Hello!

I suppose this could go to any CG forum, but this is as good of a place as any. I make a lot of items with transparency maps, and I want to optimize them. I haven't found so much info after looking. What I am wondering is, does the bit depth of the transparency map affect performance, if so, in what way, and what is recommended, if anyone knows?

Thanks!

Since you are only talking about gray-scale (Unless you mean color transparency in Poser 11) you are wasting your time with excessive bit depth. Transparency maps are essentially masks and nothing more. Your primary diffuse maps are where your detail comes in and where you need to concentrate on depth.

Yeah its mostly leaves and things like that. I mostly wonder if bit depth of grey scale opacity impacts render speed

In that case, I will contradict myself. gradations in transparency DOES impact render speed. Also, obviously how much transparency there is in an image. Keep in mind this isn't as much of an issue as it once was, but there is a difference.

In that case, jpgs are probably not the most optimal format for opacity maps? An 8bit (for leaves even lower) tga would probably be better, and turn off texture filter in the material. With a lot of leaves in a scene, any optimization counts, if it -does- have an impact on the result. I may run some benchmark renders, but I am on the hunt on things to work with for it.

This is a subject I have been looking into lately, and the short answer is, well it depends. :)

Understanding what file types do to an image will help you decide whats the best file type for your requirements.

The main effect of bit depth in an opacity maps would be seen in any graduation used in the map. Lower bit depth can create a stepping effect in a long gradient as it sets the amount of transitional colors used in between the two transitional end point colors (Or Black,white and grays in this case). Something to be very careful of in Bump of displacement maps.

For objects with a hard edges and a solid body the opacity map bit depth wouldn't really be a major factor.

jpg is a good option in most cases for texture maps due to the formats compression, which keeps shareable file sizes down and avoids giant downloads for the end user. But there are a few things to be aware of if you do choose jpg. Make sure to keep your working files in a lossless file format for example tif, psd or as a 16 bit png and only save out your high quality jpg file out when its ready for distribution. Tweaking a jpg file with multiple re-saves may create visible compression artefacts in the file, something which you really don't want especially if you have no backups. Keep the resolution of your working files as high as practical, as downsizing is a much more viable option than up sizing when finalising. Don't be tempted to push up the compression when saving the jpg to further decrease the file size with jpg, it's best to save your final files with the least compression possible. Make sure the final jpg is of the most appropriate resolution size to fit the render needs of the map, a tiny rock rarely needs 8096x8096 texture sizes a terrain will eat up 1024x1024 textures.

For realistic leaves you may also want to consider some kind of translucency map, as a heavy solid leaf looks pretty unconvincing when the sun is behind it in a render.

Most file formats do certain things better and others and some may sacrifice quality for the sake of efficiency, lossy files are generally decompressed for rendering so this means that Lossless files though bulky may be handled by your render engine faster due to not having a to convert each file at render time. Lossless files tend to be very large and will make a massive download out of any standard content. Lossy generally means lost data due to compression and this may mean visible artefacts in your textures this is especially notable with incorrect work flows for lossy file types. Also something to be considered is that Customers may prefer one file type to another for various different reasons.

It's generally a give and take kind of scenario with most file types and you will need to decide what is the priority for the image/texture type and base your decisions going forward on that. Also peeking at what others do, isn't a bad option either. :)