I want to create a slope like in attached image in Box2D Cocos2d JS.
However, I am unable to create it properly when attached sprites to it.
My code is:
new b2Vec2(0, 0),
new b2Vec2(100 / worldScale, -50 / worldScale),
new b2Vec2(200 / worldScale, 0 / worldScale)
The image dimensions is 200 * 50, and worldScale = 30.
First of all I see you're using negative coordinates (-50). Everything in Cocos2d-JS (the default viewport) is positive ({0,0} is bottom left point).
To debug slope positioning I suggest you to use Box2d DebugDraw first, to see the actual slope you've described and then to place your sprite based on those wireframes.
Cocos2d-JS will clear it's own canvas in the update function, so you'll need to put another debug canvas on top of it, for DebugDraw.
This example helped me to add debug draw to my box2d sandbox successfully
add this code to update function
var debugDraw = new Box2D.Dynamics.b2DebugDraw();
debugDraw.SetSprite(document.getElementById("test").getContext("2d"));
// test is the id of another canvas which debugdraw works on
debugDraw.SetDrawScale(30.0);
debugDraw.SetFillAlpha(0.3);
debugDraw.SetLineThickness(1.0);
debugDraw.SetFlags(Box2D.Dynamics.b2DebugDraw.e_shapeBit |
Box2D.Dynamics.b2DebugDraw.e_jointBit);
this.world.SetDebugDraw(debugDraw); this.world.DrawDebugData();
box2d use a different coordinate frame than cocos, so you need to do
transform 180 degrees. add this to the style of debug canvas
-webkit-transform:rotate(180deg); //and some other browsers' style
Related
I am trying to implement shadows into my WEBGL 2.0 Project using this tutorial
https://webgl2fundamentals.org/webgl/lessons/webgl-shadows.html
Currently I am getting really bad results like this:
Basically a ton of the terrain is being drawn in shadow that shouldn't be. The light projection is from your camera towards the direction you are looking so hypothetically you shouldn't be able to see any shdaows becuase the light projection is the same as your camera ( I am just doing this for testing until I can get this working properly)
I have everything the same as the tutorial I believe except I am using glMatrix instead of their matrix math library (shouldn't matter I would assume). Here's the thing though. I don't use a model view matrix for anything I am rendering so none of my points are on a -1,1 range. They can go out as far as -3200...ect Its just all one big terrain mesh chunked out.
I think the issue lies with how I am creating the texture matrix
textureMatrix = glMatrix.mat4.create();
glMatrix.mat4.translate(textureMatrix,textureMatrix,[0.5,0.5,0.5]);
glMatrix.mat4.scale(textureMatrix,textureMatrix,[0.5,0.5,0.5]);
glMatrix.mat4.multiply(textureMatrix,textureMatrix, projectionMatrix);
glMatrix.mat4.invert(lightMatrix,lightMatrix);
glMatrix.mat4.multiply(textureMatrix,textureMatrix, lightMatrix);
I am using the same matrix for the light projection as your normal projection, is that an issue? if anyone could help it would be greatly appreciated.
That's probably because the Y position of your light (in your example, it is much more the distance between the eye and the scene) is too big for the Z size of your shadow volume (the size of your shadow volume in the view direction.) Here if posY is inside the wireframe box :
But if you increase posY too much (i.e. your shapes get out of the shadow volume, they disappear
So you should increase the size of your shadow volume (or shrinken your scene, either way.) You cannot simulate that with the slider because they just give you the control to the two dimensions X and Y dimensions : projWidth and projHeight.
i.e. in the last code in your tutorial page, the latest parameter ("far") for example change it from 10 to 100
const lightProjectionMatrix = settings.perspective
? m4.perspective(
degToRad(settings.fieldOfView),
settings.projWidth / settings.projHeight,
0.5, // near
10) // far
: m4.orthographic(
-settings.projWidth / 2, // left
settings.projWidth / 2, // right
-settings.projHeight / 2, // bottom
settings.projHeight / 2, // top
0.5, // near
100); // far
Then you can increase posY far more :
without having your full code, it is hard to reproduce and help you. Could you not try to just inject your scene into the tutorial code ? You can bind the viewpoint with the source and orientation of the light by using the same inputs : (just adding 0.5 to X to see a bit of shadow and make sure it is properly computed.)
/*const cameraPosition = [settings.cameraX, settings.cameraY, 15];*/
const cameraPosition = [settings.posX+0.5, settings.posY, settings.posZ];
/*const target = [0, 0, 0]; */
const target = [settings.targetX, settings.targetY, settings.targetZ];
I'm brand new to corona SDK and following tutorials. I notice that when I'm positioning elements theyre not appearing as they do in the tutorials. For example:
local testRect = display.newRect( 0, 0, 50, 50 )
testRect:setFillColor( 0.5,0,0 )
In the tutorial it looks like this:
I would guess the anchor point on the rectangle would be 0.5, 0.5 and I'd have to position it 50% to the right, and 50% from the top of the upper left corner. It looks like in their example the rectangle has an anchor point of 0, 0 and is stuck to the edge of the screen by default.
Why is there a difference? i notice this tutorial is using an iphone 4.. but should that matter?
A couple of years ago, Corona SDK went to their Graphics 2.0 standard. Part of this move was to get all display.* objects to behave the same when creating them. Before Graphics 2.0, some objects the X and Y values meant top left, for others it meant center. With Graphics 2.0, all X and Y values when creating an object are the center of the object now.
If you have an older tutorial, it may be assuming that the x, y is top left. In your example you are creating the object at 0, 0 which is the top left corner of the content area. Since you're on a screen that's wider than it's defined content area, 0, 0 isn't always the top left corner of the screen.
