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View Full Version : Still life - need suggestions to get more realistic shaders


mjay85
11-28-2010, 03:28 AM
Hello everyone! I started a still life project a little while ago. The idea was to recreate a scene similar to a beautiful photograph I saw by a photographer named Cy DeCosse. Its an extremely simple scene of some lemons on a burlap background. Since that is all it is, shading and texturing are extremely important. Alex Roman just came out with a new piece that has quite a few lemons. After looking back at mine, they need some serious help.

This was created in Maya 2009. I am rendering with Mental Ray. I am using the mia_material (the newest iteration). http://michaeleurek.files.wordpress.com/2010/11/lemonnnn.jpg
Mine look completely plastic, but I cannot figure out what to change about them. It seems like the reflection is too harsh, perhaps it needs to be more diffuse? The normal map also seems to looks a bit strange. I also noticed that lemons tend to look more saturated away from the highlight. I'm am not sure how to recreate that with the shader.

Any suggestions are appreciated.

frossi
12-03-2010, 09:49 PM
First of all, I like the light intention, i think its good. About the shader, are you using a specular map, that would really help with reflections, remember in real life nothing is even, the reflection varies according to humidity of the surface, worned out edges, etc.
Second i would suggest appliying some SSS to the material, and some color variation, you can do this using a a fallof, using a texture or making it in post. The tip of the lemon, need also color variation and a lot less glossines, it looks too plastic, i think that is the main issue.

Hope that helps, still i think is a really good render!

apsteele
12-04-2010, 04:42 AM
Much like frossi, I too really like your lighting; I particularly like the contrast and the bounce lighting along the bottom side of the lemon is wonderful.

You have mentioned your observation of a lemon's saturation in relation to highlight, and you are correct. This is due to subsurface scattering (as frossi has also suggested). Also being a mental ray lighter, I am fond of a technique in which you plug a miss skin shader into the additional color of a mia_material_x. If you turn off the diffuse and turn down/off the specularity (depending on your subject matter), you are able to integrate the wonders of SSS into the convenience that is the mia_material. I suggest doing a quick google search of this, for there are an array of articles and suggestions regarding this technique that are sure to inspire!

You also mention how your normal map looks off; I think this may be a scale issue. If you look here (http://www.google.com/imgres?imgurl=http://gregbardsley.files.wordpress.com/2008/07/lemon1.jpg&imgrefurl=http://gregbardsley.wordpress.com/2008/08/01/i-give-to-you-guacamole-gregorio/&usg=__6nyHscUSSCVte6CPFow3TTZ-Q4M=&h=809&w=800&sz=76&hl=en&start=0&sig2=PFs-wV9gLkAYKUOM83gneg&zoom=1&tbnid=4tCFprDOl85BdM:&tbnh=149&tbnw=132&ei=w9H5TL2RNsGclgfu3ZG_Bw&prev=/images%3Fq%3Dlemon%26um%3D1%26hl%3Den%26client%3Dsafari%26sa%3DN%26rls%3Den%26biw%3D1440%26bih%3D764%26tbs%3Disch:1&um=1&itbs=1&iact=rc&dur=385&oei=w9H5TL2RNsGclgfu3ZG_Bw&esq=1&page=1&ndsp=29&ved=1t:429,r:3,s:0&tx=84&ty=66) at this example of a lemon, you can notice that the valleys and peaks that you have in this map are not quite as large or deep as you have. However, I feel that what you have is still useful! Perhaps with less depth (and in addition to another map that should provide those nice, pinpoint pores across the surface), you can use this map to continue to break up the spec (which as is doing splendidly so far).

My last little tidbit is concerning the spec. What is there right now is great! There just needs to be more of it- I would like to see it 3 or maybe even 4 times larger. Again, is you look at the afore mentioned image, there is a nice spread to the spec that falls off along the edges. This would be fantastic to see in your render! Perhaps toy around with a bounce card with a white surface shader to really push this.

