mapping quadrilateral to quadrilateral

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1.mapping quadrilateral to quadrilateral

Hi buddies,

I am trying to map a convex quadrilateral to a concave quadrilateral
in 2D plane, or vice visa.

Is the projective transformation a right mapping? If not, is there any
transformation good for that?

Thanks,

Yong Hu

2.overlapping quadrilaterals: culling question

Hello,

Could someone be so kind to tell me how come the green rectangle
is drawn above the red rectangle when in fact it is located below?
I think this has to do with some culling option I need to enable,
but I'm not sure how. Basically, if I draw the green rectangle
first then the pictures appears OK, but I need the drawing to
be independent of how I view it with the camera so I cannot
rely on drawing one quadrilateral or the other one first.

Can anyone please let me know how to fix this problem?

Thanks,

Neil

#include <GL/glut.h>

void drawCube(void) {
  glClear(GL_COLOR_BUFFER_BIT);
  glMatrixMode(GL_MODELVIEW);
  glLoadIdentity();
  glBegin(GL_QUADS);
    /* outer top face (red) */
    glColor3f(1.0f, 0.0f, 0.0f);
    glNormal3f(0.0f, 1.0f, 0.0f);
    glVertex3f(0.0f, 1.0f, 0.0f);
    glVertex3f(1.0f, 1.0f, 0.0f);
    glVertex3f(1.0f, 1.0f, 1.0f);
    glVertex3f(0.0f, 1.0f, 1.0f);
    /* outer bottom face (green) */
    glColor3f(0.0f, 1.0f, 0.0f);
    glNormal3f(0.0f, -1.0f, 0.0f);
    glVertex3f(0.0f, 0.0f, 0.0f);
    glVertex3f(1.0f, 0.0f, 0.0f);
    glVertex3f(1.0f, 0.0f, 1.0f);
    glVertex3f(0.0f, 0.0f, 1.0f);
  glEnd();
  glutSwapBuffers();
  glFlush();
}

void idle(void) {
  drawCube();
}

int main(int argc, char **argv) {
  glutInit(&argc, argv);
  glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE);
  glutInitWindowPosition(120, 80);
  glutInitWindowSize(640, 480);
  glutIdleFunc(idle);
  glutCreateWindow("hello");
  glMatrixMode(GL_PROJECTION);
  glLoadIdentity();
  gluPerspective(45.0, 1.0, 0.0, 3.0);
  gluLookAt(-1.0, 3.0, -1.0, 0.0, 1.0, 0.0, 0.0, 1.0, 0.0);
  glutMainLoop();
  return 0;
}

3.transform between convex and concave quadrilaterals

Hi buddies,

I am trying to map a convex quadrilateral to a concave quadrilateral
in 2D plane, or vice visa.

Is the projective transformation a right mapping? If not, is there any
transformation good for that?

Thanks,

Yong Hu

4.testing whether a point is contained in a quadrilateral

Hi Everyone-
In 2D or 3D, I'm trying to write a quick algorithm to test if a point is 
contatined in a quadrilateral.  I've come up with a couple of ideas, but 
both of them seem needlessly complex.  Does anyone know of a quick way 
to do this?  Or maybe you know of a resource I should check out.

Thanks in advance.  -spencer

5.Forming An Equilateral Triangle About The Centre Of A Planar Quadrilateral

Given a planar quadrilateral, I want to form a equilateral triangle 
about the centre of the quadrilateral, such that this triangle is of 
maximum size while still being equilateral and completely within the 
area defined by the quadrilateral.

Any thoughts on the best way of calculating such a triangle?

Adam

6. Fitting a quadrilateral to pixels

7. Smallest 4-sided polygon surrounding convex hull ( smallest convex quadrilateral)

8. Fastest ray quadrilateral intersection test