function addVertices(polygon, y, insideOffset) {
            var points = polygon.points;

            var pointsLen = points.length;
            var currentPosition = [];
            var uv = [];

            for (var k = 0; k < pointsLen; k += 3) {
                currentPosition[0] = points[k];
                currentPosition[extrudeCoordIndex] = y;
                currentPosition[sideCoordIndex] = points[k + 2];

                uv[0] = (points[k] * scale[0] - min[0]) / maxDimSize;
                uv[1] = (points[k + 2] * scale[sideCoordIndex] - min[2]) / maxDimSize;

                positionAttr.set(vertexOffset, currentPosition);
                if (hasColor) {
                    colorAttr.set(vertexOffset, color);
                }
                texcoordAttr.set(vertexOffset++, uv);
            }
        }
Get region vertex and triangle count