Opacity mapped 3D model not rendering properly

[Simon A]

I bought a bunch of low poly 3D models of trees and pants to help fill scene. Supplied in both OBJ and FBX format. The leaves are all PNG's with alpha and mapped onto simple polygons on the tree models. When rendering the transparency seems to be ignored on some leaves leading to black solid polygons where there should be transparency as per the attached image.

I have tried the Node editor, changed various parameters on the materials, and experimented with the render settings unticking all the parameters in sequence to see if it had an effect. For example I thought he solid black polygons migh be something to do with receiving shadows. I have also created a transparency mask from the UV in Photoshop turning the background solid back and foreground solid white. I have tried rendering with HDRI and the Skylight using both the Cheetah and Falcon rendering engines, same issue. Makes no difference if using the FBX or OBJ versions fo the models.

I'm probably missing something really simple but can't think of any other options, any ideas?

 

[MonkeyT]

Remember that each light in Cheetah (including HDRI) has a setting to choose between "Radiosity" and "Radiosity AND Transparency". By default, HDRI's dropdown has transparency turned off (I assume because it used to be much faster).

If you ultimately choose to use the PBR Shader in the Node Editor, remember that Transparency is handled via the alpha channel of the Diffuse Property.

 

[Simon A]

Remember that each light in Cheetah (including HDRI) has a setting to choose between "Radiosity" and "Radiosity AND Transparency". By default, HDRI's dropdown has transparency turned off (I assume because it used to be much faster).

If you ultimately choose to use the PBR Shader in the Node Editor, remember that Transparency is handled via the alpha channel of the Diffuse Property.

Thanks for the but I did have Transparency option selected in the drop down. I'll keep on experimenting.

 

[ZooHead]

Is your material refraction set to 1?

 

[Simon A]

Is your material refraction set to 1?

It was actually 1.5. Just tried 1 through to 10 and same issue but then tried something. I had created a black and white mask from the supplied UV which had an alpha channel. I had read on a forum to have the transparent part black and visible white. Just reversed this in Photoshop and works and tested with refraction 1-10. Renders in both Cheetah and Falcon. Just need to draw a more accurate mask to make it look more realistic.

 

[Charless]

@

Simon A​

would you be so kind and explain your workaround, I am encountering the same issues on purchased 3D trees

 

[Paul P]

In some instances, my memory of this (from before Falcon) is that when you import the model into Cheetah, you need to replace the leaf texture. In Photoshop, you take the leaf diffuse map and add the alpha channel map as a new channel. You then import this new combined texture into Cheetah, and add it to the leaf polygons. As others have said, use an IOR of 1 and ensure "use alpha channel" is checked, and of course the shadows set to transparency.

Other times, if the model and textures have been put together properly, the leaf diffuse texture already has the alpha channel included.

 

[Simon A]

@

Simon A​

would you be so kind and explain your workaround, I am encountering the same issues on purchased 3D trees

Hi Charles, pretty much how Paul P has said. When I purchased the tree model (from CGTrader) it came with a texture for the tree trunk plus texture for the leaves including the UV, Specular, transparency and bump maps. I had to manually add the various images to the material supplied with the model. The PNG file for Transparency supplied had the image in white and the transparency in black and so I had the same issue that you are having. I then brought that PNG into Photoshop and inverted it so the image was back and transparency white. Also made sure the HDRI light was rendering Raytrace+Transparency.

Have attached a diagram with all of my settings, hope this helps.

 

[Charless]

Hi Charles, pretty much how Paul P has said. When I purchased the tree model (from CGTrader) it came with a texture for the tree trunk plus texture for the leaves including the UV, Specular, transparency and bump maps. I had to manually add the various images to the material supplied with the model. The PNG file for Transparency supplied had the image in white and the transparency in black and so I had the same issue that you are having. I then brought that PNG into Photoshop and inverted it so the image was back and transparency white. Also made sure the HDRI light was rendering Raytrace+Transparency.

Have attached a diagram with all of my settings, hope this helps.

Hi Simon, I purchased mine from TurboSquid, but instead making a inverted version of those PNG's: did not work! I saved them as .Jpeg and it works. So now I am confused. THX for you quick reply!

 

[Simon A]

Hi Simon, I purchased mine from TurboSquid, but instead making a inverted version of those PNG's: did not work! I saved them as .Jpeg and it works. So now I am confused. THX for you quick reply!

So am I, was the transparency map PNG just two solid colours e.g black and white or was the PNG a black background with alpha channel for the visible image area? Also maybe the PNG was 16 bit and not 8 bit (no idea if this makes any difference). My guess is that the JPEG is a flat 8 bit RGB file and so works in Cheetah. Very odd though.