28
votes
Accepted
Why are quads used in filmmaking and triangle in gaming?
For 3D modeling, the usual reason to prefer quads is that subdivision surface algorithms work better with them—if your mesh is getting subdivided, triangles can cause problems in the curvature of the ...
- 2,232
20
votes
Accepted
Programmatically generating vertex normals
Computing the normal from vertex positions is quite simple using the vector cross product.
The cross product of two vectors $u$ and $v$ (noted $u \times v$, or sometimes $u \wedge v$) is a vector ...
- 4,420
9
votes
Why are quads used in filmmaking and triangle in gaming?
As @Noah Witherspoon correctly, says triangle subdivision does not work as well as quad subdivision. Although, in the beginning triangles could not be subdivided at all. However, he does not really ...
- 8,447
8
votes
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Combination of Triangles and Quads in a mesh
Topologically correct is a very vague.
I believe you think of Polygon-Meshes when you say meshes, which is to represent the surface of the object by a patch of polygons, in most cases triangles or ...
- 1,810
6
votes
Creating shared vertex normals on GPU
For an nVidia only solution you can use floating point atomic add intrinsics (like NvInterlockedAddFp32) Unlocking GPU Intrinsics in HLSL | NVIDIA Developer
I tried this on 80.000 vertex mesh and it'...
6
votes
Generate mesh from pointcloud data
one popular Real time surface reconstruction method is TSDF (Truncated Signed Distance Function) used by Microsoft for the Kinect. It is based on the VRIP method but it is faster. It is based on depth ...
- 61
6
votes
Accepted
How to calculate volume of any given 3D mesh
The triangle form of the Shoelace Formula can be extended to 3D by using tetrahedrons instead of triangles.
Pick a point, Any point can be used, even one of the original vertices of the mesh (...
- 456
5
votes
Accepted
chess-like rectangles on the mesh
I don't think it's trying to represent anything in particular.
In CG there is a concept of textures, which is a bit like painting the surface of an object a specific color/look. For example, on a car ...
- 529
5
votes
Accepted
What's the simplest, open, animation format?
For what it's worth, the glTF Tutorials contain a section on Skinning that shows how the raw vertex and joint weight data feed into a vertex shader to distort the mesh.
If you do design your own ...
- 369
5
votes
Accepted
Are vertices of each LOD version always loaded into VRAM
Many game engines have texture streaming, which means that not all mip levels of each texture are loaded at all times. The game engine will track which textures are in view and how close up they are ...
- 25.2k
5
votes
Accepted
What is the difference between a "meshlet" and just a small mesh?
A "meshlet" is a concept built around the specific architecture of how shaders work.
Shaders are invoked in work groups, even when shader stages don't explicitly represent that concept in ...
- 9,932
4
votes
Accepted
Extract visible vertices from a 3D geometry model
Idea A:
Draw an invisible mesh that will occlude the points we don't want.
Create a mesh from the point cloud.
Render that mesh to a depth buffer but not to the color buffer.
Render the point cloud ...
- 4,420
4
votes
Best way to remesh a quad 3D mesh?
I'd recommend using OpenVDB. It's quite battle-tested.
Use meshToVolume to voxelize the mesh. Then use volumeToMesh to produce ...
- 151
4
votes
Accepted
How can I perform a triangle inside test in polygon meshes?
There is an alternative method that relies on flood filling. First arrange your edge data into a loop where the edges are forming a counterclockwise loop. Then start at an arbitrary point on the loop ...
- 8,447
4
votes
exact down sampling and re-triangulation of mesh data(non-convex)
1. Method: Vertex Clustering
This is more or less a low-quality method, but depending on your mesh it could work well.
The basic idea is to partition the space into a regular grid, and then choose ...
- 1,810
4
votes
Accepted
Triangulation of vertices of an ellipsoid
If you sample the two parameters $\eta$ and $\omega$ with steps $d\eta$ and $d\omega$, then you'll get a grid of points $v_{ij} = f(i\;d\eta,j\;d\omega)$. Any four adjacent points will define a ...
- 901
4
votes
Should you measure mesh complexity in triangles or vertices?
Since you're talking about "vertex shaders" and "fragments", I assume that your question is to be interpreted in the context of real-time rendering using the graphics pipeline on a modern GPU through ...
- 523
4
votes
Accepted
Creating a Smooth 3D Mesh from a 2D Outline
One algorithm that's pretty good for this, but very difficult to implement is to find the Medial Axis of the shape and then have various profiles that are based on the signed distance from the medial ...
- 3,441
4
votes
Accepted
How to Sample 3D Points Outside and Inside the Mesh Surface
What you want is something that can perform the inside-outside test for meshes. The simplest solution would be to use Trimesh's implementation which can be ran with Embree to accelerate ray queries.
I ...
- 344
4
votes
How to Sample 3D Points Outside and Inside the Mesh Surface
I have a few suggestions:
Partition the volume by using tetrahedra within the mesh, and outside of it (in the cube). Set the probability to sample each tetrahedron to its volume divided by the inside/...
- 2,226
4
votes
Accepted
Why is the valence of regular vertices 6?
If require that all faces have the same number of sides $s$ and require that all vertices also have a certain valency $t$. We see that the following relation between edges, and faces hold for a ...
- 1,283
4
votes
Accepted
Computing vertex normals in mesh triangle soup
A very simple, but computationally expensive, way to do this is to pick a triangle, preferably one that you know has the winding you want.
Then search every triangle in the soup for triangles that ...
- 3,354
3
votes
Extract visible vertices from a 3D geometry model
Conceptually simplest would be to treat it as a ray-casting problem, representing each point as a small sphere. It should work like the shadow rays in a conventional raytracer: iterate over all of ...
- 6,870
3
votes
Accepted
Most efficient way to render many OO meshes in OpenGL
Don't copy around huge chunks of data if you don't have to.
I would delay collecting and building the final forest mesh for as long as possible.
However when you have multiple of the same mesh that ...
- 6,010
3
votes
How can I perform a triangle inside test in polygon meshes?
I've already commented on the use of flood fill and how it would be better as it's more flexible but another possible solution is scanline. (I say possible because it makes a lot of assumptions about ...
- 828
3
votes
Accepted
What is better to use for real-time computing Mesh - Plane intersection points, GPU or CPU?
doing the calculation to decide whether a point is on one side of a plane or the other is very simple (a single dot product). Doing that 3 times and having a special case when they don't match to ...
- 6,010
3
votes
Accepted
Calculating Skeleton-Deformed Mesh Normals
You're right, standard skinning pipelines don't produce correct normals. You get similar problems when using translation on joints, which is very common in facial animation. The only way to get a ...
- 46
3
votes
Accepted
Weird rendering in rectangle mesh shader AKA Why has my basic shader become a modern art generator?
I think you are not constructing the index buffer correctly. Firstly you only need 1 degenerate vertex to terminate each triangle-strip row.
You also should not need any special handling for odd/...
- 2,322
3
votes
How can I convert signed distance field to a mesh?
with CGAL you can generate mesh by implicit function. https://doc.cgal.org/latest/Mesh_3/index.html
Search for "implicit". There is an example of generating meshes from the funciton of a sphere.
- 41
3
votes
Generate mesh from pointcloud data
You can use CloudCompare or MeshLab to generate a mesh from a point cloud using many algorithms. In my experience, marching-cube method results in accurate meshes.
- 41
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