Studio rendering in mental ray

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Old 06 June 2013   #1
Question Studio rendering in mental ray

Hi everyone. I am not new to 3ds max, but I am kind of new in terms of lightning and rendering. I have a problem that has been torturing me for the past 3 days and I was hoping I could get some help here. I've googled almost everything that I can think of to no result.

I am trying to get some realistic renders of a model I've been working on, therefore I am aiming to use photometric lights with mental ray. However, as soon as I switch to photometric, the decals on the model turn black. I've tried adjusting the exposure controls, light values, even the materials themselves, but it seems that nothing I try gives results. Here are the examples.

Rendering using standard omni with mental ray and no exposure:

Notice that the BEKO logo is dark blue (How it should be).

Rendering using photometric light with mental ray and photographic exposure.

The BEKO logo, as well as other elements are rich black.

I've uploadeded some snapshots of the settings I am using in case this helps:

I am using 3ds max 2011 with final gather preset to medium.

Every bit of advice would be very much appreciated. Thank you for your time.
 
Old 06 June 2013   #2
Mental ray material? Why? Try with Arch&Design.
 
Old 06 June 2013   #3
Composite alternative

Hi blank000,

The Mental Ray material was the only solution I could find that would let me setup the decals the way that I wanted them. If I just setup the composite material on the diffuse slot (as most people advise), then the decals would inherit the parent material properties (reflection, bump, etc.) and I don't want that.

I will try to find an alternative using the Arch&Design.

Thanks for the suggestion.
 
Old 06 June 2013   #4
Your environment and effects settings aren't helping. How did you come up with these? If you're not going to use an environment map for reflections (where you have "brushed_metal.jpg - but "use map" is unchecked), and instead go for pure white like what you have set then at the very least you need to check "process background and environment maps"; otherwise, you get a straight white reflection on your reflective objects completely washing out their colors. Next, under Image Control, the midtones are turned down to 0.1 so even if the object color wasn't washed out under the white reflections, it has no output, or only a tenth. Bump this back to 1.0 and if you're going to adjust, make small incremental adjustments... maybe 0.1 or 0.2 at a time.

Once you get that fixed up, the next thing you're likely to run into is gamma problems. How are yours set? I can't tell from your material editor screen shot, but what is dictating your blue color: a color selector, or a bitmap of some sort? Your gamma settings can affect the color too, so do some research on that as well if you're still having issues getting the blue you want.

Also, check out the Blend material... it's magical.
 
Old 06 June 2013   #5
Originally Posted by LiveVertex: The Mental Ray material was the only solution I could find


Either way, you can't just plug in a texture in Mental ray material and be done with it. You must have a surface shader and work from there. Look here:
http://docs.autodesk.com/3DSMAX/15/...mber=d30e379797
 
Old 06 June 2013   #6
Composite alternative

Quote: Your environment and effects settings aren't helping. How did you come up with these?

I came up with the environment and effects settings by trial and error. I don't intend to use an environment map. The image you see there is just a leftover. I took your advice regarding the exposure settings and gave it a try.

Here are the new settings:


However, that didn't seem to do the trick.

Render with photographic exposure control:


Render with logarithmic exposure control:


Therefore I've noticed that the problem occurs only when using the photographic exposure (Notice that on the logarithmic exposure render the colors are there. I've added the Ubuntu logo as an example), which is a real bummer because I really like the realism it provides.

Lastly, I've created a standard material and added a bitmap shader with the Beko logo on the diffuse slot and this is the result (with Photographic exposure):


The colors are there, which leads me to believe this has a lot more to do with blank000's suggestion regarding the mental ray material:
Quote: Either way, you can't just plug in a texture in Mental ray material and be done with it. You must have a surface shader and work from there.

