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Mesh backside triangles culling ?

As I was reading this: https://www.reddit.com/r/GearVR/comments/3sd9gd/eve_gunjack_released_20th_november/ I saw that one of the posters wrote, referring to the video, that Gunjack devs had to manually hide backsides of the large ships. Doesn’t UE4 have backside triangles culling? Why did Gunjack devs have to do it manually? (if that’s actually the case)

Thanks.

Back face culling happens after vertex shader processing is already happened. If you have static view and angle then you can remove back faces manually at preprocess time. This save vertex processing power but will limit the view angles for those meshes.

I figured there will be some processing power savings, but is it really that much of savings to do it manually ? Quake 4 (or ETQW) had backside of the view weapon models removed permanently, and I am sure if those massive dreadnoughts in Gunjack never show other side, it would be a valid technique there too. However, as I understood, it was done in-game, depending on what side those ships face player.

Some games create multiple index buffers for meshes. Each index buffer contain just vertices that are seen by some direction. Then renderer choose best index buffer for current view angle. This was particularly helpful for PS3 where vertex shader stage was really slow.