3 channel image (RGB) example

Hi jbms,

Do you have a working example for 3 channel image on Neuroglancer? I am trying to troubleshoot if chunking on CloudVolume is failing or the shader control needs to be configured differently. Perhaps, three channel image need to be converted to a gray scale image and then chunked?

Thank you so much for your help. -m

#uicontrol vec3 color color(default="blue")
#uicontrol float min slider(default=0, min=0, max=1, step=0.01)
#uicontrol float max slider(default=1, min=0, max=1, step=0.01)
#uicontrol float brightness slider(default=0, min=-1, max=1, step=0.1)
#uicontrol float contrast slider(default=0, min=-3, max=3, step=0.1)

float scale(float x) {
  return (x - min) / (max - min);
}

void main() {
  emitRGB(
    color * vec3(
      scale(
        toNormalized(getDataValue()))
       + brightness) * exp(contrast)
  );
}

[jbms]

It turns out the problem is that the chunk size you are using, [613, 2753, 1] is too large, as it results in Neuroglancer attempting to create a 3-d texture of size [613, 2753, 3].

The developer console shows:

texture_access.ts:317 WebGL: INVALID_VALUE: texImage3D: width, height or depth out of range

On my machine, webglreport.com (under webGL2 tab) shows a maximum 3d texture size of 2048, meaning all dimensions must be <= 2048.

Currently Neuroglancer always stores each chunk as a single texture. In principle Neuroglancer could do rechunking client side to avoid exceeding the maximum chunk size, but that is not implemented.

If you rewrite your volume to use a smaller chunk size it should work. I would recommend e.g. [512, 512, 1].

[jbms]

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