Skeletal Movement
Hi I have been trying to create a skeleton made of Joints and Bones. The skeleton is done in JavaFX using circles and lines. I have manage to connect the lines (bones) at pivot points (joints). Given two pivot points it is possible to rotate a bone around its parent joint. What I am trying to achieve is for Example:
Given that there are 3 bones connected to each other at pivot points Bone A, B and C if lets say bone A is rotated around its pivot point bone B and C should move relative to bone A while maintaining their respective positions. If bone B is rotated bone C should follow.
Here are some images showing the desired effect
Shows how the bones are originally position before rotating bone B
Shows how the bones should be position after rotating bone B
The problem I am having is that I am not sure how to calculate the values in order to make this possible. I have been looking around for similar problems for a while with no luck. I was hesitant to ask the question. I hope my question was clear enough. All comments and help is deeply appreciated Thank you for your time.
Related
As the title suggest my problem lies in some representation of a sphere surface in computer memory. For simplicity, let's say we are making a chess game where the board is on a sphere. If the board was a classic flat board, then the solution is simple: use a 2D table.
But I don't know what kind of a memory structure I should chose for a sphere. Namely, what I want from this representation are:
If I move a pawn stubbornly in one direction, then I should return to the point where I started,
During such "journey" I should cross a point directly on the other side of the sphere (I mean to avoid a common "error" in a 2D game where moving pass an edge of a board will move an object to the opposite edge, thus making the board a torus, not a real sphere)
the area of one board cell should be approximately equal to any other cell
a cell should have got an associated longitude-latitude coordinates (I wrote "associated" because I want from the representation to only have got some way to obtain these coordinates from the position of a cell, not to be eg. a table with lat-long indexes)
There's no simple geometric solution to this. The crux of the problem is that, say you have n columns at the equator, and you're currently near the north poll, and heading north. Then the combination of the direction and the column number from the top row (and second from top row) must be able to uniquely identify which one of the n positions at the equator that path is going to cross. Therefore, direction could not be an integer unless you have n columns in the top (or second to top) row. Notice that if the polygons have more than three sides, then they must have common edges (and triangles won't work for other reasons). So now you have a grid, but if you have more than three rows (i.e. a cube, or other regular prism), then moving sideways on the second-to-top row will not navigate you to the southern hemisphere.
The best bet might be to create a regular polyhedron, and keep the point and direction as floating point vectors/points, and calculate the actual position when you move, and figure out which polygon you land in (note, you would have the possibility of moving to non-adjacent polygons with this method, and you might have issues if you land exactly on an edge/vertex, etc).
I'm having trouble UV mapping each side of a cube. The cube was made as a BufferGeometry where each side is a rotated copy of one side (sort of a working template) and rotated accordingly by applying a quarternion. UVs are copied as well. I'll skip any vertex coordinate I've seen before and rely on indices.
This leaves me with a total of 8 vertices and 12 faces. But I think I'm running short on vertices when I have to set all of my UVs. As obvious on the screenshot I've "correctly" mapped each side of the cube. But the top and bottom is lacking. I don't know how to set the vertex UV top and bottom faces.
Can I in some way apply several UVs on the same vertex depending on which face it is used in or have I completely lost the plot?
I could solve the problem by applying 6 PlaneBufferGeometry but that would leave me with 4*6=24 vertices. That is a whole lot more than 8.
I haven't been able to figure this one out. Either I've complete misunderstood how it works or what I'm trying to accomplish is impossible given my constraints.
With BufferGeometry, vertices can only be reused if all the attributes for that vertex match. Since each corner of the cube has 3 perpendicular normals, there must be 3 copies of that vertex.
If you have uvs, it is the same issue -- vertices must be duplicated if the uvs are different.
Study BoxBufferGeometry, which is implemented as "indexed-BufferGeometry".
three.js r.90
I am trying to create a terrain solution in ThreeJS and I'm running into some trouble with the generation of the normals. I am approaching the problem by creating a number of mesh objects using the THREE.PlaneGeometry class. Once all of the tiles have been created I go through each and set the UV's so that each tile represents a part of the whole. I also generate a height value of the vertex Y positions to create some hills. I then call the geometry functions
geometry.computeFaceNormals();
geometry.computeVertexNormals();
This is just so that I have some default face and vertex normals for each tile.
I then go through each tile and try to average out the normals on each corner.
