Hi Maloficu,
The last screenshot shows clearly the direction you like to go to. In a nutshell, you want to bake the light you get from Redshift.
I assume that the tutorials series is watched and the content is fully understood. If not, please ask. I have watched the series again this morning, and I can’t see anything significantly different from the current Sketchfab offers.
Leaves me to urgently point out to read this text:
https://help.sketchfab.com/hc/en-us/articles/201766675-Improving-Viewer-Performance
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With these three things, your target, the great series from Donovan, as well as the tips for optimization, you should have a good base.
The scene as it shows in post #11 and the given geometry/texture, requires to understand the logic that is given with the three parts listed above.
Sketchfab allows only for one material per polygon. What does this mean? If you take the tiled floor and pool, for example, it could be created with more polygons, and with that, the UVs could overlap and provide a ‘tile-repetition” to a certain degree. The balance that is now needed is the sweet spot based on mesh density and texture resolution.
There is a big but in it, as I can see, you have Ambient Occlusion [AO] and Global Illumination [GI] on (Both together kind of doubling the effect in some areas, BTW). Anyway, the light that is rendered in this quality creates unique situations for every single spot on the surface. As a result, any form of optimization with reusing texture/image information is canceled. The good news is that the mesh has no need to get any denser. However, the texture for a large model like yours and the ability to dolly-in requires dense textures, which will challenge any performance.
If the light would be without GI and AO, the model could have some more polygons, to take the UV polygons and overlap them on the texture. As an extreme, you could have a single Tile image, and for each tile needed a square polygon. Extreme…, not suggested!
We have now two extreme positions, and as usual, something between these two is the sweet spot, where details, light, and performance are nicely balanced.
There are certainly more sophisticated ideas to optimize it, but also here, the sweet-spot is between time investment and display performance.
All of those ‘scene/object-parameters’ need to be explored from the early stages of a project. Then weighted to produce from the start a priority list. This gives a more precise idea of what to do at each step of the production.
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Going through the geometry of your project, it sometimes has nearly no density, and sometimes for no reason (AFAIK) a vast destiny. Then some elements can’t be seen from the inside, but those are modeled and have UV polygons as well texture on it. Which, in return, takes space during baking and wastes pixels of the textures.
Another part that could be explored to use Normal mapping for the water surface, and keep the density there as well low.
All in all, I have too little information about the project’s target, to say anything with absolute certainty, so check my suggestions.
Let me know what the parameters of the project are, and I will follow up with more input.
Please check your object and their polygon Normal directions, they are not always perfect.
All the best