Need help with parallel light on a transparent picture texture. Earth.

dsamhartman

Hello, long time user of Bryce (since 2.0) but first time poster! Hope you pro's can help on this one!

I have a pretty firm grasp of the program, however, I'm running into a serious problem with lighting objects on a texture with transparent image using a parallel light object (or any light object). No matter how I set it, the light seems to go right through and backlight the transparency.

It's set up with 2 spheres .01 increments in difference of size.  One sphere for the earth and one for the clouds. You can see the issue on the right side of the image below.

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This occurs with the sun/sky completely turned off and blacked out, with the spheres lit by a single parallel light. (with the sun/sky turned on -as the only light source- it renders correctly, however I do need it to work with lighting objects in order to incorporate (a third sphere of) the city night lights as shown below)....

...Where I ran into the same problem (same setup of 2 spheres) to do the nightside of the earth's city lights, but in this example we're using 2 opposing parallel lights that each exclude 1 of the 2 spheres. You can see that the city lights are appearing on the day side, while the non-transparent earth sphere respects the lighting exclusion.

 

 

It's a very annoying problem for me and I dont know why it's behaving this way with that type of texture. Any help would be extremely appreciated. Thanks

Also, I would be happy to provide the source documents to anyone who is serious about troubleshooting this issue with me!

Electro-Elvis

Hi Dsamhartman

An annoying problem. I'm afraid I am not quite sure I have understood your setting completly right. Therefore I made a example with three spheres:

1. The smallest one is the earth with the suitable texture.

2. The second one is a little bit bigger than the first one. This are the city lights (which are randomly spreaded over the earth here)

3 The purple one should be the clouds.

Did I get it more or less right? If so, I run into your problem, as soon as I changed the transparancy settings of my purple material. The initial value is zero, but when I change it to any other value, the effect you described occures. It is not so obvious, but I think you can recognize it.

 

 

 

dsamhartman

Hi Electro-Elvis thanks so much for the effort trying to figure this out! And yes you are seeing a similar issue in your clouds as well. I'm assuming your city lights (which seem to be behaving correctly) are set to zero as you described in order for them to not show on the day side (with opposing parallel excluding lights too?), however for me, even if i set it to zero they show up on the day side, so thats a little maddening to see that they are working for you. Hmmmm... maybe they too are behaving wrong looking closer around malaysia and the phillipines.... hmmm hard to tell without seeing the scene.

I have even tried it with an extra hidden black sphere inside the others hoping that would cast a shadow to black out the efffect, didn't work though. Makes me wonder if the problem is inherent to transparency in the software.

I'm going to twiddle some knobs, reset the textures, double check the sky and see if your clue on the zero'ing pans out for me.

EDIT- it turns out the city lights are more problematic than I thought, due to the fact that they are blacking out the cities on the day side. Apparently there's no way to have the illumiation determine the transparency in Bryce. Looks like I'll have to make a photoshop composite of the earth and clouds using the sky illumiation and a separate rendering of the city lights.

I'd love to be proved wrong that this is just impossible to get the 3 spheres (earth, clouds, and city lights) to appear accurate in one rendering if anyone is up to the challenge. Here's a link to a directory on one of my servers with all the earth map assets. No copyright, they're all derived from nasa imagery so you may have to cite that if you do use them.

http://sokitumi.com/daz3d/

 

 

Electro-Elvis

Hi Dsamhartman

I have downloaded your scene and I'm afraid I can not help you. I have always got the same result like you. Instead of an parallel light for the city lights I tried to use a distant light. Because you can turn it around with a roller ball like the sun, I thougt I could position it in the way to match the borderline between night and day. But it is a fiddeling task and hard to get it right, and you can still see the city lights in the sunny part of the world, though they are not so bright anymore. (I have even tried out negative lights or the range option in the lighting lab - terrible results.

I think, you are right, it has to do with transparency. The materials I have used for my scene are using the "Quantize" filter option in the DTE. Therefore the filter only knows black and white. As soon as I changed the filter settings from "Quantize" to "Clip Smooth" for example, also from a black and white filter to a greyscale filter the unwanted effect appeared. 

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dsamhartman

Thanks again for the effort Electro-Elvis

Peter Fulford

I was suprised to see this issue. It seems odd, but perhaps there's a simple explanation. The cloud material needs to have "Receive Shadows" set, the planet needs to be set to "Cast Shadows", and the light needs to cast shadows.

The two examples here, which have multiple procedural cloud layers, obey those settings. Rather than city lights, in this case I've quickly adapted a cloud material to provide a sort of volcanic effect on the dark side, but the principle should be same. It is lit by a second light and both lights have had various objects excluded and included, etc. Note that I've ramped up the light intensity higher than I'd prefer to see if any back facing clouds were misbehaving.

It was fun messing about in Bryce again, even if it was just resurrecting an old file to adapt.

 

 

dsamhartman

Hello Mr. Fulford. Thank you for taking the time to give it a go, and your planet looks pretty awesome, nice work. I believe that yours are behaving correctly because they are procedural and not picture textures. This thing has already gone off to print, and ironically, with hours burned trying to get it to work, without the clouds or night lights included in the rendering. (because it just looked better as a simple globe than it did comped with those other layers)

Thanks again though!