New to Retopology- Advice needed on some stuff!

Somatrasiel

Hi everyone,

So like the title says, I'm new to retopologizing things- I'm not totally new to 3d, but I'm new to optimizing things for games and whatnot. 

On the right is the model I've made- the base of the hammer was done in Maya and the petals were added in Zbrush. I brought it back to maya to retopo, but I'm confused on how to tackle topology like this. The goal for me is to learn how to properly optimize for game assets so I don't want to just decimate/zremesh- I want to learn how to do it properly.



I've been looking at the image below as an example of something similar (protrusions on protrusions) but I have NO idea how the transparencies happened between the low outermost 'feathers'.



Any advice or examples would be greatly, greatly appreciated. 

Thanks for reading!

musashidan

Your primary concerns are silhouette and surface shading, and to a lesser extent these days when authoring for high-end, but still important, optimisation. The example you posted is great because it shows a really strong silhouette with as few triangles as needed to capture some great sculpting/texturing. The normal map is doing a lot of the work here. As for the lower feathers, you'll notice that the geo there is just a flat plane with an opacity map texture for the transparency(same with the top of the crown)

My main advice is to concentrate on capturing the silhouette(use a flat black shader or squint your eyes at the model from a medium distance) using as little geo as needed. Your own asset is mostly rounded/soft, whereas the example is mostly sharp/angular.

Zalek4

That's quite a hammer!

I would definitely agree with musashidan, the silhouette is one of the most important things when retopologizing a mesh. Judging from your right picture, I'd say you've got a good beginning going.

Also, for all your texture map information needs:
http://wiki.polycount.com/wiki/Texture_types

There's a pretty extensive section on opacity/transparency maps. 

Somatrasiel

Zalek4 said:

That's quite a hammer!

I would definitely agree with musashidan, the silhouette is one of the most important things when retopologizing a mesh. Judging from your right picture, I'd say you've got a good beginning going.

Also, for all your texture map information needs:
http://wiki.polycount.com/wiki/Texture_types

There's a pretty extensive section on opacity/transparency maps. 

musashidan said:

Your primary concerns are silhouette and surface shading, and to a lesser extent these days when authoring for high-end, but still important, optimisation. The example you posted is great because it shows a really strong silhouette with as few triangles as needed to capture some great sculpting/texturing. The normal map is doing a lot of the work here. As for the lower feathers, you'll notice that the geo there is just a flat plane with an opacity map texture for the transparency(same with the top of the crown)

My main advice is to concentrate on capturing the silhouette(use a flat black shader or squint your eyes at the model from a medium distance) using as little geo as needed. Your own asset is mostly rounded/soft, whereas the example is mostly sharp/angular.

Oh thanks so much- I didn't even realize it was JUST a flat plane. Thanks for the resource too- sometimes it just feels like there's SO much knowledge that I don't know about that it feels overwhelming.

Super thanks

Mark Dygert

I think the thin leaf details are going to be problematic when capturing a normal map, especially if you aren't going to use just a plane. If you want any kind of thickness and having the leaves break out of the silhouette is important, I would make them thicker, more like a box and not like a sharp knife edge.

2 outer edges vs 1.

  
Of course if you don't need those leaves to be part of the silhouette then conform them to the surface so they can be captured in a simple spherical shape, but they can't stick up that high and be rendered down to a simple shape. So either the low poly supports the silhouette or the high poly needs to come down and fit within the low poly space.

Somatrasiel

Mark Dygert said:

I think the thin leaf details are going to be problematic when capturing a normal map, especially if you aren't going to use just a plane. If you want any kind of thickness and having the leaves break out of the silhouette is important, I would make them thicker, more like a box and not like a sharp knife edge.

2 outer edges vs 1.

  
Of course if you don't need those leaves to be part of the silhouette then conform them to the surface so they can be captured in a simple spherical shape, but they can't stick up that high and be rendered down to a simple shape. So either the low poly supports the silhouette or the high poly needs to come down and fit within the low poly space.

Oh- thanks you so so so much- This has been the hardest part of low poly for me: trying to understand just how much the silhouette should affect the topology. Especially since in alot of examples, I see the normal/bump mapping doing so much heavy lifting.

Would you by any chance happen to have an resources on what goes into baking transparencies (like in the case of the example I posted)? I've been scouring the internet and I've gotten a little bit of a handle on what's happening, I know the concept for plants and such-but I'm still having a little trouble grasping exactly HOW they managed to get (what looks like) legit geometry out of a plane.

Zalek4

Most bakers should support transparency maps today. The ones I know definitely support it are Knald, Marmoset Toolbag 3, and Substance Designer. xNormal will allow you to report a color when a ray misses, so maybe that could work if you set it to return black.

This is a pretty solid overview of how geometry and the resulting maps can be treated for grass and other plants:
https://80.lv/articles/tutorial-grass-creation-for-games/

More in-depth walk throughs:
http://wiki.polycount.com/wiki/Foliage

In terms of resources for baking transparencies, much of the workflow will be exactly the same as baking any other map. But like all maps, there are some special cases (such as the first grass example above) where it could be slightly different. Not sure how deep you've gone down the baking rabbit hole yet, but this is always a great place to start:
http://wiki.polycount.com/wiki/Texture_Baking

Getting the result in your example is (and someone correct me if I'm wrong) similar to the technique used when baking trim sheets for environments. I can't remember where the example I'm thinking of is, but there is definitely more info on it here:
http://wiki.polycount.com/wiki/Modular_environments

Having said all that, I'm going to second Mark's above demonstration when it comes to the shapes on your hammer. It seems like they would really benefit from the thickness.

Somatrasiel

Thanks so much! I'll definitely check these out- you guys have been awesome help