topic Re: AC 11 "internal sun" settings in Visualization

AC 11 "internal sun" settings

Anonymous — Thu, 11 May 2023 12:01:57 GMT

Hello Everybody,
as there are a bunch of new settings for the Lightworks Sun (PhotoRendering Settings Dialog) i'd like to ask if there is any explanation for the settings.
I discovered, that a soft shadow is produced after changing "Shadow Transparency" to "0" (all off)
What is a "Shadow Acceleration"?

Re: AC 11 "internal sun" settings

Thomas Holm — Wed, 12 Dec 2007 15:51:16 GMT

Do a search.
Check out http://archicad-talk.graphisoft.com/viewtopic.php?p=77240#77240

Re: AC 11 "internal sun" settings

Anonymous — Wed, 12 Dec 2007 16:22:44 GMT

thanks for your answer, but it doesn't quite match. At least it doesn't give me any explanation of the settings.

Re: AC 11 "internal sun" settings

Dwight — Wed, 12 Dec 2007 16:56:41 GMT

Bernhard:

As a user who has burned hours trying to make sense of the Internal settings for the Sun in Archicad 11 to no scientific result but bitter tears, here is my reply to your query asking for explanation:

1: That the internal sun "Sun" Class "Sun" Shader is imperfectly implemented - to speak politely. After hours of experimenting, I suggest that it is a waste of time to try to control sun through this method. In my seminar, I make a joke about the light controls you refer to as if they part of a skit in the sixties American television show Candid Camera where the victim is packing eggs arriving on a conveyor belt. The shill tells him that if the eggs start coming too fast he can stop the belt by pressing a button, but it is not connected to anything. What a mess!

The attached image shows my lousy results trying to make a soft shadow using the "Sun" shader compared to hard shadow with ambient fill.

There are no meaningful or predictable results to be gained by adjusting the sun in this dialog - soft shadow settings merely produce erratic results. This sun method should only be used for hard shadows.

This shader uses what is called a "shadow mask" to generate the shadowed value. The rendering engine locates the edge of the shadow and applies a grey mask to the shadow area.

This method of generating sun should be mitigated with plenty of ambient light and a secondary sun - the sun object - manually set to shine strong blue light into the hard shadow cast from the main sun.

2: Archicad users seeking soft shadows should rely instead on the "Sun" Class "Realistic Sun" shader where actual rays are traced to provided true shadow calculations showing umbra and penumbra.

This method of generating sun should also be mitigated with plenty of ambient light and a secondary sun - the sun object - manually set to shine strong blue light into the hard shadow cast from the main sun.

Re: AC 11 "internal sun" settings

Thomas Holm — Wed, 12 Dec 2007 16:56:43 GMT

OK. Do a Google search then, like this: Search for
Lightworks "Shadow Acceleration"

It's at least possible that the results will tell you something. Me not. Guess it's Dwight's call. Buy his book and he'll be nice!

Re: AC 11 "internal sun" settings

Thomas Holm — Wed, 12 Dec 2007 17:19:42 GMT

Searching for the Shadow Acceleration, I found this resource that might be of interest to some. It contains some docs on Lightworks as well as general GDL which doesn't tell me much, but also som einteresting info on new featuers of the basic library in Archicad 11.:
http://download.graphisoft.com/ftp/techsupport/documentation/developer_docs/BasicLibraryDoc/11/

Re: AC 11 "internal sun" settings

stefan — Tue, 18 Dec 2007 08:40:16 GMT

FWIW, the "soft shadows" in ArchiCAD/LightWorks are only working when you turn of transparency in rendering. It is a bug and was mentioned to GS, but they did not fix it.

Re: AC 11 "internal sun" settings

stefan — Tue, 18 Dec 2007 11:31:20 GMT

Here is an example of soft shadows in ArchiCAD.

Re: AC 11 "internal sun" settings

Anonymous — Wed, 19 Dec 2007 20:22:58 GMT

Stefan,

Correct me if I'm wrong but in my opinion "soft shadows" have more to do with transparency then with softened edges... With less colour intensity the edges will become automaticly more vague...

Lightworks lamps are fast and easy to use rather then internal sun settings...
While using lamps, don't forget to switch off both the sun and the camera in the photorendering settings.

Lightworks sky object + 75% and sun object + 25% to start playing with...

Re: AC 11 "internal sun" settings

Dwight — Wed, 19 Dec 2007 20:39:47 GMT

With all due respect, users seeking soft shadows should investigate the Internal sun through the PhotoRendering Settings Dialog: The Class "Sun" with the Shader "Realistic Sun."

The default is a diversion angle of 5 degrees and the maximum is 30 degrees, simulating high overcast.

These shadows are actually calculated, having fine umbra and penumbra effects, not the hideous, clashing overlapping shadows made by the SunObject.

I feel, however, that most users are wrong to spend time trying to make soft shadows, both in setup and in rendering time. Using the Internal Class "Sun" Shader "Sun" set to HARD shadows is most appropriate to render architecture PROVIDED THAT adequate shadow fill light is provided through both Ambient lighting and, say, a SkyObject colored blue or a SunObject manually set to directly counter the strength of the main shadow cast in the scene. And don't forget your Undersun to avoid black soffit disease.

This advice assumes you want Kodachrome renderings - like photos made on clear sunny days.

Re: AC 11 "internal sun" settings

stefan — Thu, 20 Dec 2007 08:31:32 GMT

Joeri wrote:
Stefan,

Correct me if I'm wrong but in my opinion "soft shadows" have more to do with transparency then with softened edges... With less colour intensity the edges will become automaticly more vague...

Lightworks lamps are fast and easy to use rather then internal sun settings...
While using lamps, don't forget to switch off both the sun and the camera in the photorendering settings.

Lightworks sky object + 75% and sun object + 25% to start playing with...

I was mainly arguing that when using Lightworks, the "internal sun" has a setting called "soft shadows", which uses bitmap shadows, instead of raytracing. When you enable this option it has no effect at all when transparency in the rendering settings is enabled. They are still raytraced sharp shadows (which is fine for most purposes). However, when you disable transparency calculation, the internal sun suddenly uses the bitmapped shadow and thus all settings for soft shadow (map size etc...) are used.

Your example is a clear example that the dedicated Lightworks Lamp objects can produce a more pleasing result. But I would use the internal sun at its default for fast renderings and the realistic sun for good (slow) results.