Null Zbuffer in PGraphicsOpenGL

Programming Questions

lestermun..

Null Zbuffer in PGraphicsOpenGL

in Programming Questions • 2 years ago

Hello All,

I am using OPENGL but when I get a reference to it the the zbuffer is null. The following code is indicative of what I am trying to do and it throws an NullPointerException.

PGraphicsOpenGL p3d = (PGraphicsOpenGL) g;

float depth = p3d.zbuffer[i];

This seems odd as the documentation suggests the default is to have the depth buffer enabled. I also added hint(ENABLE_DEPTH_TEST) to make certain.

Any ideas?

Thanks,

Lester

Replies(5)

PhiLho

Re: Null Zbuffer in PGraphicsOpenGL

2 years ago

Incomplete information: no context, no error message...
Have you OpenGL declared in your size()?

lestermun..

Re: Null Zbuffer in PGraphicsOpenGL

2 years ago

The description is:

If I use:

size(400, 400, P3D);

the attached code will work but if I switch the renderer to OpenGL using:

size(400, 400, OPENGL);

Then the zbuffer member of the graphics context PGraphics3D or PGraphicsOpengGL is null.

Any help would be appreciated.

The exception is:

Exception in thread "Animation Thread" java.lang.NullPointerException

at sketch_mar26c.draw(sketch_mar26c.java:60)

at processing.core.PApplet.handleDraw(PApplet.java:1606)

at processing.core.PApplet.run(PApplet.java:1503)

at java.lang.Thread.run(Thread.java:680)

The code causing it is:

import processing.opengl.*;

float near = 100;

float far = -100;

// A boolean variable that when set to true triggers the PDF recording process

boolean recordPDF = false;

public void setup() {

size(400, 400, OPENGL);

hint(ENABLE_DEPTH_TEST);

// Antialiased lines

smooth();

// Add a view projection

float fov = PI/3.0f;

float cameraZ = (height/2.0f) / tan(fov/2.0f);

perspective(fov, (float)width/(float)height, near, far);

}

public void draw() {

// Clear buffer

background(255);

noStroke();

fill(128);

pushMatrix();{

translate(width/2, height/2 ,0);

rotateX(radians(-15));

rotateY(radians(45));

box(100);

} popMatrix();

// Get our graphics context

PGraphics3D p3d = (PGraphics3D) g;

//PGraphicsOpenGL p3d = (PGraphicsOpenGL) g; // both graphics classes fail

for( int i = 0; i < width * height; i++ ){

float depth = p3d.zbuffer[i]; // zbuffer is null!

}

lestermun..

Re: Null Zbuffer in PGraphicsOpenGL

2 years ago

And I am using Processing version 1.2.1 on a MacbookPro Running OSX 10.6.6

PhiLho

Re: Null Zbuffer in PGraphicsOpenGL

2 years ago

You mix OpenGL mode and P3D mode. No wonder it doesn't work.
Moreover, I see an interesting line in PGraphics3D.java: if (zbuffer != null) { // will be null in OpenGL and others
So, your code will work only if you use P3D mode and get a PGraphics3D object.

lestermun..

Re: Null Zbuffer in PGraphicsOpenGL

2 years ago

"Incomplete information: no context"

I don't believe I am mixing OpenGL and P3D but if you could point out where I am...

Note:

PGraphics3D p3d = (PGraphics3D) g;

is the base class for PGraphicsOpenGL and allows me to switch the rendering context in size() without changing any other code and PGraphicsOpenGL p3d is commened out but had been tried for completeness.

Interesting that the zbuffer isn't supported. Unluckily processing in 3D lacks a lot of precision, an example of which is visible cracks between quads and wireframe corners not meeting so it isn't very suitable for me.

So any ideas how to get a zbuffer when using PGraphicsOpenGL. I am thinking I should be able to use read pixels directly.