View Full Version : HDRI Rendering

06-02-2010, 05:33 PM
Hey there!

When using HDRI in Lightwave there's a few issues i've encountered that I hope you guys can help me out with.

Note: (Reflection and radiosity is enabled)

Issue #1 : Sometimes when using HDRI it appears as if the HDRI image is too big. Is it possible to scale the HDRI image. It shows off no reflection in the material, or very vague reflection when using HDRI on backdrop Image World.

http://img39.imageshack.us/img39/1827/chairupload.jpg (http://img39.imageshack.us/i/chairupload.jpg/)
Uploaded with ImageShack.us (http://imageshack.us)
The gray "steel" is set to 100% reflection with enviroment set to Radiosity/backdroup and using a imageworld HDRI image. Any idea why it doesnt recieve that typical chrome effect?

Issue #2 : Attaching HDRI image as an enviroment to the material doesnt work sometimes. Any idea what common issues for this are?(I've toggled between the different modes under reflection in enviroment with pretty much the same result as shown above. (This with Image world disabled).

Sorry this is probably just a novice mistake, but if you have any links to rendering tips and HDRI using then that would also be greatly appreciated but firstly fixing these problems would help me alot. Cheers lads.
Looking for any tip I can get for rendering and using HDRI.


06-02-2010, 07:07 PM
Lemme ask a stupid question: Did you enable reflections in the Render tab of the Render Globals toolbar?

06-03-2010, 10:34 AM
What kind of HDRI are you using?
"Image World" expects LightProbe/MirrorBall images while "Textured Environment" is for equirectangular spherical images.
You cannot scale those images when applied to the environment, these get an "infinite distance" effect.
When setup isn't correct, those images will be distorted and won't give correct reflections.

For your material:
assuming, everything is set up correctly (Material properties, render settings, etc.).
The HDRI seems to be very grey and dark and this is what you see in reflection.
For an attempt: just put a white groundplane under your bench and set material reflection properties to a "raytrace" type. If it shows up in reflection, it's the environment image that isn't an appropriate motive for your needs.

For #2: sorry, never had this issue. For Advanced Mat settings usually "raytrayce + spherical map" is used in conjunction with a spherical HDR image.

A great resource for everything hdri related is here: HDR Labs (http://www.hdrlabs.com/news/index.php)

hope, this helps - good luck

06-05-2010, 08:05 AM
RudySchneider: :thumbsup:

rsfd: Im using a spherical HDRI image called BuildingProbe. I can give you an image of it if it matters. I did some testing where I made a new scene, enabled the reflection raytrace and put on radiosity. I turned off the light. I did two renders. One where I used the HDRI image as imageworld, and one where I only used it as enviroment on the ball and had no HDRI image on the floor.

http://img202.imageshack.us/img202/3368/crapd.jpg (http://img202.imageshack.us/i/crapd.jpg/)

http://img691.imageshack.us/img691/7637/newtek2.jpg (http://img691.imageshack.us/i/newtek2.jpg/)

This brings me to two questions.

Question 1 : Why is the reflection so sharp in the ball, whilst compared to the ground it's all pixelated.

Question 2: The second image would fit my needs however the blurryness or brightness of the image is controlled by the backdrop color. If I darken it the ball becomes very sharp and chromeish just the way I want it, but the floor becomes too dark. If I brighten it then yeah, it becomes as you can see.

As I wrote the second question something came to my mind, maybe adding a white diffuse texture to the floor would prevent it from going dark? Is there another way to controll this?

Cheers and sorry for late reply.

06-05-2010, 01:13 PM

Question 1 : Why is the reflection so sharp in the ball, whilst compared to the ground it's all pixelated.

You might want to try this:
Go to Image Editor, choose "Building_Probe" and on the "Source" tab, check "Maximum Mipmap Quality".
If it's set to "off", turn it on by either selecting "low" or "high".

If you use the standard "Building_Probe" image, it's just 640px x 640px and far away from being a high quality reflection environment.
As the ball is so much smaller, the interpolation just works better.

Question 2: ...

Just assuming...
Most likely, your Material settings need some refinement:
For the chrome ball, you'll need high reflection settings (physically correct: about 70%), no specularity and very small diffuse value (about 10%).
(As the reflection on your 2nd image is so washed out, I would guess you have high diffuse settings? Or did you maybe make the hdr brighter in Image Editor?)

For physically correct Material settings use these rules of thumb:
diffuse value + reflection value = 80 - 100%
if you use specularity too:
reflection value = specularity value
(but remember: specularity does not exist in real world where only diffuse and reflection occur; specularity is a 3D trick to get "reflections" of 3D lights).

...the blurryness or brightness of the image is controlled by the backdrop color...
no. If you are using only Global Illumination (GI) without any 3D lights, you usually control the illumination power with: "Render Globals" > "Global Illumination" > "Intensity" and use a (usually blurred, low res) HDR image in the Environment (and high res image for reflection).

Nevertheless, if you use "Spherical Map" in Material's Reflection properties and a colored background for GI, then the background color in fact affects the GI too: the darker the backdrop color, the darker the GI and the higher the GI intensity must go to compensate. GI has no effect on reflectivity, it only affects the "Diffuse" property of the Materials.
But with this technique "black" can't be compensated, as black just does not emit any light. You then have to split Background color and GI color:

- use a light color for background (so you don't need super high GI intensity values)
and for the background color that is seen by the camera:
- create a small image (1x1px) of your wanted color (a .gif, .tga, .jpg is sufficient) and then go to: "Compositing Options" (ctrl-F7) and for "Background Image" choose your 1px-color-image. LightWave then uses this 1px-color-image to fill the whole camera background, but uses the "Background color" for GI.

If you use "Surface Editor > Environment > Reflection Option > Spherical Map", you can control the Brightness of reflections in Image Editor by changing the Brightness value of the Spherical Map. This affects the Reflections of any Materials which are using this Map.

The "backdrop color" setting controls... well, the backdrop color.

So, if your 2nd image is what you're after, you could try these settings for a start:

Ball: Diff=10%; Spec=0%; Reflection=70%; Surface Editor > Environment: "Spherical Map" (or "Raytrace + Spherical Map", if the Groundplane should show up in the Ball).

Groundplane: Diff=85%; color=white; Spec=0%; Reflection=10% (more or less, depending on your wanted result, but remember: Diff+Refl=max 100%)

Render Globals > Global Illumination > Intensity = 150% - 250%
(Intensity depends on the grey that you select for backdrop: the darker the grey, the higher the intensity has to go, as "a darker color spreads out less light")

Backdrop color: your wanted color (in this case: the darker the color, the higher the GI intensity must go to compensate)

...and sorry for late reply
no problem :)

06-06-2010, 03:08 AM
great help from rsfd
if you have the time you could check this site
and download the sibl plugin and some sibl sets (hdr sets of pictures ready to light a 3d scene.)

06-06-2010, 03:57 AM

Im trying the stuff you guys mentioned but I just want to say, thank you so much ;) Amazing forum! So helpful! cheers lads!

06-14-2010, 03:26 AM
Now, it's me who's late ;)

... I just want to say, thank you so much ;) ...

You're welcome! :)

Just wanted to add (can't imagine, why I could forget about this :confused: ):
This is also a great read (or better: a must read) about LW radiosity:
The "Except Radiosity Guide for LW 9.6", you find it here (http://www.except.nl/lightwave/RadiosityGuide96/index.htm)

06-25-2010, 01:34 AM
Sorry havent had time to post anything been busy at work, cheers for the link m8, and thank you all for your help ;)