Search Results

Search found 3 results on 1 pages for 'vargonian'.

Page 1/1 | 1 

• Why / how does XNA's right-handed coordinate system effect anything if you can specify near/far Z values?

  - by vargonian

  I am told repeatedly that XNA Game Studio uses a right-handed coordinate system, and I understand the difference between a right-handed and left-handed coordinate system. But given that you can use a method like Matrix.CreateOrthographicOffCenter to create your own custom projection matrix, specifying the left, right, top, bottom, zNear and zFar values, when does XNA's coordinate system come into play? For example, I'm told that in a right-handed coordinate system, increasingly negative Z values go "into" the screen. But I can easily create my projection matrix like this: Matrix.CreateOrthographicOffCenter(left, right, bottom, top, 0.1f, 10000f); I've now specified a lower value for the near Z than the far Z, which, as I understand it, means that positive Z now goes into the screen. I can similarly tweak the values of left/right/top/bottom to achieve similar results. If specifying a lower zNear than zFar value doesn't affect the Z direction of the coordinate system, what does it do? And when is the right-handed coordinate system enforced? The reason I ask is that I'm trying to implement a 2.5D camera that supports zooming and rotation, and I've spent two full days encountering one unexpected result after another.

  Read the article

• Obtaining a world point from a screen point with an orthographic projection

  - by vargonian

  I assumed this was a straightforward problem but it has been plaguing me for days. I am creating a 2D game with an orthographic camera. I am using a 3D camera rather than just hacking it because I want to support rotating, panning, and zooming. Unfortunately the math overwhelms me when I'm trying to figure out how to determine if a clicked point intersects a bounds (let's say rectangular) in the game. I was under the impression that I could simply transform the screen point (the clicked point) by the inverse of the camera's View * Projection matrix to obtain the world coordinates of the clicked point. Unfortunately this is not the case at all; I get some point that seems to be in some completely different coordinate system. So then as a sanity check I tried taking an arbitrary world point and transforming it by the camera's View*Projection matrices. Surely this should get me the corresponding screen point, but even that didn't work, and it is quickly shattering any illusion I had that I understood 3D coordinate systems and the math involved. So, if I could form this into a question: How would I use my camera's state information (view and projection matrices, for instance) to transform a world point to a screen point, and vice versa? I hope the problem will be simpler since I'm using an orthographic camera and can make several assumptions from that. I very much appreciate any help. If it makes a difference, I'm using XNA Game Studio.

  Read the article

• Managing multiple references of the same game entity in different places using IDs

  - by vargonian

  I've seen great questions on similar topics, but none that addressed this particular method: Given that I have multiple collections of game entities in my [XNA Game Studio] game, with many entities belonging to multiple lists, I'm considering ways I could keep track of whenever an entity is destroyed and remove it from the lists it belongs to. A lot of potential methods seem sloppy/convoluted, but I'm reminded of a way I've seen before in which, instead of having multiple collections of game entities, you have collections of game entity IDs instead. These IDs map to game entities via a central "database" (perhaps just a hash table). So, whenever any bit of code wants to access a game entity's members, it first checks to see if it's even in the database still. If not, it can react accordingly. Is this a sound approach? It seems that it would eliminate many of the risks/hassles of storing multiple lists, with the tradeoff being the cost of the lookup every time you want to access an object.

  Read the article

1