AlphaImage and "opacity" masks

[treddie]

Hi all.

I am experimenting with multiple textures, where the age old example of a decal on a glass surface is the perfect example. There does not appear to be any discussion of this in the forums, and the manual only hints at the use of alpha. My tests are not working however. Has anyone tried to do this yet with Octane?

Thanks!

[roeland]

You can use a mix material to mix the glass material with some paint material (could be diffuse or glossy). Connect the paint material to the material1 input, the glass to the material2 input, and set the amount input to the alpha channel of the paint texture (use an alphaimage if you have a transparent PNG image).

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Roeland

[treddie]

Now I see. Thank you.

Weird, but I can't get pngs to work...just tifs. I'm probably setting some image vs. alphaimage selection wrong somewhere. Need to get some sleep first before I delve further.

[treddie]

The TIF approach seems to work great except for one problem...I cannot seem to keep the CD surface from appearing dull. Please see attached image with comparison to what it should be. Clearly, the CD surface lacks brilliance, and the only way I can think of to brighten it up is to make it into an emitter. But if I understand correctly, that means the mesh must be an exclusive emitter mesh and cannot have other non-emitter textures assigned to other portions of the mesh.

[roeland]

The appearance of shiny objects depends a lot on the environment, so you should compare the look of the CD surface in similar scenes.

How are you rendering the CD in MR? Is it a physically based effect or a texture?

PNG images and TIFF images should both work well. If you have a transparent PNG or TIFF file for the overlay: use an alphaimage for the amount input of the mix material, and an image node for the texture of the diffuse material.

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Roeland

[treddie]

The CD surface was a digital image applied to the reflectance 0 and 90 deg. channels. Over that was placed a BDSF mirror finish.

I think you may be right about the different environments thing. But it still seems that even though I can get the intensity in the colors and all of the detail in the CD without over-exposing it, when using a Daylight environment, it seems odd that an HDR texture environment on a bright sunny day can't get close.

[treddie]

OK, I got a lot closer. I found that I didn't have my roughness and specular settings right. I actually got the best results by using a glossy texture for the CD surface with specular set quite low, and roughness = 0. Along with alpha, it masked correctly against the other material in the mix which was just clear plastic.

[heavypoly]

Has this issue been resolved yet?

This workaround doesn't really work in some cases

Is there any image format we should be using to get transparency?

[treddie]

heavypoly > Please elaborate...What is happening in your case?

[heavypoly]

heavypoly > Please elaborate...What is happening in your case?

I'm trying to mix two textures ontop of eachother in the same manner as a photoshop multiply layer blending mode. Is there a way to do this?

Or lets say I have a textured Racecar (already has an RGB texture for diffuse) and I want to add one decal ontop of everything else...is there a way to do that?