[richardfollett]

It may well be a photoshop thing.. I started with a Tif file with alpha channel. Can someone explain how I use the alpha channel to create the 255,255,255 white background that I believe is required?

Thanks

[richardfollett]

So I created a simple text file in photoshop and saved as PNG.

I presume I am getting the white because it is a bmp, so if you zoom in i see gray round each letter? How do I get round this?

[tokiop]

hello richard,

i think you should use 2 image: one similar to the above "time" for alpha, and one entirely black, so that the "bleeding" that you see white in the render will be black.

If you transpose to the tree, it will be: your black and white alpha with the tree silouhette, and a color image for the clipmap content. The color image should not be on a white background, but black/green/yellow: the color of the inner pixel in the tree color map (don't know if that's clear?).

You can also contract the tree selection of a few pixel, so that you don't see the soft transition to the white background.

[Fernando Tella]

Use two mapped layers: one ghost (Nd=1 and white transmittance) and one your material; use your alpha map for one layer and the same but inverted for the other one. Maybe you should play with remove matte options in photoshop for the alpha map.

If you still want to use only one layer you should transform the alpha image to black and white (not RGB or greyscale) and then back to RGB so it loses the greys. Maybe you could also play with levels to do so...

[richardfollett]

Thank you both. I dont really understand your answers.
All I understand from both replies is the contract/expand command in photoshop to mask the gray area around the tree.

Thanks

Rich

[Mihai]

You are getting the white borders around the clipmapped geometry because there are greyscale values in the clipmap. So if it's not 100% white, it will be fully opaque in the render when you use this map in the transmittance channel.

To expand what the others suggested, you could instead make a 2 bsdf material and instead of using this map in the transmittance channel, you use it as a weightmap for each bsdf. This way you can get variable transparency and this border will be far less visible.

So in the first bsdf, set transmittance to fully white, ND 1. Apply this map as a weightmap for the bsdf.

The second bsdf, place your color map in the refl0 slot, and apply this map also as a weightmap for the bsdf but invert it (white areas in the map mean these areas will be visible).

Ofcourse you can also make this material as 1 bsdf and use this map in the transmittance channel but then use the Threshold or Contrast commands in Photoshop to make sure there are nothing but 100% black or white pixels in the map. But for finer, smaller objects such as this text it's better to use 2 bsdfs method.

[richardfollett]

Thanks for your explaination Mihai.

So my material looks like this? Have I got al the correct settings? Im crap with materials in Maxwell...

[Mihai]

Yes, it looks ok. The weightmap for the first bsdf should be inverted, I can't see that from the screenshot. So white values in the weightmap means that part of the material will be visible.

[kami]

it should work like this. the weightmap is inverted, the window on the right still shows the texture from the other layer which is a bit confusing in the rhino plugin.
if the result is still weird: set the roughness of your first bsdf to 0. I never now if this matters, but I always put 0 there.

[tom]

I think the mask image is slightly larger than the color image, that's the problem.

[JorisMX]

In Photoshop there is a pretty useful feature for these kinda things:

filter>other>maximum
filter>other>minimum

These are for expanding and contracting B/W Images.

otherwise you can always use

select>modify>Expand
select>modify>Contract

to work on a selection instead of a mask