[feynman]

Hi,

is there a recommendation what HDR image should be used to achieve realistic materials, especially concerning the shinyness of them? Often, I have built a material that works in one or some contexts - but miserably fails in another. For example wallpaper, melamine/phenolic coated kitchen fronts and other almost white surfaces. How should one light and build such materials so they work in any context? Or is that a futile endeavour?

Thank you very much for some advice!

[eric nixon]

Have you opened the hdri in PS or HDRSHOP to see what it actually contains. The vast majority of hdr files out there, lack dynamic range. CGsource is an example of how they should be.

The simball scene is great for callibrating your materials. Its not futile at all, if you have a decent monitor and a clear view of it.

[feynman]

We bought all DOSCH HDR images and whatnots, but that's part of the problem - there are too many of 'em. I'm dealing practically only with flat non-transparent materials as found in walls, furniture, sheet metal parts; objects without any curvature. Bright colours like yellows (e.g. laminated wood) and whites (painted walls) always have too much glare when the rest looks actually ok-ish and very photorealistic - no matter which HDR image I chose.

[eric nixon]

All Dosch I've seen have wrong gamma, must be a V-ray legacy issue, (they can be converted and resaved) but then they also lack range.. in the UK dosh is slang for money esp, easily earned money, just a coincidence but you get the point.

For the material, to get a very white shiny plastic, I would use the floor preview to quickly judge the material.
Use a normal mix, with 2 bdsf's, one gloss around 17% weight, one diffuse and very white, say 245. < that should describe a very white shiny plastic.

[feynman]

Cheers, but then - which HDR image sets would you buy, if you can't afford the time to take or paint your own?

Looked for HDR images @ Wonga, Moola, Spondulicks - but no joy :)

[eric nixon]

CGsource is an example of how they should be.

And they only charge only 10 euros for two, for a free example of full-range hdr google 'ennis.exr'

I just had a thought;
If you have a perfectly flat surface and its reflecting an infinite sphere (the hdr sky) the reflection off that surface, when viewed from a distance, will only pick up a tiny point of the whole sky, therefore just a few pixels of the hdr file. And the diffuse portion of the surface will have no gradient shading, other than shadows falling upon it...

Hope that you can follow my ramble...

[feynman]

Exactly. And that's why I have the suspicion that, after all, furniture and similar objects can't be lit too well using HDR images but rather with lightsources?

If you have a perfectly flat surface and its reflecting an infinite sphere (the hdr sky) the reflection off that surface, when viewed from a distance, will only pick up a tiny point of the whole sky, therefore just a few pixels of the hdr file. And the diffuse portion of the surface will have no gradient shading, other than shadows falling upon it...

Hope that you can follow my ramble...

[Mihai]

To have better predictability when creating your materials, "calibrate" first your lighting, meaning set the material on the test object white (230 for example) then try and find the exposure that in the render will make the brightest parts 230 on the test object. This way you know that you don't make your textures too dark or too white, if you are just arbitrarily changing them based on exposures in different scenes. Don't test your materials on a flat object as reflectance may change a lot depending on viewing angle, so a sphere or similar is best to judge how it will look from all viewing angles. Two emitters would be enough to see how the highlights look, not sure why you want to use an HDR for this.

[bograt]

I just had a thought;
If you have a perfectly flat surface and its reflecting an infinite sphere.....

I have never done this in practice but I have though of mapping an hdr onto geometry to avoid problems like that, especially with interior hdris... it should help produce accurate shadows as well...

[bograt]

Anyone know whats causing this wierdness? http://www.cg-source.com/details_hdrisk ... pricat=sky
give it a spin and check out the wierd yellow crap

[Bubbaloo]

Is it a Maxwell render?

[tom]

Could you please send the scene with faulty caustics to tomATnextlimitDOTcom?

[feynman]

@Mihai Thanks, so - do you think it is 1. possible to light predominantly flat furniture with HDR images and 2. that Dosch HDR images, as Eric suggests, are not good quality? Or - should one literally create a fake room that when shooting furnitures is not visible in its entirety, but necessary for bouncing light, and use only lightsources and no HDR images whatsoever? Or - should one even re-create a photo studio setup, as far as light sources (constant light or flashes) are concerned?

So far, I understood that absolutely realistic interiors can be rendered, but I have not seen single furniture items being tackled as shot in a studio or exhibition setting.

To have better predictability when creating your materials, "calibrate" first your lighting, meaning set the material on the test object white (230 for example) then try and find the exposure that in the render will make the brightest parts 230 on the test object. This way you know that you don't make your textures too dark or too white, if you are just arbitrarily changing them based on exposures in different scenes. Don't test your materials on a flat object as reflectance may change a lot depending on viewing angle, so a sphere or similar is best to judge how it will look from all viewing angles. Two emitters would be enough to see how the highlights look, not sure why you want to use an HDR for this.

[Mihai]

Have you taken a look at the gallery?

http://www.maxwellrender.com/gallery/al ... getto4.png
http://www.maxwellrender.com/gallery/al ... getto1.png
http://www.maxwellrender.com/gallery/al ... gn/045.jpg
http://www.maxwellrender.com/gallery/al ... gn/031.jpg

There are some studio HDR lights, like these:
http://alsens.net/34237/393750/store/ph ... hts-hdr-30 (haven't tried them though)
http://www.studiohdrimaps.com/

You can also find some free ones:
http://zbyg.deviantart.com/art/HDRi-Pack-2-103458406
http://zbyg.deviantart.com/art/HDRi-Pack-1-97402522?
http://zbyg.deviantart.com/art/HDRi-Pack-3-112847728
http://oliverwolfson.com/studio-light-hdr-images/

HDR Light Studio is ofcourse very nice and they have a bunch of studio HDR lights also included. I don't know about the newer Dosch HDRs but the older ones where not so good, actually pretty bad in terms of dynamic range.

[numerobis]

Anyone know whats causing this wierdness? http://www.cg-source.com/details_hdrisk ... pricat=sky
give it a spin and check out the wierd yellow crap

I experienced similar problems with HDRIs when i raised the sun intensity of the HDRI too much in photoshop, something like a too "contrasty" image...