glDrawElements()

I can't seem to get the glDrawElement to work correctly. Could someone tell me what I am doing wrong? Thanks

Code:

#include <GL/gl.h>
#include <GL/glu.h>
#include <GL/glut.h>
#include <stdlib.h>

void init(void){
        glClearColor(0.0,0.0,0.0,0.0);
        glShadeModel(GL_SMOOTH);
}

void reshape(GLint w,GLint h){
        glViewport(0,0,(GLsizei)w,(GLsizei)h);
        glMatrixMode(GL_PROJECTION);
        glLoadIdentity();
        gluOrtho2D(0.0,(GLdouble)w,0.0,(GLdouble)h);
}

void display(void){
        GLdouble mix[]={25.0,25.0,0.0,
                        35.0,25.0,0.0,
                        35.0,35.0,0.0,
                        25.0,35.0,0.0};
        glClear(GL_COLOR_BUFFER_BIT);
        glEnableClientState(GL_VERTEX_ARRAY);
        glVertexPointer(3,GL_DOUBLE,6*sizeof(GLdouble),mix);
        glDrawElements(GL_LINE_STRIP,3,GL_DOUBLE,mix);
        glDisableClientState(GL_VERTEX_ARRAY);
        glutSwapBuffers();
}

int main(int argc,char **argv){
        glutInit(&argc,argv);
        glutInitDisplayMode(GLUT_RGB|GLUT_DOUBLE);
        glutInitWindowSize(350,350);
        glutCreateWindow(argv[0]);
        init();
        glutDisplayFunc(display);
        glutReshapeFunc(reshape);
        glutMainLoop();
        return EXIT_SUCCESS;
}

I think you want a stride of 0.

NAME
glVertexPointer - define an array of vertex data

C SPECIFICATION
void glVertexPointer( GLint size,
GLenum type,
GLsizei stride,
const GLvoid *pointer )

PARAMETERS
size Specifies the number of coordinates per vertex; must be 2, 3,
or 4. The initial value is 4.

type Specifies the data type of each coordinate in the array. Sym-
bolic constants GL_SHORT, GL_INT, GL_FLOAT, and GL_DOUBLE are
accepted. The initial value is GL_FLOAT.

stride Specifies the byte offset between consecutive vertices. If
stride is 0, the vertices are understood to be tightly packed
in the array. The initial value is 0.

pointer Specifies a pointer to the first coordinate of the first ver-
tex in the array. The initial value is 0.

this was true, I did forget to change the value from a previous code example I was doing. But it didn't fix the problem. I think i am misinerpreting how glDrawElements works.

glEnableClientState(GL_VERTEX_ARRAY);

edit: do'h, there it is.
hmmmmm... have you tried glFlush()ing at the end of your draw routine?

You're not using glDrawElements correctly. It should be used like this:

Code:

        glEnableClientState(GL_VERTEX_ARRAY);
        glVertexPointer(3, GL_DOUBLE, 0, mix);

        unsigned int indices[] = { 0, 1, 2, 3 };
        glDrawElements(GL_LINE_STRIP, 4, GL_UNSIGNED_INT, indices);

        glDisableClientState(GL_VERTEX_ARRAY);

The last parameter specifies which elements of mix[] should be used. I think it's easier to use glDrawArrays() in your program:

Code:

        glEnableClientState(GL_VERTEX_ARRAY);
        glVertexPointer(3, GL_DOUBLE, 0, mix);

        // glDrawArrays(type, begin, number_of_elements)
        glDrawArrays(GL_LINE_STRIP, 0, 4);

        glDisableClientState(GL_VERTEX_ARRAY);

ahhh thank you so much. I knew I was misunderstanding something!