Develop Reference

Opengl - Creating a mini map from a gl view

I want to create a map from some opengl code that I wrote :
In order to do that I though about taking a screen shot of the upperview of the gl screen.
Yet I cant seem to find how to do that...
any suggestions?

Similar problem has been solved in OSG example code here.
First you need to set your view such that you are looking at center from the TOP VIEW.
osg::Vec3 center = scene->getBound().center();
double radius = scene->getBound().radius();
view->getCamera()->setViewMatrixAsLookAt( center - lookDir*(radius*3.0), center, up );
view->getCamera()->setProjectionMatrixAsPerspective(
30.0f, static_cast<double>(width)/static_cast<double>(height), 1.0f, 10000.0f );
Then, you need to use some OS specific API to do similar to logic below:
osgViewer::ScreenCaptureHandler* scrn = new osgViewer::ScreenCaptureHandler();
osgViewer::ScreenCaptureHandler::WriteToFile* captureOper = new osgViewer::ScreenCaptureHandler::WriteToFile(tmpStr.m_szBuffer, "png");
scrn->setCaptureOperation(captureOper);
scrn->captureNextFrame(*_viewer);
_viewer->frame();
Of course if you are not using OSG then you need to find equivalent APIs (of library you are using) to achieve the same task.

Recenter or Reorient view with Cardboard SDK on Unity

With Unity, the CardboardHead script is added to the main camera and that handles everything quite nicely, but I need to be able to "recenter" the view on demand and the only option I see so far is to rorate the entire scene and it seems like this is something the would address first-hand and I can't find anything in the docs.
With Oculus Mobile SDK (GearVR), it would be OVRCamera.ResetCameraPositionOrientation(Vector3.one, Vector3.zero, Vector3.up, Vector3.zero); though they handle it nicely each time the viewer is put on so it's rarely needed there.

There's a "target" parameter on the CardboardHead that lets you use to another gameobject as a reference for rotation. Or you can use a dummy parent gameobject. Either way, when you want to recenter, you set this reference object's rotation so that the CardboardHead is now pointing forward. Add this function to an script on the CardboardHead (or just add it into that script):
public void Recenter() {
Transform reference = target != null ? target : transform.parent;
if (reference != null) {
reference.rotation = Quaternion.Inverse(transform.rotation) * reference.rotation;
// next line is optional -- try it with and without
reference.rotation = Quaternion.FromToRotation(reference.up, Vector3.up) * reference.rotation;
}
}

Cardboard.SDK.Recenter (); should do the trick.
Recenter orientation Added Recenter() function to Cardboard.SDK, which resets the head tracker so the phone's current heading becomes the forward direction (+Z axis).
Couldn't find the docs for the API/SDK but it's in the release notes for the v0.4.5 Update.

You can rotate the Cardboard Main to point in a certain direction.
This is what worked for me when I wanted the app to start up pointing a certain way. Since the CardboardHead points at Vector3.zero on startup if no target is assigned, I ran a function during Start() for the CardboardMain that would point in the direction I wanted.
Of course, if you're already rotating CardboardMain for some other reason, it may be possible to use this same method by creating a parent of the CardboardHead (child of CardboardMain) and doing the same thing.

This question is a bit old but for Google VR SDK 1.50+ you can do
transform.eulerAngles = new Vector3(newRot.x, newRot.y, newRot.z);
UnityEngine.VR.InputTracking.Recenter();
also, if you don't want to get confused you also need to catch the GvrEditorEmulator instance and Recenter it as well.
#if UNITY_EDITOR
gvrEditorEmulator.Recenter();
#endif
Recentering GvrEditorEmulator though doesn't seem to work very well at the moment but if you disable it you'll see the recentering works for the main camera.

