I have programmatically baked two light probes in SceneKit. Both are baked in separate scenes and are then used in a third scene. Both the lightprobes have the exact same position in the third scene. I know lightprobes are chosen to light up an object according to their position. However, in this scenario, I want a pre-filtering based on the categoryBitMask. However, this does not seem to be working.
Is the categoryBitMask ignored for lightprobes similar to ambient light?
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I'm developing an AR app for iOS that lets the user place a model in the physical world, using ARKit and SceneKit.
I've looked at this Apple sample code for inspiration. In the sample project, they use tracked raycasts to position 3D models in a scene. This is close to what I want, and what led me to assume I need to do the same to achieve the most accurate positioning.
However, when I use a tracked raycast to position my model, the model drifts around the scene a lot as ARKit updates the position of the raycast.
I get much more stable positioning when using a non-tracked raycast.
That makes me ask: what actually is the intended use case for a tracked raycast? Am I understanding this API wrong?
I've tried:
Positioning the model using an image anchor. This is very stable.
Positioning the model using a non-tracked raycast. This is about as stable as the image anchor.
Positioning the model using a tracked raycast. This drifts all over the scene.
I also understand what an AR raycast in general is for:
getting the intersection of a 2D point on the screen with the 3D geometries that ARKit is tracking.
As this post has explained already.
In Apple's example app you mentioned, raycasting is used to update the FocusSquare all the time. You don't really need it for placing your model. You can get a certain (real-world) position (using the FocusSquare) to place a model on that exact location. For this you can fetch static positon data from the FocusSquare at the moment you add your model on scene. I hope I understood corectly what you want.
So I'm using React, Three Fiber as well as the drei library and cannon for physics.
I am making an apartment viewer as a personal project in which you can walk around in - so far everything works fine. To make it later on possible to load in the apartment model from a database (and make the creation process easier for multiple models), the transformations for the light switches, aktivatable point lights and the apartments collision boxes are copied from objects within the gltf file.
To prevent the collision boxes from rendering or otherwise effecting the rendering process, they are made invisible. (I also tried to set child.castShadow = false with no effect).
For some reason the shadows are corrupted: unwanted point light shadows.
I also tried to change some properties of the original child: Object3D properties in the Apartment component (the only place where the boxes could affect the shadows), without changing results.
Another thing is that there doesn't seem to be any options to adjust shadows anymore. Properties like shadowBias, shadowMapWidth etc. are deprecated. By hovering over it I get something like #deprecated — Use shadow.mapSize.width instead. At least I couldn't find a solution to that, also because the Three Fiber documentation isn't that extensive. Just using them doesn't work either.
I'm a long-time user of SciChart, but it's an old version (3.1). I've just started using FastHeatMapRenderableSeries for the first time, and there is a requirement for a user to alter the chart's gradient stops. I've implemented a UI to do this (see image), which involves dragging markers that updates their respective gradient stop within the ColorMap's LinearGradientBrush. It's working in as much as gradient changes can be seen in the chart's HeatColorMap (not shown on this screenshot), and also in my "drag" control (a Rectangle whose Fill is bound to the ColorMap's brush).
The problem is that the colours within the chart itself don't change - perhaps I was being a little too hopeful that this would happen automatically! Is this possible, or will I have to recreate the series each time there has been a change to the gradient?
We actually have this working in a later version of SciChart. Im not sure which version exactly but it was introduced at some point. Have a look at this forum post which discusses a bug in the heatmap color map binding in v5.
In the v6 examples suite, you can drag the heat map legend and recolour the chart automatically, so we know in principle this works.
Very cool image by the way!
I have a sequence of images taken from a camera. The images consists of hand and surroundings. I need to remove everything except the hand.
I am new to Image processing. Would anyone help me in regard with the above Question. I am comfortable using C and Matlab.
A really simple approach if you have a stationary background and a moving hand (and quite a few images!) is simply to take the average of the set of images away from each image. If nothing else, it's a gentle introduction to Matlab.
