javascript - WebGL Weird Performance Drop in Chrome -

i have been trying learn webgl have made simple model loading script. thought working fine , dandy until pulled chrome's devtools timeline , saw getting ~20 fps when rendering 100 models. weird part was, cpu idle of time on each frame.

my first thought must gpu bound, seemed unlikely because shaders short , not complex. tested 10 models , again one, , did increase performance, still getting less 40 fps. pulled chrome://tracing, , saw both gpu wasn't doing each frame either. majority of each frame in crgpumain filled "processing swap", , crbrowsermain spent of time on glfinish (called "compositingiosurfacemac::drawiosurface").

processing swap appears major problem, not glfinish.

so question is, causing browser spend time on glfinish? ideas on how fix problem?

each model has 40608 elements , 20805 vertices,

update - corrected numbers of simplified mesh:

• 3140 elements
• 6091 vertices

the models pseudo-instanced data passed gpu once per frame. large number of vertices problem?

the demo can found here.

rendering code:

thing.prototype.renderinstances = function(){     if (this.loaded){         var instance;         gl.bindbuffer(gl.array_buffer, this.vertexbuffer);         gl.vertexattribpointer(shaderprogram.vertexpositionattribute, 3, gl.float, false, 0, 0);         gl.bindbuffer(gl.array_buffer, this.normalbuffer);         gl.vertexattribpointer(shaderprogram.vertexnormalattribute, 3, gl.float, true, 0, 0);          gl.bindbuffer(gl.element_array_buffer, this.indexbuffer);          for(var in this.instances){             instance = this.instances[i];             setmatrixuniforms(instance.matrix);              gl.drawelements(gl.triangles, this.numitems, gl.unsigned_short,0);          }     }  }; 

vertex shader code:

attribute vec3 avertexposition;      attribute vec3 avertexnormal;     uniform mat4 ummatrix;       uniform mat4 uvmatrix;     uniform mat4 upmatrix;      uniform vec3 ulightdirection;     varying float vlight;      void main(void) {          mat4 mvmatrix = uvmatrix*ummatrix;        //toji's manual transpose         mat3 normalmatrix = mat3(mvmatrix[0][0], mvmatrix[1][0], mvmatrix[2][0], mvmatrix[0][1], mvmatrix[1][1], mvmatrix[2][1], mvmatrix[0][2], mvmatrix[1][2], mvmatrix[2][2]);           gl_position = upmatrix*uvmatrix*ummatrix*vec4(avertexposition, 1.0);          vec3 lightdirection = ulightdirection*normalmatrix;          vec3 normal = normalize(avertexnormal*normalmatrix);         vlight = max(dot(avertexnormal,ulightdirection),0.0);     }