I'v been thinking and I want to know if this is a efficient way to make a game collision.
I am trying to make a game like Double Dragon(NES). I'm trying to copy the mechanic of moving up and down on a 2D screen but when you go back you go behind it.
But the mechanic I'm having trouble with is I want the feet to collide with an object but I'm not sure if hitTestPoint will do it so I want to use a object to be the collision detector.
The Player Collider will be attached to the feet, but I don't know how to keep the Collider on the feet of another object. I'v done it but when I do it, it is very laggy and I want to know how you guys would handle this.
Over all what I'm trying to say is. There are 2 objects, 1 of them is the player sprite and the other is the collision detector (which is also a object). I would like to know if that would be ok to use as a collision detector or is there a more efficient way of doing it.
Related
I have a rather simple react-three-fiber setup that includes cannon.js-powered physics. In the scene there is a cup -- which is modelled as a cylinder whose top radius is bigger than the bottom one -- that is placed on a surface.
When I run the code, during the loading screen everything looks fine. But when physics kick in, the cup suddenly "sinks" into the ground. Why is that? I can't make sense of that...
One theory of mine was that the "physics shape" of the cylinder is not identical with the "optical shape" that gets rendered, but even then the movement I observe still doesn't make sense with any reasonable bounding box I can imagine...
Working example: https://codesandbox.io/s/amazing-proskuriakova-4slpq
Physics are finicky and really hard to debug because you're often trying to intuit the effects of an invisible system by its effects on whatever hybrid view you have.
I notice if i bring the mass downn to a more reasonable value, like 5, the object appears to roll around like a sphere or some other shape.. so I think your theory is sound. I don't know off the top of my head what the solution is, but I do know that the only physics engine I "trust" in the js space, except for very simple simulations, is Ammo.js. It's hard to use, but is an emscripten port of a truly amazing AAA quality library. https://threejs.org/examples/?q=phys#physics_ammo_break
I would start by getting a cube and a sphere working.. once you have verified that those work as expected.. ideally using real-ish world scale units, like a 1x1x1 cube, with a mass of 1. Use a texture on the sphere so you know that its rolling like you expect. Once you have verified the simpler primitives work, move onto the more complex geometries.
Best way forward would be to make an issue on the use-cannon GH. That lib and cannon-es are under active maintenance now. Meanwhile, i believe convexpolyhydron can also do it flawlessly, see: https://codesandbox.io/s/r3f-convex-polyhedron-cnm0s
I think this requires a bit of background information:
I have been modding Minecraft for a while now, but I alway wanted to make my own game, so I started digging into the freshly released LWJGL3 to actually get things done. Yes, I know it's a bit ow level and I should use an engine and stuff...indeed, I already tried some engines and they never quite match what I want to do, so I decided I want to tackle the problem at its root.
So far, I kind of understand how to render meshes, move the "camera", etc. and I'm willing to take the learning curve.
But the thing is, at some point all the tutorials start to explain how to load models and create skeletal animations and so on...but I think I do not really want to go that way. A lot of things in working with Minecraft code was awful, but I liked how I could create models and animations from Java code. Sure, it did not look super realistic, but since I'm not great with Blender either, I doubt having "classic" models and animations would help. Anyway, in that code, I could rotate a box around to make a creature look at a player, I could use a sinus function to move legs and arms (or wings, in my case) and that was working, since Minecraft used immediate mode and Java could directly tell the graphics card where to draw each vertex.
So, actual question(s): Is there any good way to make dynamic animations in modern (3.3+) OpenGL? My models would basically be a hierarchy of shapes (boxes or whatever) and I want to be able to rotate them on the fly. But I'm not sure how to organize that. Would I store all the translation/rotation-matrices for each sub-shape? Would that put a hard limit on the amount of sub-shapes a model could have? Did anyone try something like that?
Edit: For clarification, what I did looked something like this:
Create a model: https://github.com/TheOnlySilverClaw/Birdmod/blob/master/src/main/java/silverclaw/birds/client/model/ModelOstrich.java
The model is created as a bunch of boxes in the constructor, the render and setRotationAngles methods set scale and rotations.
You should follow one opengl tutorial in order to understand the basics.
Let me suggest "Learning Modern 3D Graphics Programming", and especially this chapter, where you move one robot arm with multiple joints.
I did a port in java using jogl here, but you can easily port it over lwjgl.
What you are looking for is exactly skeletal animation, the only difference being the fact you do not want to load animations for your bones but want to compute / generate transforms on the fly.
You basically have a hierarchy of bones, and geometry attached to it. It looks like you want to manipulate this geometry "rigidly", so before sending your meshes / transforms to the GPU (the classic way), you want to start by computing the new transforms in model or world space, then send those freshly computed matrices to draw your geometries on the gpu the standard way.
As Sorin said, to compute each transform you simply have to iterate over your hierarchy and accumulate transforms given the transform of the parent bone and your local transform w.r.t the parent.
