68 lines
2.5 KiB
JavaScript
68 lines
2.5 KiB
JavaScript
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// see http://en.wikipedia.org/wiki/STL_%28file_format%29#Binary_STL
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function serialize (CSG) {
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// first check if the host is little-endian:
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var buffer = new ArrayBuffer(4)
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var int32buffer = new Int32Array(buffer, 0, 1)
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var int8buffer = new Int8Array(buffer, 0, 4)
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int32buffer[0] = 0x11223344
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if (int8buffer[0] !== 0x44) {
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throw new Error('Binary STL output is currently only supported on little-endian (Intel) processors')
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}
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var numtriangles = 0
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CSG.polygons.map(function (p) {
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var numvertices = p.vertices.length
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var thisnumtriangles = (numvertices >= 3) ? numvertices - 2 : 0
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numtriangles += thisnumtriangles
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})
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var headerarray = new Uint8Array(80)
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for (var i = 0; i < 80; i++) {
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headerarray[i] = 65
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}
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var ar1 = new Uint32Array(1)
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ar1[0] = numtriangles
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// write the triangles to allTrianglesBuffer:
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var allTrianglesBuffer = new ArrayBuffer(50 * numtriangles)
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var allTrianglesBufferAsInt8 = new Int8Array(allTrianglesBuffer)
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// a tricky problem is that a Float32Array must be aligned at 4-byte boundaries (at least in certain browsers)
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// while each triangle takes 50 bytes. Therefore we write each triangle to a temporary buffer, and copy that
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// into allTrianglesBuffer:
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var triangleBuffer = new ArrayBuffer(50)
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var triangleBufferAsInt8 = new Int8Array(triangleBuffer)
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// each triangle consists of 12 floats:
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var triangleFloat32array = new Float32Array(triangleBuffer, 0, 12)
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// and one uint16:
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var triangleUint16array = new Uint16Array(triangleBuffer, 48, 1)
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var byteoffset = 0
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CSG.polygons.map(function (p) {
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var numvertices = p.vertices.length
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for (var i = 0; i < numvertices - 2; i++) {
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var normal = p.plane.normal
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triangleFloat32array[0] = normal._x
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triangleFloat32array[1] = normal._y
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triangleFloat32array[2] = normal._z
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var arindex = 3
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for (var v = 0; v < 3; v++) {
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var vv = v + ((v > 0) ? i : 0)
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var vertexpos = p.vertices[vv].pos
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triangleFloat32array[arindex++] = vertexpos._x
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triangleFloat32array[arindex++] = vertexpos._y
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triangleFloat32array[arindex++] = vertexpos._z
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}
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triangleUint16array[0] = 0
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// copy the triangle into allTrianglesBuffer:
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allTrianglesBufferAsInt8.set(triangleBufferAsInt8, byteoffset)
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byteoffset += 50
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}
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})
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return [headerarray.buffer, ar1.buffer, allTrianglesBuffer]// 'blobable array'
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/* return new Blob([headerarray.buffer, ar1.buffer, allTrianglesBuffer], {
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type: mimeType
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}) */
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}
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module.exports = {
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serialize
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}
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