Sunday, May 18, 2014

Exterior Lighting using Sun & Sky along with Geographic location and Shadow study

Hello and welcome. In this post I will explain the procedure to setup Sun & Sky for the purpose of simulating an exterior lighting and to conduct a shadow study. I will also explain setting up a Geographic location for the project.
Exterior Lighting in AutoCAD
First of all let us have some basic understanding about an exterior scene and lighting setup. I have created a very simple scene here with some primitives. This scene can be called an exterior scene, because nothing is enclosed inside any objects. We haven’t yet placed any light in this scene, neither sunlight nor artificial, but still we are able to see the objects. That is because; there are some default lights which are automatically placed on the scene by the program so that we can see things while we create them.


The following is the workflow to setup an Exterior Lighting and to conduct a shadow study in AutoCAD
1. Setup the Lighting Units.
Go to Render Tab click on Lights Panel
The choices are GENERIC, AMERICAN and INTERNATIONAL, depending on what units you use. Use INTERNATIONAL if you are using METRIC system i.e. meters.
 2. Turn off the Default Lighting (so that what is contributing to the illumination of scene is only the lights that we introduce)
Go to Render Tab, clicks on Lights panel and click Default Lighting to turn it on & off.
Also make sure that the Visual style of your view is set to Realistic so that we can see the effects of lighting and shadows in real time in the view port. (i.e. without the need to render the scene)
3. Turn on the Sun
Under Render tab, click on Sun Status to turn on the Sun
3a. Choose a Sky option.
To get the full effects of Exterior Lighting, you must turn on Sky Background & Illumination.
Note: Sky option will only be activated if the View projection is Perspective and will not be available if the View projection is Parallel. You can right click on the View Cube and select Perspective or you can type Perspective in the command prompt and enter a value of "1" to make View projection as Perspective.
 
4. Shadows are next
The two options for SHADOWS are GROUND shadows and FULL shadows. GROUND SHADOW is the shadow which is being cast on the ground. This is a bit tricky. How can AutoCAD determines which is ground. Well for AutoCAD the plane that is passing through Z co-ordinate zero is ground plane. Everything below that is underground and everything above it above ground. This also means that even if you don’t create ground plane, the ground shadow will still be visible if the bottom Z coordinate value of the objects are ZERO.  You can verify the co-ordinate value of any point by using ID command. Just make sure that Z value is zero.

FULL SHADOW is the shadow which is being cast by objects on to other objects.

Click on the arrow next to SUN&LOCATION to access and alter Location of HORIZON , SUN DISK APPEARANCE etc.

5. We have to set the Geographic Location now. This step will ensure that our model is positioned exactly where it is to be located on the Earth, so that the shadow study and lighting analysis are accurate. Setting the location is a bit different in AutoCAD 2014, than up to 2013. In AutoCAD 2014, it is imperative to have an autodesk360 account in-order to view the map. Otherwise we should know the latitude and longitude of the location of our model. However both of them, i.e getting a autodesk360 account or knowing the co-ordinates (just search in google) is easy.
 
After Signing in to your Autodesk account, search & find the location of your project. Click on the "Drop Marker Here" to place a Geographic Marker on the Map. Choose a "GIS coordinate system" which is closer to your local area for improved accuracy.


6. Once the location is set, click on Continue to set the North direction. Move the DATE & TIME slider to see different lighting condition for different times of the day or year and to conduct a shadow study.


That is all for now and see you again in another post. I hope this tutorial was useful for you.  If you have any comments, suggestions or questions please let me know. My name is Sunil Mangatt and thanks for watching. Good bye.

 
 

No comments:

Post a Comment