[vtkusers] gradient background direction

[Florian Bruckner]

hi again,

i now use the following code to generate a 2d actor with the wanted
colorgradient in a given direction:

                background_source = vtk.vtkImageCanvasSource2D()
                background_source.SetExtent(-max_x/2, max_x/2,
-max_y/2, max_y/2, 0, 0)
                background_source.SetScalarTypeToUnsignedChar()
                background_source.SetNumberOfScalarComponents(3)
                background_source.SetDrawColor(255, 255, 255)
                background_source.FillBox(0, max_x, 0, max_y)
                background_source.Update()
                array =
background_source.GetOutput().GetPointData().GetArray(0)
                data = VN.vtk_to_numpy(array)

                color1=[10,20,30]
                color2=[150,160,170]
                colorgrad=[1.0, 0.5]
                norm = sqrt(colorgrad[0]**2 + colorgrad[1]**2)
                colorgrad=[colorgrad[0]/norm, colorgrad[1]/norm]

                L = (max_x/self.cols+1)*colorgrad[0] +
(max_y/self.rows+1)*colorgrad[1]
                for j in range(max_y + 1):
                        for i in range(max_x + 1):
                                l =
(i%(max_x/self.cols+1))*colorgrad[0] +
(j%(max_y/self.rows+1))*colorgrad[1]
                                #l = i*colorgrad[0] + j*colorgrad[1]
                                data[j*(max_x-0+1)+i][0] =
color1[0]*l/L+color2[0]*(1-l/L)
                                data[j*(max_x-0+1)+i][1] =
color1[1]*l/L+color2[1]*(1-l/L)
                                data[j*(max_x-0+1)+i][2] =
color1[2]*l/L+color2[2]*(1-l/L)

                background_actor = vtk.vtkImageActor()
                background_actor.SetInput(background_source.GetOutput())
                renderer = vtk.vtkRenderer()
                renderer.SetBackground(0,0,0)
                renderer.AddActor(background_actor)
                ....


it works but it has some serious drawbacks:
.) the for loops spend a lot of time if the resolution is big.
.) color seems to be interpolated between pixels by the renderer,
which leads to problems if the number of rows/cols != 1.
      then you should have a sharp colortransition, but this is blured
out by the renderer


does anyone have a more convenient method? can i somehow speed up the
for loops using some python tricks?

thanks
FloB



2011/8/26 Dženan Zukić <dzenanz at gmail.com>:
> I think that you can set a custom bitmap as a background. In it you can make
> any kind of gradient you like (I guess it will be smoothly stretched).
>
> On Fri, Aug 26, 2011 at 10:42, Florian Bruckner <e0425375 at gmail.com> wrote:
>>
>> hi,
>>
>> is it somehow possible to set the direction of the gradient background?
>> I would need this to make different renderers in a renderer-window
>> visible to the user.
>>
>> Adding a box around the viewports would be another possibility, but i
>> also didn't find an easy solution for this! (where no additional
>> renderers / actors / ... have to be added, which could make the
>> application slower)
>>
>> thanks
>> FloB
>>
>>
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