tessellator.startDrawing(GL11.GL_LINES);
tessellator.addVertex(ix, iy, iz);
tessellator.addVertex(ix, ay, iz);
tessellator.addVertex(ix, ay, iz);
tessellator.addVertex(ax, ay, iz);
tessellator.addVertex(ax, ay, iz);
tessellator.addVertex(ax, iy, iz);
tessellator.addVertex(ax, iy, iz);