I'm currently rendering a 3D model (Wavefront .obj format) in my Qt program. Right now, I'm rendering the model using Scene3D in QML, and I'm able to get it to display in the viewing area. What I would like to do is have a user click on the model and generate a 2D cross section of the slice that I would like to plot on a different window. I'm quite new to 3D rendering, and a lot of Qt documentation isn't very descriptive. I've been reading Qt documentation, experimenting, and searching online with no luck. How can I create 2D slices of a 3D object Model in Qt 3D, preferably in QML? What Qt libraries or classes can I use to achieve this?
Unfortunately, the fact that models are stored as a set of surfaces makes this hard. QT probably doesn't have a built in method for this.
Consider, for example, that a model made of faces might be missing a face. What now? can you interpolate across that gap consistently from different angles? What about the fact that a cross-section probably won't contain any vertices?
But, of course, it can be solved. First, just don't allow un-closed surfaces (meshes with holes). Second, for finding the vertices of your cross-section, perform an intersection between every edge in your model and the plane you're using, and if there's an intersection, there's a point there. Third, to find the edges, look at the list of vertices, and any two that are from an edge on the same polygon in the mesh should be connected by an edge in the cross section. To find which direction the edge should go, project the normal of the polygon onto the plane your using. For filling, I don't really know what to do. I guess that's whatever you want it to be.
Related
I looked for a way to create shadows in 3D javaFX programs, and since I found none, I decided to make my own. It accomplishes this by taking the shape of the 3D model, and using a projection matrix to flatten it onto a surface (I'm using the Affine class to make this matrix. There are a couple issues with it, but the most pressing is the fact that Affine doesn't seem to update the normal vectors once the projection is complete, leaving a weird lighting issue. Similarly, it doesn't seem to update the information used by PerspectiveCamera when calculating distortions.
I'm looking to auto-generate a UML class model in virtual reality using A-Frame.io (or another technology) by passing in values. Has anyone ever done something similar in the past? Not sure where to start.
Thanks
You might want to look into plantuml which is a nice UML generator. Most of it's diagrams are generated as input to graphviz's dot. Dot is a layout engine - it takes a list of nodes and connections and puts them into 2D space and then renders them to one of it's output formats - or just returns the graph, but this time with coordinates on where to draw what. You could meddle with this data and render the elements with volume but on a 2D plane with dot generated coordinates. Perhaps even you could modify it to place them in 3D space instead of a plane.
Or you could just render the plantuml output on a 2D plane, place it in 3D space and it would probably be good enough. There are even online generators for plantuml.
I know that if I rotate an object, which extends javafx.scene.shape.Shape, I can transform it into 3D space, even though it was primarily designed to be in 2D (at least as far as I know).
Let's say I have a 3D scene (perspective camera and depth buffer are used), where various MeshViews occur. Some are used for areas, others for lines. In both cases those shapes must be triangulated in order to draw them with a TriangleMesh, which is often nontrivial.
Now when I change the drawing of these lines to use the Polyline class, the performance collapse is horrible and there a strange artefacts. I thought I could benefit from the fact, that a polyline has less vertices and the developer doesn't have to triangulate programmatically.
Is it discouraged to use shapes extending javafx.scene.shape.Shape within 3D space? How're they drawn internally?
If the question is "should I use 2D Shape objects in 3D space?" in JavaFX then the answer is No because you will get all terrible performance that you are seeing. However it sounds like you are trying to make up for JavaFX's lack of a 3D PolyLine object using 2D objects and rotating them in 3D space. If that is true, instead use the free open-source F(X)yz library:
http://birdasaur.github.io/FXyz/
For example the PolyLine3D class which allows you to simply specify a list of Point3Ds and it will connect them for you:
/src/org/fxyz/shapes/composites/PolyLine3D.java
and you can see example code on how to use it in the test directory:
/src/org/fxyz/tests/PolyLine3DTest.java
Ok, here is the thing. Recently i decided i wanted to understand how Random map generation works. I found some papers and some arguments. The most interesting one was "Diamond Square algorithm" and "Midpoint Displacement". I still have to try to apply those to a software, but other than that, i ran into this site: http://www-cs-students.stanford.edu/~amitp/game-programming/polygon-map-generation/
As you can see, the idea is to use polygons. But i have no idea how to apply that a Tile-Based map, not even how to create those polygons using the tools i have (c++ and sdl). I am assuming there is no way to do it ( please correct me if i am wrong.) But if i am not, how does a non-tile map works, and how are these polygons generated?
