Texturing on really curved surfaces

[smasher_cg]

Hey guys, I'm kinda new here, and finally decided to tackle this vray little further. I'm working on my Canon A-1 camera scene, and I'm in need of texturing the negatives texture on a curvy filmstrip.
I am not so keen of texturing in Rhino, because more often I had problems with it, than not. Don't know if it is to do with my lack of knowledge or just crappy Rhino uvw, you tell me.

But here is something I would like to achieve, and asking you guys pros if it is doable in Rhino at all?



And while I'm at it. Any ideas on how to model this?

[smasher_cg]

Re: hi everyone

great post man.

LOL. seems like this forum is also not immune to spambots

[thomthom]

Re: hi everyone

great post man.

LOL. seems like this forum is also not immune to spambots

*grumble*
No, the last week or so there's been a flood of spam bots. I remove several every day. Used to be very rare that spambots got through. Mostly I think it was human spammer.
I hope that people use the Reporting feature when they see spam.

Welcome to the forum btw.

[Visa]

Re: Texturing on really curved surfaces



Seems to be quite possible
The strip is modeled using Grasshopper and the texturing is standard surface mapping. The repeat values for U and V can be obtained by simple calculations assuming you know your texture's dimensions.
1. Find out your surface's UV domain by running the '_Domain ' command
2. Repeat value = domain / texture size

[Boye]

Re: Texturing on really curved surfaces

Wow - impressive. I suspected that some kind of parametric design would be necessary to achieve the curvature after some kind of planar mapping. In 3dMax I might have used modifiers. But it would be hard - perhaps even impossible - to do this in Rhino without using Grasshopper, don't you think?

[smasher_cg]

Re: Texturing on really curved surfaces

thanks visav. You have reopened my eyes, and now I realize I was asking really stupid question
While I'm really interested in you sharing that ghx file I must say I haven't achieved any less results modeling it by just editing a curve and fiting it into position. Actually your curvature is much easier than the example I was giving

Anyway, I have struck another problem which I never needed before:
.- how to use two transparencies on one material? Right now transparency in diffuse is occupied with mask image for the little film holes. I tried adding another diffuse layer, but that did not help. Could it be that vfr supports png in diffuse channel with alpha? I haven't tried that, because I don't think so.

One more problem unrelated to this issue is that my vray keeps crashing Rhino with not so big textures. I mean, what the reasonable resolution is here? I've had jpg file that is just under 1MB and with roughly 1000x300px. Is it vray or Rhino prob? (btw, I've got 4gigs of ram, win764)

thanks guys!

[Visa]

Re: Texturing on really curved surfaces

Wow - impressive. I suspected that some kind of parametric design would be necessary to achieve the curvature after some kind of planar mapping. In 3dMax I might have used modifiers. But it would be hard - perhaps even impossible - to do this in Rhino without using Grasshopper, don't you think?

It is doable, but since Grasshopper is free, why go through all the hassle
When you're working in Rhino, always finish up your modeling before texturing. Rhino's mapping can be a real pain sometimes. Luckily, McNeel's fixing that in Rhino 5.

thanks visav. You have reopened my eyes, and now I realize I was asking really stupid question
While I'm really interested in you sharing that ghx file I must say I haven't achieved any less results modeling it by just editing a curve and fiting it into position. Actually your curvature is much easier than the example I was giving

Anyway, I have struck another problem which I never needed before:
.- how to use two transparencies on one material? Right now transparency in diffuse is occupied with mask image for the little film holes. I tried adding another diffuse layer, but that did not help. Could it be that vfr supports png in diffuse channel with alpha? I haven't tried that, because I don't think so.

One more problem unrelated to this issue is that my vray keeps crashing Rhino with not so big textures. I mean, what the reasonable resolution is here? I've had jpg file that is just under 1MB and with roughly 1000x300px. Is it vray or Rhino prob? (btw, I've got 4gigs of ram, win764)

Sometimes the solution is much simpler than we think .
For multiple levels of transparency, I usually combine the alpha maps in photoshop. And you're right, V-Ray doesn't support png transparency in textures (just tested that).
For the memory problems, I've noticed that often the main memory hog is the meshes, rather than textures. But then again, all bits of memory saved is good. The texture size I ended up in my demo picture was 392x2550, png's with a filesize around 500kB. More on memory management in this thread

And here's the grasshopper definition: http://dl.dropbox.com/u/2274849/Film%20strip.ghx

Oh, I'm aware that the curvature isn't quite that strong in my demo. Grasshopper didn't like it tighter

[smasher_cg]

Re: Texturing on really curved surfaces

thanks a lot for the grass file, I'll give it a look in a sec. edit: Awesome definition! I'm sure I'll have use of it.

And I managed to come up with the solution. I have put no map in diffuse, set the transparency to white, and put the texture into Refraction channel and put IOR to 1. And in there I edited the transparency. Is that the way?

I'll attach as soon as the image renders



p.s.
I am still not satisfied with the parts where the holes should be because it is distorted. And how do you mean combine alpha maps? To have holes AND overall transparency (say at 75%) that would mean I need to export png file, which, again, can't be used as mask?

[Visa]

Re: Texturing on really curved surfaces

thanks a lot for the grass file, I'll give it a look in a sec. edit: Awesome definition! I'm sure I'll have use of it.

And I managed to come up with the solution. I have put no map in diffuse, set the transparency to white, and put the texture into Refraction channel and put IOR to 1. And in there I edited the transparency. Is that the way?

That seems to be physically more correct solution and seems to produce some nice shadows as well .
Looks like we're both learning some new tricks

p.s.
I am still not satisfied with the parts where the holes should be because it is distorted. And how do you mean combine alpha maps? To have holes AND overall transparency (say at 75%) that would mean I need to export png file, which, again, can't be used as mask?

It looks like your film is bending sideways and thus distorting the texture. The key in getting good results using surface mapping is keeping your surface constant width and only bending perpendicular to the surface. (Did that make sense?) That's what the GH script is doing.

Grayscale png files can be used in transparency slots just like any other format. What I meant with V-Ray not supporting png transparency was that if you use a png in eg. diffuse slot, the transparent parts of the texture render as gray.

[smasher_cg]

Re: Texturing on really curved surfaces

Grayscale png files can be used in transparency slots just like any other format. What I meant with V-Ray not supporting png transparency was that if you use a png in eg. diffuse slot, the transparent parts of the texture render as gray.

Oh, wow, didn't put two and two together and actually concluded I could use gray like vrf is using! Well, don't you just love learning new stuff? Thnx again, I'll post my camera scene soon