Alpha issue

Support Materials and Textures
1

Hello,

I’ve shrink-wrapped an image with an alpha channel onto an object (in this example, an ornament graphic onto a Christmas tree mylar balloon).

The issue is where the red arrow is pointing to. I’m still showing a slight indication of the transparency. Any ideas what I should try?

I went through all of the settings which would affect the transparency, but to no avail. This will be rendered in cycles.

Here’s what I’ve tried…

  • Image texture node alpha, toggled between “Straight” and “Premultiplied”
  • Light paths - cranked up the transparent bounces to a high number
  • Material settings - toggled Render Method and some other properties
  • Made sure the shrink wrapped object and target both have the same BSDF settings (low roughness for a shiny balloon).

alpha-issue
alpha-issue523×505 237 KB

2

Is that line the edge of the alpha image?

3

Hi! Yep, that’s the edge of the alpha image.

4

It might help, if you could show the shader. Also, have you tried to massively increase the number of samples (useful to know, even if it might not be practical).

5

I have had that problem before. What’s happening is that the transparent part is affecting the shading and denoising of the surface under it. Even though it’s not visible to the camera, Cycles is still aware of its existence. One thing that helped me in the past is to remove the diffuse visibility on the shrinkwrapped object. That’s going to reduce the effect of the transparent object on the underlying surface.

diffuse

You could also remove the glossy for even more of an effect, though that would make the pattern invisible in any mirror in your scene, so it may or may not be possible.

An other thing I might try is to switch the denoiser’s pre-filter from accurate to none. This reduces the filtering in the denoising and gives a sharper result, at the cost of possibly leaving a bit of noise in reflective surfaces.

–

Finally, if all fails, you could try putting the pattern in your main material instead of using a shrinkwrapped surface. If you have a texture with an alpha, you already have everything you need to do so. Do you have the necessary understanding of material nodes to do this?

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6

This is all very helpful! I appreciate the tips. I’m going to try them out.

And regarding the incorporation of the pattern into the main material…

Problem is, the balloon object is very very dense. So any UV unwrapping or manipulation is a nightmare. What happens is, I’m given the art files from the production team, which has the diecut. I take that diecut in Illustrator, create a solid shape, then inflate it using Illustrators inflate tool. I then bring that into Blender and run a cloth simulation to blow it up and get those creases.

So what I’ve been doing is taking all of the pattern like detail, separating that out. I just use the base colors for the large portions of the mylar balloon, then I bring in an image plane to shrinkwrap that onto the object. Inevitably the prod. team has adjustments to those finer details, and it just makes sense in my head to treat those separately. That way I can enlarge the plane and move it around without much hassle. Well, at the cost of that line problem I had. :slight_smile:

But thanks again for your input!

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7

@etn249 - The Diffuse and Glossy ray visibility worked! Thanks again. Saved me from Photoshopping in post.

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