This answer will not give you directly the answers you're looking for, but hopefully will get you close enough!
The Problem
I think what blocks you is how to represent the data. You're probably used to a 2D grid that simply represent the type of each tile. As you know, this is fine to handle a tile-based map, but doesn't properly allow you to model worlds where tiles are of a different shape.
Graphs
What I suggest to you, is to see the problem a bit differently. A grid is nothing more than a graph (more info) with nodes that have 4 (or 8 if you allow diagonals) implicit neighbor nodes. So first, what I would do if I was you, would be to move from your strict standard 2D grid to a more "loose" graph, where each node has a position, a position, a list of neighbors (in most cases you'll have corners with 2 neighbors, borders with 3 and "middle" tiles with 4) and finally a rendering component which simply draws your tile on screen at the given position. Once this is done, you should be able to have the exact same results on screen that you currently have with your "2D Tile-Based" engine by simply calling the rendering component with each node who's bounding box (didn't touch it in what you should add to your node, but I'll get back to this later) intersects with the camera's frustum (in a 2D world, it would most likely if the position +/- the size intersects the RECT currently being drawn).
Search
The more generic approach will also help you doing stuff like pathfinding with generic algorithms that explore nodes until they find a valid path (see A* or Dijkstra). Even if you decided to stick to a good old 2D Tile Map game, these techniques would still be useful!
Yeah but I want Polygons
I hear you! So, if you want polygons, basically all you need to do, is add to your nodes a list of vertices and the appropriate data that you might need to render your polygons (either vertex color, textures and U/V maps, etc...) and update your rendering component to do the appropriate OpenGL (this for example should help) calls to draw your nodes. Once again, the first step to iteratively upgrade your 2D Tile Engine to a polygon map engine would be to, for each tile in your map, give each of your nodes two triangles, a texture resource (the tile), and U/V mappings (0,0 - 0,1 - 1,0 and 1,1). Once again, when this step is done, you should have a "generic" polygon based tile map engine. The creation of most of this data can be created procedurally by calculating coordinates based on tile position, tile size, etc...
Convex Polygons
If you decide that you ever might need NPCs to navigate on your map or want to allow your player to navigate by clicking the map, I would suggest that you always use convex polygons (the triangle being the simplest for of a convex polygon). This allows your code that assume that two different positions on the same polygon can be navigated to in straight line.
Complex Maps
Based on the link you provided, you want to have rather complex maps. In this case, the author used Voronoi Diagrams to generate the polygons of the map. There are already solutions to do triangulation like that, but you might also want to use other techniques that are easier to work with if you're just switching to 3D like this one for example. Once you have interesting results, you should consider implementing serialization to save/open your map data from the game. If you want to create an editor, be aware that it might be a lot of work but can be worth it if you want people to help you creating maps or to add elements to the maps (like geometry that's not part of the terrain).
I went all over the place with this answer, but hopefully it helps!
Just iterate over all the tiles, and do a hit-test from the centre of the tile to the polys. Turn the type of the tile into the type of the polygon. Did you need more than that?
EDIT: Sorry, I realize that probably isn't helpful. Playing with procedural algorithms can be fun and profitable. Start with a loop that iterates over all tiles and chooses randomly whether or not the tile is occupied. Then, iterate over them again and choose whether it is occupied or its neighbour is.
Also, check out the source code for this: http://dustinfreeman.org/toys/wall7-dustin.html
I am IT student and I have to make a project in VB6, I was thinking to make a 3D Software Renderer but I don't really know where to start, I found a few tutorials but I want something that goes in depth with the maths and algorithms, I will like something that shows how to make 3D transformations, Camera, lights, shading ...
It does not matter the programing language used, I just need some resources that shows me exactly how to make this.
So I just want to know where to find some resources, or you can show me some source code and tell me where to start from.
Or if any of you have a better idea for a VB6 project.
Thanks.
I disagree with the previous posts, a 3D renderer is actually pretty simple. A high-quality 3D renderer is hard however.
