I'm using libgdx for a school project and I need some help.
I am working on a 3d game that uses Bullet physics engine that (ndk).
I have managed to connect it and everything works, now I need to pass the physics engine all the triangles from the mesh object (that is loaded from a OBJ).
I have tried using mesh->getIndices() but it returns 0 (is it possible i have additional values that mess up the obj loader?) and vertices (the first three decimals returned from Mesh->getVertices(vertices) - this is probably wrong since the vertices arent sorted?) but collisions act strange.
Does any one know how to get all triangles from a mesh in libgdx?
Related
I am attempting to come up with a quick and efficient means of translating a 3d mesh into a projected AABB. In the end, I would like to accomplish something similar to figure 1 wherein only the area of the screen covered by the cube is located inside the bounding box highlighted in red. ((if it is at all possible, getting the area as small as possible, highlighted in blue, would increase efficiency down the road.))
Figure 1. https://i.imgur.com/pd0E20C.png
Currently, I have tried:
Calculating the point position on the screen using camera.unproject_position(). this failed largely due to my inability to wrap my head around the pixel positions trending towards infinity. I understand it has something to do with Tan, but frankly, it is too late for my brain to function anymore.
Getting the area of collision between the view frustum and the AABB of the mesh instance. This method seems convoluted, and to get it in a usable format I would need to project the result into 2d coordinates again.
Using the MeshInstance VisualInstance to create a texture wherein a pixel is white if it contains the mesh instance, and black otherwise. Visual instances in general just baffle me, and I did not think it would be efficient to have another viewport just to output this texture.
What I am looking for:
An output that can be passed to a shader informing where to complete certain calculations. Right now this is set up to use a bounding box, but it could easily be rewritten to also use a texture. It also could be rewritten to use polygons, but I am trying to keep calculations to a minimum in the shader.
Certain solutions I have tried before have worked, slightly, but this must be robust. The camera interfacing with the 3d object will be able to move completely around and through it, meaning at times the view will be completely surrounded by the 3d model with points both in front, and behind.
Thank you for any help you can provide.
I will try my best to update this post with information if needed.
I placed a standard Camera in front of a moving Actor. When I set the current view to this camera I noticed a strange behaviour: If the actor get really close to another object on the scenario (a default cube) it disappear from the view. It looks like the camera is getting into the cube. I'm pretty sure the camera is not colliding with the cube because the actor has a couple of bumpers that prevent the side where the camera is placed to collide with other objects and the whole camera mesh is placed fully 'inside' the actor. The problem maybe is related with the size of the actor that's about 40cm x 30cm x 10cm. The observed cube is 1mt x 1mt x 1mt, the minimum distance of camera from cube is around 3 cm.
Sounds to me like you're experiencing an issue with an object passing your camera's "clipping plane." In the 3D world, this is simply just draw distance minimum and maximum values. For more information on what you are experiencing, check out this brilliant explanation by Autodesk: https://knowledge.autodesk.com/support/maya/learn-explore/caas/CloudHelp/cloudhelp/2018/ENU/Maya-Rendering/files/GUID-D69C23DA-ECFB-4D95-82F5-81118ED41C95-htm.html
Now, let's fix the issue! In Unreal Engine, it's super easy. Go into your Project Settings/General Settings. There is a value called Near Clip Plane, which simply changes the minimum clipping value for Camera components. I would bet making this value smaller will fix your issue! For a visual representation, check out this tutorial by Kyle Dail: https://www.youtube.com/watch?v=oO79qxNnOfU
First off, I am not sure if this is the right place so I apologize if this belongs elsewhere - please let me know if it does. I am currently doing some prototyping with this in VB so that's why I come here first.
My Goal
I am trying to make a program to be able to log different types of information for a video game that I play. I would like to be able to map out the entire game with my program and add locations for mobs, resources, etc.
What I have
The in game map can be downloaded so I have literally just stuck this in as a background image on the form (just for now). The map that I get downloaded though is not exactly as the map appears in the game though since the game will add extra water around everything when scrolling around. This makes it a bit tricky to match up where the origin for the map is in game compared to where it would be on the downloaded map.
The nice thing though is that while I am in the game I can print my current coordinates to the screen. So I thought that maybe I can somehow use this to get the right calculation for the rest of the points on the map.
Here is an example image I will refer to now:
In the above map you will see a dotted bounding box. This is an invisible box in the game where once you move your mouse out of the longitude and latitude points will no longer show. This is what I refer to above when I mean I can't find the exact point of origin for the in game map.
You will also see 2 points: A and B. In the game there are teleporters. This is what I would use to get the most accurate position possible. I am thinking I can find the position (in game) of point A and point B and then somehow calculate that into a conversion for my mouse drag event in VB.
In VB the screen starts at top-left and is 0,0. I did already try to get the 2 points like this and just add or subtract the number to the x and y pixel position of the mouse, but it didn't quite line up right.
So with all this information does anyone know if it is possible to write a lon/lat conversion to pixels based on this kind of data?
I appreciate any thoughts and suggestions and if you need any clarification of any information I have posted please let me know and I will be happy to expand on it. I am really hoping I can get this solved!
