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++ varying highp vec3 pos;
++
++ void main() {
++ // This shader encodes the axis position into the vertex color, assuming the object
++ // is a cube filling the entire data area of the graph
++ gl_FragColor = vec4((pos.x + 1.0) / 2.0,
++ (pos.y + 1.0) / 2.0,
++ (-pos.z + 1.0) / 2.0,
++ 0.0);
++ }
++