Mental Ray for Maya 4, HDRI?

[DesignDawg]

Yes, it does indeed support HDRI.

--Although, being a MR for Maya user myself, I would say wait until Maya 4.5 and MR for Maya 1.5. Mental Ray IS --sorta-- integrated into 4, but not nearly as well as it should be. MR 1.5 should be much tighter.


Ricky

[swag]

MR supports map file format it is a floating point format and can be used for HDRI
here is a tool that convert HDR to MAP
http://www.geocities.com/atef912/tools/hdrtoxsi_gui.zip

[DesignDawg]

You can also just use floating point tiffs for HDRI.

Ricky

[wedge]

i've gotten both Floating Point TIFF files and .MAP to render in MR, but they are very dark. How do you increase the intensity? You said somewhere else to use "Color Gain slider" but the color gain slider of the environmentLambert is a color slider, not a number value. The only other number values are Alpha Gain and Alpha Offset.

[EDIT] nevermind: use Alpha Gain and check "Alpha is Luminance"

[wedge]

Created using MentalRay1.5 BETA

[wedge]

Different HDR Image, the one on the right side was altered in Photoshop to show what's actually going on...

[wedge]

Last one... MentalRay is lookin good! Can't wait for the final version!

(and maybe someday someone will write a plugin so Maya will display Floating Point TIFFs instead of giving me that ugly error message)

[alphatron]

Nice Job!

Can you please post your FG settings and some of your material settings?

[dwalden74]

Not sure if U can alter the intensity of floating point images with Color Gain and such in Maya. Usually you would have to make objects more or less radiance sensitive (you use the radiance setting in XSI´s material node, not sure wher it is in Maya, but probably in the material or shape node...?). In XSI any tampering with HDR images in its shading network results in a conversion to 8-bit color depth, therefore a loss of floating point info. Not sure if it´s the same or different in Maya.

cheers-
David

[wedge]

dwalden: yup, so far i haven't been able to alter the intensities in anything but Photoshop.

Alphatron: I used 250 FG Rays, everything else was default, at 640x480 Intermediate. The chrome sphere is a phone that has everything i "Common Material Attributes" all the way down, and Cosine Power, Specular Color, and Reflectivity all the way up.

The red sphere is also phong but with a little bit of red and some diffuse.

the rest is lambert1.

The HDR image is a lambert with the HDR tiff set as it's incandescence.

[dwalden74]

´m not sure you´re going in the right direction. There should be no need to alter the HDR files at all. What you change usually is the way a material is influenced by the HDR image (material´s sensitivity to light). If the HDR image was produced in a correct manner, you should have a very wide luminance gamma to play with (from very dark to blinding light), therfore adjusting color gain or whatever is NOT what you want to do. I didn´t even know you could even open HDR´s in Photoshop (I guess if it´s a tiff file it might work though). However, I´m pretty sure that you´re gonna´ lose all that delicious floating point info as soon as U go tampering with the image. Best advice I can give is to read over Debevec´s site *well*, then use HDR Shop for altering your images (although I can´t remember if you can do any color -correction or whatever with that tool..color correction shouldn´t even be necessary).

cheers-
David

[wedge]

HDRShop is not available for download, Hopefully it will be soon.

[P.S. You can edit or delete your posts by clicking the EDIT button at the bottom-right of each post.]

[alphatron]

The radiance material attribute has been added in mental ray for maya 1.5 for maya 4.5.

[DesignDawg]

Sorry I missed this thread after a few more questions came up. To change the "exposure" of the HDR maps, use the color gain value of the image. It's in the attribute editor under "Color balance." Yes, it's just a slider white to black, but if you click on the color box, you can put in a number for value. You CAN use values higher than 1 in Maya. This value is your exposure value. Try it out. It's true.

Ricky

[dwalden74]

I still don´t understand why you would want to change the HDR image exposure. All the light info you need should be already in there, you just make your object more or less sensitive to it (through its material properties).

:beer:
David

[alphatron]

dwalden74,

Because it's easier to change just one thing, instead of many.

[dwalden74]

OK, understandable, but I´m just not convinced it´s the right approach. It´s like looking for a fast solution to something that actually requires a bit of time setting up. Ultimately, you´ll have to tweak your geometry´s FG/GI reception on a per-object basis anyway, so what do U gain? Unless you´re just doing some simple tests and want to see fast results, fine tuning the shading in your scenes requires a bit of time, care and tweaking, even with HDR images.

:airguitar
david

[S E D A H]

hey wgeddes can you put the wip of how you do a hdri render alll.......where you connect you texture and the settings stuff like that ........ l want all the procedure ....that will be great on mental ray maya.............

