HDRI

# 1 05-02-2003 , 07:03 AM

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Well, I'll go make a very simple model in the next hours and I have decided that I want to use mental ray to illuminate the scene with a hdri image. And use a HDRI for reflections.

I have no idea if this works for me, but I want to try. I'm figuring that the results will be top notch. user added image

Stay tuned.

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# 2 05-02-2003 , 08:28 AM

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There are some hdri images at www.debevec.org if you want to take a look.

Kari
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# 3 05-02-2003 , 09:35 AM

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Step 1

Yup

been there.
Actually there are few free HDR images around, it seems.

But I'll use the ones I found on one of those sites.

The model is done. It is a 100% nurbs pen.

Here's the wireframe.

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# 4 05-02-2003 , 03:05 PM

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Can't wait!

Can you post your results including settings, and rendertime?

Cool, thanks!

Israel "Izzy" Long
Motion and Title Design for Broadcast-Film-DS
izzylong.com

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# 5 05-02-2003 , 03:53 PM

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Preliminary pictures

First Picture:
Maya raytrace renderer; Bumpmap is here, "going outwards". One dir-light which has a 1.5 deg light angle for smooth shadow-border. And three spotlights with diffuse and specular only, without shadow-casting.

Second Picture;
Mental ray; with no enabled lights. There are lights which are hidden, but that's just to get rid of the default lights. The light source is a surrounding nurbs-surface with hdri map as incandescence. The bumpmap is here "going inwards".

Default Production mode
With 10 000 Final Gather rays
Minrad = 0 (auto)
Maxrad = 0 (auto)

Min/Max Sampling = 2 and 2

Rendering time = around two hours with PIII, 600 Mhz, 384 MB SDRAM

Third picture; A mental ray, raytrace. It looks a little different than the "maya render", but I admit to having altering it. This rendering is not "optimal in any major way", its just a simple mental ray rendering.

Last edited by undseth; 05-02-2003 at 08:28 PM.

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# 6 05-02-2003 , 04:06 PM

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looks nice!! Gotta love color Bleeding. user added image

Brian

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# 7 05-02-2003 , 05:35 PM

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NICE!

Keep it going! hehe! I love it!

Thanks for the info!

Can't wait for more.....

Israel "Izzy" Long
Motion and Title Design for Broadcast-Film-DS
izzylong.com

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# 8 05-02-2003 , 05:42 PM

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Looking great undseth. Not to sound like an idiot but what is a hdri image? I know nothing about this.

Steven C.

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# 9 05-02-2003 , 05:55 PM

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Well, it is an image which has a higer dynamic range of color values (i think), in contrast to other formats which has only 0-255 steps (I think). Any manipulation with HDR images will keep some or all of the HDRI's "contrast value", as the image gets lighter or darker. I think it has something to do with floating points, but I know nothing about it yet user added image

oh, and the HDR image in my experiments, doesnt seem to be really neccessary after all I think. But I guess it is theoretically "better/more accurate", than a tif or a jpeg image to illuminate the scene.

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# 10 05-02-2003 , 06:29 PM

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Thanks, I think I have an idea. I'll do some more research.

Steven C.

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# 11 05-02-2003 , 06:56 PM

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Some results of Final Gathering

yup, based on these I'll render out a final, with an directional light.
And I might as well add an "ordinary/non FG or GI" mental ray raytrace rendering.

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# 12 05-02-2003 , 08:29 PM

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aargh

Having trouble updating pictures, here is the missing pic.

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# 13 05-02-2003 , 11:46 PM

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Have to say that I still think MR FG is the best out of the three you have there, but I wish there was a way to get MR to render faster......

Israel "Izzy" Long
Motion and Title Design for Broadcast-Film-DS
izzylong.com

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# 14 07-02-2003 , 02:02 PM

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Final post

Well, I got to try and use a true HDR image to light my scene, and it was easier than I had though.

I wondered for some time as to how, I could lower the HDRI's brightness, and although I'm not sure this is the way to do it, I simply lowered the "color gain" in the attribute editor for the image node (the materials incandescence attribute)

I tried making the hdri file darker with the freeware HDRShop, but the tools there seemed only to produce low dynamic images like jpeg, tiff and the like.

So the "color gain" was the only attribute that gave me any results. Please correct me if I'm wrong here, or If there is any other way to darken you hdr image, to lower the light in your scene.

I am satisfied with the final rendering, but although I previously stated that this rendering would be done on the basis of my earlier tests, I did not follow up, and unneccesarily set the minmax value too low, causing the rendering time to drag out to over 18 hours. I guess the rendering time could have been shortened by skipping the directional light in my scene (with special shadow attributes (1.5 deg light angle and 15 shadow rays for smooth shadow-borders)

Next time I have to figure out how to combine FG and GI.

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