From b9f6ea53df696b4c38443e891a6fdb413e43e147 Mon Sep 17 00:00:00 2001 From: Matt Date: Mon, 9 Sep 2024 21:54:17 -0700 Subject: [PATCH] Update photon-serde readme --- photon-serde/README.md | 40 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 40 insertions(+) diff --git a/photon-serde/README.md b/photon-serde/README.md index 71ec72a52..a9d26d5ab 100644 --- a/photon-serde/README.md +++ b/photon-serde/README.md @@ -22,3 +22,43 @@ The code for a single type is split across 3 files. Let's look at PnpResult: - Protobuf: slow on embedded platforms (at least quickbuf is) - Wpi's struct: no VLAs/optionals - Rosmsg: I'm not using ros, but I'm stealing their message hash idea + +## Dynamic Decoding + +Dynamic decoding is facilitated by publishing schemas to the `.schema` table in NT, and by encoding the `message_uuid` as a property on a `photonstruct` publisher. Schema names in the .schema table shall be formatted as `photonstruct:{Type Name}:{Message UUID}`. For example, here I've published Photon results to `/photonvision/WPI2024/rawBytes`. This topic has the typestring `photonstruct:PhotonPipelineResult:ed36092eb95e9fc254ebac897e2a74df`, with properties `{message_uuid': 'ed36092eb95e9fc254ebac897e2a74df'}`. It shall be legal to have published multiple versions of the same message, as long as their UUIDs are unique (which they'd better be). + +| Topic Name | Type | Type String | +|------|------|-------| +| /.schema/photonstruct:PhotonPipelineResult:ed36092eb95e9fc254ebac897e2a74df | kRaw | photonstructschema | +| /.schema/photonstruct:PhotonTrackedTarget:4387ab389a8a78b7beb4492f145831b4 | kRaw | photonstructschema | +| /.schema/photonstruct:TargetCorner:16f6ac0dedc8eaccb951f4895d9e18b6 | kRaw | photonstructschema | +| /.schema/photonstruct:MultiTargetPNPResult:af2056aaab740eeb889a926071cae6ee | kRaw | photonstructschema | +| /.schema/photonstruct:PnpResult:ae4d655c0a3104d88df4f5db144c1e86 | kRaw | photonstructschema | +| /.schema/photonstruct:PhotonPipelineMetadata:626e70461cbdb274fb43ead09c255f4e | kRaw | photonstructschema | +| /.schema/proto:geometry3d.proto | kRaw | proto:FileDescriptorProto | +| /.schema/proto:photon.proto | kRaw | proto:FileDescriptorProto | + +The struct definition for PhotonPipelineResult we retrieved from the struct schema database shown above (via the command `python.exe scripts/catnt.py --echo /.schema/photonstruct:PhotonPipelineResult:ed36092eb95e9fc254ebac897e2a74df`) is: + +``` +PhotonPipelineMetadata:626e70461cbdb274fb43ead09c255f4e metadata; +PhotonTrackedTarget:4387ab389a8a78b7beb4492f145831b4[?] targets; +MultiTargetPNPResult:af2056aaab740eeb889a926071cae6ee? multitagResult; +``` + +If we were decoding this, we'd go retrieve the struct definitions for all our nested types. For example, `PhotonTrackedTarget:4387ab389a8a78b7beb4492f145831b4` is defined by it's .schema table entry be the following. This type also demonstrates a mix of WPILib struct types (such as Transform3d), intrinsic types (such as float64), and Photon struct types (such as TargetCorner). + +``` +float64 yaw; +float64 pitch; +float64 area; +float64 skew; +int32 fiducialId; +int32 objDetectId; +float32 objDetectConf; +Transform3d bestCameraToTarget; +Transform3d altCameraToTarget; +float64 poseAmbiguity; +TargetCorner:16f6ac0dedc8eaccb951f4895d9e18b6[?] minAreaRectCorners; +TargetCorner:16f6ac0dedc8eaccb951f4895d9e18b6[?] detectedCorners; +```