Tracking Sun motion for shadows

G

graemeb

New member
Hi,
My first post. I am in the process of creating a 3D model of my house and want to be able to see shadows etc at various times of the day and of the year. I have worked out that Sun Spot is what I should be using, but am having issues with it.
Firstly, there are some presets in it, but, is there a way to add a new preset Long/Lat and save it so I do not have to continually retype co-ordinates?
Secondly, after playing around a bit it seems as though the sun in my scene is rising and setting on the wrong side of my test object. That, I assume is because my object is not correctly oriented. I also assume that the orientation comes from Modeler (is +Z True North?) and want to know if anyone can point me to the right place for working out how and where to position/rotate my objects so that they relate to the real world and work with Sun Spot to give correct shadows. I am at a loss as the only things I can find in help and even old pdf manuals relate to the basic use of the Sun Spot modifier but not how it is set up and relates to the real world. Any help would be MOST appreciated.

Thanks!
 
graemeb said:
Hi,
My first post. I am in the process of creating a 3D model of my house and want to be able to see shadows etc at various times of the day and of the year. I have worked out that Sun Spot is what I should be using, but am having issues with it.
Firstly, there are some presets in it, but, is there a way to add a new preset Long/Lat and save it so I do not have to continually retype co-ordinates?
Secondly, after playing around a bit it seems as though the sun in my scene is rising and setting on the wrong side of my test object. That, I assume is because my object is not correctly oriented. I also assume that the orientation comes from Modeler (is +Z True North?) and want to know if anyone can point me to the right place for working out how and where to position/rotate my objects so that they relate to the real world and work with Sun Spot to give correct shadows. I am at a loss as the only things I can find in help and even old pdf manuals relate to the basic use of the Sun Spot modifier but not how it is set up and relates to the real world. Any help would be MOST appreciated.

Thanks!
Click to expand...

Heya graemeb,

You pretty much have everything correct :)
Unfortunately there's no way to save a LAT/LONG preset , but whatever you type into your location settings gets saved in the scene so you only really need to do it once per project. Not that big a deal.
+ Z becomes North as far as I know.
I tested LW's sunspot modifier a while back against other packages (there used to be a bug in the maths somewhere) and from memory it's been fixed since version 11.3 (maybe earlier as my dates are hazy)

So as long as your model is orientated like it would be in real life ( with + Z being north) and everything is to / at scale then you're good to go.

Good luck with it all and welcome to the fold :D

adk
 
Hi adk,

Thanks for that. Have been fiddling around a bit and it sort of works but still does some strange stuff. I had to place a start and end point for the sun's track which I would have thought would have been calculated by the modifier, unless I am doing something wrong. I am struggling with the time-lapse factor, can't quite get my head around what the number should be for 560 frames which represents 14 hours of sun travel. I end up with the sun shining at odd times e.g. 6 am and cutting out abruptly rather than fading. I have key-framed every 40 frames with the appropriate hour set in the modifier but not sure whether I should have done that - it does produce a bit more realistic sun path.

My ultimate aim is to be able to model structures with LWCAD and then set various scenes to compare shadows during the day at various times of the year.

Are there plugins that might do this better/easier?

Thanks again,
Graeme
 
Heya Graeme,

It's been a while since I did a shadow analysis so I'm not sure if this is the correct or ideal way to approach what you need, but this is what I would do...

In your scene set your animation frame length (560 in your case)

1. Centre your light at 0,0,0 (if it's a distant light it can be anywhere so 0,0,0 is as good a place as any)
2. Add your sunspot motion modifier to your light and set the distance to 0 so that the light remains in the centre (just for visual reference)
3. Get the rotation fields to display for the light in the bottom left corner (space bar toggles the modes)
3. Set your location co-ordinates, year, month, day and hour (for when sunrise supposedly is)

Stay at frame 0 ...
This is where I tweak the hour / minutes sliders so that my light PITCH at the starting frame is 0 or as close to that as possible.

Go to frame 560 ...
Now adjust the Time Lapse slider until your light does a full days sweep of the sun (will probably be somewhere in the 2500 range) and the pitch at the final frame is 0 or as close as possible.

That's it in a nutshell. Hope it helps and it does what you want.
Let me know if that's all clear, otherwise I might spend some more time and attach a few animated gifs to demonstrate the whole thing.
It's pretty straight forward.


adk
 
Hi ADK,

Back again. Have a tendency to hibernate, swapping from Family History to 3D and other interests so not as consistent as I should be to remember new stuff - must try to be more consistent.

Followed your instructions and that makes sense but the sun colour seems way too red at the end of the day. I assume I have to set up individually for each day of the year I want to do.

I found a Sunsky tutorial which was excellent and explained the timelapse setup, but it seems as though the DP lights don't work in 2018, unless I have not set the plugins up correctly. Do you know if that is the case? The DP lights looked to be excellent and it would be a pity if they did not work in 2018.

Thanks for your help.

Graeme
 
graemeb said:
Hi ADK,

Back again. Have a tendency to hibernate, swapping from Family History to 3D and other interests so not as consistent as I should be to remember new stuff - must try to be more consistent.

Followed your instructions and that makes sense but the sun colour seems way too red at the end of the day. I assume I have to set up individually for each day of the year I want to do.

I found a Sunsky tutorial which was excellent and explained the timelapse setup, but it seems as though the DP lights don't work in 2018, unless I have not set the plugins up correctly. Do you know if that is the case? The DP lights looked to be excellent and it would be a pity if they did not work in 2018.

Thanks for your help.

Graeme
Click to expand...

Heya Graeme,

No problem on my end, just so long as you don't ping back years later and expect me to follow that same train of thought / thread :D
The sun colour could be to do with the sunlight model used Hosek-Wilkie vs Preetham. They do exhibit very different colours at mid day and sunset so that could be it.
Just the fact that you have that going tells me that you have the light colour hooked up correctly via the channel modifiers. The only other thing to check would be the Lightwave ColourSpace - should be set to sRGB rather than linear if you want WYSIWYG in VPR.

I'll upload a scene for you when I get home later tonight ... if I remember.


Al
 
graemeb said:
Followed your instructions and that makes sense but the sun colour seems way too red at the end of the day.
Click to expand...

Hmm, was this using the DP Sunsky sun color modifer? IIRC, Prometheus has had some luck with it in LW2018. OTOH, I've encountered significant issues with it here in LW2018(.0.5): Instability, and what seemed like "inappropriate" color results in a couple cases. I haven't had a chance yet to dig into precisely what was occurring yet, alas.
 
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