PushMatrix and the camera

General Discussion Other

r0bertlaw

in General Discussion • Other • 1 year ago

HI Guys

Im wondering if anyone can explain something to me or just let me know the "standard" way of doing this. Im new to 3D programming and i would like to get some advice on the whole navigating in 3d thing.. What i want to do is pretty simple, i want to place an object (just a line for now) on the origin of the 3d plane going up in the z direction. i then want to place the point cloud i have from a kinect in the 3d space. I know the offset from the origin in the real world as well as the rotations of the camera in the real world. no this is where im not to sure about how this is done normally.

As i understand so far. the camera is at the origin, and most programs i have seen translate the "subject they are wanting to see away from the origin. so the camera always stays stationary. i have seen the camera functions and havent had much success with it. what i thought of doing was to draw my "subject" at the origin, then pushmatrix() and translate to the Kinect origin and draw the point cloud then popmatrix() and set the camera to a position i want and point it at the origin. is this the right way? i have tried it and it doesnt seem to work.

Is it easier to leave the camera at (0,0,0,) and translate to my new origin and draw my "subject" then translate to the kinect origin and draw the point cloud?

any help would be great.

Thanks

Rob

Replies(2)

thunderba..

Re: PushMatrix and the camera

1 year ago

My guess would be it comes down to personal preference. I was also curious about the same subject, I decided to do a lot of different camera exercises that included mouse movement to see what was actually happening with the camera.

Here is a sketch I saved called "camera tests", i would swap out the eyeX, eyeY, eyeZ for either mouseX or mouseY and see what changes.

Hope this helps.

import processing.opengl.*;
void setup() {
size(600, 400, OPENGL);
smooth();
hint(ENABLE_OPENGL_4X_SMOOTH);
hint(DISABLE_OPENGL_2X_SMOOTH);
background(200);
noStroke();
}
void draw() {
lights();
background(200);
// ambientLight(50, 50, 255);
camera(width/2, mouseY*4, mouseX, // eyex,y,z
width/2, height/2, 0, // center loc x,y,z
0.0, 1.0, 0 // upx,y,z
);
println("mouseY*4: " + mouseY*4 + " mouseX: " + mouseX);
pushMatrix();
translate(width/2, height/2, 0);
rotate(PI/4);
fill(255, 0, 0);
// rect(-150, -25, 50, 50);
fill(255);
box(200, 100, 10);
popMatrix();
pushMatrix();
translate(width/2, height/2, 105);
rotate(-PI/4);
fill(255, 255, 204);
box(10, 10, 200);
popMatrix();
pushMatrix();
translate(width/2+15, height/2+15, 105);
rotate(-PI/4);
fill(161, 218, 180);
box(10, 10, 200);
popMatrix();
pushMatrix();
translate(width/2+30, height/2+30, 105);
rotate(-PI/4);
fill(65, 182, 196);
box(10, 10, 200);
popMatrix();
pushMatrix();
translate(width/2+45, height/2+45, 105);
rotate(-PI/4);
fill(34, 94, 168);
box(10, 10, 200);
popMatrix();
}

Also the opengl redbook has some camera information. The illustration might help.

http://www.glprogramming.com/red/chapter03.html

http://www.glprogramming.com/red/images/Image48.gif

r0bertlaw

Re: PushMatrix and the camera

1 year ago

Thanks, I got it working!

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