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LearningLightW
09-09-2008, 10:36 AM
Hi everyone!

I think I'm really confused about using hdri images. Are they or are they not supposed to be rendered? After reading a number of tutorials, it seems like they are used solely for lighting purposes and are not used as background.

I'm wondering if it's more of a preference? But when I do render the hdri image, I'm having the most difficult time getting the ground plane in my scene to match up with the hdri image itself. Any help/input would be appreciated!

Thanks!

On a side not...what do you guys think of using Maya?

SplineGod
09-09-2008, 11:15 AM
You can use them for whatever you want. HDR Images are just another file format that contains more information then standard LDR Images (24bit). You can actually use any image to light a scene if you wish.

Do you have a bit more information regarding your scene?

BetterThanLife
09-13-2008, 08:33 PM
Some people use HDRI maps as backdrops others don't. To use one as a background you really need a high resolution image in your HDRI and not all HDRI have those. I personally prefer to keep my background separate from my HDRI map. They can make some great reflections, as long as the reflection isn't a central focus of the render for the same reason.

zardoz
09-15-2008, 02:14 AM
if you go to www.hdrlabs.com you can find all the information you need. And very usefull plugins to help you use hdris.

3DGFXStudios
09-15-2008, 07:16 AM
I never use my HDRI-"probe"<--(I guess that's what you mean) image in the background.

Bliz
09-17-2008, 02:23 PM
Hi everyone!
I'm wondering if it's more of a preference? But when I do render the hdri image, I'm having the most difficult time getting the ground plane in my scene to match up with the hdri image itself. Any help/input would be appreciated!


You shouldn't really try. If you look at a lot of normal hdri based renders you'll see that the main object is on a raised platform of some sort. The cliche'd shot is an object on a kitchen table surrounded by a kitchen hdri



On a side not...what do you guys think of using Maya?

Don't worry about maya till you know you have a definitive need for it

SplineGod
09-17-2008, 02:40 PM
There are other types of lightprobes besided the spherical type. Some look like a box unwrapped and using a section of that as your background might work. Also your background image doesnt have to be the same HDRI used to light your scene.

zardoz
09-17-2008, 04:42 PM
I guess you are a bit confused about HDRI. So like I said before you could go to www.hdrlabs.com and find a lot about hdris.

But anyway I'll try to give a small explanation about them and I ask anyone here to correct me if I'm wrong.

HDRI stands for High Dynamic Range Imaging in contrast with LDRI that stands for Low Dynamic Range. What's the difference? well in an HDRI image format you can save besides the colour the luminance information also. So HDRI pictures (.hdr, .exr and others) are simply a file format that store colour like any other format (.jpg, .tga, etc) but also store light. This means that in some areas of the image where things are white (like the sun or some light source or even reflection) maybe they are not simple white (255, 255, 255) and can be higher than this.
So you can use hdri pictures to light your scene because they have the light information of the place and time where they were taken.
Do not confuse .hdr with what many in the photography community call hdri images or photos. They take 3 or more pictures of something at different exposures and then combine the information of all these photos and tone map them. They adjust the light areas and the dark areas so that you can see all the details, or maybe they tonemap these pics in their own artistic sense. And then they save a .jpg and call it a HDRI. This is not a HDRI. This is a low range pic that was obtained from combining several exposures but the resulting picture doesn't have any light information because it was saved in a file format that can't store that.

Back to hdris...so this is a file format. And you can use it in several ways. you can render your 3d scene to .hdr and then in lightwave or photoshop (or other) edit this renders exposure and other properties that you can't in a low dynamic range format like a .jpg.
Or you can use any .hdr image to light your scene. For this you need to turn on any radiosity engine.
You can of course use the .hdr as a background but the normal procedure would be:
get some and .hdr resize it to a smaller dimension, blur it and save it as an .hdr and use this smaller, blurred version to light your scene (it creates less noise), convert the big .hdr to a .jpg and use it as a background. Render your scene and save the renders in .jpg, .tga or even .hdr if you want more advanced post-production.

About the hdris that you find in the web to use as light sources....they have different shapes and so you can use them in different ways, like apply them to a dome (longitudinal hdr), or lightwave's backdrop with a spherical mapping or in lightwave's image world (distorted reflective sphere) option, or in the backdrop, even in a cube (cross .hdr) This would depend on the format the .hdr has.

I hope this helped you. My english isn't the best, so this may be confusing and anyone can/should correct me please.
tx

dreamlight
10-20-2008, 01:57 PM
I cant seem to load any HDRI images at all. It just says unsported fileformat. Im trying to load *.hdr files from www.hdrlabs.com. Im running LW 9.3.1. Anyone knows what im doing wrong? :)

shrox
10-20-2008, 03:59 PM
I guess you are a bit confused about HDRI...

Thanks Great Flying Stone Head,

this really cleared up alot for me, especially with people claiming a jpg is an HRDI.

I got Zardoz last week from Netflix, still just as bizarre as I remember, but better as well.

toby
10-20-2008, 10:04 PM
I cant seem to load any HDRI images at all. It just says unsported fileformat. Im trying to load *.hdr files from www.hdrlabs.com. Im running LW 9.3.1. Anyone knows what im doing wrong? :)
It sounds like you need to load the plugin that reads .hdrs.
Press alt-F11 (or find 'edit plugins'), hit 'scan directory', browse to the Lightwave/plugins/input-output folder, and hit ok.

toby
10-20-2008, 11:26 PM
HDRI pictures (.hdr, .exr and others) are simply a file format that store colour like any other format (.jpg, .tga, etc) but also store light. This means that in some areas of the image where things are white (like the sun or some light source or even reflection) maybe they are not simple white (255, 255, 255) and can be higher than this.
So you can use hdri pictures to light your scene because they have the light information of the place and time where they were taken.

