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+--- Thread: Location of 3D in 2D (/thread-2027.html)
Location of 3D in 2D - bmantzey - Dec 17, 2008 11:04 AM
I wasn't sure what to title this one, and I'm not having any luck finding any info about this out there. I had a hard enough time getting my 3D meshes to draw in an Orthographic projection.
So, I have these 3D objects drawing in an orthographic projection. I figured out that translating them is a little bit different because although there is a Z, you can't see any changes until it reaches a clipping plane and the unit of movement is different.
Since the units are different, I'm clueless as to how I can determine the object's size on screen or how I could determine a certain position in the mesh at all times through rotations and all.
Does anyone have any info as to how I can measure 3D objects drawn in an orthographic scene and most importantly, always identify a specific location in that mesh regardless of rotation or position? What I need is the screen space information about the objects. Thanks in advance!
Location of 3D in 2D - ThemsAllTook - Dec 17, 2008 11:16 AM
http://www.opengl.org/documentation/specs/man_pages/hardcopy/GL/html/glu/project.html
Location of 3D in 2D - bmantzey - Dec 17, 2008 10:53 PM
Oooh, no glu for me.
I'm doing an iPhone game.
Location of 3D in 2D - arekkusu - Dec 17, 2008 11:45 PM
Then you need to learn linear algebra, and implement software transform.
Location of 3D in 2D - bmantzey - Dec 18, 2008 12:07 AM
I have some knowledge of linear algebra. Thanks for narrowing it down for me. I'll just go ahead with that software transform right away. Thanks for your help, now I know exactly what to do now.
Location of 3D in 2D - AnotherJake - Dec 18, 2008 12:34 AM
Or you can grab it from the mesa source. (I never remember where that is, sorry... try google
)[edit] ... silly me, try: http://www.mesa3d.org/
Location of 3D in 2D - ThemsAllTook - Dec 18, 2008 07:59 AM
http://cgit.freedesktop.org/mesa/mesa/tree/src/glu/sgi/libutil/project.c
Code:
static void __gluMultMatrixVecd(const GLdouble matrix[16], const GLdouble in[4],
GLdouble out[4])
{
int i;
for (i=0; i<4; i++) {
out[i] =
in[0] * matrix[0*4+i] +
in[1] * matrix[1*4+i] +
in[2] * matrix[2*4+i] +
in[3] * matrix[3*4+i];
}
}
GLint GLAPIENTRY
gluProject(GLdouble objx, GLdouble objy, GLdouble objz,
const GLdouble modelMatrix[16],
const GLdouble projMatrix[16],
const GLint viewport[4],
GLdouble *winx, GLdouble *winy, GLdouble *winz)
{
double in[4];
double out[4];
in[0]=objx;
in[1]=objy;
in[2]=objz;
in[3]=1.0;
__gluMultMatrixVecd(modelMatrix, in, out);
__gluMultMatrixVecd(projMatrix, out, in);
if (in[3] == 0.0) return(GL_FALSE);
in[0] /= in[3];
in[1] /= in[3];
in[2] /= in[3];
/* Map x, y and z to range 0-1 */
in[0] = in[0] * 0.5 + 0.5;
in[1] = in[1] * 0.5 + 0.5;
in[2] = in[2] * 0.5 + 0.5;
/* Map x,y to viewport */
in[0] = in[0] * viewport[2] + viewport[0];
in[1] = in[1] * viewport[3] + viewport[1];
*winx=in[0];
*winy=in[1];
*winz=in[2];
return(GL_TRUE);
}Location of 3D in 2D - bmantzey - Dec 18, 2008 10:05 PM
Very helpful and greatly appreciated, thank you Took and Jake.