All in all, I think you are on a great path! I love the composition and light setup you have so far. I am interested in seeing how you progress :)

-as

MinaRagaie
12-04-2010, 06:49 AM
What I think is missing in order of importance...
1- SSS. Focus on softening the terminator of the light (the line between the parts where the object is lit and where it's hidden from the light)
2- Specular component. Either use area lights to produce bigger/softer specular or place a white card and use glossy reflections on the objects instead.
3- Use a bit more saturated colors on your bounce lights.

Hope this helps

kanooshka
12-04-2010, 03:30 PM
I would suggest looking at a photograph of the subject especially if you can find some in similar lighting condition.

This first image here is purely a material and texture reference:

http://hungrycaterpillar.files.wordpress.com/2007/08/lemons.jpg

Notice how the coloration changes to more of a green color near the end of the lemon. Also notice that the small dimples all over the lemon are actually a little darker inside.

Then theres this image you can use as a lighting reference:

http://farm1.static.flickr.com/206/512269687_aa4444973b.jpg

Notice how broken up the specular highlights are. Also notice how the lemons have much more red in them while the image you created is more green. Softening the terminator with SSS as Mina mentioned would help push this further. Also notice the reflections between each lemon as well as the bouncing of light between lemons.

Hope this helps you out!

mjay85
12-04-2010, 09:55 PM
Hello all, thanks so much for the replies! They are all quite helpful.

To build on your comments (with some more questions :D ) I don't think I added a spec map in the above render. Well, I was using the mia architectural shader, and there isn't a spec control, so I tried to make a reflection map. I don't think I understood it properly as it wasn't turning out correctly.

I'll rework my diffuse color map, as the color variation I added is barely noticeable. I'm unsure how to add SSS to the shader. Should I just be using the mental ray SSS shader? I am still learning a lot about shading as you can tell.

I really appreciate the help all, thank you.

Redsand1080
12-04-2010, 11:19 PM
I posted about the shader network I used to create the orange in my portfolio. Not the exact same as a lemon but a lot of the shader set up should be similar. Just click on the image in my portfolio and scroll down and you'll see it. Maybe that might give you some ideas? Just a thought.

-Justin

Kev3D
12-06-2010, 03:15 AM
Wow, Justin, that orange is very nice, I'm impressed that you were even able to get the realistic imperfections in there just using procedurals.

Michael, this project can be very helpful in learning more about the mental ray shaders.

Because the mia_material is trying to be physically accurate, it doesn't have a specular control but instead has a 'glossiness' parameter. Turn this down to get softer reflections. This would be more suitable for lemons.

Furthermore, have you looked into a linear workflow, that can be very helpful in achieving more realism.

Justin's screenshots may look really confusing but I there's a ton that you could learn from them.

mjay85
12-07-2010, 05:43 PM
Thanks again everyone for the responses. I added the SSS shader to the additional color node and instantly saw a great improvement. I have been super busy at work so have unfortunately been unable to work on it.

Apsteele, thank you for the very thorough response. I am going to read up more about the sss technique suggested. I played around with my normal map as well, and I think the main issue is that I did a really bad job unwrapping the lemon. I created a new tileable normal map, but it looks really odd when applied to my current UV set. I have never figured out the best way to unwrap a round object like that, but I am almost tempted to just simply do a straight on projection (since it will not be an animated scene). If anyone has better suggestions, I am happy to learn :D

Being new to lighting ( I am a trained animator), I am unfamiliar with things like white cards or their purpose. Is it a plane with a flat white shader for reflections? Can someone explain a typical scenario when using that?

Justin, that orange is fantastic! I am also quite amazed that everything was created with procedural textures. It is quite inspiring! The shading tree is quite confusing, but I have taken a little bit of time to try and understand it (it is a slow going process :D )

Kev, yea, I chose to do this project for that very reason. The scene is very simple, with few elements, so I thought it might be a good 'starter'. I am unfamiliar with a linear workflow, but I will try and find some information about it. Thanks for the suggestions. I'll post an updated wip shot soon.

Thanks again for taking the time everyone.

- Michael

MinaRagaie
12-08-2010, 06:49 AM
I am unfamiliar with things like white cards or their purpose. Is it a plane with a flat white shader for reflections?
Yes, but nothing is stopping you from adding a texture to it although in most cases (including yours) that is not needed. you typically place them near the Key lights

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