Alpha by texture isn't fully transparent

V-Ray V-Ray for Rhino General
1

Hi,

I tried to use the alpha from the PNG, but it doesn’t work, the alpha is semi transparent only. Did I something wrong?

-Micha

.png.png
.png.png494×740 87.3 KB

.png.png
.png.png2400×600 11.3 KB

Paint.white.decal.zip (35.9 KB)

2

Hi,

The way an alpha appears (white/black/glitched) depends on the software used to create the PNG file in the first place. As a workaround, you can try the following steps. The first one is about Opacity map. Slot there your png file and wrap it in a Color correction texture. In the Color Correction, go to Rewire Channels, for RGB channels use Inverse Alpha (01).

01.jpg
01.jpg762×1019 80.5 KB

After that go to the Bitmap - Color Manipulation and enable “Invert Texture” and “Invert Alpha” (02).
02.jpg
02.jpg762×1019 76.7 KB

The second thing is to disable the Diffuse Texture Alpha (03),
03.jpg
03.jpg762×1019 98.9 KB

the png file doesn’t have its channels properly set and that is the reason you don’t get the expected result.
We know that this is not the best solution but it will save you from modifying the texture in external image-editing software.

Kind regards,
Natali

3

Thank you for your suggestions. What would be the way to get a clean texture PNG? Would the perfect way be to have a picture with a backround color and to add an alpha map? Which background color works?

4

Hi Micha,

So there is no issue with your PNG or any other for what is worth.
The thing is that many applications (like Photoshop for example) let you work with transparency directly so you don’t really see the RBG colors for the transparent pixels.
On save PS will generate the RGB data for the transparent pixels in an automatic way and convert the opacity to an Alpha channel.
If you look at the RGB data afterwards it looks strange (blocky colorful areas surrounded by white pixels) but this doesn’t matter since the alpha is preserved in a separate channel.

If you then use the approach suggested by Natali, the rendered result will be correct.
If you want to direct the way the raw RGB data looks, you’ll have to basically paint the RGB and add an alpha channel.
Keep in mind that if you just add a BG color in PS against the existing transparency (in your example texture) the final result will not be what you expect - there will be a color bleed right at the alphas edge.

In any case, we’ll do our best to improve the workflow you’ve originally utilized.
We’ll also try to improve the workflow for decals creation in Rhino as a whole.

Regards,
Konstantin