Tutorial: Using Iray with 3Delight Skydomes
Tobor
Posts: 2,300
From time to time peeps have asked how to use their beloved 3DL skydomes with Iray. For those who haven't tried it yet, the skydome is an all-enclosing geometric object, and will not let the Iray Environment dome or Sun-Sky to penetrate. The end result is a dark scene, with no light falling onto the inside of the skydome.
Various methods have come up, including using Hexagon to chop off the front or top of the skydome, so that Iray's light will shine through. In another thread, our own Richard Haseltine reminded us about the Iray Section Plane Node feature, which some of us have used for comic effect, such as sawing a person in half. No doubt that isn't what nVidia and Daz had in mind with this section plane node!
So I thought I'd work up a short how-to on using a generic skydome designed for 3DL or Poser, and Iray. I have the old TerraDome, but most any dome with a physical geometry will work.
1. In a new scene add a character, and put some clothes on her, for goodness sake. Nobody likes nudity, you know.
2. Add your dome and texture it with the image you want.
3. Choose Front View, select the dome, and click the framing button. You should see the entire dome in the Viewport.
4. Choose Create->New Iray Section Plane Node. This adds an Iray section plane at the center of the scene. You won't be able to see anything physical, but it's there.
5. Select Iray Section Plane Node 1 in the Scene list, then Y translate it upward to about 1/4 up from the floor. This is for testing, so you can see the sectioning at work.
6. In the Iray Render tab, choose the Environment group, and choose Environment Mode-Dome and Scene. Add an HDR image -- the "Ruins" environment included with D|S 4.8 is a good one.
7. Select your character, and frame her (or him).
8. Do a test render. You/ll see the effect of the section plane: it literally cuts the top off the dome, allowing the Iray Environment to show through.
9. Go back to Front View, select Section Plane Node 1, and Y translate upward for a more reasonable cutoff. You want a large enough opening at the top of the dome to let light through, but not so large that the camera sees the sectioning.
For reference, I include two other images:
* DomeOnly shows just the Iray Environment dome, and no skydome.
* Dome-NoPlaneNode shows what happens when you load a fully enclosing skydome. This particular skydome doesn't have a ground, so some light from the Iray environment is coming in through the floor. There is no light from the top, however, because that part is being blocked off.
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Comments
Thanks. That will be very useful.
Thank you! It worked great with a environment dome I got, but it doesn't seem to work with cube shaped ones. Any idea why?
As long as it sections across the cube/tube/cone/sphere/whatever, it should work. Using the Front View makes it easier to see where the horizontal of the plane is currently at. If the plane is above the shape, there's no sectioning. If it's below the top of the shape, it should section it. If you put the plane at the height of the character, you can more readily see the sectioning it's doing. It'll even cut the head off the character if the plane is low enough. In fact, try that to ensure the plane is positioned properly.
Also make sure you don't rotate the plane, or else it won't cut horizontally.
It does not work with the skybox I have; maybe it is too small. The figure is illuminated, but the background is just black.
This may help with The skybox:-
Load the Flipmode Easy Environments Skybox (Iray the surfaces of course) load an Iray section plane node, Load a small sphere primitive and parent it to the Iray section plan - this is simple to make it more visible for placement. take the plane node up to Y Translate 13000.0 - This just makes the top invisible. I set the Iray Environment Intensity to 4.0 (This was the 'Top of the World' Enviroment) I tried this after reading your post just to see if I could make it work. It matters not what cube type enviroment you use because attaching the Sphere primitive to the plane allows you to see where it is when you raise it - just before it dissapears through the top is good - and of course one in position turn the sphere off.
Finally I got them to work; it was related to the shader of the skybox. But thanks for your help anyway, you got me to try again :)
Thanks so much for this tutorial. So pleased to be able to use my skydomes again :)
You're welcome.
Don't forget you can use the same technique with a closed interiior set that doesn't have a removable ceiling. Lower the plane so that it just sections the top of the set's geometry. That will "open" up the top, where you can now more easily light the set. As they do in the movies, it the camera sees the edge of the ceiling, you can put a small plane primitive there, and texture it with something that looks like ceiling material.
This does not seem to work for me. Tried it with the domes from Digivault Stardomes, Predatron's Essential Lights & Skies, along with BWC Skies. The figure illuminates, but only with a completely black background (the plane seems to do something, because when I intersected it with the figure, only what was below it of the figure showed up).
The plane is most definitely inside the dome, not above or below.
If the dome has physical geometry it will section with the plane. BDo a test render under 3DL to ensure the dome is properly textured.. If not enough light is entering the dome and illumintating the background, you probably need to section further down.
The same happened to me with some skyboxes, If using iray and converting the shaders of the dome to iray uber shader, check the diffuse strength and increase it to 1.0; that did the trick for me.
Rafner: Better late than never. Just learned to use Predartron's Essential Lights & Skies. Your solution is brilliant - I would have not thought of it. Difffuse strength for the the skybox to 1.0 did the trick. Thanks.