[vtk-developers] Bug in scalar color mapping?

[David Gobbi]

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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