So correct me if i'm wrong, but I think all elements in 3d graphics are meshes.
So the question is really, how do you take mesh data and create a 2d projection based on the mesh data, the camera location, rotations of camera & mesh, etc.
I realize this is fairly complicated and I would be satisfied by just knowing what the technical term for this is called so I may search and research it.
You can read about 3D projection on Wikipedia.
Related
I'm trying to create a 3D mask model from the 3D coordinate points that are stored in the txt file. I use the Marching cubes algorithm. It looks like it´s not able to link individual points, and therefore holes are created in the model.
Steps: (by https://lorensen.github.io/VTKExamples/site/Cxx/Modelling/MarchingCubes/)
First, load 3D points from file as vtkPolyData.
Then, use vtkVoxelModeller
Put voxelModeller output to MC algorithm and finally visualize
visualization
Any ideas?
Thanks
The example takes a spherical mesh (a.k.a. a set of triangles forming a sealed 3D shape), converts it to a voxel representation (a 3D image where the voxels outside the mesh are black and those inside are not) then converts it back to a mesh using Marching Cubes algorithm. In practice the input and output of the example are very similar meshes.
In your case, you load the points and try to create a voxel representation of them. The problem is that your set of points is not sufficient to define a volume, they are not a sealed mesh, just a list of points.
In order to replicate the example you should do the following:
1) building a 3D mesh from your points (you gave no information of what the points are/represent so I can't help you much with this task). In other words you need to tell how these points are connected between then to form a 3D shape (vtkPolyData). VTK can't guess how your points are connected, you have to tell it.
2) once you have a mesh, if you need a voxel representation (vtkImageData) of it you can use vtkVoxelModeller or vtkImplicitModeller. At this point you can use vtk filters that need a vtkImageData as input.
3) finally in order to convert voxels back to a mesh (vtkPolyData) you can use vtkMarchingCubes (or better vtkFlyingEdges3D that is a very similar algorithm but much faster).
Edit:
It is not clear what the shape you want should be, but you can try to use vtkImageOpenClose3D so the steps are:
First, load 3D points from file as vtkPolyData.
Then, use vtkVoxelModeller
Put voxelModeller output to vtkImageOpenClose3D algorithm, then vtkImageOpenClose3D algorithm output to MC (change to vtkFlyingEdges3D) algorithm and finally visualize
Example for vtkImageOpenClose3D:
https://www.vtk.org/Wiki/VTK/Examples/Cxx/Images/ImageOpenClose3D
What is the best way to project an arbitrary 2D polygon onto a 3D triangle mesh?
To make thing clearer, here is a visualization of the problem:
The triangle mesh is representing terrain and thus can be considered 2.5D. I want to be able to treat the projected polygon as a separate object.
This particular implementation is done in WebGL and three.js but any solution that fits an interactive 3D application is of interest.
If your question is not how to texture map the surface, then you really have to generate new 3D polygons.
You will be using some projection mechanism (such as a parallel one) that turns your 3D problem to 2D.
First backproject the surface onto the polygon plane. The polygon will be overlaid on a corresponding 2D mesh. Now for every facet, find the intersection (in the Boolean sense) of the facet and the polygon.
You will need a polygon intersection machinery for that purpose, such as the Weiler-Atherton or Sutherland-Hodgman clipping algorithms (the latter is much simpler, but works on convex windows only). (Also check http://www.angusj.com/delphi/clipper.php)
After clipping, you project to the original facet plane.
