1. #1
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    Default What exactly is Retopo?

    I see a lot of posts talking about retopo. What is it, why is it necessary and how is it done? Thanks in advance for any insights you can offer....

  2. #2
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    Default Retopology

    The process of rebuilding your model for use in a game or animation environment. The best example in these forums is the Dominance War entries. Open a few and scroll down. You'll see the Million-poly Zbrush models have been retopologized to low-poly frames and the details projected to a normal map. The limit for the challenge was 12,000 triangle polygons. This process can be done using several other softwares, the most common being Blender (because it's free). Zbrush can do it, 3DCoat, has a nice Auto Retopo function, There's a software called Topogun, which was build just for this purpose, and I posted a series of vids here on using Wings3d to do it.

    Here are some vids on the subject. Understand, your games are figuring for score, camera position, enemy movement, etc. It can't animate a "million vertices". Not at 20+ FPS. So we project our details from our High-poly model to our Low-poly model. One the computer can animate. This is where another topic comes into play. Edgeflow. Although the end product is always triangles, most animators prefer Quads for retopo. Parts such as Knees and elbows are expected to bend and so the mesh must stretch like skin, and poorly placed UV-map seams will Show through when animating, so we must get involved in the UV-mapping process and do our best to hide the seams. More organized meshes (quad meshes) with selectable edgeloops and enough geometry in these areas can help with this task. Then we must "Bake" our details (color maps and bump maps) from our High-poly model to our low-poly textures. Blender, Zbrush, and there another called XNormal that can do this.

    My personal take on the use of Sculptris for game modeling, is to use Quad meshes built in wing3d or Blender from the start, turn off Detail (Dynamic Tesselation) and just use the sculpting tools to shape the mesh I have. Then when I'm happy with my silhouette, I take the model back to Wing3d to UV-map, then come back to Sculptris to Paint. Since Sculptris allows me to paint to my Normal map, there's no need to "bake". And since I'm already using a low-poly quad model. There's no need to "retopo". Of course this means planning in the modeling process, which is the "old School" way, and pretty much ignores the "Free Creation" which Sculptris was meant for.

  3. #3
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    Default

    Wow, JDG - thanks for such a detailed explanation of the process! I will definitely check out those links you suggested. Your thoroughness is greatly appreciated!

  4. #4

    Default

    Just a heads up. Retopology in zbrush can be a real pain.

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