[vtk-developers] Bug in scalar color mapping?

[David Gobbi]

Hi Utkarsh,

Thanks for the reply.  If I use this:

  mapper->InterpolateScalarsBeforeMappingOff();

then the result is exactly the same as it was before I reverted that commit.


If I use this:

  mapper->InterpolateScalarsBeforeMappingOn();

then the result looks like the attached image, i.e. like it did in my previous
email with property->SetAmbient(0.49), property->SetDiffuse(0.51), but when
I reverse these I don't get the greyscale ambient lighting like in the
right side
of the image from my previous email.


Still, I don't get what I expect unless I set one of either the ambient or the
diffuse coefficient to zero.  Whenever they are both nonzero, I get the wrong
result.

 - David


On Mon, Sep 8, 2014 at 5:17 PM, Utkarsh Ayachit
<utkarsh.ayachit at kitware.com> wrote:
> This sounds familiar.
>
> Can you try reverting the following commit and see if that makes any difference:
>
> commit daf8c6e76ec7bb02f56dda17ce260141b7e960a5
> Author: Utkarsh Ayachit <utkarsh.ayachit at kitware.com>
> Date:   Fri Jul 18 15:30:37 2014 -0400
>
>     BUG #14828: Keep surface color from interacting with scalar color.
>
>     When using scalar coloring, if vtkScalarsToColorsPainter decided to use
>     a texture for mapping the scalars to colors, we ended up with the
>     surface color bleeding through the texture. This commit ensures that
>     such bleeding is avoided.
>
>     We don't simply use glTexEnvf (GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE,
>     GL_REPLACE), since that results in the diffuse highlights being lost.
>     By enabling GL_COLOR_MATERIAL and calling glColor3f(1,1,1), we follow
>     the same lighting/coloring path as we would when not using the texture
>     for scalar coloring.
>
>     Change-Id: I9c4db15dd0db699d5d045fa7ae27696d18828988
>
>
> Utkarsh
>
> On Mon, Sep 8, 2014 at 4:55 PM, David Gobbi <david.gobbi at gmail.com> wrote:
>> Any comments on the "scalar color mapping" problem that I sent to the
>> list last week?
>>
>>  - David
>>
>>
>> On Thu, Sep 4, 2014 at 5:33 PM, David Gobbi <david.gobbi at gmail.com> wrote:
>>> I've run into very odd behavior when I use Ambient and Diffuse
>>> coefficients in combination with vtkDataSetMapper.  This is with
>>> VTK master.
>> [ snip ]
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