Add readme documenting EVS config.json

Add an annotated version of config.json to faciliate editing by third
parties to adapt EVS to their vehicles.

Test:  Read it.
Change-Id: I6591c61ca40b188bb7fc5344b30f20bcd27ab8a8

1 files changed, 42 insertions, 0 deletions

diff --git a/evs/app/config.json.readme b/evs/app/config.json.readme
new file mode 100644
index 0000000000..982e3c96dc
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+++ b/evs/app/config.json.readme
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+// With comments included, this file is no longer legal JSON, but serves to illustrate
+// the format of the configuration file the evs_app expects to read at startup to configure itself
+// for a specific car.
+// In addition to the configuration file, an image to be used to represent the car is expected
+// to be provided in CarFromTop.png.
+// Throughout this file, units of length are arbitrary, but must all be the same units.
+// X is right, Y is forward, Z is up (right handed coordinate system).
+// The origin is at the center of the read axel at ground level.
+// Units for angles are in degrees.
+// Yaw is measured from the front of the car, positive to the left (postive Z rotation).
+// Pitch is measured from the horizon, positive upward (postive X rotation).
+// Roll is always assumed to be zero.
+
+{
+  "car" : {                     // This section describes the geometry of the car
+    "width"  : 76.7,            // The width of the car body
+    "wheelBase" : 117.9,        // The distance between the front and read axel
+    "frontExtent" : 44.7,       // The extent of the car body ahead of the front axel
+    "rearExtent" : 40           // The extent of the car body behind the read axel
+  },
+  "display" : {                 // This configures the dimensions of the surround view display
+    "frontRange" : 100,         // How far to render the view in front of the front bumper
+    "rearRange" : 100           // How far the view extends behind the rear bumper
+  },
+  "graphic" : {                 // This maps the car texture into the projected view space
+    "frontPixel" : 23,          // The pixel row in CarFromTop.png at which the front bumper appears
+    "rearPixel" : 223           // The pixel row in CarFromTop.png at which the back bumper ends
+  },
+  "cameras" : [                 // This describes the cameras potentially available on the car
+    {
+      "cameraId" : "/dev/video32",  // Camera ID exposed by EVS HAL
+      "function" : "reverse,park",  // set of modes to which this camera contributes
+      "x" : 0.0,                    // Optical center distance right of vehicle center
+      "y" : -40.0,                  // Optical center distance forward of rear axel
+      "z" : 48,                     // Optical center distance above ground
+      "yaw" : 180,                  // Optical axis degrees to the left of straight ahead
+      "pitch" : -30,                // Optical axis degrees above the horizon
+      "hfov" : 125,                 // Horizontal field of view in degrees
+      "vfov" :103                   // Vertical field of view in degrees
+    }
+  ]
+}