问题
I am creating several THREE.Lines using THREE.BufferGeometry. Initially my app had them all starting at the origin and things worked as expected. Now, I would like to be able to start (and end) them at any point.
This fiddle (http://jsfiddle.net/9nVqU/) illustrates (I hope) how changing one end of the line away from the origin causes unexpected results.
I wondered if it was because any given line follows on from the previous one - switching the start/end order didn't change anything though so if that were true, I'd expect it to break.
Maybe I have the arrays set up incorrectly or the attributes that tell THREE.js how to interpret it - I think I need 2 * 3 verts for each line but changes I made to buffer_geometry.attributes = { seemed to make things worse.
FWIW, the actual effect I'm trying to achieve is to selectively turn on and off the lines based on user input. I can do that already by changing the end position but then I lose that value and I don't want to store it elsewhere. I thought that I could move the start point to the end point to switch it off and then move the start point to the origin again to re-enable it. If there is a way to enable/disable lines individually with BufferGeometry, then that would clearly be better.
回答1:
First of all, you would have to do this:
var line = new THREE.Line( buffer_geometry, material );
line.type = THREE.LinePieces;
Second, this is not supported in r.58 , but should be.
As a work-around, you can hack WebGLRenderer.renderBufferDirect() like so:
// render lines
setLineWidth( material.linewidth );
var position = geometryAttributes[ "position" ];
primitives = ( object.type === THREE.LineStrip ) ? _gl.LINE_STRIP : _gl.LINES;
_gl.drawArrays( primitives, 0, position.numItems / 3 );
_this.info.render.calls ++;
_this.info.render.points += position.numItems;
three.js r.58
来源：https://stackoverflow.com/questions/16867293/creating-three-lines-with-different-endpoints-using-three-buffergeometry