Yes and no.
You can have your hierarchy of shapes and store a relative transform for each.
For example the "player" whould have a translation to 100,100, 10 (where the player is), and then the "head" subcomponent would have an additional translation of 0,0,5 (just a bit higher on the z axis).
You can store these as matrices (they can encode translation, roation and scaling) and use glPushMatrix and glPop matrix to add and remove a matrix to a stack maintained by openGL.
The draw() function(or whatever you call it) should look something like :
glPushMatrix();
glMultMatrix(my_transform); // You can also just have glTranslate, glRotate or anything else.
// Draw my mesh
for (child : children) { child.draw(); }
glPopMatrix();
This gives you a hierarchical setup so that objects move with their parent. Alternatively you can have a stack in the main memory and do the multiplications yourself (use a library). I think the openGL stack may have a limit (implementation dependent), but if you handle it yourself the only limit is the amount of ram you can use. Once all the matrices are multiplied rendering is done in the same amount of time, that is it doesn't matter for performance how deep a mesh is in the hierarchy.
For actual animations you need to compute the intermediate transformations. For example for a crouch animation you probably want to have a few frames in between so that the camera doesn't just jump to the low position. You can do this with a time based linear interpolation between the start and end positions, but this only covers simple animations and you still have to implement it yourself.
Anything more complicated (i.e. modify the mesh based on the bone links) you would need to implement yourself.
my question is just about choosing the right approach because i'm not sure about the solution.
i got 3d model in my project, at some point i want to show animated disassembly , the object is made of somthing like 200 pieces.
so animating with keyframe one by one is time consuming.
the animation i'm looking for is like explosion from the center of the object so the parts will just move out of its center.
example image:
what would you do?
what is the best way to manage such task?
I would code it. Maybe I am biased because I am a programmer, but animating it would be a pain.
So I would import the model into Unity3d. Then I would grab all the parts and store them in a list. Once I have the 200 parts then I can do anything I want to them.
I would then proceed to attach rigibodies and box colliders to them all -- this can be done programmatically. Then you can initiate the explosion by adding a velocity to each part. If you want to be fairly realistic and have something that is fairly random you can give each object mass and then use the equation F=ma for the explosion. That is, each part will get different acceleration depending on the mass they have.
I'm using Farseer and XNA on on WP7. I have 2 objects in my game. The first one is a wall generated from a bitmap. The second one is a player controller - in fact it's just a circle object. This circle follows player's finger.
I need a certain behavior - probably it's very basic, but I can't figure out how to google it. It's a collision detection that just wouldn't allow the controller to come into the wall. It shouldn't bounce. It should just try to follow the finger but not enter the wall.
I know it's not hard to implement it on my own, but if I'm using a physics engine and it happens to offer such a functionality it would be a shame not to take advantage of it. :)
you need to use a BoundingBox object, and check collision VS the object (you should create a BoundingSphere wrapping it)
http://www.riemers.net/eng/Tutorials/XNA/Csharp/Series2/Collision_detection.php
I have a hierarchical animated model in DirectX which loads and animates based on the following DirectX sample: http://msdn.microsoft.com/en-us/library/ee418677%28VS.85%29.aspx
As good as the sample is it does not really go into some of the details of animation that I'd like. For example, if I have a mesh which has a running animation and a throwing animation as seperate animation sets how can I get the throwing animation to occur for bones above the hip and the walking animation to occur for bones underneath the hip?
Also if I wanted to for example have the person lean left or right would I simply have to find the bone for the hip and multiplay a rotation matrix by its matrix? In this case I think the matrix is m_amxBoneOffsets?
Composing multiple animations to a single one is usually the job of an animation system, something that is way out of scope of the D3D sample.
Let's look at your 2 examples:
running and throwing
Well, in this case you could apply the animation for the lower part of the body from the running animation and the animation for the upper part of the body from the throwing animation. And you'd get a very crappy result.
The how is just a matter of knowing which bones are where in the bone palette (something that depends on how they are stored, and in which order, but nothing inherently hard. The definite reference should be the documentation of the tool generating the animation data)
In practice, you're better off with a blending of the 2 animation. This is, in general, is hard, and software packages exist out there that do this for you. Gamebryo, e.g.
Or, an animation of a running guy who throws is different enough from a standing guy who throws that you might be better off having 2 animations.
Leaning
If you apply a rotation matrix to the root bone, you'll simply rotate your whole character.
Now if you rotate the next bone in the hierarchy (from the spine), you'll get all the bones that depend on it to rotate likewise. It will probably do what you want, but there's a sure way to find out. Try it!
Well the thing is the running animation SHOULD affect the throwing animation slightly. What you need to look into is animation blending.
I'm sure Valve wrote a good paper on how they implemented it in Counter-strike many years ago. Its not on the valve site though so I'm not sure where I got this memory from ...