[solved] gluProject

Graphics and GPU Programming Programming

Started by O-san September 29, 2010 08:06 AM

3 comments, last by O-san 13 years, 6 months ago

1,900

Author

September 29, 2010 08:06 AM

I am trying to get the screen coordinates of my world coordinates using gluProject. I am using this bit of code to get my different matrices:

glMatrixMode(GL_PROJECTION);glLoadIdentity();glOrtho(-(windowWidth()/2)/Zoom, (windowWidth()/2)/Zoom, -(windowHeight()/2)/Zoom, (windowHeight()/2)/Zoom, -1000, 1000);glGetDoublev( GL_PROJECTION_MATRIX, mProj );glGetIntegerv(GL_VIEWPORT,mViewp);glMatrixMode(GL_MODELVIEW);glLoadIdentity();// ... translate and rotate the camera glGetDoublev( GL_MODELVIEW_MATRIX, mModl );

Then later I want to use gluProject:

gluProject(world.x,world.y,world.z,mModl,mProj,mViewp,&winx,&winy,&winz);

The gluProject function call returns GL_TRUE but my winx, winy and winz do not correspond to screen coordinates. My world is rendered orthographically (using glOrtho). The winX value seem to look better, the winY value is just bad.

The video below shows the problem. The text "The sword" should be laying where the sword is.

" target="_blank">Youtube
Hires

Any help appreciated!

[Edited by - O-san on September 30, 2010 7:09:39 AM]

Erik Rufelt

5,903

September 29, 2010 08:17 AM

Seems like both your X and Y values are inverted. Try using Height-Y and Width-X.
Seems like your Y-values are inverted. Try using Height-Y. X looks like it just has a static offset a bit to the right of the sword.

Gage64

1,235

September 29, 2010 08:22 AM

Not sure, but is world.x/y/z the world space position of the sword, or the object/local space position? I think it should be the latter.

Also, I don't know if this matters, but that code doesn't call glViewport().

OOP Articles | C++: A Dialog (free book) | Thinking in C++ (free book) | Google Books - Free preview for many books

O-san

1,900

Author

September 29, 2010 10:01 AM

Thanks for the replies! I am at work right now. I will try inverting the Y value once I get home.

O-san

1,900

Author

September 30, 2010 01:59 AM

Got it working now. I had to flip the winY value as well as swapping the world.x and world.y and make them negative. I'm using a coordinate system which has larger values coming towards the camera instead of the default, other way around.

I forgot to mention I fetch the mViewp variable when I setup the orthographic view.

For those who are interested, it looks like this in the end:

if(gluProject(-world.y,-world.x,world.z,mModl,mProj,mViewp,&winx,&winy,&winz)==GL_TRUE){    screenx=winx; // OK    screeny=window.getHeight()-winy;}

Thanks!

[solved] gluProject

This topic is closed to new replies.

Popular Topics

Recommended Tutorials

[solved] gluProject

This topic is closed to new replies.

Popular Topics

Recommended Tutorials

Reticulating splines