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Using Topology

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Joined: 30 Nov 2006
Posts: 26

PostPosted: Fri Dec 01, 2006 8:10 am    Post subject: Using Topology Reply with quote

Well yet another question for me for you guys. Today i just started using topology and its a little frustrating. As you know I am texturing a road and would be in need of using topology on the upper,lower,and inner edges of the road.

When using topology what type of map do you use, the usual Displacement type map?

There's currently no tutorials on topology and i'm stuck on reading the manual over and over trying to grasp it.

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Joined: 04 Nov 2005
Posts: 342

PostPosted: Fri Dec 01, 2006 10:56 pm    Post subject: Reply with quote

This is a high level description of topo maps and their use.

Most surfaces you deal with are not completely flat. In the past, the only way to create some variation in a slab surface was to use a polygon post process, or displacement maps during render time. During demolition most surfaces don’t remain completely flat either. Chips break away and cracks and distortion occur. Topo maps were are added to help these two problems. Topo maps are used to adjust slab surfaces dynamically.

Topo Maps work in a similar fashion as displacement maps. They push or pull on the mesh vertices along the mesh normals. The amount of displacement is based on the maps luminosity for each point computed by its uv coordinate in the map. (Same as texture maps)

Topo maps are divided up into the four regions of a slab: upper, lower, inner and outer edges. Each map will effect only a particular region. There is also a before and after map. The before map is what displacement you wish to apply to the slab at the start, and the after map is what you wish to see at a later frame. The blending between the before and after maps is controlled via a target control surface (ie. Deform, pressure, secondary, or cracks).

Say you wanted to punch a hole through a wall, and roughen up the edges around the hole break area. We’ll keep the start slab smooth by attaching nothing to the before topo map, and attach a fractal map to the after map that will roughen up the slab surface. Use the same deform control surface that was used to punch the hole through the wall to blend in the after map. Run the sim, and the area surrounding the hole break will roughed up at the same speed as you deform control surface.

Topo maps have additional uses for inner and outer edges. They allow you to add beveling to the edges. Something that is very important for high quality renders. Ramps are used here to give precise control. Additional points can be added to the edges as well for this purpose.

When using topo maps you should always try to use hard quads. This is important because you need the extra geometry for smooth displacement. To keep your sims quick during creation time, make adding topos and hard quads the last step in your simulation setup, just before rendering. Ofcourse, they can always be turned on and off as necessary later.

No doubt that a tutorial for topos would be very useful. Hopefully we’ll have one soon. In the meantime, experiment a bit, once you understand the concept behind them, I think you’ll find them very useful.

Hope this sheds some light on the topic.

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Joined: 30 Nov 2006
Posts: 26

PostPosted: Sat Dec 02, 2006 2:48 am    Post subject: Reply with quote

Thanks alot man, I will have to play with these this weekend.
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