Apply a post process to a RenderTargetTexture

[HugoMcPhee]

I'm trying to show a render target texture on a plane that shows a post processed version of the scene.
I can get the render target texture to draw the scene to the plane, but I can't get a post effect to work on it

Here's my example code
 

            var postProcessConvolution;            var renderTarget = new BABYLON.RenderTargetTexture("depth", 1024, newScene,false, true);            newScene.customRenderTargets.push(renderTarget);            renderTarget.renderList = newScene.meshes;            renderTarget.onBeforeRender = function () {                postProcessConvolution = new BABYLON.ConvolutionPostProcess("convolution", BABYLON.ConvolutionPostProcess.EdgeDetect2Kernel, 0.7, mainCamera);            }            renderTarget.onAfterRender = function () {                postProcessConvolution.dispose();            }

I thought it would apply the process, then render the texture, then dispose the post process. 
Without the .dispose() the post process is applied to the whole scene every frame.

has anyone succesfully done this before?
 

[HugoMcPhee]

Instead of trying to use a post process, I just used the fragment shader part (.fragment.fx) from the posteffect in a new "ShaderMaterial" and applied that onto the plane, then I passed the renderTargetTexture to that ShaderMaterial and the effect was the same.

Here's what the final code was
 

var kalideMaterial = new BABYLON.ShaderMaterial("kalideShader", newScene, "./kalideMat",{    attributes: ["position", "uv"],    uniforms: ["worldViewProjection"]});backBackDrop.material = kalideMaterial;kalideMaterial.setTexture("textureSampler", renderTarget);