Hi, i wrote following source code, it works alomost well, I have the squad before my camera even if i move or rotate the camera. But there is a small problem. If i move camera in way of axe Y, or i rotate it , the quad is moving. If i move the camera on axe Y so just a little bit. Does somebody know how could i make it work ? glMatrixMode(GL_PROJECTION); glPushMatrix(); glRotatef(0,1,0,0); glRotatef(0,0,1,0); glRotatef(0,0,0,1); glLoadIdentity(); glOrtho(0,100,0,133,-10,10); glMatrixMode(GL_MODELVIEW); glBegin(GL_QUADS); glColor3f(1,1,0); glVertex3f(0,10,0.1); glVertex3f(100,10,0.1); glVertex3f(100,0,0.1); glVertex3f(0,0,0.1); glEnd(); glMatrixMode(GL_PROJECTION); glPopMatrix(); glMatrixMode(GL_MODELVIEW);

I don''t know if this helps, but....
What''s the point in doing all these lines
glRotatef(0,1,0,0);
glRotatef(0,0,1,0);
glRotatef(0,0,0,1);
You seems to rotate about every axis in 0 degrees?
And you use pushMatrix(); and then LoadIdentity()? If you''re going to reset to Identity Matrix anyway, why bother push the Matrix.
Anyway, I''d rather write something more like this....
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0,100,0,133,-10,10);
glMatrixMode(GL_MODELVIEW);
glBegin(GL_QUADS);
glColor3f(1,1,0);
glVertex3f(0,10,0.1);
glVertex3f(100,10,0.1);
glVertex3f(100,0,0.1);
glVertex3f(0,0,0.1);
glEnd();

ok, firstly, it's good practise to never use the projection matrix for anything other than projection..

secondly, the use of glPush/Pop matrix is so you can save the current matrix for use at a later time... in effect, a way to 'undo' transofrmations you make...

ie, a prime example of this is a camera - scene graph style system...

ie,
all in modelview btw,



load matrix - camera

push matrix (save the camera matrix)..

mult matrix - object1 (move to where object1 is from the camera)

draw object 1...

pop matrix (we don't care about object1's position anymore) - in effect reload the camera

push matrix (save the camera again)

mult matrix - object2

etc...



does this help clear up the use of push/pop matrix? if it doesn't I can try a bit harder


for a more general view, a copy of the current matrix is simply being pushed onto the top of a statck of matrices when calling pushMatrix, and popped off the top and loaded with popMatrix..

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[edited by - RipTorn on November 26, 2002 12:09:09 AM]

It doesn''T work, I wrote that
I''m think that the quad is drawn behind the camera => I need to get the camera in pushmatrix to x0,y0,z0 and 0 angle on x,y,z, loadidentity should do it. bat anyway it still doesn''t work
glLoadIdentity();
glPushMatrix();
glLoadIdentity();

glOrtho(0,100,0,133,-10,10);
glBegin(GL_QUADS);
glColor3f(1,1,0);
glVertex3f(0,10,1);
glVertex3f(100,10,1);
glVertex3f(100,0,1);
glVertex3f(0,0,1);
glEnd();
glPopMatrix();

It doesn''T work, I wrote that
I''m think that the quad is drawn behind the camera => I need to get the camera in pushmatrix to x0,y0,z0 and 0 angle on x,y,z, loadidentity should do it. bat anyway it still doesn''t work
glLoadIdentity();
glPushMatrix();
glLoadIdentity();

glOrtho(0,100,0,133,-10,10);
glBegin(GL_QUADS);
glColor3f(1,1,0);
glVertex3f(0,10,1);
glVertex3f(100,10,1);
glVertex3f(100,0,1);
glVertex3f(0,0,1);
glEnd();
glPopMatrix();

It doesn''T work, I wrote that
I''m think that the quad is drawn behind the camera => I need to get the camera in pushmatrix to x0,y0,z0 and 0 angle on x,y,z, loadidentity should do it. bat anyway it still doesn''t work
glLoadIdentity();
glPushMatrix();
glLoadIdentity();

glOrtho(0,100,0,133,-10,10);
glBegin(GL_QUADS);
glColor3f(1,1,0);
glVertex3f(0,10,1);
glVertex3f(100,10,1);
glVertex3f(100,0,1);
glVertex3f(0,0,1);
glEnd();
glPopMatrix();