User:ColinMarmond/GSoC 2023/Final Report

GSoC 2023: add shader node previews

Project recap

This project was about implementing a way to view the effect of a node used in a shader graph. The approach taken was to render a preview scene with the result of what the shader graph would look if it ended with this node. Actually a new rectangle area is added with the node so that the user can have all nodes effect in sight.

A small video can better explain what the purpose exactly is:

What I did during this project

Optimisation introduction The task of rendering the preview for every node is expensive so the goal is to re-render the smallest amount of previews while not underestimating the changes. It's all about how much previews we redraw for each change in the node-tree (less false positive as possible).

When the project was active, those links were the threads I used to communicate: https://devtalk.blender.org/t/gsoc-2023-shader-editor-node-preview-weekly-reports https://devtalk.blender.org/t/gsoc-2023-add-a-shader-preview-node-feedback

Prepare the ground for the main functionality

In order to start coding the main functionality, I had to update some older designs existing in Blender before, such as:

• Move the existing node previews (Compositor nodes) to an overlay. PR #108001
• Use ImBuf structure for the compositor nodes. PR #110064

Implement this functionality as a whole (MVP: Minimal Viable Product)

In order to be able to merge something one day, I had to start simple and then add more things later. This first commit took advantage of the node-tree update functions to launch a new render containing the preview scene with a ViewLayer for each previewed node. In this patch, a trick is used to improve efficiency of the non-shader nodes (only textures and math) previews: we use the AOV pass to generate the previews for those nodes. This allows the rendered to render all AOVs previews with just one ray per pixel. PR #110065

Incrementally improve the MVP

After adding the main functionality, some things were missing and had to be fixed or improved. It mainly concerned design, and some improvements in the preview routing. Pull requests: PR #110958PR #110945PR #110949PR #111041

Curent state of this project and things left to do

The project is nearly complete (functionality wise), but some things are not yet merged or not finished at this point. Regarding the work in progress patches, there are:

• PR #111040: UX(User Experience) for the preview area size in the shader/compositor node editors
• PR #110725: Use individual node preview refresh (reduce the number of false positives)

Those patches are non-blockers for the main functionality, and I probably finish that after the end of Google Summer of Code. Some things are still to be coded and improved. Just to list a few:

• improve performances
• improve the UX
• rendering tweaks

Here is a task tracking the progresses of this project (all todos for future work): #110353

My thoughts

First time GSOC for me, and it has been an extremely interesting experience. My contribution to the Blender project started few years ago and it was a pleasure to officially be recognised for this.

I learnt many things in multiple areas, such as:

• communication
  • learn to exchange with more ease with the community and the other developers of Blender
  • manage the successes and fails with my mentor
  • make decisions out of everything people are saying in the chat and forum
  • take more time to discuss the designs before coding
  • the whiteboard is the greatest ally
• work time
  • deal with interrogations, doubts
  • improve the work efficiency
  • improve my comprehension of the review process
  • learn about some C++ functions and alternative uses
• project management
  • figure out that doing easily maintainable and integrated changes is in most cases better than introducing new structures (even if they can be more appropriate sometimes)
  • maintain a working environment (git/build folders)

I would thank every developers of the Blender team (Brecht, Jacques, Hans) and the other ones present in the chat to help. The users participating in the feedback thread were of an incredible help to determine designs and alternatives.

Thank so much everyone for the trust, I tried my best this summer and I'm looking forward to completing other similar projects in the future.