This the way it's currently setup:
Mental ray -> On the shader channel I have a composite map -> On the bottom layer inside the composite I am using the material to shader (which has an arch&design setup to give the white paint) and on the top layers I am using bitmaps with masks to add the decals (Beko logo in this example). The blue color is dictated by the image.
I also had a lot of headaches when setting up the decals on the model. As mentioned above, I don't want the decals to inherit the reflectivity and other properties of the parent material. Using mental ray seemed to work perfectly until I started playing with the environment effects.

Is there a correct recipe for adding decals ?
rox44, I will try with the Blend material as you suggested although it's not quite clear to me how I can use it to add multiple decals. Thanks for the advice.

Thank you for all your help.
 
Old 06 June 2013   #7
Originally Posted by LiveVertex: This the way it's currently setup:
Mental ray -> On the shader channel I have a composite map -> On the bottom layer inside the composite I am using the material to shader (which has an arch&design setup to give the white paint) and on the top layers I am using bitmaps with masks to add the decals (Beko logo in this example). The blue color is dictated by the image.



Unfortunately, i am not a Mental ray material expert, so i can't help you there, but i can say if it's not working you're doing it wrong
You're trying to plug in an composite map in surface slot. That wont work, doesn't matter that somewhere in that composite you've put a "material to shader". Surface slot must have a surface shader.

Quote: Is there a correct recipe for adding decals ?


Plane decals are easy, but you need different material properties on them. You have two options.
- Use completely different geometry for decals. Create a plane and place it crazy near to where it's supposed to be. Unless you have super closeup no one will notice. Use cutout map, and go nuts with materials.
- Or, as rox44 suggested, use blend material. Set up one material for decals, another one for machine. Determine where is which with a mask (you'll have to unwrap your model). Also, you can have a blend within a blend, we need to go deeper
 
Old 06 June 2013   #8
I suggest you use something like Arch/Design shader and copy the composite material in to the reflection level slot. This will make the decals non-reflective and keep the colour.

You can also use it in any material along with Mask to knock out any area you don't want to be reflective.
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Old 06 June 2013   #9
Originally Posted by LiveVertex: I came up with the environment and effects settings by trial and error. I don't intend to use an environment map. The image you see there is just a leftover. I took your advice regarding the exposure settings and gave it a try.

However, that didn't seem to do the trick.

Sorry to lead you astray... I was testing on 2014, and now at the office I can test on 2011 and sure enough, colors don't go completely black like they do in 2014, which seems to confirm that it's the use of the mental ray material. Objects will render completely black if there are errors in the materials applied to those objects. Your new teapot test with standard material renders properly... time to pull the plug on the mental ray material.

As you can see from Dario's and Dan's posts, there are several ways to get similar results. The blend material might be overkill for straight flat printed decals/stickers, but I like to use it because it's very flexible, allowing two completely different materials (standard, a&d, mr, etc) with completely different looks (color, reflectivity, bump, etc) interacting with whatever mask map you can dream up. For your BEKO logo, make a blue material (is it metallic, or have glossy/blurry reflections - you make it how you want) and drop it in one slot, use your white paint material with sharp reflections in the other slot, and place a black and white of the BEKO image file in the mask slot. If the letters come out white on blue, then swap the order of the two materials or invert the mask map. Nest this material into another blend material for another decal, or maybe a better idea would be to use these materials in a multi-sub object material if you were planning to do several. I also like the composite map since you can add numerous decals with one map, but it does have its limitations as you are discovering.

In the end it's probably 6 in one half dozen in the other... just depends on your workflow and what you're more comfortable doing, and how detailed you want to get.
 
Old 06 June 2013   #10
Thumbs up

Thank you for all your help rox44. I've played around with blend and it works. I found it to be easier if I rethink my textures in an attempt to avoid nested blend materials. I am unwrapping the object and using blend with the unwrap texture. Then I apply UVW map to tweak the position. It works great.

Here is one render:


Of course, I still have to do a lot of tweaking to the exposure and lights, but the materials work.

Thank you all for your help.
 
Old 06 June 2013   #11
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