I wouldn't describe it quite like that, there isn't really 'light information', it's all color. Instead of storing values from 1 to 255, hdr's store any value, in floating point (%). Switch your image viewer to FP and click on a render to see the values. FP images can also store more colors, it's not limited to 255 shades of each red/green/blue.

Jpg, tga's, etc. acually can be used for lighting if you wanted to, but their maximum intensity is 100% white, about as bright nightime with no moon...



Do not confuse .hdr with what many in the photography community call hdri images or photos. They take 3 or more pictures of something at different exposures and then combine the information of all these photos and tone map them. They adjust the light areas and the dark areas so that you can see all the details, or maybe they tonemap these pics in their own artistic sense. And then they save a .jpg and call it a HDRI. This is not a HDRI. This is a low range pic that was obtained from combining several exposures but the resulting picture doesn't have any light information because it was saved in a file format that can't store that.
I've seen this too, and if they're jpg's they're not hdr's, but this is how hdr's are made, combining at least three LDR images, shot at different exposures, together (usually jpg). So what they should be saying is that they're made 'using' high dynamic range.


Back to hdris...so this is a file format. And you can use it in several ways. you can render your 3d scene to .hdr and then in lightwave or photoshop (or other) edit this renders exposure and other properties that you can't in a low dynamic range format like a .jpg.
Or you can use any .hdr image to light your scene. For this you need to turn on any radiosity engine.
You can of course use the .hdr as a background but the normal procedure would be:
get some and .hdr resize it to a smaller dimension, blur it and save it as an .hdr and use this smaller, blurred version to light your scene (it creates less noise), convert the big .hdr to a .jpg and use it as a background. Render your scene and save the renders in .jpg, .tga or even .hdr if you want more advanced post-production.

About the hdris that you find in the web to use as light sources....they have different shapes and so you can use them in different ways, like apply them to a dome (longitudinal hdr), or lightwave's backdrop with a spherical mapping or in lightwave's image world (distorted reflective sphere) option, or in the backdrop, even in a cube (cross .hdr) This would depend on the format the .hdr has.

I hope this helped you. My english isn't the best, so this may be confusing and anyone can/should correct me please.
tx
HDR's are also excellent for reflections. Ideally you'd want to use the small blurred hdr for lighting and a large sharp hdr for reflections.

zardoz
10-21-2008, 02:39 AM
yep toby thanks for the corrections (well most of the stuff I said here is what I understood from HDRI the book from blochi...).
I said that besides color an hdr format stores light because actually in an hdr file every pixel has the 3 rgb values (that go from 0 to 255) and then in an extra part of the file (from what I read it can even be in the metadata) or channel these files have a value that is used in some formula (in an exponent) to 'multiply' the rgb values stored in the pixels and this way getting the high dynamic range. So I understood that these files store color and then 'light intensity' that multiplies the colors. But yes, after the conversion all that we get are color values that go beyond the 256 values we get in a ldr picture.

Thanks Great Flying Stone Head,
this really cleared up alot for me, especially with people claiming a jpg is an HRDI.
I got Zardoz last week from Netflix, still just as bizarre as I remember, but better as well.

lol yep it will always be very bizarre. I was a young kid when I first saw zardoz and it was "mind blasting" like Russel Peters says...the next day in school me and my mates only talked about this...so when starting my online life I decided to use zardoz as my nick. Two or three years ago some of my friends gave me the dvd as a gift...and I have to say it's still wrapped...lol

dreamlight
10-21-2008, 02:58 AM
It sounds like you need to load the plugin that reads .hdrs.
Press alt-F11 (or find 'edit plugins'), hit 'scan directory', browse to the Lightwave/plugins/input-output folder, and hit ok.

Thanks Toby, allthough it appears not to be the problem in this case.
I got it working, but its really weird...

On a 32 bit system with 4 Gb of RAM, i loaded a pretty heavy scene with lots of high rez textures. Heck, some of them were even missing. Apparently i ran out of RAM, as i got the same error when trying to load a .JPG texture.

Now, i tried this on a 64 bit system with 8 Gb of RAM, and it works great. Same LW version - same plug ins.

So - this looks to be a memory issue - that LW tells is a unreadable file format issue...

No wonder i was confused! :)

pixelranger
10-21-2008, 03:30 AM
you are totally correct zardoz, but the "extra" channel (the exponent of the rgb values) is just one way to keep the range in the file in the smallest way possible (like a compression, or actually it IS a lossless compression). It is not some extra info not found in LDR imaging. Just a way to store the extra accuracy.
It would be the same as storing LDR images in rgbe with 64 colors in r, g and b and then a number in the "e" channel that multiplies r, g and b up to 256.
The light position comes from the xy coordinates of the image so that is the same in LDR and HDR (except for the increased accuracy where small lightsources are blown out and becomes larger in the LDR images).

pixelranger
10-21-2008, 04:31 AM
As for what LearningLightW asks for, you seldom want to include the HDR image in the render, and certainly not in the same pass as the 3d objects. Usually the hdr images are too low resolution to hold up as nice backgrounds, plus they are projected onto a virtual (more virtual that your 3d objects even, hehe) sphere that is infinately or at least equally far way from the camera wherever you turn it, so it doesn't provide any parallax or depth or anything.
One thing you can do is build the environment while projecting the hdr image onto the mesh spherically, but the best thing is taking "shot images" or photos of what you want in your background and composite on top of them, maybe modeling mock up geometry onto which you camera project the shot images (assuming you capture your own hdr on location) and using the hdr image only as light source or reflection source.