-29.2861>,<17,18.2146,-28.2146>,<3,18.2146,-28.2146> }
>>>>> triangle
>>>>> {<3,18.2146,-28.2146>,<1,19.2861,-29.2861>,<19,19.2861,-29.2861> }
>>>>> triangle
>>>>> {<1,19.2861,-29.2861>,<3,18.2146,-28.2146>,<3,14.286,-24.286> }
>>>>> triangle
>>>>> {<3,14.286,-24.286>,<1,13.2146,-23.2146>,<1,19.2861,-29.2861> }
>>>>> triangle
>>>>> {<3,15.7146,-25.7146>,<17,15.7146,-25.7146>,<17,16.786,-26.786> }
>>>>> triangle
>>>>> {<17,16.786,-26.786>,<3,16.786,-26.786>,<3,15.7146,-25.7146> }
>>>>> triangle {<5,14.286,-24.286>,<7,14.286,-24.286>,<7,18.2146,-28.2146> }
>>>>> triangle
>>>>> {<7,18.2146,-28.2146>,<5,18.2146,-28.2146>,<5,14.286,-24.286> }
>>>>> triangle
>>>>> {<9,14.286,-24.286>,<11,14.286,-24.286>,<11,18.2146,-28.2146> }
>>>>> triangle
>>>>> {<11,18.2146,-28.2146>,<9,18.2146,-28.2146>,<9,14.286,-24.286> }
>>>>> triangle
>>>>> {<13,14.286,-24.286>,<15,14.286,-24.286>,<15,18.2146,-28.2146> }
>>>>> triangle
>>>>> {<15,18.2146,-28.2146>,<13,18.2146,-28.2146>,<13,14.286,-24.286> }
>>>>> }
>>>>>
>>>>> I'd like to extrude it following the y axis.
>>>>>
>>>>> I know I can do it using the "prism" fonction by keeping only the
>>>>> triangles
>>>>> points without the y coordinate, but it's kinda boring to do it
>>>>> manually.
>>>>>
>>>>> Maybe there is a solution to extrude every kind of 2D or 3D objects
>>>>> along an
>>>>> axis !?
>>>>>
>>>>>
>>>>> Thanks in advance for your reply.
>>>>>
>>>>>
>>>>
>>>> There is no surefire way to do that.
>>>> You can:
>>>> scale the mesh by a very large value along the Y axis and take the
>>>> intersection with a box of the desired thickness.
>>>> intersection{
>>>> object{Your_mesh scale<1, 1e6,1>}
>>>> box{<1,1,-30><19,-1,-20>}
>>>> }
>>>>
>>>> Extract the outermost points and use them to define a prism.
>>>>
>>>> Use an external programm to create a pre-extruded prism.
>>>>
>>>>
>>>>
>>>>
>>>> Alain
>>>
>>> Thanks for your reply but I'm afraid these ways to do it won't be ok
>>> for me.
>>>
>>> To extract the outermost points will request any kind of programm to
>>> do it, then
>>> I can't and I don't want to use an external programm.
>>>
>>> I've tried the first solution, I see what you meant by scaling it
>>> along the y
>>> axis, but the example I gave is a inclined plane surface made of
>>> triangles, so
>>> scaling it along y only creates another plane surface.
>>>
>>> Let's say there is only one triangle in my mesh, like that :
>>>
>>> mesh {
>>> triangle {<0,0,0>,<1,0,1>,<1,1,0>}
>>> }
>>>
>>> How can I extrude it using only the 3 dimensions coordinates of the 3
>>> points of
>>> the triangle. Of course I would like something quick and easy to do
>>> because I
>>> have to extrude more complex mesh (like the one on my first post)
>>>
>>>
>>>
>>>
>>>
>>
>> Sory, but there is no easy solution.
>>
>> You can make your mesh solid by adding an inside_vector, BUT, the
>> resulting solid mesh don't have any side. You can intersect it from a
>> box that is very slightly smaller than the mesh. It ONLY works IF the
>> mesh is square.
>> Whener you don't see the side of the box, there sill be no side. Any
>> opening will also be invisible.
>>
>> If the mesh is some arbitrary non-square shape, you'll only get the
>> top and bottom faces.
>>
>> Also, whenever you have an even number of coplanar triangles you get
>> an opening.
>>
>> Another solution would be to have the mesh in a text file, read that
>> file in a loop and construct your prism definition from that.
>>
>> Then, if you want the top and bottom to follow the vertical shape of
>> the mesh, you'll need to cut away the prism with the mesh itself using
>> intersection for the top and difference for the bottom. Here again,
>> you need a mesh made solid using inside_vector y.
>>
>> Not realy easy, but you can automate the process, so you only need to
>> code it once.
>>
>>
>>
>>
>> Alain
>
> I'm thinking something along the lines of saving the mesh as a separate
> file and reading the file and writing a new file after replacing each
> triangle with a group of triangles.
>
> Let's say a triangle has corner co-ordinates T1, T2 and T3 and you want
> to extrude it in direction of vector V1
>
> You then replace
> triangle{T1,T2,T3}
> with the following:
> ////////////////////////////////////////////////////////
>
> triangle{T1,T2,T3}// original triangle
>
> triangle{T1,T2,T1+V1} //side of T1 and T2
> triangle{T1,T2+V1,T1+V1} //
>
> triangle{T2,T2+V1,T3} // side of T2 and T3
> triangle{T2+V1,T2,T3+V1} //
>
> triangle{T1,T3+V1,T3} // side of T3 and T1
> triangle{T1+V1,T3+V1,T3} //
>
> triangle{T1+V1,T2+V1,T3+V1}// Original triangle fully displaced by
> vector V1
>
> //////////////////////////////////////////////////////////////////////////////
>
>
> -Nekar Xenos-

Good. That way, you ensure that you preserve the original shape for the 
top and bottom.

Make it into a mesh:
mesh{triangle{T1,T2,T3}// original triangle
triangle{T1,T2,T1+V1}    //side of T1 and T2
triangle{T1,T2+V1,T1+V1} //
triangle{T2,T2+V1,T3}    // side of T2 and T3
triangle{T2+V1,T2,T3+V1} //
triangle{T1,T3+V1,T3}    // side of T3 and T1
triangle{T1+V1,T3+V1,T3} //
triangle{T1+V1,T2+V1,T3+V1}// Original triangle fully displaced by vector V1
}

It's easier to apply a texture that way.
You should then put all meshes into an union.


Alain

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