I'm trying to code a 3d wall like
http://www.flashloaded.com/flashcomponents/3dwall/
The shape I am looking to create is like a bath or arena where it is a curve cornered rectangle with sloping sides.
The image below shows what i'm trying to achieve if viewed from above. I hope that helps.
Can anyone give me some ideas on the maths to create this shape using primitive rectangle shapes.
Thanks,
Josh
http://en.wikipedia.org/wiki/Matrix_multiplication
http://en.wikipedia.org/wiki/Transformation_matrix
http://www.devmaster.net/wiki/Transformation_matrices
A rectangle has 4 3D points (vectors)
Define a vector this way
To move/rotate/scale just multiply each vector by the transformation matrix.
This matrix rotates around X-axis:
For perpective projection (camera) look at: http://en.wikipedia.org/wiki/3D_projection
For example: you can create rectangles and rotate them around an axis to create a cylinder like this:
(source: flashloaded.com)
your pit:
note: the angle is not correct, it should be pi-a (180ยบ-a)
create all rectangles centered at origin (0,0,0), then rotate them as needed and move to desired position. I recommend you to code the matrix routines first like rotate(), move(), scale() and a simple paint function (just line drawing, without perspective) the rest is just playing with the matrices.
Related
I try to use 2 ellipses to detect a collision if they overlap. I have to rotate the ellipses but I can't figure out how this works. I'm working with the "com.badlogic.gdx.math.Ellipse" class but it seems to have no method for rotating. Any ideas? Thx in advance!!
Unfortunately, LibGDX doesn't have in-built rotating functions for ellipses.
Instead, I'd either be resorting to a circle in which rotation does not matter, or use polygons to check intersection.
Polygons are formed through an array of float values (vertices), where, every even element of the array is the horizontal component (x) and the odd, the vertical component (y).
Polygon polygon1 = new Polygon(vertexSet1);
Polygon polygon2 = new Polygon(vertexSet2);
Then, by using an Intersector, you can then check whether these polygons have intersected. The more vertices, the more accurate your shape will be. Just remember to have 6 or more elements in your vertex array, as the 6 floats will give 3 (x, y) points which is the minimum required for a polygon.
if (intersector.overlapConvexPolygons(polygon1, polygon2) {
//do your intersection code
}
The polygons themselves have commands to translate, scale and rotate, allowing for the rotations you mentioned above.
I'm using Bullet physics engine in a simulation.
I have a 3D node in my scene and i want to use a cylinder collision shape for it.(Yellow object)
Problem is that when i create a btCylinderShape , its Pivot point is in center of the cylinder,
but my 3D object has a different pivot point which is not in center (Its at bottom of cylinder for example)
So when i update my scene, collision shape doesn't match the 3D object as you can see in shot.
How can i change btCylinderShape pivot point to be in bottom instead of center?
you have to use compound shape.
try search for: bullet physics center of mass
https://code.google.com/p/jbullet-jme/wiki/CenterOfMass
http://bulletphysics.org/Bullet/phpBB3/viewtopic.php?f=9&t=2209
I have an hourglass like vector shape and I'd like to use it to mask an image. I'd like to feather the edges - have a soft falloff in transparency that follows the contours of the hour glass. Any ideas how I can do this?
I tried using a gradient fill on a closed shape (using beginGradientFill() and curveTo() functions) but that falloff doesn't follow the contour of the vector shape, it can only go one direction.
Maybe there is a better solution but until somebody comes up with it... I assume you could do the following:
Draw whatever shape you want to use as mask into a transparent bitmap.
Scale a bit the bitmap down (or use a matrix while drawing its bitmapdata).
Apply a blur filter to it.
Put the bitmap's center to the masked clip's center so they are aligned.
Set the masked clip's cacheAsBitmap property to true.
I want to use HTML5 canvas to draw a large circle and then evenly space x number of circles around it's path,
So far I have modified this: http://jsfiddle.net/m1erickson/pL5jP/
To this: http://jsfiddle.net/dQUxy/6/
I can get them how I want if I draw them manually like so (example)
Draw(startx, starty);
Draw(startx+47, starty+47);
Draw(startx+80, starty+80);
Not very elegant. What would be the mathematical solution to drawing say, 14 circles evenly spaced around the path?
Never mind, I found raphael.js which did the job elegantly
http://raphaeljs.com/hand.html
This is my firs excursion on the HTML5 canvas, I have working knowledge of jQuery and Javascript.
I'm trying to create a "spinning globe" effect with it.
The idea is to have a circle and meridians "spinning" on it, to give the effect of a rotating globe.
I've drawn the circle and now I'm trying to create lines that start from the right (following the curve of the circle), move towards the centre straightnening up (in the middle they are straight) and follow the inverse curvature on the left, ending with the circle.
I'm trying to do this with the HTML5 canvas and jQuery but I'm not sure of where to start... should I create an arc and then try to animate it?
I'm even wondering if the canvas is the right tool or if I should use anything else.
Any suggestion is welcome!
Sebastian
You could use a quadratic bezier curve, which is basically just a curve with a start point, an end point, and a "control point" in the middle, which is what you would want to change as the globe spins. In this case, all of your lines would start and end at the north and south poles, respectively, of your "globe". For example, to make one of these lines:
// start drawing a line
canvas.beginPath();
// move the the top of your globe
canvas.moveTo(0,0);
/* draw a curve with the control point specified by the first two args,
* end point by the second two:
* (in your case, the control point would be in the middle of the globe) */
canvas.quadraticCurveTo(control_point_x, control_point_y, 0, 50);
// finish drawing, stroke and end
canvas.stroke();
canvas.closePath();
You would also have to take in to account how you will clear the lines after each frame, of course.
See: The Canvas element API, Complex Paths
This is what I got, didn't have the time to proceed any further: http://jsfiddle.net/Z6h3Z/
I use bezier curves where the two control points are in a sort of oval arc centered at the poles.
What I got stuck at is the distribution of points along the arc to look more realistic.