Week 5 blogpost

docs/source/posts/2023/2023-07-03-week-5-joaodellagli.rst

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+Week 5: All Roads Lead to Rome
+==============================
+
+.. post:: July 03, 2023
+   :author: João Victor Dell Agli Floriano
+   :tags: google
+   :category: gsoc
+
+
+Hello everyone, time for another weekly blogpost! Today, we will talk about taking different paths to reach your objective.
+
+Last Week's Effort
+------------------
+After having the FBO properly set up, the plan was to finally *render* something to it. Well, I wished for a less bumpy road
+at my :doc:`last blogpost <2023-06-26-week-4-joaodellagli>` but as in this project things apparently tend to go wrong, 
+of course the same happened with this step. 
+
+
+Where the Problem Was
+---------------------
+Days passed without anything being rendered to the FBO. The setup I was working on followed the simplest OpenGL pipeline of rendering to 
+an FBO:
+
+1. Setup the FBO
+2. Attach a texture to it's color attachment
+3. Setup the shader to be used in the FBO render and the shader to render the FBO's Color Attachment
+4. Render to the FBO
+5. Use the color attachment as texture attached to a billboard to render what was on the screen
+
+But it seems like this pipeline doesn't translate well into VTK. I paired again on wednesday with my mentors, Bruno and Filipi, to try to figure out 
+where the problem was, but after hours we could not find it. Wednesday passed and then thursday came, and with thursday, a solution: 
+Bruno didn't give up on the idea and dug deep on VTK's documentation until he found a workaround to do what we wanted, that was retrieving a 
+texture from what was rendered to the screen and pass it as a texture to render to the billboard. To do it, he figured out we needed to use
+a different class, `vtkWindowToImageFilter <https://vtk.org/doc/nightly/html/classvtkWindowToImageFilter.html>`_, a class that has the specific
+job of doing exactly what I described above. Below, the steps to do it:
+
+::
+
+   windowToImageFilter = vtk.vtkWindowToImageFilter()
+   windowToImageFilter.SetInput(scene.GetRenderWindow())
+   windowToImageFilter.Update()
+
+   texture = vtk.vtkTexture()
+   texture.SetInputConnection(windowToImageFilter.GetOutputPort())
+
+   # Bind the framebuffer texture to the desired actor
+   actor.SetTexture(texture)
+
+This is enough to bind to the desired actor a texture that corresponds to what was prior rendered to the screen.
+
+
+This Week's Goals
+-----------------
+Having a solution to that, now its time to finally render some KDE's! This week's plans involve implementing the first version of a KDE
+calculation. For anyone interested in understanding what a Kernel Density Estimation is, here is a brief summary from this 
+`Wikipedia page <https://en.wikipedia.org/wiki/Kernel_density_estimation>`_:
+
+
+   In statistics, kernel density estimation (KDE) is the application of kernel smoothing for probability density estimation, i.e., a 
+   non-parametric method to estimate the probability density function of a random variable based on kernels as weights. KDE answers a 
+   fundamental data smoothing problem where inferences about the population are made, based on a finite data sample. In some fields 
+   such as signal processing and econometrics it is also termed the Parzen–Rosenblatt window method, after Emanuel Parzen and Murray 
+   Rosenblatt, who are usually credited with independently creating it in its current form. One of the famous applications of 
+   kernel density estimation is in estimating the class-conditional marginal densities of data when using a naive Bayes classifier, 
+   which can improve its prediction accuracy.
+
+This complicated sentence can be translated into the below image:
+
+.. image:: https://github.com/JoaoDell/gsoc_assets/main/images/KDE_plot.png
+   :align: center
+   :alt: KDE plot of 100 random points
+
+That is what a KDE plot of 100 random points looks like. The greener the area, the greater the density of points. The plan is to implement 
+something like that with the tools we now have available.
+
+Let's get to work!
+