# JeffNiko

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Programmer
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Programming
1. ## How to get PhysX forces for Novint Falcon

Im trying to emulate the Novint Falcon demo where your "hand" is holding one end of a rubberband with a rubber ball at the other end. Using the Falcon, you can swing the ball around and feel the forces of the ball tugging the rubber band. I have the PhysX scene all set up and running - a kinectic actor that gets updated each frame with the position of the Falcon handle. Then, a dynamic actor that approximately mirrors the position of the kinamatic actor through a distance joint with maxdistance of zero, so the velocities can be computed. Then - a sphere to represent the rubber ball, attached to the dynamic actor representing the handle position, using a distance joint with a min and max distance to 5, so we have a "user movable hand attached to a rubber ball by a 5 unit rubber band". I can swing it around with the Falcon, and the ball behaves believably. Now, I need to read the forces that are exerted on the dynamic handle actor to send them to the Falcon. I cant seem to find any functions provided in the PhysX that return the FORCE exerted on an actors center of mass. For example, even if the ball and rubber band are at rest, I should still feel a downward force resulting from the gravity in the scene, so the getLinearVelocity or getLinearMomentum arent what I need.
2. ## Cant get a stable planet orbit...

D3DXVECTOR3 dir = planet.pos - star.pos; float d = D3DXVec3Length(&dir); float dt = (float)period * timescale; D3DXVec3Normalize(&dir, &dir); planet.acc *= 0.0f; planet.acc = -g*(star.mass)/(d*d)*dir; planet.pos += planet.vel*dt + planet.acc*.5f*dt*dt; planet.vel += planet.acc*dt; I cant seem to create a stable orbit. Can someone tell me what I'm missing?
3. ## Creating a D3DX Rotation matrix from 3 orientation vectors

Well that's much more straight-forward than I expected... lets give that a shot. Thanks!
4. ## Creating a D3DX Rotation matrix from 3 orientation vectors

OpenNI's Kinect SDK returns the orientation of a particular skeleton joint in the form of 3 unit-length vector[3]'s representing the X,Y and Z axes after the orientation is applied. How does one go about converting these vectors to an orientation or rotation matrix for use in a Direct3D application?
5. ## How to ID3DXSprite-Draw a face from a cube map

I have created a IDirect3DCubeTexture9 and rendered to its 6 faces. Now, I want to use ID3DXSprite->Draw to just render one of the faces to the backbuffer for display. The problem is that Draw takes a IDirect3DTexture9, and the cube texture interface will only give me a IDirect3DSurface9 for a given face. How do I go from the "suface" to the "texture" for the Draw? --- edit - Answer: IDirect3DDevice9->StretchRect() (no need to use Sprite) :-) [Edited by - JeffNiko on December 4, 2010 8:38:02 PM]
6. ## Need help with simulation: paint on spinning paper

Remember the spinning art toys of the '80s where a machine rapidly spins a white paper card and you drop paint on to it to create art? I want to do a just-for-fum XNA simulation of that. I'm a bit familar with physics programming, ie, forces, acceleration, velosity, and a few of the simplest methods of numerical integration. I've googled for a while, and haven't come across any material that gives me an idea of what physics forces are at work on the paint particles. Can anyone out there give me some advice, or point me to some source code or other artices that could get me going on this?
7. ## efficient mesh management?

No need to burn it into your skin... just remember that 'LP' means "LONG POINTER". :-)
8. ## Render to desktop revisited...

The responses are much appreciated. ActiveDesktop seems to have been removed from Vista and Win7 - but it might have been an acceptable option, since its just a "for fun" project for me. I'd prefer, though, just an executable that draws to the desktop. The null handle didn't work: IDirect3DDevice9->Clear() failed, because it couldnt work out the size of the window that it didn't get a handle for... :-) Any other ideas?
9. ## Render to desktop revisited...

I'm interested in generating a realtime desktop background for my Vista (Ultimate) or Win7, similar to DreamScene, but instead of video, I want D3D10 generated 3D graphics - The background moves, but the icons displayed over it remain unchanged. I googled and searched for ways to do this, but the results that I got back were pre-Vista. Considering DreamScene in Vista Ultimate, it seems that MS should have given us a fairly straighforward way to achieve this with Vista / Win7 / D3D10 / D3D11... EDIT: BTW, using VS9/C++. [Edited by - JeffNiko on May 15, 2009 2:44:29 PM]
10. ## [XNA 3.0] What asset types can I use in XBox games?

I googled for an hour and searched creators.xna.com, but I cant find anything that tells me what asset formats are supported in XBox 360 games. Can anyone tell me or point me to this information? Can you create custom importers and processors that run on XBox? Thanks in advance.
11. ## Win32: PeekMessage() issue invalid message

I think you need to use PM_REMOVE instead of PM_NOREMOVE... otherwise, any messages stay in queue to be processed over and over again.
12. ## ovPlanet / Direct3D precision

I just learned about ovPlanet. I want to experiment with it, but at first glance, it looks like it only spits out vertex data in double precision. I believe that DX10 supports double precision values, but my laptop is limited to DX9. I looked at ovPlanet's forums, and they are stone empty. Does anyone know if ovPlanet can be told to provide single precision float values? If not, am I forced to convert so many double position, normal and txcoord values to float before rendering each frame? This will be detrimental on the framerate, won't it? Any advice to help me overcome this obstacle would be greatly appreciated.
13. ## Physx only at nVidia's cards?

From the nVidia site (re: the nVidia PhysX drivers): "Supports only AGEIA PhysX processors and software runtimes" "Does NOT include NVIDIA GPU PhysX Support" This means to me, now that they have taken over the drivers, that they have not added support for their OWN hardware yet, and ONLY the old Ageia physics cards are supported. I have one of the Ageia cards, and am pretty happy that nVidia has taken over... I've always been pleased with how nVidia keeps updating drivers. Hopefully, they will keep supporting the old Ageia cards, and not phase them out.
14. ## Need help with LUA / VS2008

I am having trouble trying to use LUA in my VS2008 C++ application. I need C++ to call LUA functions and LUA to call C++ functions. I tried downloading the static .lib and header for LUA 5.1.3 from LuaBinaries, but it's compiled for VS2005, and I could not get it to link properly in VS2008 (luaopen_math used undefined reference _HUGE). I also tried downloading the source and was able to create a project, and get it to compile and create lua.exe and luac.exe, but Im not sure how to go from that point (an EXE) to using lua_dofile() and the other functions in my c++ code. Does anyone have a LUA 5.1.3 / VS2008 static library project, or even just the .lib and headers?
15. ## VS2008: Multi-Project Solution Setup

Im using C++ in Visual Studio 2008, and I'm familiar with writing my games in one project within a solution. Now I want to tackle a client-server multiplayer game. I have created my solution, MyGameSolution, with a project, MyGameServer. Then, I add a second project to the solution, MyGameClient. Of course, the server and client will have many classes in common. Where is the efficient (or necessary) place to put the class files for the common classes? Server project? Client project? A new common folder? I realize I should be able to decide whats best for my situation, but I cannot seem to find a configuration that allows me to have two projects referencing the same classes so don't have to have a separate copy of the files in each project folder. Thanks in advance for any instructions or advice.