Encoding VertexData question

CesiumJS
1

Anyone got an example of the opposite of this decoding example

e.g how would you encode the same buffers back the other way. Sorry I am not very good with bit shifting code

var u = 0;
var v = 0;
var height = 0;

function zigZagDecode(value) {
    return (value >> 1) ^ (-(value & 1));
}

for (i = 0; i < vertexCount; ++i) {
    u += zigZagDecode(uBuffer[i]);
    v += zigZagDecode(vBuffer[i]);
    height += zigZagDecode(heightBuffer[i]);

    uBuffer[i] = u;
    vBuffer[i] = v;
    heightBuffer[i] = height;

}****

2

I went back through some old posts on this forum and got some good tips so it might be something like below. Let me know if I missed something.

var i;

var prev_u = 0;

var prev_v = 0;

var prev_height = 0;

function zigZagEncode(value) {

return (value << 1) ^ (n >> 31);

}

for (i = 0; i < vertexCount; ++i) {

u = zigZagEncode(uBuffer[i] - prev_u); // get delta and encode

v = zigZagEncode(vBuffer[i] - prev_v);

height = zigZagEncode(heightBuffer[i] - prev_height);

addRow(“vertices”, [uBuffer[i], vBuffer[i], heightBuffer[i]], [u, v, height]);

prev_u = uBuffer[i];

prev_v = vBuffer[i];

prev_height= heightBuffer[i];

uBuffer[i] = u;

vBuffer[i] = v;

heightBuffer[i] = height;

}

3

I think you’ve got it right. This seems like a good reference and it matches what you have for the encode:

Do you mind linking to the forum threads that helped you figure it out? Might be good for anyone else stumbling on this!

4

Comments by Kevin Ring helped in this case for what was going on and zigzag encoding I simply googled around.
https://groups.google.com/forum/?hl=en#!searchin/cesium-dev/delta%7Csort:date/cesium-dev/ajm2fgZ1L6c/7xqKGzsjyz0J

https://groups.google.com/forum/?hl=en#!searchin/cesium-dev/delta%7Csort:date/cesium-dev/IpcBEvjt-DA/Y8iF87hQ8R8J