HDRI? am i missing something?

[Tim Saunders]

i've been trying to figure out what the majic is about hdri images. i've read up on the help files in viz about hdri's used for both backgrounds and/or reflection maps, but i don't see what the difference is compared to a regular image. i ran into a link from evermotion that was preaching like hdri or die. what am i missing?

[Christopher Nichols]

i've been trying to figure out what the majic is about hdri images. i've read up on the help files in viz about hdri's used for both backgrounds and/or reflection maps, but i don't see what the difference is compared to a regular image. i ran into a link from evermotion that was preaching like hdri or die. what am i missing?

 

 

Well you are not going to see much difference it you use low quality HDRI, since their dynamic range is fairly low. But you will really see a difference with high quality ones.

 

What are you using to render?

[vertexART]

Try DoschDesign HDRI's, they are good. I think there are some free ones too.

Or post some pics of your attempts, so we can see what the problem is.

cheers

[Tim Saunders]

chris, i was hoping you would see this. for the moment i'm using vray free. and there's really no problem. i guess my question is, what is there purpose? i see that they can be loaded as an environment or a reflection map, but why would i benefit from that over using a plain old jpeg image? i have heard of using them as a dome sky, but once again, why wouldn't i use a regular image? i know they are made up of an increased amount of contrast, but where/how does that help me?

[anvaraziz]

hey dude ..

 

first take a search on google...

 

HDRI differs a lot from JPG

 

here it is

HDRI Or High Dynamic Range Illumination. This method is relatively new in GI. This uses the actual light probe value of a real scene in the real world taken through with special equipment to produce a 360° view of a scene, and stores the information of the light from all areas in the scene in a spherically mapped image called HDR. The renderer uses that information to shoot light from and provides even more photo-realistic rendering.

 

 

In computer graphics and cinematography, high dynamic range imaging (HDRI for short) is a set of techniques that allow a far greater dynamic range of exposures than normal digital imaging techniques. The intention is to accurately represent the wide range of intensity levels found in real scenes, ranging from direct sunlight to the deepest shadows.

http://en.wikipedia.org/wiki/HDRI

[Christopher Nichols]

well... I COULD explain it... OR, you could simply get my first DVD and see why...

 

It basically comes down to this. LDR (low dynamic range images) such as JPG etc... clamp color from 0 to 255 (in an 8 bit world)... which if you normalize it is 0 to 1 (just scale 255 to 1)

 

HDRI is a floating point image meaning the color value can be anything. 0, 1, 0.21242, 0.0000121, 0.1234221... more importantly it can go higher than 1: 2, 5, 4.564, I have even seen really high quality HDRIs with 35,000+ values for things like the sun.

 

This is important values because:

 

1 - for diffuse lighting, you can get true values of lighting

2 - same thing for specular value... plus you can still get sharp bright values in reflections of bright light sources when using a fresnel falloff

3 - when you blur things for lets say defocus or motion blur, you can get the correct blooms and streaks.

[Sawyer]

In Chris' DVD he covers this really well but...

 

The HDR image rendered in 2:01 the fake HDR (HDR file saved out as jpg) rendered in 1:14 (on the left).

 

Note the lighting from the sun in the image. There are no lights in the scene.

[IC]

i've been trying to figure out what the majic is about hdri images. what am i missing?

 

You're missing the difference between getting instant realistic lighting/ reflections and painstakingly faking it.

 

Try Paul Debevec's Light Probes available free from his site.

 

Just as an aside: Using a slightly blurred probe will drastically improve render times as HDR renders are quite slow due to the amount of light information involved.

[STRAT]

hdri's really do give reflections that 'real deal' feel with regard to the extreme contrasts and colour values all in the same image.

 

but as for normal IBL? well yes, a hdri map will give a different result than a normal jpg, but nothing worth getting excited about imo.

 

i think hrdi is pretty over-hyped. it can work wonderfully in your reflections, but you need the correct situation to make it worth while and noticable. not worth the faffing about 75% of the time imo.

[IC]

Yeah I'd agree with that.

This one has an HDRI as an environment map in the glass material for reflections but I used the background image for lighting (IBL)

[erevan]

Hi to everybody, I'm a rookie.

