Mental Ray - Shaders

[DBKenn]

I have issues with doing scenes at real world scale. I’m a graphic designer and I’d like to beable to render package designs. Thats the paper rendering questions. Anyway, say if I hand an object that in real life is 2 ft x 2 ft. In the viewport it clips. I deal with real scale for a few number of projects because I do things like game design and stuff. I use real world scale because I read, or someone told me to do it that way for rendering. Use mm for lights and what not for Mr.

and also any more on rendering realistic paper materials/ packaging. Thanks.

[ienrdna]

I have noticed that using low values on fast misss shaders produce nasty artifacts. Only way I found to get rid of them is make lightmap 300% of rendersize and that creates killer render times. Are there other ways to deal with them?

[joske]

Yes. Physically incorrect “object lights” is trivial to implement (mental ray has had them for a long time)

Physically correct “object lights”, that does not mean “bring the noise” are very difficultto implement. And at least for max, the product designers do not want to introduce features that at least can be used physically correct.

You can do object lights in max with the francesca geo shader trick, but you’ll quickly see it isn’t terribly useful and more gimmicky than an actual useful tool. Either you have a non physical falloff (like linear, or none), or the noise leveles (or render time, to combat them) are prohibitive.

/Z

a workaround for square shaped ‘object lights’:
bin doing some testing with the new skyportals
one could use them as glowing light squares in the scene
ad a little glare and voila, instant neon light object…

• they transmit photons!! ok there’s no physical correctness any more, but you can make it look great
  here’s a testrender with a skyportal on the cieling (and also one in the window)
  

[MasterZap]

a workaround for square shaped ‘object lights’:
bin doing some testing with the new skyportals
one could use them as glowing light squares in the scene
ad a little glare and voila, instant neon light object…

• they transmit photons!! ok there’s no physical correctness any more, but you can make it look great

Actually it’s completly physically accurate, and the portals are explicitly written to be able to double as light cards!

1. Open their “advanced” rollout and set their “source” to “Custom map” but don’t actually put in any map (It’ll default to “white”)
2. Make it “Visible To Renderer”
3. Now “muluiplier” can be interpreted as a cd/m^2 luminance value - crank it up!
4. Add glare, as noted above for a neat look.

Bingo, physically correct low-noise photon emitting light card shader.

/Z

[joske]

SWEAT !

[simmsimaging]

and the portals are explicitly written to be able to double as light cards!

Thanks for that - they work great! I have two questions about using them though: would it be a good rule of thumb to also use them to replace other types of area lights as well as light card materials? They seem to render cleaner and faster than other illuminated mats and area lights. Also - is there a way to build in a gradient so they reflect/show up in renders as a softer edged square - more like a real light box might? I tried grad maps in the “custom” slot but they just show up as solid anyway.

Thanks in advance
b

[machadoj]

I would like to know how to edit my “base.mia” in Max.

I open the file, do the necessary changes, and when I go to save the Windows Vista doesn’t allow me. I do the changes in Note pad, but can’t do the saving one.

Thanks in advance.

[JeffPatton]

Is it marked “read only” by windows? If so you should be able to right click on the file and un-check read only and then save the file (assuming that’s the problem and not something in Vista).

[machadoj]

No, it’s unchecked “read only”.

I was trying to make the changes you’ve pointed in your blog about:

• 3ds Max 2008 Portal light tip-.

I don’t know what to do…would it be possible sending me the “base.mia” file already modified?

Thanks again,

Jomar Machado

[machadoj]

sorry…

[machadoj]

sorry…

[machadoj]

Sorry triple posts…Maybe my connction is out of order too.

[dave-3d]

a very simple and quick light solution (Jeff’s asphalt material used here). Basically one point light inside each light, with a glass mesh covering the light cone itself and mudelled to have a slight texture in it. Not very real, but again, it’s an example of how common sense can work.

That is the way I basically did it a while ago on a little test using the glare lume (also looks like jeff has done something very similar for the damp patches on his asphalt). I used a standard MrSpot for lighting - no FG or GI. The glare was just used to glare the light bouncing around - no added diffuse textures to the glass material on the lenses, just glass. I’ll need to post this scene file when I dig it out … think I was using max 8.

Animation is on my website : http://www.dmmultimedia.com/3dtips_04c.htm

Dave

[MikeBracken]

Also - is there a way to build in a gradient so they reflect/show up in renders as a softer edged square - more like a real light box might? I tried grad maps in the “custom” slot but they just show up as solid anyway.

You can add the gradient (or whatever texture) ,then drag into the mat editor, then change the mapping to “planar from object XYZ”.

Regards,
Mike

[simmsimaging]

You can add the gradient (or whatever texture) ,then drag into the mat editor, then change the mapping to “planar from object XYZ”.

Great - thanks!

b

[simmsimaging]

You can add the gradient (or whatever texture) ,then drag into the mat editor, then change the mapping to “planar from object XYZ”.

I don’t seem to be doing this correctly, but not sure what is wrong. It either renders as black, doesn’t show at all, or goes black and I get Mental Ray errors popping up. I’ve tried all the mapping options and no joy (world xyz, object xyz etc) and I’ve tried using gradients, HDRI loaded as bitmaps, etc. Just for the hell of it I even tried putting a UV Mapping modifier on the sky portal light but that just crashed Max

You’ve been able to get this to work?

Thanks,
b

[MikeBracken]

Yep, it works fine here. I used a gradient , an american flag texture, and a couple other maps.
I will try to post a screen shot tomarrow.

Regards,

Mike

[simmsimaging]

I will try to post a screen shot tomarrow.

If you have time that would be appreciated. I’ve had no luck at all putting even an HDRI in the custom slot and having it affect the sky portals reflection/ direct render.

b

[MasterZap]

Is it marked “read only” by windows? If so you should be able to right click on the file and un-check read only and then save the file (assuming that’s the problem and not something in Vista).

Nah, it’s vista insanity. You have to start notepad as administrator with that “run as administrator” thingamabob. At least that’s what I had to do (only I use visual studio, not notepad, so maybe you need a powertool like visual studio to edit a text file in Vista… gak)

/Z

[drdubosc]

I’m looking for ways get a shader to isolate projecting convex edges, corners, as a base for wear and tear, burnishing, other effects.

( I can’t get Tom Cowland’s tc_curvature shader to work. If somebody could point me towards info on how to write .mi flies for 3ds, that would be great.)

Got this far by baking an AO map of the object with its normals flipped, and applying the map to the right-way-out version, using it as a blend mask. It’s a bit laborious… Has anybody written this ‘flipped AO’ as a regular shader?

Is this reinventing the wheel? Perhaps there’s a better way?