Still messing around with megapov's HDRI support. I thought my IRTC entry
for this round might make a good probe so I decided to give it a try.
Not much to the image just some old chess pieces I modelled a while ago.

Any comments/advice appreciated. There are no light sources just HDR.

Sean

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> Any comments/advice appreciated. There are no light sources just HDR.

The image itself lacks contrast IMHO. It would also be nice to have a 
direct HDRI <-> non HDRI comparison (Simply use an image of a "normal" 
render of your background as pigment for the second one).

I really like those chess pieces! You say they're older, have you some 
more images of them?


Florian

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Florian Brucker <tor### [at] torfboldcom> wrote:
>
> I really like those chess pieces! You say they're older, have you some
> more images of them?
>

Thanks, I made them a couple of years ago they are only CSG and the two
pieces I didn't show are the worst ones. (especially the knight). If you
want I can post the source in the source news group.

I will try the other render technique and post the difference.

Sean

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Florian Brucker <tor### [at] torfboldcom> wrote:
> > Any comments/advice appreciated. There are no light sources just HDR.
>
> The image itself lacks contrast IMHO. It would also be nice to have a
> direct HDRI <-> non HDRI comparison (Simply use an image of a "normal"
> render of your background as pigment for the second one).
>
Hmmm, I have re-rendered the non-HDRI image now just using a normal image
map. I must admit I am a bit confused as I can not tell any difference
between the two images. I would appreciate it if anyone can tell me what I
must be doing wrong with my HDR attempt.

Sean

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> Hmmm, I have re-rendered the non-HDRI image now just using a normal image
> map. I must admit I am a bit confused as I can not tell any difference
> between the two images. I would appreciate it if anyone can tell me what I
> must be doing wrong with my HDR attempt.

The only difference between an HDR image and a normal image is that the HDR
image is capable of storing color values greater than one (and also very
tiny values in high resolution). It would appear that your HDR image isn't
taking advantage of this. If the scene it came from doesn't have any
brighter-than-one spots (which appears to be the case), you won't benefit
from using HDRI.

 - Slime
 [ http://www.slimeland.com/ ]

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"Slime" <fak### [at] emailaddress> wrote:
> > Hmmm, I have re-rendered the non-HDRI image now just using a normal image
> > map. I must admit I am a bit confused as I can not tell any difference
> > between the two images. I would appreciate it if anyone can tell me what I
> > must be doing wrong with my HDR attempt.
>
> The only difference between an HDR image and a normal image is that the HDR
> image is capable of storing color values greater than one (and also very
> tiny values in high resolution). It would appear that your HDR image isn't
> taking advantage of this. If the scene it came from doesn't have any
> brighter-than-one spots (which appears to be the case), you won't benefit
> from using HDRI.
>
>  - Slime
>  [ http://www.slimeland.com/ ]

Thanks for the answer, I assume I can achieve this by adding a very bright
light source. I will try again and see if I can improve the image.

Sean

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> Thanks for the answer, I assume I can achieve this by adding a very bright
> light source. I will try again and see if I can improve the image.

Also consider making the sky_sphere very bright, since the sky is usually a
significant source of light especially relative to the inside of a room.

To see the real benefit of using HDRI, use a low reflection value on your
objects. With a normal image background that has a maximum value of 1, an
object with reflection .3 will only reflect a maximum brightness of .3. But
if the background image is HDRI, and it has, say, a maximum value of 3, the
object will reflect a brightness of .9 even though its reflection value is
low.

 - Slime
 [ http://www.slimeland.com/ ]

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> Hmmm, I have re-rendered the non-HDRI image now just using a normal image
> map. I must admit I am a bit confused as I can not tell any difference
> between the two images.

That's why I told you to test it with a normal scene :) I missed those 
very bright highlights typical for HDRI renders, but I wasn't sure what 
the reason was...

Your knight is not that bad: It could use some more spheres on the 
middle part (so the viewer won't recognize the single spheres), but for 
CSG only it's fine, IMHO.

Florian

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"Slime" <fak### [at] emailaddress> wrote:
>
> Also consider making the sky_sphere very bright, since the sky is usually a
> significant source of light especially relative to the inside of a room.
>
>
>  - Slime
>  [ http://www.slimeland.com/ ]

OK, I think I am getting there.. My HDRI image now looks fairly different
from the plain image map version, the highlights are starting to show up
quite nicely. I did try lowering the reflection values a bit on a different
image but I preferred this one with the higher values (The highest is only
0.45).
Thanks for the advice, I think I still need to experiment with HDR a bit
more but you have helped increase my understanding a lot, and thanks to
Florian for picking up on the problem without even seeing the contrasting
image. (How did you do that!)

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Preview of image 'chesshdrfull refl.jpg'

> I really like those chess pieces! You say they're older, have you some
> more images of them?
>
Thanks, the source is now available in the p.b.s group.

sorry it's not very readable (I've never been much good at commenting source
code!!)

Sean

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