why Particle system with shader doesn't work? three.js

问题

Hi can anyone help me whith this? I have this shader, it works with THREE.Mesh but doesn't with THREE.Particlesystem?

I want each particle to have a portion of a given map(texture) and change their positions accordingly, something like this http://www.chromeexperiments.com/detail/webcam-displacement/?f=webgl

<script id="vs" type="x-shader/x-vertex">


            uniform sampler2D map;

            varying vec2 vUv;

            void main() {

                vUv = uv;

                vec4 color = texture2D( map, vUv );
                float value = ( color.r + color.g + color.b ) / 3.0;

                vec4 pos = vec4( position.xy, value * 100.0, 1.0 );

                                gl_PointSize = 20.0;

                gl_Position = projectionMatrix * modelViewMatrix * pos;

            }

        </script>

<script id="fs" type="x-shader/x-fragment">

            uniform sampler2D map;

            varying vec2 vUv;

            void main() {

                gl_FragColor = texture2D( map, vUv );

            }

</script>

回答1:

ParticleSystem doesn't really support UVs as there aren't faces, just single points. Texture mapping particles is done with gl_PointCoord (IIRC), but that gives you same mapping for every particle. In order to give different portion of the same texture to each particle, you should use BufferGeometry, which in the latest version of three.js supports all attributes including custom ones (and it is very efficient and fast!). You'd then supply a vec2 offset attribute for each particle: you get the correct UV from this offset and the gl_PointCoord.

来源：https://stackoverflow.com/questions/15697898/why-particle-system-with-shader-doesnt-work-three-js