View Full Version : Hrdi

04-29-2004, 04:50 PM
What is it and how can I use it to inject photo realism into my renders.

I have seen some amazing things done with it but I dont really know what it is.


04-29-2004, 05:23 PM
Heres a cheap way to use hdri

Load a scene
Set the backdrop color to white-under the Scene tap
Enable Radiosity-Set to Backdrop Only
Set Ray Per Evaluation to something low to start-like 2x6
Enable shadow noise reduction
Test render
Tweak settings and lights to your desire

That's how I created the attached.

04-29-2004, 05:31 PM
Uh, that's just Global Illumination or Radiosity rendering - HDRI or "High Dynamic Range Imaging" is a technique whereby a high bit-depth image (such as Cineon, OpenEXR etc.) is used to light a scene in conjunction with Radiosity. Put simply, the HDRI image is used as a backdrop (LightWave's Image World plugin works for this) which the renderer then uses to decide the brightness of the scene lighting as well as the colour of the light - it helps create a more realistic lighting model and is especially useful in compositing CGI into live footage.

04-29-2004, 05:45 PM
What I'm saying is instead of spending money on HDR images right away, just use the backdrop color or the Texture Environment (with a gradient); that's hdri as well inside of LW.

04-29-2004, 06:10 PM
In my own super basic terms it is this-

normal image files are 8 bits per channel

8 for gree
8 for red
8 for blue
and maybe 8 for alpha

hence 32bit

Almost all video cards and monitors handle only this range of color info in an image. White is white, black is black...and no further.

HDRI images can be much higher than this.
say something like 96bit depth. Each channel has a lot more info than can be seen on your monitor, but LW's internal image sees this info and uses it. One way is to light and "shade" a scene with it when doing a radiosity render. All of the bright parts of the HDRI image become "lights" that will illuminate your scene and or give you "true like" reflections and lighting.

So where a normal image has just white the HDRI could have "super white" or stronger white light in it. This will corispond to having a brighter "light" coming from that part of the image.

The best way to understand it is to use it in some tests on metal surfaces and for HDRI global illumination of a simple object in a scene. If you have FPrime it makes it a lot easier too...

04-30-2004, 07:34 AM
OK, thanks, I am dying to try it, but HOW?

Can someone direct me to a tutorial? DO I need extra software to do it? I do have FPrime.

04-30-2004, 02:05 PM

I tried your solution i.e. the steps, but I don't get
the 'shadow' border you have in your example render.

My object looks just flat on the white backdrop, to 2D and not near 3D.

Any lights or additional settings I am missing?


05-01-2004, 06:29 AM
Sounds like your lights are two bright and are drowning your shadows.

Check that shadows are enabled-Render Options and Light Properties Panels

Note that the white backdrop will produce shadows regardless to whether shadows are enabled; when radiosity is used.

Most importantly, adjust the diffuse values of the ground plane and the object(s). If the diffuse values are too high, the objects brightness will drownout the shadows.

Reduce the Global Light Intensity to 30%-Gobal Illum Panel

Reduce the Ambient Light Intensity to 0%-Gobal Illum Panel

Add a ground plane to receive the shadows. Set the ground plane's alpha to "constant black"-Items Properties. In the end, the alpha will let you seperate the object from the final image and composite it (see attached).

I know this seems more difficult that I first described. But as you gain experience, you will check these items without thinking and you will see that it is actually that easy.

Check out the tutorial on the game pad in the Newtek tutorial section.

Hope this helps you.


05-01-2004, 07:24 AM
Here is a good write up on HDRI images.


05-10-2004, 09:06 AM
A good way to create HDR images is to use HDR shop it's free.


You take a picture of your enviroment using different exposures and HDR shop will combine them into a HDR file which Lightwave can use. If you get hold of a light probe as well you can do 360 degree shots.