Rotate instance in vertex shader

Question

I'm learning about instanced buffer geometries and trying to extend LambertMaterial shader to rotate each instance.

  #define LAMBERT
  mat4 rotationX( in float angle ) {
    return mat4(    1.0,        0,          0,          0,
            0,  cos(angle), -sin(angle),        0,
            0,  sin(angle),  cos(angle),        0,
            0,          0,            0,        1);
  }

  mat4 rotationY( in float angle ) {
    return mat4(    cos(angle),     0,      sin(angle), 0,
                0,      1.0,             0, 0,
            -sin(angle),    0,      cos(angle), 0,
                0,      0,              0,  1);
  }

  mat4 rotationZ( in float angle ) {
    return mat4(    cos(angle),     -sin(angle),    0,  0,
            sin(angle),     cos(angle),     0,  0,
                0,              0,      1,  0,
                0,              0,      0,  1);
  }

        // instanced
        attribute vec3 instanceOffset;
        attribute vec3 instanceColor;
        attribute vec3 instanceRotation;
        varying vec3 vLightFront;
        varying vec3 vIndirectFront;
        #ifdef DOUBLE_SIDED
            varying vec3 vLightBack;
            varying vec3 vIndirectBack;
        #endif
        #include <common>
        #include <uv_pars_vertex>
        #include <uv2_pars_vertex>
        #include <envmap_pars_vertex>
        #include <bsdfs>
        #include <lights_pars_begin>
        #include <color_pars_vertex>
        #include <fog_pars_vertex>
        #include <morphtarget_pars_vertex>
        #include <skinning_pars_vertex>
        #include <shadowmap_pars_vertex>
        #include <logdepthbuf_pars_vertex>
        #include <clipping_planes_pars_vertex>
        void main() {
            #include <uv_vertex>
            #include <uv2_vertex>
            #include <color_vertex>
            // vertex colors instanced
            #include <beginnormal_vertex>
            #include <morphnormal_vertex>
            #include <skinbase_vertex>
            #include <skinnormal_vertex>
            #include <defaultnormal_vertex>
            #include <begin_vertex>
            // position instanced
            transformed += instanceOffset;
            #include <morphtarget_vertex>
            #include <skinning_vertex>
    #include <project_vertex>
    mvPosition =  rotationX(250.0) * rotationY(90.0) * rotationZ(25.0) * vec4(position, 1.0);
            #include <logdepthbuf_vertex>
            #include <clipping_planes_vertex>
            #include <worldpos_vertex>
            #include <envmap_vertex>
            #include <lights_lambert_vertex>
            #include <shadowmap_vertex>
    #include <fog_vertex>
        }
        `

After digging through google I went with something like this but it doesn't rotate them at all. They are all just the same position any number I input.

Don't know if this is the proper transformation. How should i properly extend the shader to add rotation?

Answer 1

When using THREE.InstancedMesh, you can use instanced rendering for all build-in materials and transforming each instance independently. Check out the following example that demonstrates this approach:

https://threejs.org/examples/webgl_instancing_dynamic

The idea is to use InstancedMesh.setMatrixAt() in order to set a local transformation to each of your instances in your animation loop.

If you still want to use InstancedBufferGeometry for some reason, you can use the following example as a code template:

https://threejs.org/examples/webgl_buffergeometry_instancing_lambert

It shows how you enhance MeshLambertMaterial with instanced rendering.

three.js R113