[vtk-developers] Bug in scalar color mapping?

[Utkarsh Ayachit]

Doh! Here you go.

On Tue, Sep 9, 2014 at 10:53 AM, David Gobbi <david.gobbi at gmail.com> wrote:
> Hi Utkarsh,
>
> The "attached patch" seems to be missing.
>
>  - David
>
> On Tue, Sep 9, 2014 at 8:44 AM, Utkarsh Ayachit
> <utkarsh.ayachit at kitware.com> wrote:
>> David,
>>
>> Try the attached patch and then set
>> SetScalarMaterialModeToAmbientAndDiffuse() on the mapper.
>> ScalarMaterialMode is the thing here. When set to
>> SetScalarMaterialModeToDefault(), which is the default, it determines
>> which material component should track the scalar color based on which
>> coefficient is greater (see vtkOpenGLScalarsToColorsPainter.cxx:175).
>> The patch fixes an issue where the painter was not respecting the
>> material mode set on the mapper.
>>
>> Utkarsh
>>
>> On Mon, Sep 8, 2014 at 8:15 PM, David Gobbi <david.gobbi at gmail.com> wrote:
>>> 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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