Ring around the decal

I was doing a project trying to put picture and text onto a transparent window, like a store might do for their display. All went well in modeling, but there was a white ring around the displayed graphic where the alpha channel transitioned from white to black. I’ve tried to do it before with similar results. I made sure that there was no white edge in the graphic itself.

That is most irritating, and what is worse, after concerted efforts to find a way for it to render properly, I had to move the project over to 3ds Max. :mad:

I used 2.49, has this bug been fixed in 2.5?

In the render panel try changing from Sky to Premul or Key. If that doesn’t work do a search on these forums as this type of question has been asked a zillion times.

Sky - If a World has ‘sky’, this is filled in in the background. The alpha is not altered, but the transparent colours ‘contaminate/overshadow’ the background colours, which makes the image less suitable for post-processing.
Premul - or Pre-Multiply. The ‘Sky/background’ is never filled in. The alpha in the picture is delivered as “Pre-multiplication”; a white pixel with an alpha value 0.5 becomes: (RGBA bytes) 128, 128, 128, 128. The colour values are thus pre-multiplied by the alpha value in advance. Use “Premul” alpha for post-processing such as filtering or scaling. Remember to select the RGBA option before saving. When Blender reads RGBA files, “Premul” is considered the standard.
Key - The ‘Sky’ is never filled in. The alpha and colour values remain unchanged. A white pixel with an alpha value of 0.5 becomes: (RGBA bytes) 255, 255, 255, 128. This is especially clear when rendering Halos. The complete transparency information is in the (hidden) alpha layer. Many drawing programs work better with colour “Key” information than alpha information.

There is also a premul button where you add a texture, can’t remember if this is also needed.


Thanks. I’ll check it out.

So far, turning off the oversampling (OSA) has improved the image the most, but not enough. Sky, Premul and Key didn’t seem to affect it much. I’ll look further in the forum.

You might get better results posting this question in Texturing and Lighting as this is a texture question.