The problem is (I think) with the normals, but I don't really know what to call this problem. Each of the normals on the plane's corners point in the same direction as the face when created. This makes the terrain look like a flat shaded object. To prevent this I thought perhaps what I needed to do was make sure each vertext normal (each corner) had the same averaged normal as its immediate neighbours normals. I.E each corner of each tile has the same normal as all the immediate normals around it from the adjacent planes.
figure A
Here I am visualising each of the 4 normals on the mesh. You can see that at each corner the normals are the same (On top of eachother)
figure B
EDIT
figure C
EDIT
Figure D
Except even when the verts all share the same normals it still comes up all blocky <:/
I don't know how to do this... I think my understanding of what needs to be done is incorrect...?
Any help would be greatly appreciated.
You're basically right about what should happen. The shading you're getting is not consistent with continuous normals. If each all the vertex-faces at a given location have the same normal you should not see the clear shading discontinuities in your second image. However the image doesn't look like simple face normals either, at least not to my eye.
A couple of things to look at:
1) I note that your quads themselves are not planar. Is it possible your algorithm is assuming that they are? the non-planar quad meshes don't have real 'face normal' to use as a base.
2) Are your normalized normalized after you average them? That is, do they have a vector length of 1?
3) Are you confident that the normal averaging code is actually using the correct normals to average? The shading in this does not look like completely flat shaded image where each vertex-face normal in a quad is the same - if that were the case you'd get consistent shading across each quad although the quads would not be continuous. This it possible your original vertex-face normals are not in fact lined up with the face normals?
4) Try turning off the bump maps to debug. Depending on how the bump is being done in your shader you may have incorrect binormals/bitangents rather than bad vert normals.
Instead of averaging at each vertex / corner the neighborhood normals you should average the four normals that each vertex has (4 tiles meet at each vertex).
I opened my calendar today and it had a puzzle inside. There are six pieces, and I suppose I have to make them into a cube... I tried to solve it and failed hard. So I decided to try to solve it with programming....
I made them into polygons (not sure if that was a good idea), but have no clue how to rotate them and/or check if any shape collides with any other shape.
The shapes are these:
TL;DR: I'm looking for help with checking every possible combination of these shapes to see if they make a cube. In other words, how can I rotate and check polygons (or something else that represents these pieces) for intersection?
Making them into polygons is not the correct abstraction for this problem.
See, what you have are the 6 sides of the cube, but now you have to figure out how to rotate them. Each polygon has on its edge 12 small squares that are either on or off and must match with the ones next to it. This is a very discrete problem.
The entire cube has 8 (vertices) + 12 * 2 (edges) small cubes on the edges.
Each face, when placed into the cube, will occupy some of those small cubes.
You need to
1) make a mapping that maps the face into the whole cube on the given face, in the given orientation
2) do a search for the configuration where no small cubes are occupied twice.
I'm working on a 3D tile based game and I'm using AABB collision detection. For every cube that the player is intersecting, I find the axis along which the player is intersecting the cube the least, and push the player out of the cube along that axis.
Depending on the order that the cubes are checked in, this can cause problems when sliding along the edge of multiple cubes. I have created a diagram that should explain the problem:
http://imgur.com/mmK0W.png
Arrow #1 is the attempted movement of the player. The other arrows are the collision response.
In the left diagram, collision is tested against the right cube first, causing the player to be pushed to the left, and then upwards. (bad)
In the right diagram, collision is tested against the left cube first, causing the player to be pushed upwards, at which point the player is no longer intersecting the other cube. (good)
Any ideas on what the most efficient way to solve this might be? Or any better ways to handle the collision response?
Thank you.
A discrete implementation forces you to inject some continuous math in the system, only when required (cubes / directions overlap).
For each cube c1, c2 ... ci with which the user cube (uc) intersects at the time of the check, you want to find out which cube was "touched" first - there is only one, as in real life. Consider the direction d of uc, and, taking the amount of uc in ci (overlapping) find the position of cu at the time it "touched" ci.
Determine which cube was "touched" first cj (the one that required the most rollback on the d axis - the sooner in time) and use only this one to calculate the collision reaction.
Not only you'll reach accuracy. but it will help if all cubes are moving, have different speeds etc...
From your diagram, it seems you want the smallest move that minimises the overlap between the player and the cubes. Each cube with overlap will try to "push" the player in two orthogonal directions. Can you do something like pick the minimum push of the maximum pushes in each direction?
You might implement a kind of hybrid broad phase when your two (or more) stationary cubes in a row can be combined into one larger rectangle. Test against the larger rectangle first. It will give you the results of your green check mark and be faster than checking each cube anyway. Then, after that, only if you need to, check against the individual cubes.
A collision can push an object on 1 axis only. To determine the axis to push:
else -- not this
elseif -- change to this
if w > h then
push x
elseif h > w then
push y
end
This works if your tiles are aligned.
Use circles to avoid the stick on unaligned tiles