[swag]

Here is a tut for HDRimages lighting
http://www.br1.org/2002/postnuke/html/modules.php?op=modload&name=Sections&file=index&req=viewarticle&artid=2&page=1
you can also take a surface shader or map the tiff or map file in the lambert incandescenes channel there are some ways to do it try yourself

have someone experience with MR custom shader how i can do extreme realistic glas or a glow or velvet shader ...
and so on i think MR is very powerful but how we get this power :)

[S E D A H]

thx swag really nice tut

[Gentle Fury]

yes you can do hdri lighting in MR, the only problem is that you have to have the image in the BG, i tried using render layers (which 1.5 is SUPPOSED to support) but all i get it black. All i want is the ability to render using hdri and have a blank BG for compositing purposes! Does anyone know if there is a way to either :

1. Render using an HDR image without having a sphere in clear view.

or

2. Get the damn render layers to work!!! So you can have the sphere in its own layer and turn it off, therefore getting the right effect and nothing in the bg.

here's what i was playing with :) Kind of a cross between a dynamics test and a MR test :) There arent any lights in the scene.

Happy Rendering!!!

[alphatron]

Simple solution Gentle Fury,

You just turn visibility off in the sphere's mental ray attributes. Works perfectly.

[Gentle Fury]

Hell yeah, that is awesome...........now i can start working on a lil comp project i wanted to do :)

[kfc]

MR for Maya.
really good stuff. I've rendered this image just now with HDR maps. it takes me about 19 minutes on dual P4 xeon 1.7 with 1 gig rams.
I still thinks it's rendering speed is kinda slow. maybe they should improve on this field. u know, it's much slower than FR.

Happy Renderings!

[Gentle Fury]

Mental Ray tends to drag a lil, but for good reason. It actually calculates the way light bouces.....it doesnt fake it like all the quick programs.......the cool thing about it however is that you have so many options to tweek you can speed it up considerably by using default GI accuracy and a lower FG and still get some nice results!

Mental Ray Rules!! The DOF and MO-Blur is the bomb too!


Happy Rendering!!!!

[Gentle Fury]

Here is an image i just rendered out of MR using HDRI for lighting and reflection:

http://exurostudios.com/render_tests/image_lighting_truck.jpg

http://exurostudios.com/render_tests/image_lighting_truck_rear.jpg

http://exurostudios.com/render_tests/overhead_truck.jpg

The truck has no textures yet at all, just colors....and i havent even tweaked anything yet! Thats my first render out of that scene!!! Again i say! Mental Ray RULES!!!!!

[Mikkel Jans]

How long time did it take to render?

[dwalden74]

Hi Gentle Fury-

I would suggest turning up the radiance on the truck´s materials...it´s still very flat looking and many details are lost in the darker areas (wheels, underside, etc.). It looks very CG IMHO, and not very "dynamic". Even using an HDR image for lighting/reflections, you still always have to tweak your materials values (I think I said this earlier...)

:beer:
David

[lilgit]

if you have a reflective object and it is reflecting an hdri enviroment (or has enviro mapped to it)..an image of some windows lets say... if you wanted to boost how much light appears to be coming through those windows, to the point where the white light is covering the window frames and is a dominant bright white in the reflections....is this not adjusted by using the hdr map's colour gain setting in the material editor to set its exposure ?

setting the reflective object material sensitivity to the reflections sets them overall and cant edit this exposure effect

i understand the new radiance material setting in mr 1.5 boosts the overall light a material casts in final gather, and has nothing to do with exposure or hdr specifically.

[dwalden74]

hmm, good question. I'm not sure about this. Will the color gain boost only the most luminant areas? The thing to remember about HDR, is that it's not really what you see in the HDR image that represents the amount of light contained within. You can visualize HDRI's under different exposure settings, yet these settings don't actually change the information in the image itself; it's just a different way of viewing the floating point data (lowering or raising the gamma to "see" finer detail in blown out areas, for example).

XSI, for example, has no color gain parameter, and as soon as you color correct that HDRI you reduce the bit depth to 8-bit, therefore you don't usually want to do that. The materials have a radiance setting, which makes them more or less effected by FG/HDR calculations depending on the value. So if you wanted to boost the amount of "appeared" light in the reflections, you would probably increase the reflectivity of the object, then see if the radiance setting needs to be adjusted. I haven't played around much with HDR in Maya, so I'm not sure if Maya's settings allow alternative possibilities in adjusting HDR receptance.

One thing just occured to me however: in XSI you can mix the HDRI with, for example, a constant black (or whatever) material in order to increase/decrease the amount of light emitted by your HDRI-mapped object. This may be analogous to ajdusting color balance/color gain in Maya (but I don't think so). It is the same thing as using a blend node in Maya to blend between an HDR image projection and another node of your choice to get the final color/luminance output of your environment sphere, or whatever object you use as a FG light emitter.

:beer:
david

[Gentle Fury]

Originally posted by dwalden74
Hi Gentle Fury-

I would suggest turning up the radiance on the truck´s materials...it´s still very flat looking and many details are lost in the darker areas (wheels, underside, etc.). It looks very CG IMHO, and not very "dynamic". Even using an HDR image for lighting/reflections, you still always have to tweak your materials values (I think I said this earlier...)

:beer:
David

Thanks :) But as i said i havent done anything by way of texturing yet...........just flat shaders with color added and reflectivity on :) it was just to test out HDRI in MR......but thanks for the comments...

Oh, and it takes like 1.5 mins to render a frame........not too bad for a GI, Final Gather image with lots of reflectivity......and production quality anti-alias.


Happy Rendering!!!!

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