The name of the problem you are trying to solve is "Image Segmentation". The Wikipedia page here: wiki is a good start.
If lighting consistency isn't a problem for you, I'd suggest starting with simple RGB thresholding and see how far that gets you before trying anything more complicated.
Have a look at OpenCV, a FOSS library for computer vision applications. Specifically, see the Video Surveillance module. For a walk through of background subtraction in MATLAB, see this EETimes article.
Can you specify what kind of images you have. Is the background moving or static? For a static background it is a bit straightforward. You simply need to subtract the incoming image from the background image. You can use some morphological operations to make it look better. They all depend on the quality of images that you have. If you have moving background I would suggest you go for color based segmentation. Convert the image to YCbCr then threshold appropriately. I know there are some papers available on it(However I dont have time to locate them). I suggest reading them first. Here is one link which might help you. Read the skin segmentation part.
http://www.stanford.edu/class/ee368/Project_03/Project/reports/ee368group08.pdf
background subtraction is simple to implement (estimate background as average of all frames, then subtract each frame from background and threshold resulting absolute difference) but unfortunately only works well if 1. camera has manual gain and exposure 2. lighting conditions do not change 3.background is stationary. 4. the background is visible for much longer than the foreground.
given your description i assume these are not the case - so what you can use - as already pointed out - is colour as a means of segmenting foreground from background. as it's a hand you are trying to isolate best bet is to learn the hand colour. opencv provides some means of doing this. if you want to do this yourself you just get the colour of some of the hand pixels (you would need to specify this manually for at least one frame) and convert them to HUE (which encapsulates the colour in a brightness independen way. skin colour has a very constant hue) and then make a HUE histogram. compare this to the rest of the pixels and then decided if the hue is simmilar enough.
Now that <BevelBitmapEffect> (amongst other effects) has been depreciated, I'm looking to see how I could re-create the exact same thing in a Shader Effect (including it's properties of BevelWidth, EdgeProfile, LightAngle, Relief and Smoothness).
I'm somewhat familar with pixel shading, mostly just colors manipulation of the whole image/element in Shazzam, but how to create a bevel elludes me. Is this a vertex shader and if so, how would I get started? I have searched high and low on this but can't seem to find an inkling of information that would allow me to get started in reproducing <BevelBitmapEffect> in a custom Effect.
Or, based on a comment below, is this 3D in WPF and if so, are there code libraries out there for recreating a <BevelBitmapEffect> that mimics the one that came with previous versions of WPF?
To create the bevel you need to know the distance from the edge for each pixel (search in all directions until alpha=0). From this you can calculate the normal then shade it (see silverlight example). As you mentioned there isn't much content about bevels but there are some good resources if you search for bump mapping/normal mapping to which the shading is similar. In particular this thread has a Silverlight example using a pre-calculated normal map.
To do everything in hardware ideally you would use a multipass shader, WPF's built-in effects are multipass but it doesn't allow you to write your own.
To workaround this limitation:
You could create multiple shaders and nest your element in multiple controls applying a different effect to each one.
Target WPF 4.0 and use Pixel Shader 3.0, for the increased instruction count. Although this may be a too high a hardware requirement and there is no software fallback for PS 3.0
Do some or all of the steps in software.
Without doing one of these you'd be lucky to do a 3 or 4 pixel bevel before you reach the instruction limit as the loops needed to find the distance increase the instruction count quickly.
New Sample
Download. Here is an example that uses PixelShader 3.0. It uses one shader to find the distance (aka height) to the edge, another (based on the nvidia phong shaders) is used to shade it. Bevel profiles are created by adjusting input height either with code or a custom profile can be used by supplying a special texture. There are some other features to add but it seems easily performant enough to animate the properties. Its lacking in comments but I can explain parts if needed.
There's a great article by Rod Stephens on DevX that shows how to use System.Drawing to create the WPF effects (the ones that used to exist, such as Bevel) and more. You've gotta register to view the article though, it's at http://www.devx.com/DevXNet/Article/45039. Downloadable source code too.