3D viewer: add forgotten shader update code

This code was added to also handle buffer geometries alongside regular
gemetries for picking.

django/applications/catmaid/static/libs/catmaid/shader.js

@@ -0,0 +1,56 @@
+
+(function(CATMAID) {
+
+  CATMAID.ShaderLib = {
+
+    // Original by Mikola Lysenko. MIT License (c) 2014, from:
+    // https://github.com/mikolalysenko/glsl-read-float/blob/master/index.glsl
+    encodeFloat: [
+      "#define FLOAT_MAX  1.70141184e38",
+      "#define FLOAT_MIN  1.17549435e-38",
+      "",
+      "lowp vec4 encode_float(highp float v) {",
+      "  highp float av = abs(v);",
+      "",
+      "  //Handle special cases",
+      "  if(av < FLOAT_MIN) {",
+      "    return vec4(0.0, 0.0, 0.0, 0.0);",
+      "  } else if(v > FLOAT_MAX) {",
+      "    return vec4(127.0, 128.0, 0.0, 0.0) / 255.0;",
+      "  } else if(v < -FLOAT_MAX) {",
+      "    return vec4(255.0, 128.0, 0.0, 0.0) / 255.0;",
+      "  }",
+      "",
+      "  highp vec4 c = vec4(0,0,0,0);",
+      "",
+      "  //Compute exponent and mantissa",
+      "  highp float e = floor(log2(av));",
+      "  highp float m = av * pow(2.0, -e) - 1.0;",
+      "  ",
+      "  //Unpack mantissa",
+      "  c[1] = floor(128.0 * m);",
+      "  m -= c[1] / 128.0;",
+      "  c[2] = floor(32768.0 * m);",
+      "  m -= c[2] / 32768.0;",
+      "  c[3] = floor(8388608.0 * m);",
+      "  ",
+      "  //Unpack exponent",
+      "  highp float ebias = e + 127.0;",
+      "  c[0] = floor(ebias / 2.0);",
+      "  ebias -= c[0] * 2.0;",
+      "  c[1] += floor(ebias) * 128.0; ",
+      "",
+      "  //Unpack sign bit",
+      "  c[0] += 128.0 * step(0.0, -v);",
+      "",
+      "  //Scale back to range",
+      "  return c / 255.0;",
+      "}"
+    ].join("\n")
+  };
+
+  CATMAID.insertSnippetIntoShader = function (shaderSource, insertionPoint, glsl) {
+    return shaderSource.replace(insertionPoint.regex, glsl + insertionPoint.replacement);
+  };
+
+})(CATMAID);