Alpha Channel, Trees, Vray - HELP

[CurryPork]

Hi forum, I need some alpha channel help. I don't know if it's a Vray setting or a Sketchup setting.

Basically, I have some 2D and 3D trees sketchup trees, but I cannot get them to render correctly in VRAY for sketchup. How can I fix the alpha channel?

Thanks

[thomthom]

You need to extract the alpha channel as a grayscale image. Then add that to the transparency slot in the diffuse channel. V-Ray doesn't read the alpha channel from PNG images, so it need to be separate.

[CurryPork]

How do you extract the alpha channel? I can't even find the PNG file from these trees. The 2D might be possible with Photoshop, but how would you extract from the 3D tree?

[Gaieus]

How did you get these trees? What the images used in them is needed is a clip map (if you can get the original png files, you can create these clips easily in PS).

[CurryPork]

Here are the trees. I got them either from here, the internet or the warehouse. But my point is how can you extract the PNG or the alpha channel from these sketchup files.

[thomthom]

Right click the material in the SU material editor, choose "Extract Texture Image". Save the file to disk and open in your image editor of choice to extract the alpha channel.

[CurryPork]

Thanks Thom, I tried right clicking everywhere and cannot find that feature.

[thomthom]

Sorry. Be in the list of materials. Not in edit mode. (The "Select" tab next to "Edit")

[CurryPork]

Thanks Thom. I learned something new.

I got the alpha channel out of the tree now. Do you know how to make it work in Vray?

I assign a PNG as a bitmap in the COLOR slot in DIFFUSE and the alpha layer as a bitmap in the TRANSPARENCY slot in the DIFFUSE. But when I render in Vray it's not working... any suggestion?

Thanks

[CurryPork]

OK, I got it to work... thanks.

[chango70]

So how did you get it to work?

[CurryPork]

I have it working for the 2D tree and this works for the 3D tree as well. So, just extract the alpha channel from the original texture as Thom described.

In VRAY, apply the original texture in the Color slot and the alpha in the transparent slot. Render and this solves it.

Thanks Thom.

[chango70]

Thx I just tried it myself and it works.

[devran]

Hi Fellowcombatants listen!!! First You download the tree from warehouse... click on the component open it then rightclick and save the png. then open in Photoshop and rightclick on the icon in the layers menu and choose choose pixels... change to channels menu and create a alpha channel... this channel is saveable as a new picture... rightclick on the alpha channel and save as a new picture... thats all.... ( sorry for all non Photoshop users)... ciao devran

[tvicari]

You guys rock . . thanks for the tips, works great I have been looking for this solution for a long time. Thanks for making an effort and sharing knowledge.

[jdcarling]

Hey all,

I read this post and have figured out how to create the alpha channel in photoshop for a tree, but cannot find the location to insert the png properly in the material editor - diffuse - transparency. I clicked the lower case, then switched the left panel to TEXBITMAP but coudl not insert the alpha channel PNG anywhere... any tips.

[jdcarling]

Hey All,

I read this post and have figured out how to create the alpha channel in photoshop for a tree, but cannot find the location to insert the png properly in the material editor - diffuse - transparency. I clicked the lower case, then switched the left panel to TEXBITMAP but coudl not insert the alpha channel PNG anywhere... any tips.

[thomthom]

In the Transparency slot of the diffuse layer - add a TexBitmp:

vfsualpah.png

[kalu]

Hi thomthom:

I have this dilema, I read the post all perfect. I try to mimic the results and I want to know what I am doing wrong. I attach the tree and the images for the render. Please let me know what I am doing wrong. I use Sketchup Pro 8 and Vray 1.48.89. Some of the leaves show as a rectangular green. I have no Idea why.

Here is the link to the 3D model of the tree:

https://rcpt.yousendit.com/1023169415/e ... 1248da71be

Thank you!!!!

[thomthom]

That's because you didn't map the backside of the faces. You can even see that in SketchUp.

I'm guessing you imported this from another 3d format?
Because of that you lost the backside information. Many other 3d apps doesn't display anything on the backside of faces. You have to explicitly enable it.

To quickly transfer UV mapping from one side to another, use this plugin: viewtopic.php?f=323&t=18992&p=155759#p155759

[kalu]

Thank you ThomThom, aweomse your plugin, I have that problem when Import 3DS trees...

This is the result:

[thomthom]

Nice

Where's that top tree from?

[kalu]

Is from ASGVIS, I need to use for a Tutorial that I work right now.

[teris]

i've tried it... but it didn't work out... i wonder what part i've missed...

[teris]

i've tried it using vray 1.48.xx,,, it works... just use the color texture as transparency option... but when i tried it using vray 6 with the explanation above,,, it still didn't work... i still wonder... help me out guys... thanks...

[bac9-flcl]

Isn't there a way to utilize normal transparency types supported in SketchUp? I'm talking about alpha channels in .png/.tga/etc textures.

I have a vast library of transparent materials, but all of them have transparency data inside, not as a separate file - and it is very inconvenient for me to make separate images with alpha, just to meet weird V-Ray standards. Is it possible (in V-Ray material editor) to assign alpha channel of e.g. RGBA .tga texture to be used as transparency map?

[andybot]

There is a check box in the material diffuse layer to "use color texture as transparency" for just such files.

[ali64risk]

rightclick on the alpha channel and save as a new picture... thats all

I tried but I could not...
please someone explain more?
(right clicking on alpha channel in Photoshop gave me 2 options: "duplicate channel" and "save channel"... where I can save alpha channel as png?)

[nomeradona]

ali.. what they were talking was the workflow for the old version. the new vray version, dont worry, just follow what andybot said.

[ali64risk]

just follow what andybot said.

thank you
yes it is working