View Full Version : Looking for info on Non solid objects

12-08-2006, 05:30 AM
Hi folks

I am doing a project on 'non solid objects' and I thought it might be wise to pop in and ask any of you guys if you had read anything interesting either books , or on the web (sites/journals etc) that I should look out for.
I am just starting so anything from the ground up would be great. I just thought someone here may have a bit of knowledge and could point me in the right direction.

some of the things I will eventually cover are stuff like, cloth and liquids for example so any info on these would also be cool. I was after something that explains what non solid onbjects are in general and how they can be achieved in the likes of lightwave 3d.

anyway enough waffle , if you have got a great link or a good book to buy pls let me know , thanks

12-10-2006, 12:51 AM
Edit: sorry gave info on solid object, misread your post.

12-10-2006, 01:19 AM
Lightwave is a non solid modeler. A non solid model is like a skin wrapped to make up an object. The skin is made up of vertexes which connect to each other to form polygons. Each side of a polygon has a normal, when the normal is missing on a polygon the polygon appears to be invisible on that side of the polygon. Lightwave's default is to use single side polygons or one normal. This helps in reducing the amount of time it takes to render. However some objects like a cup require that both sides of the cup have normals so you can not see through the cup. This is accomplished by modeling both sides of the cup mostly to give thickness, or to add a backside normal to the polygon which is great when you don't require any thickness.
To verify that lightwave is a non solid modeler, you can select a polygon on an object and delete the polygon, you will find that the object is hollow. In order to see the inside walls of the object the normals of the object must be facing inwards. Polygons can be flipped (for example when rendering a room you can render just the inside of that room without having additional rendering time for the outside walls since they are not required the polygons are flipped inwards to help save render time) or the backside normal can be enabled.
For more information go to the wikipedia for Polyhedron (http://en.wikipedia.org/wiki/Polyhedron), surface normals (http://en.wikipedia.org/wiki/Surface_normals)
Hope this helps,

12-10-2006, 05:55 AM
not only does it help it is also very interesting thanks for that silk , I will check out those links also.