<p>I have a fairly complex-shaped object I've modeled, and in creating the LOD meshes, I've merged some verts, deleted some and even added some after in cases where this manipulation produced an n-gon. The UVs look fine, but these meshes have slightly different topology and vertex placement in some spots. Is this okay? What are the ramifications?</p>

CC BY-SA 4.0
2021-05-16T17:16:37.577Z
I don't understand this question. LODs *have to have* different topology. "Topology" refers to the connections between vertices. If two meshes have different numbers of vertices and triangles, the topology cannot be the same. Unless you have a different definition of "topology". Can you explain what exactly it is you are concerned about?
Nicol Bolas
CC BY-SA 4.0
2021-05-16T22:42:19.123Z
Maybe I'm not using the term correctly. I always assumed it meant the way that the components (vertices and edges) were laid out. I didn't only take away edge loops, in some cases I had to add/subtract edges and merge them etc.  In a case where there were two edge loops between two UV seams, I even took the original two away and added a single edge loop so that it would be squarely in the center rather than biased towards a particular direction. That means that some of the edges/loops in the lower-poly aren't present in the higher poly. Would this create a performance penalty/problem?
Logan J
CC BY-SA 4.0
2021-05-17T05:35:08.773Z
Topplogy in mathematics and computer graphics mean different things.
joojaa
CC BY-SA 4.0
2021-05-17T08:41:04.607Z
Maybe you can edit your question and clarify a bit more what exactly you did. Especially when we are talking about performance details matter a lot. For example, how is your buffer layed out?
wychmaster
CC BY-SA 4.0
2021-05-18T00:47:47.650Z
Even using the mathematical definition, exploiting topological differences in LOD are routine. Consider the case of displaying a map; it's routine for lakes and islands disappear when you zoom out. I'm unclear what "performance" means here. Is this a question about real-time APIs, or data structures for ray tracing, or what?
Pseudonym
<3d><performance><optimization>
Is there a Performance Penalty for LOD objects with different topology?
Logan J
# Is there a Performance Penalty for LOD objects with different topology?

(Asked by: username_0 on 2021-05-16)

I have a fairly complex-shaped object I've modeled, and in creating the LOD meshes, I've merged some verts, deleted some and even added some after in cases where this manipulation produced an n-gon. The UVs look fine, but these meshes have slightly different topology and vertex placement in some spots. Is this okay? What are the ramifications?

**Tags:** 3d, performance, optimization

> **Comments:**
> **username_1**: I don't understand this question. LODs *have to have* different topology. "Topology" refers to the connections between vertices. If two meshes have different numbers of vertices and triangles, the topology cannot be the same. Unless you have a different definition of "topology". Can you explain what exactly it is you are concerned about?  
> **username_0**: Maybe I'm not using the term correctly. I always assumed it meant the way that the components (vertices and edges) were laid out. I didn't only take away edge loops, in some cases I had to add/subtract edges and merge them etc.  In a case where there were two edge loops between two UV seams, I even took the original two away and added a single edge loop so that it would be squarely in the center rather than biased towards a particular direction. That means that some of the edges/loops in the lower-poly aren't present in the higher poly. Would this create a performance penalty/problem?  
> **username_2**: Topplogy in mathematics and computer graphics mean different things.  
> **username_3**: Maybe you can edit your question and clarify a bit more what exactly you did. Especially when we are talking about performance details matter a lot. For example, how is your buffer layed out?  
> **username_4**: Even using the mathematical definition, exploiting topological differences in LOD are routine. Consider the case of displaying a map; it's routine for lakes and islands disappear when you zoom out. I'm unclear what "performance" means here. Is this a question about real-time APIs, or data structures for ray tracing, or what?  

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## 0 answers

