uniform float tile_size;

void main(void) {
gl_PointSize = tile_size;
// gl_PointSize = 12;
}

glEnable(GL_TEXTURE_2D);
glEnable(GL_POINT_SPRITE);
glEnable(GL_VERTEX_PROGRAM_POINT_SIZE);

GLint unif_tilesize = glGetUniformLocation(*shader program*, "tile_size");
glUniform1f(unif_tilesize, 12);

_coord = gl_TexCoord[0].xy;