[vtkusers] rescaling glyphs.??

[David Gobbi]

Hi Rakesh,

This will have to be the last email that I answer in this discussion.

Since every glyph is at a different position, you will have to do the
computation for every glyph.

The result of the dot product is the depth.  Once you have the depth,
you must compute the scale factor.  Here's a hint: the scale factor
will be proportional to 1/depth.

Good luck.

   David


On Tue, Feb 9, 2010 at 7:13 AM, Rakesh Patil <rakeshthp at in.com> wrote:
> hello sir,
>
> Now suppose, i have to show glyphs at following positions:
>
> 78.23564 8.28372 -5
> 78.32127 8.32736 -10
> 78.34723 8.42864 50
> ...
> 80.23574 9.37256 1800
>
> then, for each point i need to calculate the difference and get the dot
> product with projection direction??
>
> is the result of these dot products the scale factor??
> Coz in that code i didnt find and depth parameter.. only position is there..
> Am i correct??
>
> Thanks
>
> ---------- Original message ----------
> From:David Gobbi< david.gobbi at gmail.com >
> Date: 09 Feb 10 19:05:11
> Subject: Re: rescaling glyphs.??
> To: Rakesh Patil
>
> Let camera position be p1, which you can get from camera->GetPosition().
>
> Let object position be p2, i.e. the position of a glyph.
>
> The vector "v" is the p2 - p1:
> v[0] = p2[0] - p1[0];
> v[1] = p2[1] - p1[1];
> v[2] = p2[2] - p1[2];
>
> That's all there is to it.
>
>
>
> On Tue, Feb 9, 2010 at 6:24 AM, Rakesh Patil wrote:
>> Hello sir,
>>
>> Thanks a lot for you guidance. Please pardon me if am going wrong at any
>> point.
>> I'm am still not clear with this point what you said
>>
>> "The depth is the dot product of the camera's direction-of-projection with
>> the vector from the camera's position to the object's position."
>>
>> what exactly is a vector from the camera's position to object's position??
>>
>> Thanks
>