Processing 1.0 - Processing Discourse - openGL, zooming out and objects disappear

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Index › Programming Questions & Help › OpenGL and 3D Libraries › openGL, zooming out and objects disappear

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openGL, zooming out and objects disappear (Read 2425 times)

zonk

openGL, zooming out and objects disappear
Jun 12^th, 2009, 9:55am

Hello there,

i want to develope a simple presentation tool with processing.
Basicly is should work like this:
The various slides ( .png`s and .jpgs) are arrangend on one big surface. When changing the slides the camera zooms out,
heads towards the new slide and zooms in again.

Im using openGL and here is the problem:
When zooming out and the z-axis reaches values
more than 6000 the slides seem to disappear.
I`m not really into openGL and couldn`t
figure out a sollution yet.

P3D works well but is slow and the zoomed out slides look ugly.
I`m on Leopard 10.5.7 and NetBeans 6.5.1 IDE.

Thanks in advance.

sim

koogy God Member Offline Posts: 788	Re: openGL, zooming out and objects disappear Reply #1 - Jun 12^th, 2009, 11:04am sounds like things are being clipped by the far clipping plane http://www.falloutsoftware.com/tutorials/gl/gl0.htm how are you setting up your view?

zonk

Re: openGL, zooming out and objects disappear
Reply #2 - Jun 12^th, 2009, 11:24am

Hello,

thanks for the quick answer.
The view is set with the camera() command.

here`s the code. No x- and y-movement of camera yet, only zooming :).

import processing.core.*;
import processing.opengl.*;

PImage a;
PImage b;
PImage c;
PImage d;

void setup() {
size(1024, 768, OPENGL);
imageMode(CENTER);
a = loadImage("data/alex.png");
b = loadImage("data/black_forest.jpg");
c = loadImage("data/mouse.jpg");
d = loadImage("data/abgabe_8.png");
}

public void draw() {
background(200);

camera(width / 2, height / 2,(float) ((height/2.0) / tan((float) (PI * 60.0 / 360.0)))+ mouseY * 100,
width / 2, height / 2, 0,
0, 1, 0);
System.out.println(mouseY * 100);
image(a, 200, 200);
image(b, 200, 800);
image(c, 800, 200);
image(d, 800, 800);

}

koogy God Member Offline Posts: 788	Re: openGL, zooming out and objects disappear Reply #3 - Jun 12^th, 2009, 2:19pm the frustum() function allows you to define near and far. file:///opt/processing-1.0.3/reference/frustum_.html i've no idea whether that interferes with camera() though. i will have a play with your code.

koogy God Member Offline Posts: 788	Re: openGL, zooming out and objects disappear Reply #4 - Jun 13^th, 2009, 1:56am actually, perspective() is what you need. http://processing.org/reference/perspective_.html

koogy

Re: openGL, zooming out and objects disappear
Reply #5 - Jun 13^th, 2009, 1:56am

i added this after the camera call and the clipping at 6000 stopped (see above - by default the backplane is set to 10 * cameraZ)

// see manpage
float fov = PI / 3.0; // 60 degrees
float cameraZ = (height / 2.0) / tan(fov / 2.0);
perspective(fov, float(width)/float(height), cameraZ / 10.0, 10000); // 10000 = backplane

koogy

Re: openGL, zooming out and objects disappear
Reply #6 - Jun 13^th, 2009, 1:57am

(i also changed the camera to

float distance = (mouseX * 10) - 20;
camera(0, 0, (float) ((height/2.0) / tan((float) (PI * 60.0 / 360.0))) + distance,
0, 0, 0,
0, 1, 0);

which puts the camera on the z axis and the image centre at the origin - i find it easier to visualise. you'll need to change the image positions to match this. i used:

// 4 images resized to 200x200 each, centred on origin
image(a, 100, 100, 200, 200);
image(b, 100, -100, 200, 200);
image(c, -100, 100, 200, 200);
image(d, -100, -100, 200, 200);
)

(apologies for multiple messages, i can't for some reason, post anything complex)

zonk YaBB Newbies Offline Posts: 4	Re: openGL, zooming out and objects disappear Reply #7 - Jun 13^th, 2009, 12:15pm Hey, works great. Thanks for helping. Unfortunately there seems to be another problem. The slides are stretched. Guess that this is initiated by the perspective(); call. The display of the slides has to be pixel accurate. I need to change the position of the clipping plane without applying a perspective.

zonk YaBB Newbies Offline Posts: 4	Re: openGL, zooming out and objects disappear Reply #8 - Jun 13^th, 2009, 1:00pm strange things, when i call default perspective(); without values there is no image stretching. when i call perspective(); and insert the default values given in the reference the images are streched.

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