I've started directly to do my first renders with HDRI, so I haven't had time to see the differences with other ways of illuminating, but... Even with clear skyes HDRs the shadows have nothing to do with what I was expecting.

The shadows are just too diffused. I am using Vray and there are no options to control that.

Am I using them wrong? They are supposed to be like that?

[STRAT]

yes, rendering your scenes using a hdri map for IBL (image based lighting) can give you fairly un-expected results, especially for the beginner or un-initiated the shadows and even main lighting effects can sometimes be quite diffuse and 'noisey'. this is where experience and knowlege of your renderer will sort these problems out.

 

personally, for normal IBL, i'd advise use a plain old bitmap (ie, jpg, tiff, tga etc etc). you'll find the image/lighting quality much easier to predict and control, and, other than a nominal render slowdown in most cases, you wont gain any noticable wow factor or realism from using hdri for IBL.

[Tim Saunders]

thanks everyone for your great responses. based on what chris, sawyer and iain are saying i would get the most accurate contrast values in my lighting and shadows (and much more that can be explained in the dvd, yeah it's on my shopping list). so what really "wowed" me is that no lights were used in the samples sawyer posted. in the viz help they explained how hdri can be loaded in with the sky color on a skylight. is this what your talking about with diffuse lighting, or do i load the hdri straight in as the environment map and don't load any lights in the scene at all?

 

and from what strat is saying, does it primarily benefit in animations? what is image based lighting?

[IC]

Image based lighting is really just mapping an image to an inward facing sphere and making it luminous. Add radiosity and the colours of the image provide ambient light. HDR is perfect for this as it holds so much light information.

 

There are other ways to do it in each 3d app but that's the basics of how it works. It mimics real life ambient light from sunlight diffused through the atmosphere.

[Jeff Mottle]

Thought I'd also point out http://www.hyperfocaldesign.com/ Some of you may know this site from their sky textures, but Jay has just revamped to the site as a community for HDRI. He has some tutorials and articles on there and will be adding more all the time. He has also just released a new hi-res HDRI sky collection. (You can get it from the CGA store as well)

[Christopher Nichols]

if you think you can't get sharp shadows from ILB in Vray... think again:

 

http://www.spot3d.com/vray/images/stuff/hdr_tests/skyprobe_0011.png

http://www.spot3d.com/vray/images/stuff/hdr_tests/dome_light3.png

http://www.spot3d.com/vray/images/stuff/hdr_tests/dome_light_all.png

 

 

Disclaimer: This is new with Vray's fancy domelight system, still not released to the public.

[Tommy L]

 

 

Disclaimer: This is new with Vray's fancy domelight system, still not released to the public.

 

Christopher, do you know when this is going to be available? Is there any news of a new vrsion of vray?

Thanks,

Tom.

[Christopher Nichols]

Christopher, do you know when this is going to be available? Is there any news of a new vrsion of vray?

Thanks,

Tom.

 

I know nothing specific, like the anyone else. But from what they tell us, not to long from now.

[Tim Saunders]

makes sense. so from what iain is saying you asign the map to the dome. whan you say make it luminous, does that simply mean giving the self illumination some value? here's another thought. it is so easy these days to find high quality back ground images for free on the internet. is it possible to have the hdri do the lighting work with the dome, but have a seperate background image/reflection map, or does that defeat the purpose? it just seams like a lot of $ for images that may or may not even give me the backdrop or reflection that i want.

[skala67]

For those of you using C4D, it is very simple to get excellent results with HDR's. In your material, turn off all channels except the luminance channel. this is where you add your HDRI image. you can play with the brightness in two ways. first with the brightness slider in the luminance channel (which can have entered values above 100%) changing this value effects the brightness of the map itself and sometimes washes out completely if the brightness is too high. the other way is in the Illumination channel (that is if you are using advanced render) you can change the 'Generate GI strength' value to get different results without affecting the saturation of the image map in the luminance channel. Create a sky object and apply your material to it, and thats it. I have been using the radiant sky HDRI's from Dosch Design and have been very happy with the results. Once you add an Omni light as a sun source (brightness around 60-70% and a light orange color) even with just hard shadows, you get great overall exterior lighting.

Ok thats alot of writing...for now