What the minimum configuration for the program I need to build 3D Graphics from scratch, for example I have only SFML for working with 2d graphics and I need to implement the Camera object that can move & rotate in a space
Where to start and how to implement vector3d -> vector2d conversion functions and other neccessary things
All I have for now is:
angles Phi, Xi, epsilon 1-3 and some object that I can draw on the screen with the following formula
x/y = center.x/y + scale.x/y * dot(point[i], epsilon1/epsilon2)
But this way Im just transforming "world" axis, not the Object points
First you need to implement transform matrix and vector math:
Mathematically compute a simple graphics pipeline
Understanding 4x4 homogenous transform matrices
The rest depends on kind of rendering you want to achieve:
boundary polygonal mesh rendering
This kind of rendering is the native for nowadays gfx cards. You need to implement buffers for:
depth (for filled polygons without z-sorting)
screen (to avoid flickering and also serves as Canvas)
shadow,stencil,aux (for advanced rendering techniques)
they have usually the same resolution as target rendering area. On top of this you need to implement supported primitives rendering at least point,line,triangle. see:
Algorithm to fill triangle
on top of all this you can add textures,shaders and whatever else you want to ...
(back)ray tracing
this kind of rendering is very different and current gfx HW is not build for it. This involves implementing ray/primitives intersections computation, Snell's law and analytical representation of meshes. This way you can also do multi-spectral rendering and more physically accurate effects/processes see:
How can I render an 'atmosphere' over a rendering of the Earth in Three.js? hybrid approach #1+#2
Algorithm for 2D Raytracer
How to implement 2D raycasting light effect in GLSL
Multi-Band Image raster to RGB
The difference between 2D and 3D ray tracer is almost none the only difference is how to compute perpendicular vector ...
There are also different rendering methods like Volume rendering, hybrid methods and others but their implementation is usually task oriented and generic description would most likely just mislead ... Here some 3D ray tracers of mine:
back raytrace through 3D mesh
back raytrace through 3D volume
I am working on a library for procedural texture generation (https://github.com/mikera/clisk) which is starting to come together quite nicely.
I'm now trying to work out good ways of producing tileable 2D textures.
One approach that seems plausible is to map the (0,0) - (1,1) 2D texture space onto a surface within a 3D texture in such a way that the surface connects the left and right edges and top and bottom edges of the texture (e.g. a torus). In doing so, that should ensure that the 2D texture is automatically tileable.
Since I already have good (non-tileable) 3D textures (perlin noise, fractal noise etc.) this seems like it would be a good way to allow the creation of tileable 2D textures from an arbitrary 3D texture.
So my quesyions:
Is this a valid technique?
If so, what kind of surface should I map onto in order to minimise distortions / get an good looking tiling effect?
Any pitfalls to be aware of?
Using 3D noise for this will produce distortion, the answer is to use 4D noise, though that is not the only way - you can also make the 2D function tileable.
Here's a couple of useful links:
http://www.gamedev.net/blog/33/entry-2138456-seamless-noise/
Introduces the 4D method
https://gamedev.stackexchange.com/questions/23625/how-do-you-generate-tileable-perlin-noise
Has multiple answers for this: making the 2D tileable, 3D with distortion, and the 4D method
I have a black and white 2D drawing of a silhouette (say, a chess piece) that I would like to rotate around an axis to create a 3D object.
Then I want to render that 3D object from multiple angles using some sort of raytracing software, saving each angle into a separate file.
What would be the easiest way to automatically (repeatedly) 1. get a vector path from the 2d drawing 2. create the 3D model by rotating it 3. import it into the raytracer.
I haven't chosen a specific raytracer yet, but Sunflow has caught my eye.
Texturing/bump mapping would be nice but non-essential
The modeling feature you're looking for is a Lathe.
Sunflow can import 3ds files and blender files.
I've never used blender, but here's a tutorial for using the lathe to make a wine glass. You'd replace the silhouette of the wine glass with your shape:
http://www.blendermagz.com/2009/04/14/blender-3d-lathe-modeling-wine-glass/
Blender is FOSS, you can down load it here:
www.blender.org/download/get-blender/ (can't post more than one link, so you'll have to type this one in yourself :-)
I found a pretty cool site where you can do this online, interactively:
http://www.fi.uu.nl/toepassingen/00182/toepassing_wisweb.en.html
No great detail revolution but maybe you can find the code and extend it to your needs.