Wikitude

Hi Wikitude Team,

I have a few questions regarding the positioning and scaling of 3D Models in the real world with a GPS coordinate.

I created with Blender some pipes with the following unit factor, 1 unit = 1 meter.

After that I converted the pipes with your converter tool to wt3 files. I didn't changed any properties of the pipes with your converter tool, just plain import and export.

I then created a simple Android App with the JS SDK. To load the wt3 files I'm using this code snippet:  

pipe.js

function Pipe(data) {
    this.data = data;

    this.pipeLocation = new AR.GeoLocation(
        this.data.location.latitude,
        this.data.location.longitude,
        AR.CONST.UNKNOWN_ALTITUDE);
    // this.data.model
    // "file://sdcard/Leitungsnetze/earth.wt3"
    console.log(this.data.location.latitude + ", " + this.data.location.longitude);
    this.model = new AR.Model(
        this.data.model, {
        onLoaded: this.worldLoaded,
        scale: {
            x: parseFloat(this.data.scale.x)*0.1,
            y: parseFloat(this.data.scale.y)*0.1,
            z: parseFloat(this.data.scale.z)*0.1
        },
        rotate: {
            x: parseFloat(this.data.rotation.x),
            y: parseFloat(this.data.rotation.y),
            z: parseFloat(this.data.rotation.z)
        },
        translate: {
            x: parseFloat(this.data.translation.x),
            y: parseFloat(this.data.translation.y),
            z: parseFloat(this.data.translation.z)-20
        },
        onClick: Pipe.prototype.getOnClickTrigger(this)
    });

    /*
     * Erstellen einer Grafik die anzeigt in welcher
     * Richtung sich das AR-Modell befindet.
     */
    this.indicatorImage = new AR.ImageResource(this.data.indication);
    this.indicatorDrawable = new AR.ImageDrawable(this.indicatorImage, 0.1, {
        verticalAnchor: AR.CONST.VERTICAL_ANCHOR.TOP
    });

    this.obj = new AR.GeoObject(this.pipeLocation, {
        drawables: {
           cam: [this.model],
           indicator: [this.indicatorDrawable]
        }
    });

    return this;
}

I also implemented three slider to change AR.context.scene.maxScalingDistance, AR.context.scene.minScalingDistance and AR.context.scene.scalingFactor:

index.html

<h4>MinScalingDistance</h4>
    <input class="singleSlider" type="range" min="1" value="1" max="1000" step="1" onchange="World.setMinScaling(value)">
    <h4>MaxScalingDistance</h4>
    <input class="singleSlider" type="range" min="1" value="100" max="1000" step="1" onchange="World.setMaxScaling(value)">
    <h4>ScalingFactor</h4>
    <input class="singleSlider" type="range" min="0.0" value="0.1" max="1.0" step="0.001" onchange="World.setScalingFactor(value)">

index.js 

setMinScaling: function(value) {
        AR.context.scene.minScalingDistance = parseInt(value);
        console.log("minScalingDistance: " + value);
    },
    setMaxScaling: function(value) {
        AR.context.scene.maxScalingDistance = parseInt(value);
        console.log("maxScalingDistance: " + value);
    },
    setScalingFactor: function(value) {
        AR.context.scene.scalingFactor = parseFloat(value);
        console.log("scalingFactor: " + value);
    }

Actually I want to place my 3D pipes on their real-world counter parts, but I have some problems with the positioning and the scaling, or I just don't understand the documentation on this topic. 

See my attached images (Scaling_Issue_02.png and Scaling_Issue_01.png), for both images I had totally different Values for the various scaling parameters, but for me the sizes of the pipes looks always the same.

What I not understand is, why I have to scale my pipes, for example by the factor of 0.1 or something else. It feels a little bit arbitrary and I have no clue how to find the right values to get my real-world-scaling pipes.

So what is the best way to scale my pipes correctly, so that they match with their real-world counter parts? 

Another question is the positioning. Where are the 3D-Models anchored when I give them a location? Is it the middle of the 3D-Model or the origin of the 3D-Model, which I specifiy for example with Blender? So in my case I use always the location where the origin of my Pipes are, but because of the scaling issue, I have trouble to validate the correct positioning of my Pipes.

I have also attached two 3D-Models which I'm using (geom_8.wt3, geom_0.wt3).

Ok I solved one little piece of my problems. 

I thought that the z component of the translation is responsible for the vertical position of a model.

I changed this

translate: {
            x: parseFloat(this.data.translation.x),
            y: parseFloat(this.data.translation.y),
            z: parseFloat(this.data.translation.z)-20
        },

 to

translate: {
            x: parseFloat(this.data.translation.x),
            y: parseFloat(this.data.translation.y)-5,
            z: parseFloat(this.data.translation.z)
        },

Everything else still remains unclear to me. 

Hi Eva,

actually yes, but i don't get my head around SDU and DBS :(.

Normally I have no idea how big my pipe models are, but it should have the same size in AR then the real pipe, so that they should overlap.

By the way the documentation says

Is it actually possible to disable the scaling in a way it is currently working? My models have the same dimension then their real life counter parts (in meters). In theory they should overlap perfectly.

Hi Daniel,

thank you very much for this detailed explaination! 

What you mentioned about DBS and SDU for 3D-Objects is something I also discovered. I implemented some range slider to change the values for AR.context.scene.maxScalingDistance, AR.context.scene.minScalingDistance and AR.context.scene.scalingFactor. I actually didn't noticed any changes for the size of my 3D-Models for different values of these settings.

I also totally agree with you that the accuracy of the internal smartphones GNSS-Receiver is not good enough. Google has some nice tricks to get in a city better results (Wifi and cell tower support), but I guess thats not common for all areas in the world. I also implemented a Kalman-Filter to smooth out spikes, but yeah a total overlay will actually not be possible with consumer grade hardware. Possible I have to connect an external low-cost GNSS-Receiver over Bluetooth with a good antenna to my Smartphone, to get better results.

About the scaling of a 3D-Model. currently I use the factor of 0.1 and the objects are still to big. How can i actually determine the right scaling value? is there any rule I can adopt? I created my 3D-Models in meter, so 1 Unit in Blender should be 1 Meter. 

And lastly, is the anchor point for a GPS-Coordinate is always the origin of a 3D-Model?

Best Regards

Robert

Hey Daniel, 

again thank you very much for this detailed explaination.

Currently I had no time to verify what you said about the binary FBX export. In Blender I use a modified version of a batch exporter for fbx and I have first to check if it use the binary version or the ascii version. I think it might be the binary version because that would explain why my 3d-objects are all to big in the AR-View. Next week I can give you further feedback about that.

Have a nice weekend

Robert