Get a bunch of 3D data, triangles are simplest.
Learn about homogenous coordinates and the great 4x4 matrix for transforms.
Define a camera by a position and a rotation (expressed in the 4x4 matrix).
Transform your 3D geometry by this camera.
Perform the perspective divide and scale to your window. This converts your 3D data to 2D.
Render the data as 2D.
Now you're going to lose out on a depth buffer, so stick to wireframes in the beginning. :-)
Don't listen to these nay-sayers, go out and have some fun!
Many years ago I made a shaded triangle renderer that used library calls to draw the triangles. It's a rather naive approach but you would be able to achieve the same result using VB6. I got all the maths & techniques from "Computer Graphics principles and practice" by Foley et al. Some parts are out of date now but I think you'd find it very helpful for this project and it can be bought 2nd hand at reasonable prices from Amazon for example.
One simple approach could be:
Read model file as triangles
Transform each triangle using matrices to account for camera position
Project triangle points onto 2D
Draw 2D triangle (probably using GDI)
This covers wireframe viewing. To extend this to hidden surface removal you need to work out which triangles are in front. Two possible ways:
Z-order sorting the triangles and drawing the ones furthest from the camera first. This is simple but inefficient if there are a lot of triangles and can give overlapping triangle effects when the order is not quite correct. You also have to decide how to sort the triangles - e..g by centroid, by extents...
Using a software depth buffer. This will give better results but is more work to implement. You will have to write your own triangle drawing code so cannot rely on GDI. See bresenham's line algorithm and related algorithms for doing filled triangles for how to do this.
After this you'd also need some kind of shading based on lighting. The calculations are covered in Computer Graphics principles and practice. For simple shading you can stick with drawing triangles using gdi , but if you want to do gouraud or phong shading the colour values vary across a triangle. One way around this is to sub-divide the triangle into smaller triangles, but this is inefficient and won't give very nice looking results. Better would be to draw the triangles yourself as required above for the software depth buffer.
A good extension would be to support primitives other than triangles. Basic approach would be to split primitives into triangles as you read them.
Good luck - could be an interesting project.
VB6 is not the best suited language to do maths and 3D graphics, and given that you have no previous knowledge about the subject either, I would recommend you to choose something different (and easier).
As it's Visual Basic, you could try something more form-oriented, that is the original intent of the language.
There is the 3D engine list which lists three engine in pure basic (an oxymoron) + Source code and of them one is in Visual Basic (Dex3D)
DeX3D is an open source 3D engine
coded entirely in Visual Basic from
Jerry Chen ( -onlyuser#hotmail.com ).
Gouraud shading
Transparency
Fogging
Omni and spot lights
Hierarchical meshes
Support for 3D Studio files
Particle systems
Bezier curve segments
2.5 D text
Visual Basic source
More information, screenshots and the
source can be found on the Dex3D
Homepage. (<= Dead Link)
EGL25 by Erkan Sanli is a fast open source VB 6 renderer that can render, rotate, animate, etc. complex solid shapes made of thousands of polygons. Just Windows API calls – no DirectX, no OpenGL.
VBMigration.com chose EGL25 as a high-quality open-source VB6 project to demonstrate their VB6 to VB.Net upgrade tool.
A 3D software renderer as a whole project is fairly complex if you've never done it before. I would suggest something smaller - like just doing the 3D portion and using lines to do the rendering OR just write a shaded triangle renderer (which is the underpinnings of 3D renderers anyway).
Something a little simpler rather than trying to write a full-blown 3D software renderer on the first go - especially in VB.
A software renderer is a very difficult project and the language VB6 is not indicated at all ( for a task like this c++ is the way.. ), anyway I can suggest you some great books I used:
Shaders: http://wiki.gamedev.net/index.php/D3DBook:Introduction_%28Volume%29
Math: 3D Math Primer for Graphics and Game Development
There are other 2 books. Even if they are for VB.NET you can find some useful code:
.NET Game Programming with DirectX 9.0
Beginning .NET Game Programming in VB .NET
I think you can take two ways either go the Direct X way and use DirectX 8 that has VB 5-6 support. I found a page http://www.gamedev.net/reference/articles/article1308.asp
You can always write a engine group up but by doing so you will need some basic linear algebra like Frank Krueger suggests.