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charliedz
05-08-2009, 08:58 PM
hello all...

having some issue pulling off an effect with mental ray in maya.

i'm trying to create an effect similar to the one shown below where i have a white plastic surface with a lcd display shining through.

i created the lcd text as a surface and put it behind the plastic. how do i make the lcd display illuminate light? do i assign a surface shader in conjunction with final gather? thats what i tried right now, and its not working.

as of now, i've assigned a plastic material / blinn materia to the main surface and turned transparency a bit up. the text is another blinn material with the "glow intensity" in special effects turned up. it doesn't seem to be quite working. the glow intensity does not come through at all, and the color and effect of the text is muted if not eliminated by the main surface.

the first image is how it turned out, the 2nd image is with the main surface removed.
here is the link to original file.
http://www.geocities.com/dzjunction/render_alarm_2.mb.zip

thoughts / ideas? :confused:

thanks

http://www.geocities.com/dzjunction/lcd_display.jpg

Galakgorr
05-08-2009, 09:12 PM
the "glow" you're thinking of is less glow and more translucency... the LED display is behind a translucent plastic overlay

since glow is a post effect, it won't show up if another surface is occluding it. it's not really emitting any light as far as maya is concerned.

make the LED display a surface shader or some other simple shader with ambient color channeled into it (to make it self-illuminating.) then make the plastic surface above it a slightly translucent material.

you'll also get much better results if you use mental ray's mia_material... the transparency/translucency options are much better than anything you'll get out of maya's software shaders.

MAV4d
05-08-2009, 09:14 PM
always do the glows in post... its much easier and looks much better


what i would do is assign the mib light surface and let FG calc the light. or a red shader with the value turned up past 1 (hsv)

-Mike

MAV4d
05-08-2009, 09:15 PM
also that reference picture you posted looks more like subsurface scattering than transparency

i guess you could just blur the refractions a bit to get it fake sss

charliedz
05-08-2009, 09:27 PM
yikes! haha, i will def try to tackle these concepts this weekend. thanks for explaining that glow is a post effect, i was wondering why it didn't see it till the end of the rendering computation.

MAV4D, what do you mean "do the glows in post?" im not sure i know what a post process in mental ray refers to.... i thought i just assign proper materials / shaders then lighting and thats it.

also, concerning subsurface scattering, if i were to attempt to go down that path instead of a simple translucency, where/how would i start that?

thanks!

Galakgorr
05-08-2009, 10:53 PM
i don't recommend using SSS in this case because scattering only responds to lights, so if you wanted the scattering to originate from the exact shape of the LED display, you would have to make your LED display a light rather than just a mapped surface. that could be kind of a pain. plus, it's more expensive to render.

try using a mia_material_x as the white surface, and play with the transparency/translucency settings. translucency is calculated as a fraction of your overall transparency, keep that in mind when you're setting values. also, the refractions become important here... try playing with the glossiness value of your refractions to adjust how fuzzy the image showing through is. and make sure your translucent shader is set to "thin-walled."

since that top layer is translucent and refracting, you'll need another layer behind it, which would be where the majority of the white color is coming from. so your layers would look like this in cross-section:

-----------translucent plastic coat-------------
//////////////////////////////////////////////////////
-----------LED display-------------------------
//////////////////////////////////////////////////////
-------------solid white plastic-----------------

anevsky
05-09-2009, 02:49 PM
use the layering as Galakgorr describes at the end of his reply.

Adding glow in post - means you emphasize or add the glow not in the rendering but in another application after (post) the rendering is done. If your doing stills it would be an image editing software - or if you are rendering animation - a compositing app like after effects \ shake \ nuke etc.

You can render out only the text part - and then in another software use that layer to add glow to the text in your rendered image. this could be done either by selecting through alpha or color selection. This is the best way to control things like glow \ transparency.

Personally I often use an RGB pass where I assign a surface shader with solid color (red, blue, green, yellow etc.) to objects I want to tweak in post. I later use this pass in my compositing app by making selection \ keying particular colors and thus particular objects can be tweaked and color corrected without affecting the rest of the image.

charliedz
05-09-2009, 04:43 PM
thanks guys for the responses.

i've been working on this for hours, and i feel like i'm getting nowhere. i should mention that this is my first time working with shaders / materials / mental ray. and so im trying to figure out so many things at once. :hmm:

Galakgorr...
im trying your strategy and the results im getting are below. as you can see, i'm grossly botching something up.

the top layer is mia_material_x, and set to full translucency, and 0 transparency. (there are a lot of options in mia material, and i've tried a lot of different things without knowing what many of them really do..., and nothing seems to make it right)

the LCD display is just a BLINN shader thats red (HSV) with the V set to 2

the back layer is just a generic white plastic shader

the 1st image is with the top plastic layer (translucent layer) removed, just to verify what the lcd and back layer look like.

the 2nd image is with the top layer on. i can't seem to get anything to show through (barely) unless i have the transparency almost maxed out. and when doing so, the back plastic surface looks black instead of white :curious: all my colors are white in the MIA material attribute settings, so im not sure why its black.

---------------------------------------------

anevsky

what is an rgb pass? and if i understand the post processing workflow, in my case i would render a separate rendering of only the LCD with nothing else in the scene. then add glow to that, and use the result of that as an additional layer on top of my initial rendering?

