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Alpha-mask textures, avatar baking, and memory. 
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Joined: 2012-01-19 03:18:40
Posts: 134
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I noticed recently that the alpha mask that came with a garment was based on a 1024x1024 texture. Now, we all know that big textures on items in-world are slow to load and use up memory, but I realised that I don't know the story on alpha-masks.

I vaguely recall that the process of baking skin, clothing etc. textures onto your avatar standardises the "size" of the texture that is displayed in-world. Are there negative consequences for using big 1024x1024 textures in alpha-masks? Given their purpose, it seems a bit pointless, and my experiments suggest that there is very little visual difference between the effect of a 1024x1024 texture in an alpha, compared to 512x512, 256x256, or even 128x128.


2019-06-12 23:42:04
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Joined: 2009-03-17 18:42:51
Posts: 4180
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Not sure what "alpha mask" you are referring to... In the viewer code, "alpha masks" are used at the rendering level, but you seem to be speaking about the textures used in the Alpha wearable assets.

In the former case, the alpha mask size is not under your control (it's managed in the viewer code).

In the second case, all the textures that contribute to backing on a SL shape body are combined (either viewer side, in OpenSIM and old SL days, or (bake) server side now in SL) and result in one texture only (the baked texture) to be attributed to each body part (head, upper body and lower body); baked textures are also currently reduced to a 512x512 size (which should be increased to 1024x1024 once Back on Mesh is rolled out on bake servers). It means that there is no practical impact in using large textures in Alpha layers: all what will be used in the end for rendering (and downloaded/seen by others' viewers), are the 3 baked textures.

Textures used on mesh body/parts are another issue: they do render at the size their creator made them (modulo the discard level which depends on distance, LOD factor, texture area, etc). The larger the textures (and with material there can be up to three per face), the heavier it will weight on rendering power and memory usage. The specular and normal maps of a face bearing a material could be using smaller textures with little change in rendered aspect, but very few creators would use that kind of optimization, instead going for the 1024x1024 max size for all textures...


2019-06-13 00:05:34
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Joined: 2012-01-19 03:18:40
Posts: 134
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Thank you, Henri, for your helpful reply.
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you seem to be speaking about the textures used in the Alpha wearable assets.
That is exactly correct. I had in mind the alpha-masks in Inventory that one puts on as part of an outfit to hide parts of ones avatar.
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In the second case, all the textures that contribute to backing on a SL shape body are combined (either viewer side, in OpenSIM and old SL days, or (bake) server side now in SL) and result in one texture only (the baked texture) to be attributed to each body part (head, upper body and lower body); baked textures are also currently reduced to a 512x512 size (which should be increased to 1024x1024 once Back on Mesh is rolled out on bake servers). It means that there is no practical impact in using large textures in Alpha layers: all what will be used in the end for rendering (and downloaded/seen by others' viewers), are the 3 baked textures.
So there is no penalty for using 1024x1024, and no benefit to using less than 512x512. I will bear that in mind.
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The larger the textures (and with material there can be up to three per face), the heavier it will weight on rendering power and memory usage. The specular and normal maps of a face bearing a material could be using smaller textures with little change in rendered aspect, but very few creators would use that kind of optimization, instead going for the 1024x1024 max size for all textures...
No, they certainly don't, often using multiple large textures even on small components that one can barely see, or large textures with little or no detail. I stumbled over this inspiring blog years ago: https://pennycow.blogspot.com/2013/06/b ... -life.html


2019-06-13 04:44:19
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