"Picking" with the mouse

Graphics and GPU Programming Programming

Started by Colby_ March 28, 2012 10:56 PM

4 comments, last by spooderw 12 years ago

100

Author

March 28, 2012 10:56 PM

I've read tutorials on this, but I can't seem to get it to work. I don't think I understand what exactly is going on at all. What I'm trying to do is get the number of objects (and later the actual objects) that are intersected by a ray cast from the center of the screen. (Or where the mouse is)

Heres what I have to so far, and it's printing -1 always.

	    glLoadIdentity();

	    glRotatef(pit, 1.0f, 0.0f, 0.0f);

	    glRotatef(yaw, 0.0f, 1.0f, 0.0f);

	    glTranslatef(-x, -y, -z);



	    glRenderMode(GL_SELECT);

	    IntBuffer i = ByteBuffer.allocateDirect(64).asIntBuffer();

	    glGetInteger(GL_VIEWPORT, i);

	    gluPickMatrix(canv.getWidth() / 2, canv.getHeight() / 2, 1.0f, 1.0f, i);

	    gluPerspective(60f, 1.0f, 0.0001f, 1000.0f);

	    world.draw();

	    int hits = glRenderMode(GL_RENDER);

	    System.out.println(hits);

	    glLoadIdentity();

	    glRotatef(pit, 1.0f, 0.0f, 0.0f);

	    glRotatef(yaw, 0.0f, 1.0f, 0.0f);

	    glTranslatef(-x, -y, -z);

	    world.draw();

spooderw

123

March 28, 2012 11:30 PM

[font=arial,helvetica,sans-serif]If you're trying to select objects in a 3D world with the mouse, check out [color=#000000]gluUnProject.[/font]

Colby_

100

Author

March 28, 2012 11:44 PM

[font=arial,helvetica,sans-serif]If you're trying to select objects in a 3D world with the mouse, check out [color=#000000]gluUnProject.[/font]

I've seen that also, but I dont quite understand the parameters

spooderw

123

March 28, 2012 11:58 PM

Nehe's got a tutorial for that.

Colby_

100

Author

March 29, 2012 02:10 AM

Nehe's got a tutorial for that.

Looking from that tutorial, I was able to convert the C code to Java. However, it returns things such as 0, NaN, or sometimes insane coordinates, even if the point is on top of a rendered polygon. Am I missing a step?

	float[] screenToWorld(int x, int y) {

		IntBuffer viewport = ByteBuffer.allocateDirect(16 * 4).asIntBuffer();

		FloatBuffer modelview = ByteBuffer.allocateDirect(16 * 4).asFloatBuffer();

		FloatBuffer projection = ByteBuffer.allocateDirect(16 * 4).asFloatBuffer();

		float winX, winY;

		glGetFloat(GL_MODELVIEW_MATRIX, modelview);

		glGetFloat(GL_PROJECTION_MATRIX, projection);

		glGetInteger(GL_VIEWPORT, viewport);

		winX = (float) x;

		winY = (float) viewport.get(3) - (float) y;

		FloatBuffer winZ = ByteBuffer.allocateDirect(1 * 4).asFloatBuffer();

		glReadPixels(x, (int) winY, 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, winZ);

		FloatBuffer pos = ByteBuffer.allocateDirect(3 * 4).asFloatBuffer();

		gluUnProject(winX, winY, winZ.get(0), modelview, projection, viewport, pos);

		float[] raw = new float[3];

		pos.get(raw);

		return raw;

	}

spooderw

123

March 30, 2012 12:33 AM

[quote name='spooderw' timestamp='1332979106' post='4926168'] Nehe's got a tutorial for that.

	float[] screenToWorld(int x, int y) {

		IntBuffer viewport = ByteBuffer.allocateDirect(16 * 4).asIntBuffer();

		FloatBuffer modelview = ByteBuffer.allocateDirect(16 * 4).asFloatBuffer();

		FloatBuffer projection = ByteBuffer.allocateDirect(16 * 4).asFloatBuffer();

		float winX, winY;

		glGetFloat(GL_MODELVIEW_MATRIX, modelview);

		glGetFloat(GL_PROJECTION_MATRIX, projection);

		glGetInteger(GL_VIEWPORT, viewport);

		winX = (float) x;

		winY = (float) viewport.get(3) - (float) y;

		FloatBuffer winZ = ByteBuffer.allocateDirect(1 * 4).asFloatBuffer();

		glReadPixels(x, (int) winY, 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, winZ);

		FloatBuffer pos = ByteBuffer.allocateDirect(3 * 4).asFloatBuffer();

		gluUnProject(winX, winY, winZ.get(0), modelview, projection, viewport, pos);

		float[] raw = new float[3];

		pos.get(raw);

		return raw;

	}

[/quote]

My java is really rusty, so I could not tell you specifically what may be wrong with your code...

"Picking" with the mouse

[font=arial,helvetica,sans-serif]If you're trying to select objects in a 3D world with the mouse, check out [color=#000000]gluUnProject.[/font]

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"Picking" with the mouse

[font=arial,helvetica,sans-serif]If you're trying to select objects in a 3D world with the mouse, check out [color=#000000]gluUnProject.[/font]

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