Blurring and transparency - shadow under furniture

After about 12 attempts, all in different ways, I admit defeat: I can't get a transparent, blurred texture into SL.

The thing is: you can get transparency, obviously, by using an alpha channel. You can also paint a blurred shape onto a transparent background, in Photoshop. However, selecting the blurred shape for an alpha channel will result in a mixture of the shape and white (when what one wants is a mixture of the shape and transparency.) Anti-aliasing or not is of no consequence.

What I'm trying to do is make shadows for my furniture. A shadow should be a dark shape, blurred at the edges, which you give a high transparency in SL.

Anyone have any clever ideas? I've run out of them.

Thanks, Xylo

Let me add: I can get to the point where everything looks fine when I save it to my hard disk: a transparent canvas with a splash of blurred grey on top of it. But when I upload to SL, the transparency changes into white, in spite of using an alpha channel.

If your transparency is turning white, it's because you either have too many or too few channels present. Make sure you have one, and ONLY one, alpha channel in your image, and that you're saving as 32-bit TGA. If you have more than one alpha channel, they will be composited in the TGA as a fully white alpha, making your image completely opaque. If you save at any other bit depth than 32, the alpha channel will not be present in the TGA.

Where you seem to be going wrong in your thought process here is you're confusing layer transparency with alpha transparency. The fact that you mentioned painting onto a transparent background is telltale of this. TGA files are inherently layerless, so no layer properties will ever be present in them. If your a TGA, all you know is channels; nothing else exists.

I'd encourage you to abandon your previous notion of how to make shadow textures, and go with the following process instead:

1. Create a new image, paint the background layer completely black, and leave it that way. We won't be doing anything else with layers at all.
   
   
   
2. Go to the Channels Palette, and create a new channel. By default it will be called "Alpha 1".
   
   
   
3. Turn on visibility for Alpha 1, and turn off visibility on all three RGB channels. Click once on the name of Alpha 1 to activate the channel so you can paint on it.
   
   
   
4. Paint in white whatever shape you want your shadow to be.
   
   
   
5. Apply a fairly generous Gaussian blur to Alpha 1. This will remove all the hard edges between white and black, adding in lots of gradations of gray, which will diffuse your shadow. Hard shadows in SL tend to look fairly unconvincing, as they rarely match the primary light source, the sun. Diffuse shadows are usually much more effective.
   
   
   
6. Save as 32-bit TGA, and upload to SL. Apply the texture to a prim, and you'll see that your shadow looks quite dark at this point, very opaque, since most of it is solid white in the alpha channel. Adjust the transparency of the prim surface in SL to your liking. The less transparent you set it, the darker the shadow will be. For subtle shading, use high transparency. For high contrast shadows, use low transparency.

I hope that helps. Happy shading.

That worked perfectly. Thank you for your extensive and clearly written reply, Chosen!

Xylo