I have an airplane. I use rectangle for bounding this airplane to detect collision and it works great. When the airplane begin falling down I rotate airplane's texture, but rectangle remains unchanged. I don't know how to rotate it. I need to rotate it with airplane's texture because my shell doesn't collide the airplane's tail and cabine.
How to rotate rectangle or perhaps create polygon shape to wrap all airplane? Any help will be appreciated!
#jellyfication's answer points to raycasting, but a different and also simple approach you could implement is the Separating Axis Theorem. The links below will show you in detail what the algorithm is about and how to implement it. They also have some interactive demos so you get the 'feel' for what the algorithm is doing.
http://www.metanetsoftware.com/technique/tutorialA.html
http://www.sevenson.com.au/actionscript/sat/
http://www.codezealot.org/archives/55 (this one has a lot of code)
http://gamedev.tutsplus.com/tutorials/implementation/collision-detection-with-the-separating-axis-theorem/
Good luck!
Use the polygon class to and draw your bounding Box.
Then within the polygon class there is a method to rotate.
Rotate and move the polygon with the plane.
Related
I know that there is rectMode(CENTER) of both rectangles and ellipses, but what about other shapes like triangles and quad shapes?
It's going to be hard to write a long reply because the answer is no, there isn't a rectMode() for triangles or shapes you create using the quad() or vertex() functions.
You could use the translate() function to translate to the center of the shape, and then draw all of the points relative to that. That would also solve the question that I think you're trying to ask about then calling the rotate() function.
This might be a stupid question but I'm stuck and can't get passed it. I'm making a isometric game and I have my map built using tiles, I just followed this tutorial to build the map, http://www.binpress.com/tutorial/creating-a-city-building-game-with-sfml/137. But now I don't know how to add character sprites. Do I have to add these sprites using tiles as well or do I just draw the the sprites into position of the screen. Any help would be much appreciated.
As far as I can tell from the engine, just follow the "Textures and Animations" guide and draw the Animation to the screen after you have drawn the tiles. This isn't a complicated engine, so you are only working with 2D sprites being drawn to the screen (the 3D effect is merely tricks of painter's algorithm to make it work...there is no z-axis from what the tutorial indicates)
The depth is done by the order of tile rendering
The same goes for objects,players,etc... Let assume plane XY is parallel with the ground and Z axis is the altitude. Then your grid would be something like this (assuming diamond shape layout):
Order of rendering
You have to handle object,players and stuff sprites in the same way as tiles (and in the same time). so you should render all cells in specific order dependent on your grid layout and sprite combination equation. If your sprites can overwrite already rendered stuff then you should render from the most distant tiles to the closest to the "camera". In that case the blue direction arrow on above image is correct and Z axis should be increasing in the most inner loop.
So now if you got any object,player or stuff placed in cell (x,y,z) then you should render it directly after the cell (x,y,z) was rendered prior to rendering any other cell.
To speed up is a good idea to have objects and players in your tile map as a cell. But for that you have to have the tiles in the right manner and also your map representations must be capable of doing so.
I want to create a simple shape, let's say, a circle, it might have transparency, colors, etc. but it's still a simple circle.
In every tutorial I see, people use sprites. I am not sure what should I use for my case.
Should I use a sprite with a circle or should I try and draw the shape myself?
What are the advantages of each method?
Is there a line dividing them or is it just experience to know which one to use?
GPU geometry is composed of triangles or line segments so it'll be inefficient to draw a circle in this way, it'll require too many triangles for it to look smooth.
The two more efficient ways to do that are:
Use a sprite
Use a shader and draw the circle. Check ShaderToy, more specifically the "Shapes" preset.
Assume I have a camera defined by its position and direction, and a box defined by its center and extents (three orthogonal vectors from the box center to face centers). Face is visible when its outer surface is facing the camera and invisible when its inner surface is facing it.
It seems obvious that depending on box position and orientation there may be 1-3 faces of the box visible. Is there some clever way how to determine which faces are visible? An obvious solution would be to compute 6 dot-products of the face normal against the face-camera vector for each face. Is there a better way?
Note: perspective projection will be used, but I do not think it matters, the property of "facing camera" seems independent to a projecting.
I believe the method you described is the normal way to do this. It's a very fast calculation so you shouldn't be worried too much about speed. This is the same method they use to reduce the number of calculations for ray-triangle intersection algorithms. If the front of the face isn't visible, the method doesn't continue calculations for that face. See this paper for a c++ implementation of this algorithm. It's in the first half of the calculations. http://jgt.akpeters.com/papers/MollerTrumbore97/code.html
The only cleverness is that if a face of the cube is visible, the opposing face definitely isn't. At least in a regular perspective projection.
Note that the opposite might not be true: if a face is invisible, the opposing face might be invisible too. This is because the type of projection does matter. Imagine the cube being really up close to the camera, which is looking straight at one face. Then rotate the cube slightly, and while with a parallel projection, another face would immediately become visible, in a perspective projection this doesn't happen.
Context: trying to take THREE.js and use it to display conic sections.
Method: creating a mesh of vertices and then connect face4's to all of them. Used two faces to produce a front and back side so that when the conic section rotates it won't matter from which angle the camera views it.
Problems encountered: 1. Trying to find a good way to create a intuitive mouse rotation scheme. If you think in spherical coordinates, then it feels like just making up/down change phi and left/right change phi would work. But that requires that you can move the camera. As far as I can tell, there is no way to change actively change the rotation of anything besides the objects. Does anyone know how to change the rotation of the camera or scene? 2. Is there a way to graph functions that is better than creating a mesh? If the mesh has many points then it is too slow, and if the mesh has few points then you cannot easily make out the shape of the conic sections.
Any sort of help would be most excellent.
I'm still starting to learn Three.js, so I'm not sure about the second part of your question.
For the first part, to change the camera, there is a very good way, which could also include zooming and moving the scene: the trackball camera.
For the exact code and how to use it, you can view:
https://github.com/mrdoob/three.js/blob/master/examples/webgl_trackballcamera_earth.html
At the botton of this page (http://mrdoob.com/122/Threejs) you can see the example in action (the globe in the third row from the bottom).
There is an orbit control script for the three.js camera.
I'm not sure if I understand the rotation bit. You do want to rotate an object, but you are correct, the rotation is relative.
When you rotate or move your camera, a matrix is calculated for that position/rotation, and it does indeed rotate the scene while keeping the camera static.
This is irrelevant though, because you work in model/world space, and you position your camera in it, the engine takes care of the rotations under the hood.
What you probably want is to set up an object, hook up your rotation with spherical coordinates, and link your camera as a child to this object. The translation along the cameras Z axis relative to the object should mimic your dolly (zoom is FOV change).
You can rotate the camera by changing its position. See the code I pasted here: https://gamedev.stackexchange.com/questions/79219/three-js-camera-turning-leftside-right
As others are saying OrbitControls.js is an intuitive way for users to manage the camera.
I tackled many of the same issues when building formulatoy.net. I used Morphing Geometries since I found mapping 3d math functions to a UV surface to require v little code and it allowed an easy way to implement different coordinate systems (Cartesian, spherical, cylindrical).
You could use particles instead of a mesh I suppose but a mesh seems best. The lattice material is not too useful if you're trying to understand a surface mathematically. At this point I'm thinking of drawing my own X,Y lines on the surface (or phi, theta lines etc) to better demonstrate cross-sections.
Hope that helps.
You can use trackball controls by which you can zoom in and out of an object,rotate the object,pan it.In trackball controls you are moving the camera around the object.Object still rotates with respect to the screen or renderer centre (0,0,0).