[vtkusers] flat shading in vtk

[David Gobbi]

On Wed, Jan 27, 2010 at 7:54 AM, David Doria <daviddoria+vtk at gmail.com> wrote:
> On Mon, Jan 25, 2010 at 4:55 PM, David Gobbi <david.gobbi at gmail.com> wrote:
>> Oh, that's what you meant. Set "Ambient" to 1, and set "Diffuse" and
>> "Specular" to 0.  That should completely eliminate all directional
>> lighting.
>>
>>   David
>>
>>
>> On Mon, Jan 25, 2010 at 2:43 PM, Liam Kurmos
>> <quantum.leaf at googlemail.com> wrote:
>>> On Mon, Jan 25, 2010 at 9:18 PM, David Gobbi <david.gobbi at gmail.com> wrote:
>>>> Try property->SetInterpolationToFlat().
>>>
>>> That produced flat shading, but the shading is still dependant on the
>>> surface normals. (just not interpolated/smoothed like gourad).
>>> What i want is a constant colour. Obviously that will mean object
>>> won't look very 3d but that is what i want in this case (i want to
>>> measure how much area of an object i can see by how many pixels of its
>>> colour i can count in the render window)
>>>
>>> I thought property->ShadingOff()/SetShading(0) sounded promising but
>>> they don't seem to be having any effect (i have a coloured sphere and
>>> it still gourad shaded).
>>>
>>> Also, I managed to turn the lights of with
>>> ren1->SetAutomaticLightCreation(0);
>>> but then i discovered there isn't an 'emissive color' property in vtk.
>>>
>>> Liam
>>>
>>>
>>>
>>>>
>>>>  David
>>>>
>>>> On Mon, Jan 25, 2010 at 2:05 PM, Liam Kurmos
>>>> <quantum.leaf at googlemail.com> wrote:
>>>>> Is there an easy way to disable shading in vtk?
>>>>> I want all pixels drawn for a polygon to be constant colour,
>>>>> independent of surface normals.
>>>>>
>>>>> I'm going to try having only an emissive color and turning off a
>>>>> lights, but now i'm stuck turning off the default light.
>>>>>
>>>>> ren1->RemoveAllLights();
>>>>>
>>>>> doesn't seem to be having any effect.
>>>>>
>>>>> searches like
>>>>>
>>>>> "site:vtk.org/Wiki/VTK/Examples getLights"
>>>>>
>>>>> are coming up blank, so i wonder if i'm on the right track.
>>>>>
>>>>> any help much appreciated,
>>>>>
>>>>>
>>>>> Liam
>
> Here is a demo:
>
> http://www.vtk.org/Wiki/VTK/Examples/Visualization/FlatShading2
>
> SetDiffuse(0) and SetSpecular(0) make the actor black, but adding
> SetAmbient(1) makes it so bright that it is just a white window!
> SetAmbient(.5) seems to do the trick.
>
> Thanks,
>
> David

David, let me explain.

The background in your example is white.  The actor is white, too.  So
of course, if the ambient light coefficient is set to 1.0, then
everything will be white.

Please change your example so that the actor is some color other than
white, and then you can set ambient to "1.0".

Also, this example should not be called "Flat Shading".  It should be
called "No Shading" or "No Directional Lighting".  Flat shading has a
very specific definition in computer graphics:
http://en.wikipedia.org/wiki/Shading#Flat_vs_smooth_shading

   David