OTOY Forums

Hey there! Let me cut to the chase.

I have a plane with an Octane specular material applied. My opacity map was still leaving the "ghost" of the plane, never letting it be truly transparent in any area.

I then disabled my map and set the texture's opacity to zero which, I thought, would completely turn it invisible. Instead, this:



If the embed isn't working: https://imgur.com/vjot3rl

see behind that boat? There's clearly a plane behind it, even though the opacity is set at zero. I've tried switching it to every material type, unplugging all my maps, creating new materials. Any way you slice it, that ghost of my plane is always there. Any help would be greatly appreciated!

Please attach image to your post by attachment button and put a sample scene. You may be using Bitmap not ImageTexture.

Hey! Unfortunately, my scene file is covered under an NDA, so I can't share it here, but I can attach the picture again and any other info that might be helpful!

This is probably one of those instances where the problem is obvious to you, because you are intimately familiar with the image and with your own expectations. To others, though, it can be essentially invisible. Can you explicitly point out the render ghost by highlighting the image, or share two images, one with the ghosting object rendered fully opaque? How about the image along with a shot of the resulting alpha channel? A stripped down example scene file with the proprietary content stripped out would be the best option, of course.

It took me several seconds to even see a boat. At first I saw a little block of concrete stuck in the limbs of a chrome tree at night. I have no idea what this image is *supposed* to look like.

I'm guessing what you are seeing is ether a surface attribute other than opacity, such as reflection, shadow, etc., or that your ray depth may not be set high enough.

I just ran into this as well, in a file that originated with 2018.1. I had to disable the opacity attribute in order to get the render to look correct.

@frankmci

Understood, sorry my image wasn't sufficient. Unfortunately, when working on these crazy huge projects, every image released into the world needs multiple levels of approval from all the producers above me, which is frustrating when time is a major constraint.

This is the best I can do for now: A view of the viewport with some relevant info pulled up.

Per my original post, there's a plane in this scene as indicated by the plane in the attached viewport. I have brought up the opacity section of the texture to demonstrate the ImageTexture is disconnected and the float value for Opacity is set to 0. Despite the opacity having a value of 0, you can see in the Octane render viewport of the second image I have attached again that the plane is clearly visible in the scene.

@jayroth

I guess the issue is, when I disable the opacity channel in C4D's default texture view, it just makes the plane 100% opaque when I'm trying to make it 100% transparent. In theory, with an opacity level of 0, it should be completely invisible and shouldn't be reflecting or casting shadows or anything. That's why I'm so puzzled.

Did you set the Index to 1?

aoktar wrote:Please attach image to your post by attachment button and put a sample scene. You may be using Bitmap not ImageTexture.

Good luck so!

klarwin wrote:Hey! Unfortunately, my scene file is covered under an NDA, so I can't share it here, but I can attach the picture again and any other info that might be helpful!

Even though you cannot post the exact scene, can you re-create something that will still show the problem.

klarwin wrote:@frankmci

Understood, sorry my image wasn't sufficient. Unfortunately, when working on these crazy huge projects, every image released into the world needs multiple levels of approval from all the producers above me, which is frustrating when time is a major constraint.

This is the best I can do for now: A view of the viewport with some relevant info pulled up.

Per my original post, there's a plane in this scene as indicated by the plane in the attached viewport. I have brought up the opacity section of the texture to demonstrate the ImageTexture is disconnected and the float value for Opacity is set to 0. Despite the opacity having a value of 0, you can see in the Octane render viewport of the second image I have attached again that the plane is clearly visible in the scene.

@jayroth

I guess the issue is, when I disable the opacity channel in C4D's default texture view, it just makes the plane 100% opaque when I'm trying to make it 100% transparent. In theory, with an opacity level of 0, it should be completely invisible and shouldn't be reflecting or casting shadows or anything. That's why I'm so puzzled.

@klarwin: Ah, ok, now I see it! The viewport shot is very helpful. To my eye, that ghost in the render looked very much like the triangular patch of specular highlight just above the upper right corner of the sail. I had no idea it wasn't supposed to be there.

You may not be used to thinking of materials this way, but in Octane, Opacity does not equal visibility. Opacity is only one component of the way light rays interact with a surface. For instance, a glass surface may have zero opacity (not in real life, but close enough) but it still reflects, refracts, transmits and diffuses light rays. Again, zero opacity does not mean invisible. There's also the issue of direct and indirect rays, shadow casting, ambient occlusion, etc. etc. etc. I see in your material that Opacity is zero, but what about Roughness, Reflection, Refraction, and so on? One common culprit for ghosts is the Transmission value. I believe the default is 95% That will make a 5% ghost even on a 0% Opacity, 1 Index of Refraction surface. Definitely check that one.

It looks like you also have a lot of layered, intersecting, overlapping, reflective/refractive/transparent/transmitting surfaces in this scene. Which render kernel are you using? Do you have enough ray depth for each surface attribute to render properly? When too low, you can end up with ghosts/blocks/artifacts where too many surfaces overlap, not allowing the rays through.

I hope that helps you track down the source of your problem.