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Member Since 01 Mar 2010
Offline Last Active Apr 12 2016 06:33 PM

Topics I've Started

The Problems about the FPS Camera

21 March 2013 - 05:24 AM

Hi,every one,

   I am a novice in the 3D math.currently , I am tortured by a problem about the rotation of a FPS camera.hope someone can help me .

   please allow me to assume that the discussion is based on OpenGL conversion.

   suppose the FPS camera is placed at the initial state in which the three axis of camera are aligned with axis of world frame.


   I firstly pitch the camera around the x axis of world frame, and then yaw the camera around the y axis of world frame.so I can get the following equation(column-major) : 

   camera_orientation_matrix_1 = yaw_yworld_matrix * pitch_xworld_matrix =  rotateY(yaw_angle)  *  rotateX(pitch_angle);


   some reference  informs me that I can get the same orientation by using the local rotation matrix but applied in a reverse order.

   so I firstly yaw the camera with local y axis of camera, then pitch the camera around the local x axis of the camrea.

ie: camera_orientation_matrix _2 = pitch_xlocal_matrix * yaw_ylocal_matrix = rotateX(pitch_angle) * rotateY(yaw_angle) ;


   since the  camera_orientation_matrix_1 equals camera_orientation_matrix _2, I derive the following:

        rotateY(yaw_angle)  *  rotateX(pitch_angle) === rotateX(pitch_angle) * rotateY(yaw_angle) ;

  but the above equation is a fallacy,Is there anyone can tell me where is wrong? Thanks! smile.png

The Batch Processing for the Texture Baking

18 November 2012 - 03:54 AM

Hi all:
I want to apply a global illumination method to a batch of 3D building models and save the lighting effect as another texture. I am novice in this filed ,
Is there any library or SDK(maya?) availble for me which can do the texture baking task in the batch?

the library computing intersection between a plane and a mesh

08 November 2012 - 05:00 AM

Hi,every one:
I want to slice a triangular mesh with textures into several pieces by a plane.
Is there any open source library that can do the job reliably?
thanks for answering my question!Posted Image

the precision problem in 16 bit Z-Buffer

13 September 2012 - 08:26 PM

Hi ,all:
I am working at a project that aims to develop a virtual globe system by using WebGL.
We have made the system work, but there is z-fighting problems.
I have heard from others that there exists a solution that use a perspective projection matrix,a matrix different from the projection matrix used in the OpenGL,which can resolve/relieve the precision problem.
Does anyone known the equation of the projection matrix? Thank you very much!

Quaternion from latitude and longitude

14 June 2012 - 09:43 PM

Hi ,all,

I want to get a quaternion from the latitude and longitude. could any one hell me how to construct the quaternion?

the coordinate frame details:
given that the Z axis points to the north pole. The X axis points to the intersection of the prime meridian and the equator, in the equatorial plane. The Y axis completes a right-handed coordinate system, and is 90 degrees east of the X axis and also in the equatorial plane.

it seems that I can get the quaternion from multiplication from QLat=(sin(lat),0,0,cos(lat)) and QLon=(0,0,sin(lon),cos(lon)), ie Quat = Qlat*Qlon,but the result is incorrect when applying it to the camera.Is there any mistake ? Thanks you very much!