--------------------------------

i've included the orig file if there needs to be any diagnosing. i'm sure that whatever i'm messing up is probably extremely basic. i think what i'm trying to do is suppose to be very basic. i've gone through lots of various dvd tutorials, etc... but none of that really matters when it comes time to do your own specific projects. aye

(http://www.geocities.com/dzjunction/render_alarm_3.mb.zip)
lcd_mental_ray.zip (http://www.geocities.com/dzjunction/render_alarm_3.mb.zip)

again, definately appreciate the help.

thanks

Galakgorr
05-09-2009, 10:02 PM
hello again

checked out your scene... here's what i noticed right away.

the blinn you're using as the LED display shader wasn't giving off any of its own light... unless you put some value into the Ambient Color channel, a blinn isn't going to be self-illuminated, which an LED display definitely is. so switch that to a surface shader, or a mia_material with a non-zero value for "additional color."

next, when using the mia_material, remember that translucency is a function of transparency. when you move the translucency slider, you're deciding what percentage of your transparency is going to be translucent. so for translucency to work, your shader needs to have some transparency. the blackness you were seeing behind the display is because your non-transparent surface was casting a shadow!

i threw together a crappy example to show you how i set things up. the LCD is a surface shader, there's a transparent plane in front of it with a slightly refractive translucent coating, and immediately behind it is a white plastic surface. this surface is set to "thin-walled" under the advanced refraction tab, so it acts as if it has some width to it even though it's a flat plane.

the documentation on the mia_material is, oddly enough, really good. you should read it.

as far as an RGB pass... it's just a separate render layer where you assign surface shaders of pure red, green, and blue assigned to different objects that you want to be able to edit in post. assign a black surface shader with zero matte opacity to everything else. then in after effects or shake or whatever you can use the red, green, and blue channels of that image to act as mattes for different effects, like color correction or blurs or whatever.

charliedz
05-10-2009, 03:33 PM
galakgoor,

thanks. been chuggin along and here's what we got. using the multilayer method of a transparent layer on top causes a problem.

you can see through to the back surface which is very noticeable on the right side as seen in the 1st image.

i tried moving the back surface forward, but when i do that, you lose the refractions and blurs of the lcd as well as causing artifacts along the bottom. (2nd image)

the real surface i am emulating doesn't have a transparent layer and seems to just illuminate through a relatively matte plastic surface.

so, i made the top surface a plastic again, the same as the back surface, and added incandescence + ambient color. i turned up translucency very high with some transparency and here is what i get. its looking closer to desired result except for,

1. the shadow that the top layer is creating and made visible by transparency.
how can i eliminate that specific shadow?

2. you can see some artifacts on the surface towards the right. this seems to result from making the translucency weight less than 1. if i make it 1, the surface looks clean, except the lcd digits come out really blurry, so there needs to be some translucency.
any idea how to avoid such artifacts?

lcd_render.zip (http://www.geocities.com/dzjunction/render_alarm_3.mb.1.zip)

thanks

Galakgorr
05-12-2009, 05:20 PM
if you need to eliminate shadows, you can always just tell your transparent object not to cast shadows. it's in the attribute spreadsheet. or tell the object receiving the shadow not to receive shadows.

the artifacts you're getting towards the right, looking at the third image you posted, are due to glossy reflections/refractions on the surface. increase your samples for one, or the other, or both. if your glossiness value is less than 1.0 for either of those values, you need to worry about how many samples you're using in order to get a clean result. 32 is usually a good amount to work with, although for some situations you might need to go higher.

charliedz
05-14-2009, 03:53 PM
galakgoor,

sorry for the very basic question, but where do i set the samples?

is it the min / max sample level setting under "raytrace / scanline quality" in render settings?

thanks!

Galakgorr
05-14-2009, 08:28 PM
glossy samples are shader-specific, they are in the attributes for each mia shader, one for glossy reflections, one for glossy refractions

in the help files there is extensive documentation on all of these settings, look under mental ray > architectural guide

Hehud
05-15-2009, 08:54 AM
By using the mia_material_X with additional color and AO color bleeding

need some adjusments but that work...
and put a mia_material_Thin glass(preset) on the first surface

Is well explain on the autodesk website maya section (with video by the way )

hope that help...

charliedz
05-16-2009, 10:34 AM
huhud,

thanks for the suggestion on an additional method. i'm really learning a lot.

so i'm working on it now and have a couple more questions.

1. i've turned on AO, and simply giving the ambient light the right color already produces a close result. can you clarify or explain whats going on? how is this different from using a BLINN with ambient light turned up? i have a very basic undestanding of AO. if i undestand correctly, AO creates dark and light areas based on the distance between objects. so is that use of AO coming into play here, or was using AO only a way to get ambient light within a mia material?

2. concerning color bleeding. thats where reflected colored light is reflected back to a lighter surface. but when you suggested that, did you mean that using AO would automatically create color bleeding, or is there any extra steps to actually create that effect?

3. lastly, possible to link me to the video about mia_thin_glass? i didn't see any mia material_thin_glass preset or material in maya 2009 / mac. i only saw a regular mia_material with a thin option. i also searched maya help in autodesk site and found an explanation about regular mia_material with thin wall option. is this is?

but was unable to locate any information about thin_glass or a video.

thanks! :cool:

gfx3d
05-16-2009, 03:08 PM
:thumbsup: :arteest::applause: thanks for all explanation

Hehud
05-20-2009, 02:49 PM
http://usa.autodesk.com/adsk/servlet/item?siteID=123112&id=9974388

here some couple of video and the last one is dedicated for the mia material

the thin wall is on the mia material

the color bleed is on the mia material_X only with color bleeding option

Blinn is good but simple Mia is complex..

for most of the mia material there some preset on the top Right part just choose the one you want glass chrome metal that help

hope that help...

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