[vtkusers] VtkUnstructuredGrid SetOpacity

[Bhanu Hariharan]

David, Thanks for replying.

When I flip, I see blue AGAIN. Is that what you expect with the external
surface rendering logic you explained?

What is not clear is even if there are 2 surfaces, shouldnt I be seeing a
blend of blue and green?
And shouldnt it be same whether I see from top or flipped?

Bhanu


On Wed, Jan 25, 2012 at 4:26 PM, David E DeMarle
<dave.demarle at kitware.com>wrote:

> When you flip the object around, do you see only green?
>
> In any case, the typical mapper people use for surface rendering,
> vtkDataSetMapper, extracts the external surfaces. With that there is no
> possibility to see the inner cells even with opacity.
>
> You could instead send the data through something like the shrink filter,
>  to  break up the object so that all cells are unconnected and thus
> external. Surface rendering with opacity then might to what you want.
>
> However, it is much better to use volume rendering. That will be much
> faster and consume less memory.
>
> David E DeMarle
> Kitware, Inc.
> R&D Engineer
> 21 Corporate Drive
> Clifton Park, NY 12065-8662
> Phone: 518-881-4909
>
>
>
> On Wed, Jan 25, 2012 at 4:58 PM, bhanu <bhanu at petrotel.com> wrote:
>
>> Hi,
>>
>> I am using VtkUnstructuredGrid to render a simple volume wherein each grid
>> cell in the 3dvolume has 8 world coordinates. Each grid cell has a color
>> associated with it and I am using a vtkLookUpTable for this. When I use
>> SetOpacity(1) and see the top view, I expect to see the top layer alone
>> since I have set an opacity of 1.0. And that works fine.
>> Now When the opacity is changed to anything less than 1 (even 0.99), it
>> seems the top layer vanishes and all I see from the top is the bottom most
>> layer.
>> For example, if top most layer is green and the bottom most layer is blue
>> (with inbetween layers shades of lighter green), with opacity less than
>> 1, I
>> see all blue from the top. I was expecting mixed colors( green and blue).
>> What am I missing.
>>
>> How do you see a transparent grid using VtkUnstructuredGrid and Opacity
>> property. Should I not be using Scalar Opacity for such a problem. Is this
>> where one uses Gradient Opacity.
>> Can anyone please paste some code to direct me here.
>>
>> Thanks,
>> Bhanu
>>
>> --
>> View this message in context:
>> http://vtk.1045678.n5.nabble.com/VtkUnstructuredGrid-SetOpacity-tp5431453p5431453.html
>> Sent from the VTK - Users mailing list archive at Nabble.com.
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