• Create Account

### #Actualt_guen03

Posted 17 February 2012 - 01:18 PM

Thanks for your reply Goldberg, but these slides doesn't answer my question. Furthermore they dont use the zFail method with a inifite projection matrix. The slides describe another way, where cliping is done at the near plane and conventional zPass method is used.

But there is one thing in common with my problem. They use vectors with w = 0 to extend vertices in one direction. The slides just say, OpenGL is required to draw homogenous coordinates with w = 0 correctly. But what shall this mean. Isn't it only the projection matrix i use, which determines if my vertices are drawed correctly. With the standard projection matrix, homogenous coordinates with w = 0 get mapped to a z coordinate of (f+n)/(f-n), which is >1, thus the vertices shouldn't get drawed correctly. So i don't understand why the slides state they would.

Additionally, at the slides, directions ( vectors with w = 0 ) get extruded in the direction the direction points, but how you can see in my sketches, all directions get only extruded to the far plane and never in the direction to the near plane.

Obviously i am wrong, could someone tell me where ?

### #3t_guen03

Posted 17 February 2012 - 01:17 PM

Thanks for your reply Mark Goldberg, but these slides doesn't answer my question. Furthermore they dont use the zFail method with a inifite projection matrix. The slides describe another way, where cliping is done at the near plane and conventional zPass method is used.

But there is one thing in common with my problem. They use vectors with w = 0 to extend vertices in one direction. The slides just say, OpenGL is required to draw homogenous coordinates with w = 0 correctly. But what shall this mean. Isn't it only the projection matrix i use, which determines if my vertices are drawed correctly. With the standard projection matrix, homogenous coordinates with w = 0 get mapped to a z coordinate of (f+n)/(f-n), which is >1, thus the vertices shouldn't get drawed correctly. So i don't understand why the slides state they would.

Additionally, at the slides, directions ( vectors with w = 0 ) get extruded in the direction the direction points, but how you can see in my sketches, all directions get only extruded to the far plane and never in the direction to the near plane.

Obviously i am wrong, could someone tell me where ?

### #2t_guen03

Posted 17 February 2012 - 01:16 PM

Thanks for your reply Mark Goldberg, but these slides doesn't answer my question. Furthermore they dont use the zFail method with a inifite projection matrix. The slides describe another way, where cliping is done at the near plane and conventional zPass method is used.

But there is one thing in common with my problem. They use vectors with w = 0 to extend vertices in one direction. The slides just say, OpenGL is required to draw homogenous coordinates with w = 0 correctly. But what shall this mean. Isn't it only the projection matrix i use, which determines if my vertices are drawed correctly. With the standard projection matrix, homogenous coordinates with w = 0 get mapped to a z coordinate of (f+n)/(f-n), which is >1, thus the vertices shouldn't get drawed correctly. So i don't understand why the slides state they would.

Additionally, at the slides directions ( vectors with w = 0 ) get extruded in the direction the direction points, but how you can see in my sketches, all directions get only extruded to the far plane and never in the direction to the near plane.

Obviously i am wrong, could someone tell me where ?

### #1t_guen03

Posted 17 February 2012 - 01:15 PM

Thanks for your reply Mark Goldberg, but these slides doesn't answer my question. Furthermore they dont use the zFail method with a inifite projection matrix. The slides describe another way, where cliping is done at the near plane and conventional zPass method is used.

But there is one thing in common with my problem. They use w = 0 coordinates to extend vertices in one direction. The slides just say, OpenGL is required to draw homogenous coordinates with w = 0 correctly. But what shall this mean. Isn't it only the projection matrix i use, which determines if my vertices are drawed correctly. With the standard projection matrix, homogenous coordinates with w = 0 get mapped to a z coordinate of (f+n)/(f-n), which is >1, thus the vertices shouldn't get drawed correctly. So i don't understand why the slides state they would.

Additionally, at the slides directions ( vectors with w = 0 ) get extruded in the direction the direction points, but how you can see in my sketches, all directions get only extruded to the far plane and never in the direction to the near plane.

Obviously i am wrong, could someone tell me where ?

PARTNERS