projecting unprojected radar images into osmdroid

I have written a radar weather app using osmdroid for map tiles, and manually overlaying NOAA ridge radar data. Everything Is working great except that the radar images are unprojected, while the openstreetmap tiles are in transverse Mercator projection. The weather lies within the bounds it should but the data is distorted.
I see three ways to fix this (in order of preference) but am having trouble with all three:
1) find a source of radar data already projected in mercator - hours of Googling later, I've found nothing
2) programmatically reproject the images right after I download them. Does anyone know a good API for this?
3) project them on the fly, perhaps with openlayers.im reading that can openlayers reproject,but can it be used over top of an osmdroid mapview?
Any ideas? Thanks for any help
Mike

GDAL is the way to go. There is no official Android build that I know of however some people have been successful in getting it running on Android. For example, Nutiteq has a build in the libs folder of their AdvancedMap3D sample project. Put the contents of both armeabi folders in your project's lib folder and you should be able to access the GDAL packages.
Then take a look at the GDAL in Java page. Look at the gdalinfo.java sample to get a feel for how to load and examine the parts of a GDAL dataset. To reproject your dataset, you will do something along the lines of:
SpatialReference sr = new SpatialReference();
sr.ImportFromProj4("+proj=merc +datum=WGS84");
String result[] = new String[1];
sr.ExportToPrettyWkt(result, 1);
String oldProjection = mDataset.getProjection();
String newProjection = result[0];
Dataset newDataset = gdal.AutoCreateWarpedVRT(mDataset, oldProjection, newProjection, gdalconst.GRA_NearestNeighbour, 0.0);
Dataset savedDataset = mDriver.CreateCopy(outpath, newDataset, 0, new String[] { "COMPRESS=LZW", "PREDICTOR=2" }, null, null);
newDataset.delete();
savedDataset.delete();
You may need to make a few adjustments, but that should get you most of the way there.

Zooming in/out on Android Webview without a set limit

In my current project I need my users to be able to scroll over and zoom in on large SVG
Images. A major problem i encountered though, is the limit the android WebView class puts on zooming in and out. Is there any way I can remove or change these limits to my own likings?
The standard zoom controls do not seem to support releasing these boundries.
If my question is unclear, or if I need to elaborate on my question do not hesitate to ask.
Greets,
Wottah

Since no one seems to have come up with a different solution than using reflection - I'm not aware of any alternatives at this point - I wrote up a quick code snippet that illustrates how to bypass the upper limit on the zoom-in action.
Note that the code below will only work on ICS, and possibly Honeycomb, but I currently don't have a tablet lying around to inspect if the inner workings rely on the same ZoomManager class. Gingerbread, Froyo and Eclair all appear to implement the zooming functionality more or less directly in the WebView class. With the example below it should be fairly easy to add some code to also take those operating systems into account.
// just set an Activity's content view to a single WebView for this test
WebView mWebview = new WebView(this);
setContentView(mWebview);
// retrieve the ZoomManager from the WebView
Class<?> webViewClass = mWebview.getClass();
Field mZoomManagerField = webViewClass.getDeclaredField("mZoomManager");
mZoomManagerField.setAccessible(true);
Object mZoomManagerInstance = mZoomManagerField.get(mWebview);
// modify the "default max zoom scale" value, which controls the upper limit
// and set it to something very large; e.g. Float.MAX_VALUE
Class<?> zoomManagerClass = Class.forName("android.webkit.ZoomManager");
Field mDefaultMaxZoomScaleField = zoomManagerClass.getDeclaredField("mDefaultMaxZoomScale");
mDefaultMaxZoomScaleField.setAccessible(true);
mDefaultMaxZoomScaleField.set(mZoomManagerInstance, Float.MAX_VALUE);

