[vtk-developers] Bug in scalar color mapping?

[David Gobbi]

Hi Utkarsh,

I found the difference between my program and your script. I was using
the vtkDataSetMapper, but if I use the vtkPolyDataMapper instead then
I see the correct behavior as ScalarColors.py.  And, of course, if I
use the vtkDataSetMapper in ScalarColors.py then it shows the odd
behavior that I described previously.

So now, the question is why vtkDataSetMapper is giving different
results than vtkPolyDataMapper.

 - David

On Tue, Sep 9, 2014 at 9:14 AM, Utkarsh Ayachit
<utkarsh.ayachit at kitware.com> wrote:
> BTW, in my script, you can hit "t" to swap the ambient/diffuse coefficients.
>
> On Tue, Sep 9, 2014 at 11:13 AM, Utkarsh Ayachit
> <utkarsh.ayachit at kitware.com> wrote:
>> Here's my test script. With the patch applied, I don't see the ambient
>> and diffuse colors bleed in anymore.
>>
>> On Tue, Sep 9, 2014 at 11:11 AM, David Gobbi <david.gobbi at gmail.com> wrote:
>>> I added SetScalarMaterialModeToAmbientAndDiffuse() and applied the
>>> patch, but it had no effect.  The results were exactly the same as in
>>> my first email.
>>>
>>> I'll have to look through the code to figure out what the intended behaviour is.
>>>
>>>  - David
>>>
>>> On Tue, Sep 9, 2014 at 8:56 AM, Utkarsh Ayachit
>>> <utkarsh.ayachit at kitware.com> wrote:
>>>> 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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