double sided thin and uvs

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lape
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double sided thin and uvs

Post by lape » Mon Nov 18, 2013 12:27 am

Hi,

I struggle with the double sided thin material, I really don't understand how to use it with Skindigo. :(

Attached is a picture with two leaves. One with a simple diffuse texture, which renders fine, and one with the double sided thin material. It's a copy of the leaf which works fine, but when I use double sided thin and use the texture for the frontside, the uvs seem to get messed up.

Can anybody push me in the right direction? My version is 3.6.26.
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test ds2.jpg
test ds.jpg
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Re: double sided thin and uvs

Post by fused » Mon Nov 18, 2013 12:49 pm

lape wrote:Hi,

I struggle with the double sided thin material, I really don't understand how to use it with Skindigo. :(

Attached is a picture with two leaves. One with a simple diffuse texture, which renders fine, and one with the double sided thin material. It's a copy of the leaf which works fine, but when I use double sided thin and use the texture for the frontside, the uvs seem to get messed up.

Can anybody push me in the right direction? My version is 3.6.26.
Hi lape,

in general you just need to assign textures (or colours or shaders) to the front and back materials linked in the double sided material ("leaf" and "back" in your scene). These materials can just be diffuse materials.

It looks like you have some sort of UV mapping issue there. You could try it on a simpler mesh first.

Yves

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Re: double sided thin and uvs

Post by lape » Mon Nov 18, 2013 8:08 pm

Hi Yves,

it really is a uv issue. Diffuse works fine.

I already tried the uv tools by Whaat (thank you for this!) and the uvmapper, but I failed. The structure of the mesh is quite complicated, I was not able to map the texture on it (tried for about 4 hours). It always gets distorted...

Don't know if Whaat reads this, perhaps he can give me a hint... though I already followed his tutorials.

cheers,
Lars
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Re: double sided thin and uvs

Post by galinette » Mon Nov 18, 2013 11:08 pm

Apparently, you have defined no texture in the Sketchup material tool (only in the indigo material tool). This means sketchup will not generate proper uvs. If you add by hand your leaf texture to Sketchup material properties, it should work.

Indigo texture and sketchup texture are two independent properties, and if the latter is not there, no UVs are generated. You can use any dummy texture for that as it will not be rendered (useful for textureless ISL materials)
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Re: double sided thin and uvs

Post by lape » Tue Nov 19, 2013 4:06 am

galinette wrote:Apparently, you have defined no texture in the Sketchup material tool (only in the indigo material tool). This means sketchup will not generate proper uvs. If you add by hand your leaf texture to Sketchup material properties, it should work.
ok, this works! But now it seems that my mesh needs to have the right uvs for front and back. The front looks good, but the back is messed up.
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Re: double sided thin and uvs

Post by Pibuz » Mon Nov 25, 2013 8:54 pm

Using two sided materials as they are now conceived it's nearly impossible to SU users. SketchUp doesn't provide proper UVmapping tools, and working THIS long for a leaf is beyond dispute, at least for me.

My former workflor was setting a front texture (most of the times it meant keeping the UV texture coming from the imported or external-referenced OBJ), applying a phong shader and setting a 30% opacity.

..maybe some sort of special SU integration should be made to use this fantastic material. I really can't wait to use it, but now it requires too much work :( :( :(

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Re: double sided thin and uvs

Post by ENSLAVER » Mon Nov 25, 2013 10:05 pm

lape wrote:
galinette wrote:Apparently, you have defined no texture in the Sketchup material tool (only in the indigo material tool). This means sketchup will not generate proper uvs. If you add by hand your leaf texture to Sketchup material properties, it should work.
ok, this works! But now it seems that my mesh needs to have the right uvs for front and back. The front looks good, but the back is messed up.
Can you post an image of the issue? Also the images you are trying to use for front/back/alpha.

I believe UVs are only applied to the normal facing side of a polygon and then projected through. Instead of thinking of the plane as a piece of paper you could draw UVs on both sides of, a single sided object is more like a thin piece of tissue with the UVs projected through it. As long as your images line up it should be ok, though I am completely unfamiliar with sketchup and the implementation of the material.

Edit: Added images: You can see that the Front (green), Back (purple), and Alpha all are in the same position for each image (I combined them into one image to make uploading easier).
Attachments
ivy1.jpg
23ivy1.jpg

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Re: double sided thin and uvs

Post by lape » Mon Nov 25, 2013 10:31 pm

The problem was the mesh itself, and some wrong settings of the uvs.

Fortunately I know somebody who uses 3dsmax, so asked him to change the uv settings and export the file as 3ds.

Imported this in sketchup, and now it works! But Pibuz is right, it's really hard to achieve these uv settings with Sketchup, even if you use tools like uvmapper or roadkill, at least if it's a complicated mesh. You can spend hours to scale and distort the texture....

Thank you for your help, I will post my results using the doublesided thin material later :mrgreen:
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Re: double sided thin and uvs

Post by CTZn » Mon Nov 25, 2013 10:42 pm

You can spend hours to scale and distort the texture....
UVing is the stage at wich most 3D'ers wannabe choose bakery instead.
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Re: double sided thin and uvs

Post by bubs » Thu May 01, 2014 10:35 pm

Lape,

Since you seem to have managed to get this to work in SketchUp can I run through a work flow...

Am I correct in thinking that you need 3 materials for the thin mesh;
1 which you paint to both sides and set mat type as 'double sided thin' and then the 2 materials that you want to actually use? Similar to the use of a blend material...

I'm not having much success with this...

Thanks in advance

bubs

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Re: double sided thin and uvs

Post by lape » Fri May 02, 2014 7:35 am

bubs wrote:Lape,
Am I correct in thinking that you need 3 materials for the thin mesh;
1 which you paint to both sides and set mat type as 'double sided thin' and then the 2 materials that you want to actually use? Similar to the use of a blend material...
bubs
Right! See attached screenshot.
But I really can't recommend to use it in Sketchup, I always have problems with uvs.... :?
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doublesided.jpg
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Re: double sided thin and uvs

Post by bubs » Fri May 02, 2014 10:07 pm

Thanks Lape!
I am just trying this with pre-existing tree models to try and get the leaves looking more realistic so UV shouldn't be an issue as the leaves are already mapped.

Did you find a r_f value / ior combo which worked well? I seem to have the back face becoming almost white if I set the r_f at anything below 1.0...

At the minute for the 'sun through leaves' look I actually get better results just going with a phong / diffuse transmitter blend...

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Re: double sided thin and uvs

Post by Zom-B » Fri May 02, 2014 10:38 pm

bubs wrote:Did you find a r_f value / ior combo which worked well? I seem to have the back face becoming almost white if I set the r_f at anything below 1.0...
The r_f get mapped with a "thickness map" that let leaf vains etc. let less light pass. Brighter colors are marking more transmission here.
You need a colored transmittance map if your leafs look white, thats the most common mistake here :)
Last edited by Zom-B on Fri May 02, 2014 10:58 pm, edited 1 time in total.
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Re: double sided thin and uvs

Post by bubs » Fri May 02, 2014 10:45 pm

bubs wrote:You need a colored transmittance map if your leafs look white, thats the most common mistake here
Yes!!! That's the ticket! working like a charm now! Thanks Zom-B :D

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Re: double sided thin and uvs

Post by Zom-B » Fri May 02, 2014 11:00 pm

bubs wrote:
bubs wrote:You need a colored transmittance map if your leafs look white, thats the most common mistake here
Yes!!! That's the ticket! working like a charm now! Thanks Zom-B :D
Glad I could help, looking forward for a updated Forest scene, together with that awesome frog :lol:
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