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101 Sep 18, 2005 at 09:58

Hi, guys, i am totally newbie in OpenGL, now I am studying on movement in OpenGL, and I can control a square’s movement, but it seems cannot do a smooth movement such as diagonal movement when i press UP and LEFT, it cannot keep moving towards diagonal direction, I dont know how, can anyboday explain in details to me?? thanks a lot and best regards!!!

#### 3 Replies

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101 Sep 18, 2005 at 10:32

http://www.gamedev.net/community/forums/topic.asp?topic_id=345960

the problem (i guess) is that you use a switch and break after your cases. in the code you posted at gamedev, you check for up, and break out of it while not checking other cases, so if you press both up and left you don’t move diagonal but only in the up direction. like people said on gamedev, use ifs and check all combinations.

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101 Sep 19, 2005 at 02:47

You don’t have to check all combinations. You just check for the 4 basics without using any elses or a switch/case.

if( key == GLUT_KEY_UP )
b += 5.5f;
if( key == GLUT_KEY_DOWN )
b -= 5.5f;
if( key == GLUT_KEY_LEFT  )
a -= 5.5f;
if( key == GLUT_KEY_RIGHT )
a += 5.5f;

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101 Sep 19, 2005 at 14:31

that’s what i meant with all combinations, in stead of stopping checking after the first ‘hit’, checking all other possibilities that are left