public class TesselatorRenderer {

    private static final double MAX = 1.05;
    private static final double MIN = -0.05;

    public void render(double x, double y, double z, Pos... markerPos) {

        GL11.glBlendFunc(GL11.GL_DST_COLOR, GL11.GL_SRC_COLOR);
        GL11.glDisable(GL11.GL_TEXTURE_2D);

        OpenGlHelper.glBlendFunc(774, 768, 1, 0);
        GL11.glColor4f(1.0F, 1.0F, 1.0F, 0.5F);
        GL11.glPushMatrix();
        GL11.glPolygonOffset(-3.0F, -3.0F);
        GL11.glEnable(GL11.GL_POLYGON_OFFSET_FILL);
        GL11.glEnable(GL11.GL_ALPHA_TEST);
        final boolean hadBlend = GL11.glIsEnabled(GL11.GL_BLEND);
        GL11.glEnable(GL11.GL_BLEND);
        final Tessellator tessellator = Tessellator.instance;
        tessellator.startDrawingQuads();
        tessellator.setTranslation(-x, -y, -z);

        float redPart = 1.0f;
        for (final Pos m : markerPos) {
            tessellator.setColorRGBA_F(redPart, 0, 0, 0.5f);
            if (m != null) {
                renderMarker(m, (int) x, (int) y, (int) z);
            }
            redPart *= 0.6;
        }

        tessellator.draw();
        tessellator.setTranslation(0.0D, 0.0D, 0.0D);
        GL11.glDisable(GL11.GL_ALPHA_TEST);
        GL11.glPolygonOffset(0.0F, 0.0F);
        GL11.glDisable(GL11.GL_POLYGON_OFFSET_FILL);
        GL11.glEnable(GL11.GL_ALPHA_TEST);
        if (!hadBlend) {
            GL11.glDisable(GL11.GL_BLEND);
        }
        GL11.glEnable(GL11.GL_TEXTURE_2D);
        GL11.glDepthMask(true);
        GL11.glPopMatrix();
    }

    private void renderMarker(Pos m, int x, int y, int z) {
        final Tessellator tessellator = Tessellator.instance;
        tessellator.addVertex(m.x + x + MIN, m.y + y + MAX, m.z + z + MIN);
        tessellator.addVertex(m.x + x + MIN, m.y + y + MAX, m.z + z + MAX);
        tessellator.addVertex(m.x + x + MAX, m.y + y + MAX, m.z + z + MAX);
        tessellator.addVertex(m.x + x + MAX, m.y + y + MAX, m.z + z + MIN);

        tessellator.addVertex(m.x + x + MIN, m.y + y + MIN, m.z + z + MIN);
        tessellator.addVertex(m.x + x + MIN, m.y + y + MIN, m.z + z + MAX);
        tessellator.addVertex(m.x + x + MIN, m.y + y + MAX, m.z + z + MAX);
        tessellator.addVertex(m.x + x + MIN, m.y + y + MAX, m.z + z + MIN);

        tessellator.addVertex(m.x + x + MAX, m.y + y + MAX, m.z + z + MIN);
        tessellator.addVertex(m.x + x + MAX, m.y + y + MAX, m.z + z + MAX);
        tessellator.addVertex(m.x + x + MAX, m.y + y + MIN, m.z + z + MAX);
        tessellator.addVertex(m.x + x + MAX, m.y + y + MIN, m.z + z + MIN);

        tessellator.addVertex(m.x + x + MIN, m.y + y + MIN, m.z + z + MIN);
        tessellator.addVertex(m.x + x + MIN, m.y + y + MAX, m.z + z + MIN);
        tessellator.addVertex(m.x + x + MAX, m.y + y + MAX, m.z + z + MIN);
        tessellator.addVertex(m.x + x + MAX, m.y + y + MIN, m.z + z + MIN);

        tessellator.addVertex(m.x + x + MIN, m.y + y + MAX, m.z + z + MAX);
        tessellator.addVertex(m.x + x + MIN, m.y + y + MIN, m.z + z + MAX);
        tessellator.addVertex(m.x + x + MAX, m.y + y + MIN, m.z + z + MAX);
        tessellator.addVertex(m.x + x + MAX, m.y + y + MAX, m.z + z + MAX);

        tessellator.addVertex(m.x + x + MIN, m.y + y + MIN, m.z + z + MAX);
        tessellator.addVertex(m.x + x + MIN, m.y + y + MIN, m.z + z + MIN);
        tessellator.addVertex(m.x + x + MAX, m.y + y + MIN, m.z + z + MIN);
        tessellator.addVertex(m.x + x + MAX, m.y + y + MIN, m.z + z + MAX);
    }

    /**
     * Draws the position markers.
     *
     * @param event
     */
    @SubscribeEvent
    public void drawMarkers(RenderWorldLastEvent event) {
        if (CraftBot.bot) {
            final EntityLivingBase player = Minecraft.getMinecraft().renderViewEntity;
            final double x = player.lastTickPosX;
            final double y = player.lastTickPosY;
            final double z = player.lastTickPosZ;

            this.render(x, y, z, new Pos(1, 0, 0));
        }
    }
}