Hi -

I'm having trouble with HDRIs and have formed some questions that I hope some light (no pun intended) can be cast on.

Untransparented Poser Eyebrows/Lashes.  It seems that some HDRI maps I use produce transparented brows and lashes while others with the same rendering settings (ie. all transparency light throughs checked) do not.  Is that true?  Can the properties of the individual HDRI maps make or break that?

One render I did produced an overall blue tint to the model - all transparencies worked in that render.  What's up with that?

Are there steadfast rules to rendering with HDRI?  SkyLight only?  Indirect only?  Either or both ok? Also, are high intensities recommended?  Should one leave the intensity setting of the HDRI map area at 100% and only make higher intensities at the SkyLight/Indirect Light levels?

I think I read once that adding a bulb light to the scene can fix the no transparency on the brows and lashes no matter what - is that true?

Is there a tute or difinitive list somewhere that addresses everything HDRI (for carrara 5 pro)?

Thanks if anyone can help with any of those - I've spent a lot of time experimenting without getting difinitive results so I'm finally asking.  Thanks.

David

Ok, to add to the confusion, after trying various other HDRI maps, I reopened the first HDRI I tried with my scene and model.  This was the one that rendered the model blue but had transparent brows and lashes.  Now the brows and lashes are not transparent so some thing screwed that up.  It could be now that the brow and lashes would render transparent with the other HDRI maps I tried but something got tripped up and won't fix itself until I likely start a fresh document and reimport the Poser model.

I'm going to start over and try one of the maps that didn't render blue... and see what happens.

Bother....  Here's another question I wondered about.  Do some HDRI maps work with Carrara while others don't.  Is there a type that's usuable and one or more that are not?

David

Yes, you need polar, i believe. I think hdri shop calls them panoramic.

What hdr maps are you using? The ones that come with Carrara? I've never heard of hdri messing up transparency on an object.
Have you checked that BOTH light through transparency options in the Render room have been switched on?
Also double check that the transparency files have come over correctly from Poser to Carrara in the Texture room - look in the Transparency or Alpha channels.
Have you got any images you can post to show this problem?

Carrara uses polar hdr maps (AKA panoramic or longitude/latitude according to HDRShop), basically any hdr map fills a rectangular image space. The manual says Carrara hdr files should "completely fill the rectangle of the image", sort of like a photo. So look for that type of hdr file.

Attached Link: Examples

In the pic, you'll find some of the renders.  You'll see that the hair object never failed on transparency which I thought was... perplexing.   As I said in my first post, all transparency boxes were checked on - both in the GI section and regular options section.

Image A - was what was produced after the first render that worked with transparency but rendered blue.  All the renders after that had no brow and lash transparency.   One of those is Image B.  To me, the lighting on the model doesn't seem to match considering the brightness of the light coming from the upper right in the back of the image.

Image C - must be one of those wrong HDRI files for Carrara as it (along with some others I tried) only produced a background image to the horizontal halfway point...

Image D - after rebooting and reimporting my poser file, I was able to get consistant brow and lash transparency.  However, I also rendered each new image to a new window.  Prior to that I had been rendering over bad renders.  I wonder if that had something to do with the transparency checkbox not reading itself properly... or something.   Also Image D uses the same HDRI file as Image A; it's been rotated 180 degrees though and seems to match better lighting wise.  (In fact, the brightness on the model I think must be coming from that bright right side in Image A which is now behind the camera on the left since it was rotated.

So my conclusions are to use the proper HDRI, and to always do new renders to a new window.

I have seen temp issues like you described myself in other situations.

I have an HDRI problem also...
Here is an overlaped image where two HDR images were used to render the same object.  Why is one so horrible and the other just fine?
http://i7.photobucket.com/albums/y255/jubjub64/WeirdHDRIRender.jpg

Here are a couple of HDRI issues to be aware of: 1) As Anastasis20 commented, there are TWO places to check "Light throught transparency". The first one is in the render room at the top of the Property Tray. The second one is a little further down in the Global Illumination portion of the Property Tray. Both must be selected. 2) Resolution of the HDRI maps affect the quality of the render. Most of the maps available for free are low resolution. Strange lighting occurs with this. To help "disguise" the low resolution HDRI maps, you must increase the photon count in the Global Illumination portion of the Property Tray and increase the Interpolation Precision of the lighting. Interoplation basiclly allows Carrara to guess about the light instead of actually doing the math to figure it out saving time on the render. Increasing it forces Carrara to do more math and will increase render time. How much should you increase Photons and Interpolation? There is no specific answer. It's whatever looks best in your image based upon the HDRI map and design of your scene. Mark

Well the HDR image that renders poorly was supposed to be a very high resolution image.  I got it from http://www.debevec.org/Probes/. It is the St. Peter's Basilica HDR image.  I'll have to check out the light through transparency and photons and such.

The 2 places for GI get a lot of people.

I found that just adjusting the Lighting quality form "Fast" to "Best" made the renders much better.  It seems that the St. Peters HDR image had the worst results out of all.

Sometimes the lighting setting does make a difference.