I'm trying to animate a trajectory of a particle on a spherical surface in manim. I made the sphere semi-transparent so it's easy to say when the particle is on the front side and when it is on the back side of the sphere. However after I plot the trajectory, even the parts that are supposed to be behind the sphere are the same color as the ones in front of it.
As you can see this issue is not present in the coordinate axes. The parts of axes that are inside of the sphere have different color, because the semi-transparent surface is between them and camera.
I'm using the following code
S=Sphere(center=(0,0,0), radius=1.09,resolution=(15, 15)).set_opacity(0.4)
S.set_color(GRAY)
self.add(axes,S)
for i in range(100):
self.play(Create(Traj[i]))
Where Traj is an array consisting of line elements of the trajectory.
Even if I set the sphere opacity to 1, I can still see the whole trajectory, even if most of it should be behind the spehre. How to make the sphere cover the back part of the trajectory?
Related
I have a list view with "Hero" icons on the left. When I click a list item, it loads the next screen with the article text and the Hero image (which animates nicely/automatically to the correct spot on the 2nd screen).
I would have thought that was the "tough" part, but I'm now trying to get a curved shape as the top background of the 2nd screen. I would love to make it a drawn vector shape, as opposed to a bitmap and even have it drip/bounce onto the page, but at the moment...
I'm just trying to figure out how to:
draw a vector shape
have it as the background of a screen with other widgets on top (see purple curve on 2nd screen below)
I made a full sample for your curved shape in a gist here
I used CustomPainter to draw on a canvas then, with some geometric calculations, I achieved the curved shape.
Final result
How I draw it?
Before coding and on a Whiteboard I determined somethings:
My Canvas Area:
The canvas dimensions I need to draw that shape (which equals to Flutter widget's dimensions).
How and where my brush will move?
how means: what are the APIs I need to draw that shape on the canvas using the Path class.
e.g. lineTo() for a straight line, quadraticBezierTo() for a curve.
where means: Where are the points (coordinates) I need to draw the whole shape. (see yellow and green dots in the image above)
Points (coordinates) Calculations:
I used some geometric equations to calculate the coordinates. e.g. Point on a circle’s circumference
All of my calculations depend on the canvas size, that gives me a responsive shape.
Full sample here!
I am currently trying to map textures using image labels onto 2 different triangles (because im using right angle wedges so i need 2 to make scalene triangles), but here is the problem, I can only set positional, size, and rotational data so I need to figure out how I can use this information to correctly map the texture onto the triangle
the position is based on the topleft corner and size of triangle (<1,1> corner is at the bottom right and <0,0> corner is at top left) and the size is based on triangle size also (<1,1> is same size as triangle and <0,0> is infinitely tiny) and rotation is central based.
I have the UV coordinates (given 0-1) and face vertices, all from an obj file. The triangles in 3D are made up of 2 wedges which are split at a right angle from the longest surface and from the opposite angle.
I don't quite understand this however it may be help to change the canvas properties on the Surface GUI
I am trying to draw a curved 3D line (doesn't matter if it made by a cylinder, rectangle, etc) on a ARSCNView (Renders using SceneKit).
I currently have something like this which renders lines using SCNCylinder but not sure how to curve them.
I tried using SCNShape from UIBezierPath to no success. Because I already have 3d point points not 2D points and using this method I can't have different Y axis (aka up) in ARKit.
I have successfully implemented shadow maps in my engine but the problem is the shadow map doesn't cover the whole scene. If I make the shadowmap large shadow quality will drop. So I'm trying make my shadows move with camera. I can do this if I can calculate the 8 world space positions of camera frustum vertices.
So how can I calculate world space positions of camera frustum vertices ? I'm working with Directx if it changes the way how it's calculated.
Thanks.
The frustum (near plane, far plane, fov) is in view space so multiplying it with an inverse view matrix will move it into world space. If you use DirectXMath (which I recommend) you can utilize the bounding frustum object. An example code might look something like this:
DirectX::BoundingFrustum frustum;
DirectX::BoundingFrustum::CreateFromMatrix(frustum, camera.getProjectionMatrix());
DirectX::XMMATRIX inverseViewMatrix = DirectX::XMMatrixInverse(nullptr, camera.getViewMatrix());
frustum.Transform(frustum, inverseViewMatrix);
BoundingFrustum docs: https://msdn.microsoft.com/en-us/library/windows/desktop/microsoft.directx_sdk.directxmath.boundingfrustum(v=vs.85).aspx
If your frustum is big and you have to view a large area (e.g. outdoor scene) then even a large moving shadow map might not be enough (or it takes a huge amount of memory). One technique to solve this is called cascaded shadow maps (CSM). In CSM more precise shadow maps are rendered close to the camera and less precise shadows are rendered in the distance where the low quality is not visible anyway. Here is a CSM tutorial in case you are interested: https://msdn.microsoft.com/en-us/library/windows/desktop/ee416307(v=vs.85).aspx
I've written a little app using CoreMotion, AV and SceneKit to make a simple panorama. When you take a picture, it maps that onto a SK rectangle and places it in front of whatever CM direction the camera is facing. This is working fine, but...
I would like the user to be able to click a "done" button and turn the entire scene into a single image. I could then map that onto a sphere for future viewing rather than re-creating the entire set of objects. I don't need to stitch or anything like that, I want the individual images to remain separate rectangles, like photos glued to the inside of a ball.
I know about snapshot and tried using that with a really wide FOV, but that results in a fisheye view that does not map back properly (unless I'm doing it wrong). I assume there is some sort of transform I need to apply? Or perhaps there is an easier way to do this?
The key is "photos glued to the inside of a ball". You have a bunch of rectangles, suspended in space. Turning that into one image suitable for projection onto a sphere is a bit of work. You'll have to project each rectangle onto the sphere, and warp the image accordingly.
If you just want to reconstruct the scene for future viewing in SceneKit, use SCNScene's built in serialization, write(to:options:delegate:progressHandler:) and SCNScene(named:).
To compute the mapping of images onto a sphere, you'll need some coordinate conversion. For each image, convert the coordinates of the corners into spherical coordinates, with the origin at your point of view. Change the radius of each corner's coordinate to the radius of your sphere, and you now have the projected corners' locations on the sphere.
It's tempting to repeat this process for each pixel in the input rectangular image. But that will leave empty pixels in the spherical output image. So you'll work in reverse. For each pixel in the spherical output image (within the 4 corner points), compute the ray (trivially done, in spherical coordinates) from POV to that point. Convert that ray back to Cartesian coordinates, compute its intersection with the rectangular image's plane, and sample at that point in your input image. You'll want to do some pixel weighting, since your output image and input image will have different pixel dimensions.