Calculation of trasparency in shadow casting GDL command?

[Anonymous]

My question is:

How can I influence the shadow casting of transparent surfaces in GDL billboard objects in case of using the Lightworks rendering engine?
Are there any GDL commands for it?

See problematic example below.
Don't suggest me to cut around all the leaves instead of using Alpha channels...

[Djordje]

Zoltán wrote:
How can I influence the shadow casting of transparent surfaces in GDL billboard objects in case of using the Lightworks rendering engine?

Where does the billboard object come from?

[Anonymous]

I made it myself following the example of the "Intro to Object Making.pdf" cook-book found in the Graphisoft documentation folder of AC 9. (I added some extra functions as well). (BTW. there is an error in the book, it suggests for AC 9 users to use the hotline command instead of the line command in the 2D description however hotline without the line command is invisible.)
It uses a picture of the AC 7.0 Library by default. See attachment.
But the situation is the same with all the billboard plants of any AC library.
Everything seems to be correct if in the photorendering the sun is situated opposite to the camera, but if it is somewhere behind the camera, the above mentioned effect occurs.

[Karl Ottenstein]

Hi Zoltan,

I downloaded your object, and did not have any problems at all rendering it with Lightworks. See attached. I just placed it and it worked. Perhaps a screenshot of your LW rendering settings might help reveal what's happening for you. If you are using sunobject and skyobject (as I did below), post screenshots of there settings.

Attached is straight out of AC. (Normally I would desaturate the garish colors.)

I just searched for all instances of HOTLINE in the Object Making book ... and I think you didn't understand what David was saying. He does say the right thing each time, and in each example: the hotline is an optional addition for AC9. It is not a substitute for the LINE2 itself.

Cheers,
Karl

[Anonymous]

You or your machine seems to be a genius. I've been trying it with all the settings but nothing changed. I tried with Ligtworks and Z-buffer as well. See attachments. (It also contains the screenshot.)
I also tried with a default library part from the 9 library. (Billboard tree 9 LW.jpg) the result is the same.
The only way to get a correct render is using the old built in rendering motor and checking the use transparency button at the shadows setting.
Could this depend on any hardware? I also had a look at my registry settings. I didn't find anything special in the LightWorks Rendering section. But what does the writ LGA file entry mean?
Another question: with which GDL command can I get the proportion of a loaded images's sides? I want to write on option for the object the way that it automaticallly takes the correct "A" and "zzyzx" parameters.depending on the loaded image.
BTW Thanks for explaining the hotline2 command. You were right I misunderstood it's functionality.
I wish there would be a GDL Reference Guide printed in Hungarian like for 6.0... there is not even a pdf, only in English. I'm still using my old 6.0 book, it looks like a salad...

Balázs

[Karl Ottenstein]

OK. The plot thickens. (And, is it Zolt or Balazs? 😉 )

The image I generated used only the skyobject and sunobject, and had only lamps enabled.

Your settings have the sun, ambient, camera all at 100% and have lamps enabled too. Generally, you never want to use the Camera light as it tends to ruin the lighting of a scene. In this case, it is the camera light that seems to cause the problem. Using your settings, I see the transparent areas as well.

Turn the camera light off and render again. Then, turn off the sun and ambient and insert a sunobject and skyobject - changing their default colors to yellow sun, etc.

(Using LW effectively is not that easy or obvious ... hence the need for Dwight Atkinson's book, coming 'soon'.)

See this message from Greg Kmethy of GS about a possible cause of what you are seeing:
http://archicad-talk.graphisoft.com/viewtopic.php?p=27388#27388

Now, if you follow his link there, you'll see that defining a material for Lightworks in GDL is way more complex!

I don't know what the "Write LGA file" registry key might be for. Also don't know of an easy way to retrieve the pixel dimensions of an image located in the library.

Karl

[Anonymous]

First: Let's stay at Zoltán (I have several names)

THX for the useful link.
I combined the suggestions with the linked script. (It took about one hour understanding the DEFINE MATERIAL and IND commands. %-) Everything is fine. Actually my own billboard bushes function better then the AC library's 🙂 The correct material definition should be corrected in the object making cook-book.
I'm getting confused. Not only the material definitions but also the lightening settings got complicated. (Or maybe the previously offered rendering options were too primitive but comfortable...)
I tried once the skyobject but it strongly influences all the colors what I think is confusing together with the material definitions. At least I have good experiences with the sun object...
BTW The Lightworks presentations cook-book contains explications only for few Lightscape definitions. There are hundreds of settings without any explication so I'm looking forward reeding Dwight Atkinson's book. I hope it will have a Hungarian translation once...
So, the answer for my original question "Are there any GDL commands for it?" is that "Yes, in the material definitions."
Again thanks for your help!