Overlays in osmdroid-android-3.0.3.jar

I'd previously managed to incorporate OpenStreetMaps into my application using osmdroid-android-3.0.1.jar with the great assistance of the answer to my question
Porting a Google Maps app to Osmdroid - problem with overlay
I've now upgraded to using the 3.0.3 jar and can't get my overlay to display.
My app can switch display from Google Maps to OSM and display the same overlay consisting of lines and texts on top of either. The alternative displays each run in their own activity for now, as the classes are similar but do not have absolutely identical methods, or at least they didn't have in 3.0.1. (Ultimately I'd like to use the Osmdroid wrapper jar to combine them in one activity and reduce the duplicate code, but that's a question for a later date) Right now I'd like to get the same functionality as I had with the now deprecated 3.0.1 jar using the new 3.0.3 version.
With the new jar, I still get the mapview displayed OK but the overlay has disappeared. I've had to make some changes to the code, as the 3.0.1 onDraw() method has now been replaced with draw() (just like Google) in the MapOverlay extends org.osmdroid.views.overlay.Overlay class.
All the code in the previous onDraw() (now draw) method has been copied verbatim from the answer to the question referred to above, It worked fine, although I confess to not fully understanding the concepts of worldsize, bounding boxes and the transformation described.
I notice that the method
final Point upperLeft = org.osmdroid.views.util.Mercator
.projectGeoPoint(boundingBox.getLatNorthE6(), boundingBox.getLonWestE6(),
zoomLevel + tileZoom, null);
is now deprecated, and I had to remove tileZoom and
final int tileZoom = projection.getTileMapZoom();
to get it to compile.
When I get to the code in the draw() method, I can see in the debugger that all the data necessary to draw the overlay is still present and correct. The drawing is done by lines such as canvas.drawLine(....) and canvas.drawText(....). I've not used the extra parameter to the function (boolean shadow) at all.
My redrawOverlay() method remains as:
private void redrawOverlay() {
mGpt = mMapVw.getMapCenter();
if (mmapOverlay == null)
mmapOverlay = new MapOverlay(this);
mmapOverlay.setEnabled(true);
List<Overlay> listOfOverlays = mMapVw.getOverlays();
int ovlSize = listOfOverlays.size();
if (ovlSize > 1)
listOfOverlays.remove(1);
listOfOverlays.add(mmapOverlay);
mMapVw.invalidate();
}
(The Google listofOverlays.clear() shouldn't be used as osmdroid 3.0.1 had element 0 as the map itself - hence the remove(1))
I'm wondering what I have to do to modify the existing 3.0.1 code to work with 3.0.3? I'm hoping that one of the authors of might read this question.
Update
By adapting the Minimap overaly as suggested in the answer to the question referred to above, the draw() method for drawing an overlay from top left to bottom right, now becomes:
#Override
protected void draw(Canvas pC, MapView pOsmv, boolean shadow) {
if(shadow)
return;
Paint lp3;
lp3 = new Paint();
lp3.setColor(Color.RED);
lp3.setAntiAlias(true);
lp3.setStyle(Style.STROKE);
lp3.setStrokeWidth(1);
lp3.setTextAlign(Paint.Align.LEFT);
lp3.setTextSize(12);
// Calculate the half-world size
final Rect viewportRect = new Rect();
final Projection projection = pOsmv.getProjection();
final int zoomLevel = projection.getZoomLevel();
int mWorldSize_2 = TileSystem.MapSize(zoomLevel) / 2;
// Save the Mercator coordinates of what is on the screen
viewportRect.set(projection.getScreenRect());
// DON'T set offset with either of below
//viewportRect.offset(-mWorldSize_2, -mWorldSize_2);
//viewportRect.offset(mWorldSize_2, mWorldSize_2);
// Draw a line from one corner to the other
pC.drawLine(viewportRect.left, viewportRect.top, viewportRect.right, viewportRect.bottom, lp3);
}
This works OK

Let me try to suggest a few things:
In the new jar build, calling getOverlays().clear() will no longer remove the map tile overlay. Calling remove(1) may be incorrect now since the map tile overlay is no longer in position 0.
The projection has a method that will get you the screen coordinate rectangle of what is currently on the screen. You can check the coordinates you use to draw your lines with against this rectangle to make sure they intercept it.
Take a look at the new TileSystem class. Anything that was deprecated can be recreated using these functions.