Thanks!
EDIT:
I also want to mention I am not sure if there is an exact pixel to lat/lon point for the in game map. I.e. the in game map could be 1 pixel = 100 latitude or something. So I might also need to figure out what that conversion number is?
Some clarifications about conversion between the pixel location to 'latitude and longitude'.
First the map in your game is in a geometry coordinate system, which means everything lies in 2D and you can measure the distance between two points by calculate the pixel position.
But when we talk about longitude and latitude, we are actually talking about a geography coordinate system, which is a '3D' model of the sphere oabout the surface of the earth. All the maps on earth are abstracted from 3D to 2D through one step called projection. Like google maps or your GPS. In this projection process, the 3D model converted to 2D model but there is always some part of the map will be tortured, so that same distance in pixels on a map could be different in length in reality.
So if you don't care about the accuracy then you can consider the geometry point as geography point. Otherwise, you need to implement some GIS library to handle the geodesic distance and calculate the geography point based on the projection coordinate system.
Hi stackoverflow community,
This is a continuation of a question I asked 6 months regarding calculating the area and position of dynamically formed rectangles. The solution provided for that worked a treat but now I want to take this a step further.
Some background - I'm working on a puzzle game using Cocos2D/Box2D were the player draws lines on the screen. Depending on were the player draws, I want to then work out the area and position of polygons that appear as a result of the drawn lines.
In the following image, the black border represents a playing area, this will always be the same shape. The grey lines are player drawn and will always be straight. The green square is an obstacle. The obstacle objects will be convex shapes. The formed polygons (3 in this case) are the blue areas and are the shapes I'm trying to get the coordinates and area for.
I think I'll be fine with working out the area of a polygon using determinants but before that, I need to work out the coordinates of the blue polygons and I'm not sure how to do this.
I've got the lines (x,y) coordinates for both ends, the coordinates for the obstacle and the corner coordinates for the black border. Using those, is it possible to work out the coordinates of the blue polygons or am I approaching this the wrong way?
UPDATE - response to duffymo
Thanks for your answer. To explain further, each object mentioned is defined and encapsulated in a class i.e. I've got a Line/Obstacle/PlayingArea object. My polygon object is encapsulated in a 'Rectangle' object. Each one of these objects has it's own properties associated with it such as its coordinates/area/ID/state etc...
In order to keep track of all the objects, I've got an over-seeing singleton object which holds all of the Line objects / Obstacle objects etc in their own respective array. This way, I can loop through say all Lines and know were each one has been drawn by the player.
The game is a bit like classic JezzBall so I need to be able to create these polygon shapes when a user draws a line because the polygon shape will be used as my way of detecting if that particular area contains a ball. If not the area needs to be filled.
Since you already have the nodes and edges for your polygons, I'd recommend that you calculate the centroids, perimeters, and areas using contour integration You can express the centroids and areas as contour integrals using Green's theorem.
You can use Gaussian quadrature to do piecewise integration along each edge.
It'll be fast and accurate; it'll work on polygons of arbitrary complexity.
UPDATE: Objective-C is an object-oriented language. I don't know it myself, but I believe it's based on ideas from C and C++. Since that's the case, I'd recommend that you start writing more in terms of objects. Arrays of coordinates? They need to encapsulated together. I'd suggest a Point abstraction that encapsulates a point (id, x, y) together. Make a Grid that has a List of Points.
It sounds like users supply the relationship between Points to form Polygons. That's not clear from your description, so it's not a surprise that you're having trouble implementing it.
I vaguely remember seeing something in OpenGL (not ES, which was still at v1.0 on the iPhone when I came across this, which is why I never used it) that let me specify which edges of my polygons were considered outlines vs those that made up the interior of faces. As such, this isn't the same as the outline of the entire model (which I know how to do), but rather the outline of a planar face with all its tris basically blended into one poly. For instance, in a cube made up of tri's, each face is actually two tris. I want to render the outline of the square, but not the diagonal across the face. Same thing with a hexagon. That takes four tris, but just one outline for the face.
Now yes, I know I can simply test all the edges to see if they share coplanar faces, but I could have sworn I remember seeing somewhere when you're defining the tri mesh data where you could say 'this line outlines a face whereas this one is inside a face.' That way when rendering, you could set a flag that basically says 'Give me a wireframe, but only the wires around the edges of complete faces, not around the tris that make them up.'
BTW, my target is all platforms that support OpenGL ES 2.0 but my dev platform is iOS. Again, this Im pretty sure was originally in OpenGL and may have been depreciated once shaders came on the scene, but I can't even find a reference to this feature to check if that's the case.
The only way I know now is to have one set of vertices, but two separate sets of indices... one for rendering tris, and another for rendering the wireframes of the faces. It's a real pain since I end up hand-coding a lot of this, which again, I'm 99% sure you can define when rendering the lines.
GL_QUADS, glEdgeFlag and glPolygonMode are not supported in OpenGL ES.
You could use LINES to draw the wireframe: To get hidden lines, first draw black filled triangles (with DEPTH on) and then draw the edges you are interested in with GL_LINES.