Camera related documentation needs improvement regarding touch/screenspace

Issue details

Camera.unproject does not return original value

Reproduction steps/code

    public void create() {
        Vector2 tmpvec = new Vector2();
        tmpvec.set(0, 0);

        Stage stage = new Stage(new ScreenViewport());
        stage.stageToScreenCoordinates(tmpvec); // has the correct screen coords;
        stage.screenToStageCoordinates(tmpvec);
        System.out.println(tmpvec); // prints (0, -1), should be (0, 0)
    }

Due to the following line in Camera (-1 at the end):

https://github.com/libgdx/libgdx/blob/c0c1f515df54092cb47717f43f022db02cf7e328/gdx/src/com/badlogic/gdx/graphics/Camera.java#L197

Intended?

Version of LibGDX and/or relevant dependencies

1.9.10

[jusw85]

OpenGL for reference, specifically gluProject and gluUnProject, compiled and run on Arch Linux/Mesa 3D.

gluProject — map object coordinates to window coordinates gluUnProject — map window coordinates to object coordinates

The window size is 300x300, and (0,0) is the point at the centre of the screen.

#include <stdio.h>
#include <GL/gl.h>
#include <GL/glut.h>

void displayFunc(void)
{
    GLdouble posX, posY, posZ;
    GLdouble winX, winY, winZ;
    GLdouble resX, resY, resZ;
    GLdouble modelview[16];
    GLdouble projection[16];
    GLint viewport[4];
    glGetDoublev(GL_MODELVIEW_MATRIX, modelview);
    glGetDoublev(GL_PROJECTION_MATRIX, projection);
    glGetIntegerv(GL_VIEWPORT, viewport);
    posX = 0.0;
    posY = 0.0;
    posZ = 0.0;

    gluProject(posX, posY, posZ, modelview, projection, viewport, &winX, &winY, &winZ);
    printf("window: %f %f %f\n", winX, winY, winZ);
    // window: 150.000000 150.000000 0.500000

    gluUnProject(winX, winY, winZ, modelview, projection, viewport, &resX, &resY, &resZ);
    printf("pos: %f %f %f\n", resX, resY, resZ); 
    // pos: 0.000000 0.000000 0.000000
}

int main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE);
    glutInitWindowSize(300, 300);
    glutCreateWindow("Test glProject glUnProject");
    glutDisplayFunc(displayFunc);
    glutMainLoop();
    return 0;
}

[NathanSweet]

@mark6412 Don’t ask for help on an issue tracker. See: https://github.com/libgdx/libgdx/wiki/Getting-help

Seems a bit unfortunate to need to think about touch space coordinates. Ideally we’d have only screen space and world space.