Atmoshere only for render

Started by Tokmyra, January 04, 2022, 03:00:23 PM

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Tokmyra

I look around the forums and I didn't see anything that matches what I want to do.  Maybe someone can help out.  I just need a sky, no land or clumps of clouds at a 0 prospective angle and a 0 elevation.  Its for just a sky map.  I import everything in to Houdini so my terrain is a specific size. What happen is the cloud and haze make a ground plane you can see in the render.  I posted a render and circled what I'm talking about.  I tried all kinds of thing and I'm still struggle busing it.

My opinion has changed a lot about the software.  The more I use it the more I like it in my hobbyist pipeline.  There are a few features I'd like to see like roads and OSM import capability.

Thanks in advance,

Joe

Kevin Kipper

Hi Joe,

Based on your reference image and description, you can eliminate the cloud clumps by unchecking the ENABLE button for each cloud layer. 

In a similar way you can remove the terrain's displaced features (mountains/valleys) by selecting the nodes in the Terrain group in the Node Network pane and disabling them by pressing the D key on your keyboard.  You'll be left with an non-displaced landscape, that should appear mostly black or very dark, but it will still be influenced by the atmosphere settings. If you disable the Planet's RENDER SURFACE checkbox the terrain will not render, but you'll be looking through the haze/atmosphere and that may not be what you're after either. 

In the Render settings you can crop your image so that it renders only the sky.

Zero perspective is a function of changing the Camera setting from perspective to orthographic.  An elevation of 0 implies that the camera's Y axis position is set to 0. 

It would be helpful to know how you intend to use the image in Houdini, specifically how you intend to project it, so that we know if a spherical image is your best approach or some other method.

WAS

#2
Yeah, atmosphere only HDRI's are usually just cropped, so the ground isn't there. So the south pole of the HDRI is actually the horizon of the photo they took.

To do this in TG you could do as Kevin said with a crop.

You could also put your atmosphere height limits higher, and put your camera higher, so the "haze ground" is lower in the 360 image.

Update: With that crop image, you can still make it a equirectangular image if you make sure the crop is a 2:1 ratio, and than in Photoshop you can make the bottom equirectangular by using the polar coordinates (rectangular to polar), and then using the clone tool or something to fix the hard seam. If there is no hard seam, the image needs to be roated vertically. Once you have the seam fixed you do Polar Coordinates again, and this time use Polar to Rectangular. The image will now have the bottom repeatable.

WAS

#3
Update to the update, because the 360 is seamless, and the edge at crop 0.5 is the same, it's actually pretty much seamless. there was just a tiny little area that didn't repeat in polar. So the crop may just be ready to go.

Tokmyra

Thanks for the quick Reply.  Cropping is what I have been doing in Photoshop.  Because the haze with no terrain on was costing me more render time.  Between the two of you you answered my question.  I use HDRI's in Houdini as the environment light. Terragen EXR files give a real good lighting contrast.  The spherical map is exactly what I use.  Hodini can determine from the file what it needs.  I does not matter if its box, spherical, or tube.  You can also manually change it.   I will normally have a real world terrain, That I will bring in direct to Houdini.  I will probably do the real world terrains in Terragen once I learn much more about it.  Because its a hobby and I travel 80%.  I don't always get a ton of time to really study the tutorials.  I'm working on it, slowly and everyone has been great.  Thank you all for your support.

Joe

cyphyr

If you are using Houdini you could of course just "Clip to positive Y hemisphere" in the environment node.
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