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.
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'm working on an application for Android & iOS to show points of interest over the camera. ARkit & ARcore has poor compatibility nowdays.
Could you recommend me some library to do this? If it comes with an example, better! I know viro-media, but I don't understand how to do this using that library.
I don't want 3D models, just markers over the camera, similar to the attachment image.
To do this with Viro React -- and in AR in general -- the trick is to recognize that there are two coordinate systems:
The local coordinate system of your device, which we'll call 'AR space'. In Viro, this is centered at the user's initial position when the application starts, and is in meters.
Geographic coordinates (latitude and longitude).
To position the overlays, you have to convert your content from geographic coordinates into AR space. This is a two-step process. First project the spherical geographic coordinates onto a 2D plane -- the Web Mercator is great for this. Then translate the projected coordinates by the device's initial projected position.
The device's initial projected position can be derived by projecting its initial geographic position. In Viro React, you can use the Geolocation module to grab this when the user starts the app.
Finally, you'll need to do a similar transformation for the user's bearing: converting from compass direction to device orientation in AR space.
For this to work well you'll likely have to figure out how handle inaccurate geolocation lookups (e.g. what happens if the location retrieved from the device is inaccurate), and may also have to account for drift: over time the two coordinate systems may start to fall out of sync.
The last part, creating the info cards, is easy with Viro -- you either pre-bake the images with text and use ViroImage, or if the cards need to be more dynamic you can use a ViroFlexView.
I am also interested in this one and I'm trying out ViroReact!
I find a bit difficult to understand how to make this work when the lat's and long's have been converted to x-y-values. What should the z-value be?
Let's say you have the lat-lon coordinates [59, 10] as the user location you want to show where [59, 11] is relative to your location. How to you build that in a ViroARScene?
<ViroNode position={ **userLocationFromLatLonCartesian** }>
<ViroBox position={ **poiLocationFromLatLonToCartesian** }/>
</ViroNode>
So how do you calculate the scale, position and rotation, so that the object will be visible?
Seem like https://github.com/proj4js/proj4js is a library that could provide conversions from latlon to x-y values
I found that both android and ios AR sdk support location base AR View refererence:
https://developers.google.com/ar/develop/ios/geospatial/quickstart and https://developer.apple.com/documentation/arkit/argeoanchor
I understand that CalculateFrustumPlanes() in Unity3D returns an array of Plane objects, each representing a different frustum plane, but I can't find any documentation to suggest which element is which?
for example
[0] = Front
[1] = Back
etc.
I need to calculate whether a point in space (like the centre point of a Bounding volume) is in the camera frustum, for a Quad tree system.
What is exactly the order of the Planes in the returned array is not documented (and I don't know it).
Anyway I think you can figure it out without much effort: you just need to put the camera in a well know orientation and check the normal value's of each Plane.
I need to calculate whether a point in space (like the centre point of
a Bounding volume) is in the camera frustum, for a Quad tree system.
For a Quad Tree system, I think the intersection between the frustum and a GameObject's AABB is enough, so you don't even need to know exactly the order of the Plane's in the array to compute it. You can just use GeometryUtility.TestPlanesAABB.
Order: left, right, bottom, top, near, far.
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'm using a 3d engine and need to translate between 3d world space and 2d screen space using perspective projection, so I can place 2d text labels on items in 3d space.
I've seen a few posts of various answers to this problem but they seem to use components I don't have.
I have a Camera object, and can only set it's current position and lookat position, it cannot roll. The camera is moving along a path and certain target object may appear in it's view then disappear.
I have only the following values
lookat position
position
vertical FOV
Z far
Z near
and obviously the position of the target object.
Can anyone please give me an algorithm that will do this using just these components?
Many thanks.
all graphics engines use matrices to transform between different coordinats systems. Indeed OpenGL and DirectX uses them, because they are the standard way.
Cameras usually construct the matrices using the parameters you have:
view matrix (transform the world to position in a way you look at it from the camera position), it uses lookat position and camera position (also the up vector which usually is 0,1,0)
projection matrix (transforms from 3D coordinates to 2D Coordinates), it uses the fov, near, far and aspect.
You could find information of how to construct the matrices in internet searching for the opengl functions that create them:
gluLookat creates a viewmatrix
gluPerspective: creates the projection matrix
But I cant imagine an engine that doesnt allow you to get these matrices, because I can ensure you they are somewhere, the engine is using it.
Once you have those matrices, you multiply them, to get the viewprojeciton matrix. This matrix transform from World coordinates to Screen Coordinates. So just multiply the matrix with the position you want to know (in vector 4 format, being the 4ยบ component 1.0).
But wait, the result will be in homogeneous coordinates, you need to divide X,Y,Z of the resulting vector by W, and then you have the position in Normalized screen coordinates (0 means the center, 1 means right, -1 means left, etc).
From here it is easy to transform multiplying by width and height.
I have some slides explaining all this here: https://docs.google.com/presentation/d/13crrSCPonJcxAjGaS5HJOat3MpE0lmEtqxeVr4tVLDs/present?slide=id.i0
Good luck :)
P.S: when you work with 3D it is really important to understand the three matrices (model, view and projection), otherwise you will stumble every time.
so I can place 2d text labels on items
in 3d space
Have you looked up "billboard" techniques? Sometimes just knowing the right term to search under is all you need. This refers to polygons (typically rectangles) that always face the camera, regardless of camera position or orientation.