GSoC: Week 6 Blogpost

docs/source/posts/2023/2023-07-10-week-6-joaodellagli.rst

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+Week 6: Things are Starting to Build Up
+=======================================
+
+.. post:: July 10, 2023
+   :author: João Victor Dell Agli Floriano
+   :tags: google
+   :category: gsoc
+
+
+Hello everyone, time for a other weekly blogpost! Today, I will show you my current progress on my project and latest activities.
+
+What I did Last Week
+--------------------
+Last week I had the goal to implement KDE rendering to the screen (if you want to understand what this is, check my :doc:`last blogpost <2023-07-03-week-5-joaodellagli>`_). 
+After some days diving into the code, I finally managed to do it:
+
+.. image:: https://raw.githubusercontent.com/JoaoDell/gsoc_assets/main/images/buffer_compose.png
+   :align: center
+   :alt: KDE render to a billboard
+
+This render may seem clean and working, but the code isn't exactly like that. For this to work, some tricks and work arounds needed to 
+be done, as I will describe in the section below.
+
+Also, I reviewed the shader part of Tania's PR `#791 <https://github.com/fury-gl/fury/pull/791>`_, that implement ellipsoid actors inside
+FURY. It was my first review of a PR that isn't a blogpost, so it was an interesting experience and I hope I can get better at it.
+
+It is important as well to point out that I had to dedicate myself to finishing my graduation capstone project's presentation that I will attend 
+to this week, so I had limited time to polish my code, which I plan to do better this week.
+
+Where the Problem Was
+---------------------
+The KDE render basically works rendering the KDE of a point to a texture and summing that texture to the next render. For this to work, 
+the texture, rendered to a billboard, needs to be the same size of the screen, otherwise the captured texture will include the black background. 
+The problem I faced with that is that the billboard scaling isn't exactly well defined, so I had to guess for a fixed screen size 
+(in this example, I worked with *600x600*) what scaling value made the billboard fit exactly inside the screen (it's *3.4*). That is far from ideal as I 
+will need to modularize this behavior inside a function that needs to work for every case, so I will need to figure out a way to fix that 
+for every screen size. For that, I have two options:
+
+1. Find the scaling factor function that makes the billboard fit into any screen size.
+2. Figure out how the scaling works inside the billboard actor to understand if it needs to be refactored.
+
+The first seems ok to do, but it is kind of a work around as well. The second one is a good general solution, but it is a more delicate one,
+as it deals with how the billboard works and already existing applications of it may suffer problems if the scaling is changed. 
+I will see what is better talking with my mentors. 
+
+Another problem I faced (that is already fixed) relied on shaders. I didn't fully understood how shaders work inside FURY so I was 
+using my own fragment shader implementation, replacing the already existing one completely. That was working, but I was having an issue 
+with the texture coordinates of the rendering texture. As I completely replaced the fragment shader, I had to pass custom texture coordinates
+to it, resulting in distorted textures that ruined the calculations. Those issues motivated me to learn the shaders API, which allowed me 
+to use the right texture coordinates and finally render the results you see above.
+
+
+This Week's Goals
+-----------------
+For this week, I plan to try a different approach Filipi, one of my mentors, told me to do. This approach was supposed to be the original 
+one, but a communication failure lead to this path I am currently in. This approach renders each KDE calculation into its own billboard,  
+and those are rendered together with additive blending. After this first pass, this render is captured into a texture and then rendered to 
+another big billboard. 
+
+Also, I plan to refactor my draft PR `#804 <https://github.com/fury-gl/fury/pull/804>`_ to make it more understandable, as its description still dates back to the time I was using the 
+flawed Framebuffer implementation, and my fellow GSoC contributors will eventually review it, and to do so, they will need to understand it.
+
+Wish me luck!