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gl.cpp

//FILE:         gl.cpp
//AUTHOR:       Nathan Cournia <nathan@cournia.com>

#include "gl.h"

void
gl::init( unsigned int width, unsigned int height )
{
        //clear color is blah
        glClearColor( 0.0f, 0.0f, 0.0f, 0.0f );

        //nive perspective correction
        glHint( GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST );

        //set viewport
        glViewport( 0, 0, width, height );

        //set frustrum
        glMatrixMode( GL_PROJECTION );
        glLoadIdentity( );
        gluPerspective( 45.0f, (float)width / (float)height , 0.1f, 100.0f );

        //switch to modelview matrix
        glMatrixMode( GL_MODELVIEW );
        glLoadIdentity( );
}

//0,0 at lower left
//current matrix is set to modelview
void
gl::enable_2d( GLsizei w, GLsizei h )
{
        //save enable bits
        glPushAttrib( GL_ENABLE_BIT );

        //set the viewport
        glViewport(0, 0, w, h);

        //save the projection matrix and reset it
        glMatrixMode( GL_PROJECTION );
        glPushMatrix( );
        glLoadIdentity( );

        //go into orthogonal mode (0,0 in lower left)
        glOrtho(0.0, (GLdouble)w, 0.0, (GLdouble)h, -1.0, 1.0);

        //save modelview matrix and reset
        glMatrixMode(GL_MODELVIEW);
        glPushMatrix( );
        glLoadIdentity( );

        glDisable(GL_DEPTH_TEST);
        glDisable(GL_CULL_FACE);
}

void
gl::disable_2d( void )
{
        //get old modelview matrix
        glMatrixMode(GL_MODELVIEW);
        glPopMatrix( );

        //get old projection matrix
        glMatrixMode(GL_PROJECTION);
        glPopMatrix( );

        //get old enable bits
        glPopAttrib( );
}

void
gl::render_image( const rectf& rect, const gl::texture& tex )
{
        tex.bind( );
        glBegin( GL_TRIANGLE_STRIP );
                //upper left
                glTexCoord2d( 0.0, 1.0 );
                glVertex2f( rect.x, rect.y + rect.h );
                                
                //lower left
                glTexCoord2d( 0.0, 0.0 );
                glVertex2f( rect.x, rect.y );

                //upper right
                glTexCoord2d( 1.0, 1.0 );
                glVertex2f( rect.x + rect.w, rect.y + rect.h );

                //lower right
                glTexCoord2d( 1.0, 0.0 );
                glVertex2f( rect.x + rect.w, rect.y );
        glEnd( );
}

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