Can I have an explication what is wrong of initializing my voxel, when I move the camera the voxel disappear, I’m sure it’s my bounding sphere is not correct, but how can I fix it ?
Thx you,
@Marco13 can you help me on this ?
Thank you,
Voxels are a relatively new feature, which is one reason for why I may not know all the details here. But I’ll try…
Right now, your voxelPrimitive defines the modelMatrix, which is supposed to move the primitive to a certain position on the globe. This does seem to work in general (although I’m not sure whether the orientation of the primitive is correct here). But there is another matrix that might be better suited for this, namely the VoxelProvider#globalTransform.
The difference appears to be, roughly speaking, that the voxelPrimitive.modelMatrix is more “local”. This is what you can edit with the ‘Voxel Inspector’. When you open the ‘Voxel Inspector’ in your sandcastle, then it shows values like “Translation X = -1214991,7329005932”, which basically is “the global placement on earth” (and these values can not be edited sensibly).
When defining the voxelProvider.globalTransform instead, this will place the primitive at the respective position on earth, and you can still use the ‘Voxel Inspector’ to change the “Translation X”. (It is 0 initally, and you can move the primitive along -10 … +10).
(Maybe someone else can give a profound recommendation of whether to use the modelMatrix or the globalTransform…?)
About the voxels disappearing when moving the camera:
This is not directly related to the bounding sphere. The bounding sphere is correct, which can be seen by flyToBoundingSphere ending up with the voxels centered accordingly. But when you use flyToBoundingSphere and afterwards drag the camera to rotate it, then it will basically rotate around the point on the surface of the earth that you clicked. And given that the voxel object is 25km above earth, it wildly rotates … out of sight.
One way of solving this could be to set the camera reference frame, using camera.lookAtTransform. There still are some degrees of freedom, related to the final orientation of the camera and its behavior when dragging the view. But the following sandcastle applies the two suggested changes:
- It uses the
globalTransform(not entirely sure what to prefer here) - It uses
camera.lookAtTransforminstead offlyToBoundingSphere
This centers the voxel primitive, allows you to modify it with the ‘Voxel Inspector’, and the camera rotates around the reference frame that is defined by the voxel bounding sphere. Maybe this can serve as a basis for further adjustments that you may need for your application case.
@Marco13 thx you, but why the voxel disappear when i zoom out ?
Roughly speaking: The zooming speed (and the speed of many other interactions that affect the camera) depend on the height above the ground. When you’re looking at the whole earth, then zooming is fast. When you’re near the ground, then zooming is slow.
(Otherwise, when you open the viewer, you’d have to zoom for a very long time until you are zoomed to a certain city, for example).
Here’s a screencap from your original sandcastle with different heights: First with 25 meters. There, you can zoom with the mouse wheel or right mouse drags. When it’s 2500 meters, the zooming is so fast that you’re quickly zooming past that 1x1x1 meter cube.
Now, you started at 25000 meters (!), meaning that the zooming is really fast, and it’s nearly impossible to keep that small cube inside the view.
There are different ways to change this behavior, of course. But I think that setting the camera reference frame is the easiest and most important one here.
For further details, you can have a look at Cesium Sandcastle or ScreenSpaceCameraController - Cesium Documentation and consider opening a new thread when there are specific questions about how to tweak the controls and interaction.
@Marco13 look at this example :
I just move the camera a little bit, but the voxel disappear.
And when I came back to the same position, the voxel is not here anymore.
@Marco13 and the debugdraw show that the origin center is in the middle of the earth :
maybe it’s the problem ?
This seems to be related to the modelMatrix vs. globalTransform change. I’ll check again what might be the preferred solution here.
Regardless of that:
When you change
new Cesium.Cartesian3(0.0, 0.0, 25000.0), // altitude offset in meters
to
new Cesium.Cartesian3(0.0, 0.0, 5.0), // altitude offset in meters
then it should work in both cases.
If you want to place the object at a certain height, then you have to take this into account when setting the camera reference frame.
But more specifically: In how far is the sandcastle that I posted earlier not what you are looking for?
@Marco13 Thx for the information, I need to let the user move the camera freely around the globe.
There is a discrepancy between these requirements. You can either have “slow” controls that allow you to move and rotate around a cube that has a size of 1x1x1 meter. Or you can have “fast” controls that allow you to “move the camera freely around the globe”, which has a size of 6378000 x 6378000 x 6378000 meters.
Maybe it helps to describe more clearly what you are actually trying to visualize, how large the thing is that you want to visualize, and which role the globe (and global camera navigation) play there. When you want to visualize some voxels with the size of 1x1x1 meters at the north pole, then it’s hard to imagine why the user wanted to suddenly (manually) navigate to the south pole…
It’s not a voxel of 1x1x1 meter that i want to see. It’s more a 100 meters large and maybe more.
Still, it’s not clear for me what the expected behavior of the camera is.
Imagine you are looking at a 100x100 meter object. You’d probably expect the camera to move roughly 100 meters when dragging the mouse once across the screen, so that you can easily and intuitively inspect this object.
But when dragging the camera across the screen moves it by 100 meters, then you’d have to drag it across the whole screen roughly 200000 (!) times to move to the other side of the globe. You have to adjust the navigation speed depending on the scale of the object that you want to inspect.
Will the object be on the surface of the globe, or will it be somewhere in space?
Actually the camera always look at the center of the globe. And it use the mouse to look around and zoom in or out.
Imagine the center (“view point”) of the camera is at the center of the globe. And the “eye point” (i.e. the camera iself) is at the surface, looking at this 100x100 meter object, on the ground. Now you are dragging the mouse from the left side of the screen to the right side of the screen. Should the camera move 100 meters, or should it move to the other side of the earth?
The camera move around freely, its the mouse sensitive that tell the speed to move around the globe.
@marco13 yes thank you, how do make it bigger ? by example 100m,100m,100m ? with the matrix ?
thx you, have a good day