I'm guessing your config.lua is setting the width to 320 and the height to 480 (always listed as if the device was in portrait mode). But you're using an iPhone 5 screen, which means the top left corner is -44, 0. This explains why the image isn't all the way to the left edge.
I am sure the anchor points they using are 0.5,0.5.
I suggest you check your build.settings file .. I tried the code and got the same result they had ..
Again CHECK your build.settings file
Hello in a game I'm making using lua in Marmalade Quick,I have run into a problem with the physics.
I have a normal downward y gravity and have some notes that is affected by that.
Now I want to add some objects that "fly" horizontally on the X axis but I can not get it to work.
so one of the notes looks like this:
sky2 = director:createSprite(dw, 40, "textures/tractor.png")
physics:addNode(sky2, {type="dynamic"})
sky2.physics:setGravityScale(0)
my first thought was to
just add the following to an update listener
if(gameplaying == true) then
sky2.x = sky2.x-2.5
unfortunately this does not work after the node has got added physics
then I was looking into using
sky2.physics:applyapplyLinearImpulse or sky2.physics:applyForce
I used it like this
sky2.physics:applyapplyLinearImpulse(-10, 0, -20, 40)
The problem here is that the node then correctly moves along the axis but it is spinnig around (torque effects)..
Is there away to stop this or what am I doing wrong,,
thanks..
Found out that the Marmalade Quick Documentation was wrong, and to not input both a px and a px value but just 0 so sky2.physics:applyapplyLinearImpulse(-10, 0) this will apply the impulse at the centre of mass and make it move straight.
I'm learning Corona SDK and am new to lua as well (i mainly do ruby and some javascript).
I have a bar that i want to fill up as the user does stuff. I've set it up as follows:
--outer rectangle
powerBar = display.newRect(210, 6, 24, 9)
powerBar.strokeWidth = 1
powerBar:setStrokeColor(254,203,50)
powerBar:setFillColor(0,0,0,0)
--inner rectangle which fills up
powerBarFill = display.newRect(211,7,0,7)
powerBarFill:setFillColor(234,183,30)
When the "stuff" happens, i add 1 to powerBarFill.width, which i thought would make it grow from left to right. But, it's actually growing out from the centre, ie its x is in the centre and the width extends either side from that.
Whats the best way to keep the left side static and grow the right side? Can i set it so that it's x position is actually on the left hand side rather than in the middle? Seems like that might do it.
cheers in advance
I've run into this problem as well when creating a progress bar. The problem is with the rect's reference point. The default reference point is in the center of an object, as you've noticed. You can use object:setReferencePoint() to change it. I believe you want to use the display.BottomLeftReferencePoint value:
powerBar:setReferencePoint(display.BottomLeftReferencePoint)
Keep in mind that you have to set this value before you set your x,y values. So in your case you'll need to set the reference point after creating the rectangle, and then assign values to x,y again (even though you already did this in the newRect constructor):
powerBar = display.newRect(210, 6, 24, 9)
powerBar:setReferencePoint(display.BottomLeftReferencePoint)
powerBar.x, powerBar.y = 210, 6
If it's width is from the X position on both sides:
1) It should start at:
Centre - (Width when it's full / 2)
2) Every frame, add:
incrs = 1 --Amount to increase by
width = width + incrs
x = x + incrs / 2
How to make a 2d world with fixed size, which would repeat itself when reached any side of the map?
When you reach a side of a map you see the opposite side of the map which merged togeather with this one. The idea is that if you didn't have a minimap you would not even notice the transition of map repeating itself.
I have a few ideas how to make it:
1) Keeping total of 3x3 world like these all the time which are exactly the same and updated the same way, just the players exists in only one of them.
2) Another way would be to seperate the map into smaller peaces and add them to required place when asked.
Either way it can be complicated to complete it. I remember that more thatn 10 years ago i played some game like that with soldiers following each other in a repeating wold shooting other AI soldiers.
Mostly waned to hear your thoughts about the idea and how it could be achieved. I'm coding in XNA(C#).
Another alternative is to generate noise using libnoise libraries. The beauty of this is that you can generate noise over a theoretical infinite amount of space.
Take a look at the following:
http://libnoise.sourceforge.net/tutorials/tutorial3.html#tile
There is also an XNA port of the above at: http://bigblackblock.com/tools/libnoisexna
If you end up using the XNA port, you can do something like this:
Perlin perlin = new Perlin();
perlin.Frequency = 0.5f; //height
perlin.Lacunarity = 2f; //frequency increase between octaves
perlin.OctaveCount = 5; //Number of passes
perlin.Persistence = 0.45f; //
perlin.Quality = QualityMode.High;
perlin.Seed = 8;
//Create our 2d map
Noise2D _map = new Noise2D(CHUNKSIZE_WIDTH, CHUNKSIZE_HEIGHT, perlin);
//Get a section
_map.GeneratePlanar(left, right, top, down);
GeneratePlanar is the function to call to get the sections in each direction that will connect seamlessly with the rest of your world.
If the game is tile based I think what you should do is:
Keep only one array for the game area.
Determine the visible area using modulo arithmetics over the size of the game area mod w and h where these are the width and height of the table.
E.g. if the table is 80x100 (0,0) top left coordinates with a width of 80 and height of 100 and the rect of the viewport is at (70,90) with a width of 40 and height of 20 you index with [70-79][0-29] for the x coordinate and [90-99][0-9] for the y. This can be achieved by calculating the index with the following formula:
idx = (n+i)%80 (or%100) where n is the top coordinate(x or y) for the rect and i is in the range for the width/height of the viewport.
This assumes that one step of movement moves the camera with non fractional coordinates.
So this is your second alternative in a little bit more detailed way. If you only want to repeat the terrain, you should separate the contents of the tile. In this case the contents will most likely be generated on the fly since you don't store them.
Hope this helped.