Re: Model View Transformation
"Mohan Parthasarathy" <[email protected]> Wed, 15 Oct 2008 10:10:35 -0800
| Newsgroups | gmane.games.devel.opengl |
|---|---|
| Organization | Fat City Network Services, San Diego, California |
| Message-ID | <[email protected]> |
------=_Part_6046_28232529.1224090666815 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline Hi, I am able to see the cube. So, my view volume should be right, no ? I was mainly trying to understand my observations as to what happens when i move around the camera ? What do you mean by "in the direction of the camera" ? Can you explain ? thx mohan On Tue, Oct 14, 2008 at 6:50 PM, priyadarshi <[email protected]>wrote: > You are not setting up the projection matrix correctly. Both the near > plane and far plane( of the view volume) should be located in the > direction in which camera is looking. > All objects outside the view volume will be culled so make sure the cube > is inside the view volume. > > > Hi, > > > > I am drawing a cube (2 units on all sides) that extends from -1 to 1 on > Z > > axis. I have defined a view volume (parallel projection) that covers 3 > > units > > on all sides (glOrtho (-3.0, 3.0, -3.0,3.0,-3.0,3.0). The cube faces are > > differently colored so that i know what faces i am looking > > at. The camera by default is at (0,0,0). > > > > 1) glTranslate on Z axis with 0.0, 1.0 and 2.0, i see the front face. If > i > > move greater than 2.0 units, i see the back face. I am unable to explain > > this. Isn't the camera pointing towards the -Z axis at the begninning ? > > Then > > why am i seeing the front face. Then when i cross 2 units, i see the back > > face. I am unable to understand this. To see the front face, don't i have > > to > > be in front of the cube i.e something like -1.1 ? Also, for seeing the > > back > > face, don't i have to move forward at least 1.1 and then turn around ? I > > am > > confused. > > > > 2) glTranslate on Z axis with values > 4.0 or -4.0, i don't see the > cube. > > I > > can see that the camera/viewpoint is too far. What is too far ? How do i > > know that i have gone too far without trying different values ? > > > > > > Thanks for any help. > > mohan > > > > ----- > FAQ and OpenGL Resources at: > http://www.geocities.com/SiliconValley/Hills/9956/OpenGL > > -- > Author: priyadarshi > INET: [email protected] > > Fat City Hosting, San Diego, California -- http://www.fatcity.com > --------------------------------------------------------------------- > To REMOVE yourself from this mailing list, send an E-Mail message > to: [email protected] (note EXACT spelling of 'ListGuru') and in > the message BODY, include a line containing: UNSUB OPENGL-GAMEDEV-L > (or the name of mailing list you want to be removed from). You may > also send the HELP command for other information (like subscribing). > ------=_Part_6046_28232529.1224090666815 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline <div dir="ltr">Hi,<br><br>I am able to see the cube. So, my view volume should be right, no ? I was mainly trying to understand my observations as to what happens when i move around the camera ? What do you mean by "in the direction of the camera" ? Can you explain ?<br> <br>thx<br>mohan<br><br><br><div class="gmail_quote">On Tue, Oct 14, 2008 at 6:50 PM, priyadarshi <span dir="ltr"><<a href="mailto:[email protected]">[email protected]</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> You are not setting up the projection matrix correctly. Both the near<br> plane and far plane( of the view volume) should be located in the<br> direction in which camera is looking.<br> All objects outside the view volume will be culled so make sure the cube<br> is inside the view volume.<br> <div><div></div><div class="Wj3C7c"><br> > Hi,<br> ><br> > I am drawing a cube (2 units on all sides) that extends from -1 to 1 on Z<br> > axis. I have defined a view volume (parallel projection) that covers 3<br> > units<br> > on all sides (glOrtho (-3.0, 3.0, -3.0,3.0,-3.0,3.0). The cube faces are<br> > differently colored so that i know what faces i am looking<br> > at. The camera by default is at (0,0,0).<br> ><br> > 1) glTranslate on Z axis with 0.0, 1.0 and 2.0, i see the front face. If i<br> > move greater than 2.0 units, i see the back face. I am unable to explain<br> > this. Isn't the camera pointing towards the -Z axis at the begninning ?<br> > Then<br> > why am i seeing the front face. Then when i cross 2 units, i see the back<br> > face. I am unable to understand this. To see the front face, don't i have<br> > to<br> > be in front of the cube i.e something like -1.1 ? Also, for seeing the<br> > back<br> > face, don't i have to move forward at least 1.1 and then turn around ? I<br> > am<br> > confused.<br> ><br> > 2) glTranslate on Z axis with values > 4.0 or -4.0, i don't see the cube.<br> > I<br> > can see that the camera/viewpoint is too far. What is too far ? How do i<br> > know that i have gone too far without trying different values ?<br> ><br> ><br> > Thanks for any help.<br> > mohan<br> ><br> <br> </div></div>-----<br> FAQ and OpenGL Resources at:<br> <a href="http://www.geocities.com/SiliconValley/Hills/9956/OpenGL" target="_blank">http://www.geocities.com/SiliconValley/Hills/9956/OpenGL</a><br> <br> --<br> Author: priyadarshi<br> INET: <a href="mailto:[email protected]">[email protected]</a><br> <br> Fat City Hosting, San Diego, California -- <a href="http://www.fatcity.com" target="_blank">http://www.fatcity.com</a><br> ---------------------------------------------------------------------<br> To REMOVE yourself from this mailing list, send an E-Mail message<br> to: <a href="mailto:[email protected]">[email protected]</a> (note EXACT spelling of 'ListGuru') and in<br> the message BODY, include a line containing: UNSUB OPENGL-GAMEDEV-L<br> (or the name of mailing list you want to be removed from). You may<br> also send the HELP command for other information (like subscribing).<br> </blockquote></div><br></div> ------=_Part_6046_28232529.1224090666815-- ----- FAQ and OpenGL Resources at: http://www.geocities.com/SiliconValley/Hills/9956/OpenGL -- Author: Mohan Parthasarathy INET: [email protected] Fat City Hosting, San Diego, California -- http://www.fatcity.com --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [email protected] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB OPENGL-GAMEDEV-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).