Planar projection on both sides of my object

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  10 October 2012
Unhappy Planar projection on both sides of my object

Hello,

I am trying to achieve what should be straightforward, but is proving to be an incredibly complex process - applying some 'decals' to a polygon model. I have successfully managed, using a few planar projections into a layered texture, to achieve this. However, when I turn my model around, there are the same projected textures (TIFFs with alpha channels - even though Maya refuses to recognise the alphas) showing on the other side (the other side of the model, not the faces).

I have searched around and found a few cumbersome, hugely time-consuming suggestions from years back, but surely Maya, after numerous updates, has some kind of "don't pointlessly show this texture on the other, unwanted side" option somewhere? I certainly hope so. Texturing a model is such a pain in Maya - is it this bad in other 3D software?

Hoping someone has some suggestions, so I don't have to resort to applying textures to individual faces.

Many thanks,

Paul
 
  10 October 2012
It would ofcourse be easier to tell you what the problem is if you showed us a picture.
Thinking logical on the subject, if you have only one material on your model and the 2 sides have the same uv space, you will ofcourse have the same decals/textures on both sides.

I dont really see how you would get away from that.

you can always just select the faces you want another decal on or nothing and uv map it and place it on another position in the uv editor.
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  10 October 2012
I've gone with the 'selecting faces' route - I'm working on a model that someone else created, and I daren't even look at the UV Window - it looks like a bucket-full of raw spaghetti - a complete mess.

One other thing I'm finding impossible to do, is getting Maya to recognise any alpha channels in my TIFFs (Photoshop RGB TIFFs, no compression, no layers) if I connect them to a planar projection node. It seems to just throw away the alpha data. I read about this problem occurring on Maya version 7ish - it seems that Autodesk can't be bothered to fix it. Or maybe I'm missing something. I hope it's the latter and I can be easily 'shown the way'!

Thanks,

Paul
 
  10 October 2012
Isnt it just the viewport that doesnt show the transparancy?

Im not having any problems with tiffs made in ps.
Try switching to high quality viewport. then it shows the transparency.

I really would recommend you to create correct uvs.

that way you wont have any suprises later on. is it a compliacted model to uv map?
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  10 October 2012
you need a two/double sided texture.

http://www.creativecrash.com/tutori...e-sided-texture
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  10 October 2012
Originally Posted by gmask: you need a two/double sided texture.

http://www.creativecrash.com/tutori...e-sided-texture


I dont think this is the case here. He says its NOT the other side if the Faces but the other side of the model.
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  10 October 2012
gmask - isn't that for applying a different texture to each side of a face? That's not what I'm after - I'm modelling a DSLR camera and just need to apply 'decals' to appear on the camera body next to the appropriate knob. But, for example, if I have a 'play' icon on the back of the camera, it also appears on the front surface of the camera.

I'm just selecting bunches of faces and applying textures. But I still can't get Maya to work with alpha channels if I use a planar projection. It just completely ignores them. I've managed to do a kinda workaround

You can easily replicate it - create a cube, apply a new material, add a file texture to the color, import a file with an alpha - voila, there's your cube with transparent bits.

but...

if you create a cube, apply a new material, add a file texture 'as projection' to the color, import a file with alpha, your cube has no holes. I've tried every permutation of connecting the alpha, transparency etc. of the file node to the projection node, and thence to the material' alpha/transparency, but it just doesn't work. Crappy Maya.

The workaround I've created is to connect the alpha from the projection to the X input of a 'reverse' node, and connect the X output of that to the transparencyR, transparencyG and transparencyB of the material.
 
  10 October 2012
Originally Posted by hellopaul: The workaround I've created is to connect the alpha from the projection to the X input of a 'reverse' node, and connect the X output of that to the transparencyR, transparencyG and transparencyB of the material.


Ugh.. yeah maya and alpha channels has always been a little weird.
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  10 October 2012
Ah yeah - for that theory about connecting the alpha channels to work, I had to go via a layered texture. Ludicrously complex. And completely useless if the image is not just black and white - because it's using the luminance as an alpha, anything red (for example) shows up as 50% opaque. Oh well, I'll just have to create another node and another file which is just an alpha channel. Thanks Maya for making something that would have taken me 5 minutes on Strata Studio Pro 20 years ago take all bloody day.
 
  10 October 2012
I can agree that some things in Maya could work better but still dont understand why you would want to use the project node when texturing those things.

2 months ago we made some dlsr for nikon and we didnt have any problems doing it the "face" way.

Here is one render from that project.

http://i.imgur.com/ZV6R8.jpgi.imgur.com/
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  10 October 2012
Hmm..

I just tried this myself and was able to project the rgb and alpha with a single projection node and without having to invert the alpha.

I created a projection node and then connected the file image to the image input and then to the Transparency input. I then connected the transparency out from the projection node to the transparency input of the shader and it rendered as expected.
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  11 November 2012
Huh. It's a mental ray problem. I thought I'd just do a quick demo to show what I mean, so made a cube, applied a Blinn material, selected a few faces, applied another Blinn material, projection-mapped a file (RGB TIFF with an alpha) to the color & transparency (exactly as I and gmask have been doing)...rendered it with Maya software and got this:

My first question is how to make the original texture (the cyan Blinn) show through under the TIFF. But the spanner in the works is mental ray (which I've been using all along). Exactly the same scene rendered with mental ray (with Raytracing on, Production Quality preset) gives this rather unfortunate mess:


...which is a bit of a pain. I've completed the project now; I used unnecessarily complex layered textures and stuff; this is a shader network for just one 'decal':

....maybe I would have avoided a lot of headaches by NOT using mental ray. Oh well, live and learn.

- Paul
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  11 November 2012
I tied using a Targa (with alpha channel) instead of the TIFF. Exactly the same results (Maya software render = good, mental ray = ignores alpha channel). I also tried saving the TIFF as IBM PC byte order instead of Mac. No difference.

LZW compression is OFF - I know Maya doesn't like that.

- Paul
 
  11 November 2012
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