viewing problem, would like to use 1-100 and not 0.1-1

Hi,

I have a probelm when drawing in 3d. For some reason when drawing a line from 1-100 it is massive but if i draw a line from 0-1 it is the size i expect.

How can i make it so that if i draw a line from 1-100 it draws as 0-1?

Cheers, this will make my life so much easier.

If I understood your post correctly, you should play around with glTranslatef()

Try:
glTranslatef(0,0,-100);

just before your drawing code. The three parameters are a vector to move the “camera”, and you should play around with the values to achieve the effect you want.

The size of the line will also depend on your ortho or perspective settings.

Let’s say you have a ortho setting of 1 unit x 1 unit. Then a line from 0 to 1 would fill the screen.
But if you have a ortho setting of 100 units x 100 units then a line drawn from 0 to 100 would look the same.

I would look at your projection matrix settings first to try and correct this problem. Can you post how you are setting up your projection matrix?

Originally posted by Andrew Davey:
[b]Hi,

I have a probelm when drawing in 3d. For some reason when drawing a line from 1-100 it is massive but if i draw a line from 0-1 it is the size i expect.

How can i make it so that if i draw a line from 1-100 it draws as 0-1?

Cheers, this will make my life so much easier.[/b]

yes that i can, although i dont know what you need so i will give what i think you want:

``````	//reset the current viewport
//viewport creates a scene that will draw stuff in
glViewport(0,0,w,h);

glMatrixMode(GL_PROJECTION);

//enables and sets up perspective viewing for the simulation
//angle, ratio, z range
gluPerspective(45.0f,(GLfloat)w / (GLfloat)h,0.1f,150.0f);

glMatrixMode(GL_MODELVIEW);
``````

n.b. ortho View? i havent set one up, not completely sure what it does.

You project matrix tell openGL how we view the scene, sort of like settings on a lense of a camera.

Ortho projection is like your looking down at a piece of paper. and everthing is draw to scale without adjustment for distance. So a if you where looking down at a cube without any rotation would look like a square. Also the x/y limits are the same for the any z distance.

Perspective projection adjust the object to give them a 3D depth. Under perspective the same cube would be able to see no only the top but the sides .
Under perspective projections your x/y limits change with the z axis. Where a line draw at z max maybe in view at x/y (100,100) but not in view at z min.

Are you changing the z value when you draw your line?

Also maybe that it is you need to be drawing in ortho mode to get the effect you want.

Originally posted by Andrew Davey:
[b]yes that i can, although i dont know what you need so i will give what i think you want:

``````	//reset the current viewport
//viewport creates a scene that will draw stuff in
glViewport(0,0,w,h);
``````

glMatrixMode(GL_PROJECTION);

//enables and sets up perspective viewing for the simulation
//angle, ratio, z range
gluPerspective(45.0f,(GLfloat)w / (GLfloat)h,0.1f,150.0f);

glMatrixMode(GL_MODELVIEW);
``n.b. ortho View? i havent set one up, not completely sure what it does.[/b]``