I have a 3d scene (with pointclouds and some other objects). I implemented algorithm to pick the closest point to the mouse for a pointclouds. But my problem is : I have several objects in my scene, so when I try to pick an object (or a point inside a pointcloud), I go through all the objects on my scene, I look for the more suitable point for each of them (accordingly to distance to the raycast or angle (which is better)). At this stage, I don't know how to find the point of which object is the most suitable in all situations.
Explanation : I want to find a point very close to the raycast but also quite close to my camera to pick visible objects (points) only.
So I need to find a way to mix : closest point to the raycast and closest point to the camera. Do you have some ideas or widespread solution in 3d ? Thanks for your help.
Related
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.
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.
I'm working on an iPad application and that's my problem:
I elaborated an algorithm to know if a point is inside a polygon, in an image. So I need when touching the Image, to know the coordinates of the touched point and then do an action using those coordinates (an NSLog to make the example easy), the problem is that I can't use an IBAction on an UIImageView, and so can't recover the point's coordinates. Thanks for any help
I think at first you have to make polygon which fit to your image. And then you can use touchesBegan:withEvent: to get the coordinate of touch point and judge whether the point is inside of polygon or not.
Here is similar question like yours.
How to get particular touch Area?
I think this is a little difficult work, so maybe you would better use cocos2d library which have collision judgement function.
http://box2d.org/forum/viewtopic.php?f=9&t=7487
But also I think iOS is well constructed for handling touch, so this is beneficial effort for you.
I would really love if someone could tell me how to tell whether 2 objects have touched (An image or a button) I know how to make them draggable but not how to tell if they have touched and to do something when they touch!
Thanks!
If you never rotate the objects, you can use CoreGraphics functions.
BOOL objectsTouch = CGRectIntersectsRect(object1.frame, object2.frame);
This requires of course that the two objects are in the same superview. Otherwise you have to transform the frames using functions of the NSView.
The classical approach is to calculate a minimal circle that encompasses each object, then calculate the distance between circle centers (Pythagorean theorem) and see if it's less than R(object1 circle) + R(object2 circle). If less then you have to get down and dirty with bit mapping or some other scheme, but if greater then you can assume the objects don't touch.
I'm fairly new to game programming (but not to programming) and I want to create a space ship which leaves a trail on the screen. Now my problem is to come up with a solution how to detect if the trail left from the ship forms a closed shape - eg. if the ship left a trail around an object, the object is caught inside its trail so to speak.
The direction I'm thinking is to draw the path of the trail on an image not visible on the screen and every now and then try to fill it with certain color and then check if fill is caught within the trail path. However it seems like a lot of overhead.
Any ideas how to do that? I'm using cocos2d if that's of any help
In game programming you often need to think more mathematically than visually.
First does your ship continuously leaves a trail on the screen? If yes, then it will be easier to know when the shape closes : you just have to remember the coordinate where your ship started to leave a trail, then wait for the trail to approach this coordinate another time (for example within a radius of 10 pixels, or else the user will need to be really accurate to hit exactly the same pixel to close the shape).
The visual representation of the trail is only here for the user, you'll never use it to compute anything. What you will do is to keep in memory the path followed by the ship's trail : a polygon, which is nothing else than the list of coordinates it followed.
Then after you know that your shape is closed, you have to determine if an object is inside your polygon or not. It's possible that objective-c or cocos2d (I don't know much about it) already contains a built-in function to know if a point is inside a polygon. In java there is the Polygon class which makes this really easy. If you don't find anything you can do it yourself, there are already great answers about this subject on SO, here is a nice one : How can I determine whether a 2D Point is within a Polygon?