Calculating the new x position

[lcass]

Hi ive been looking on the internet for a post from 1999 about 3d graphics algorithms if anyone could link to that it would be great and would solve the entire issue.

here is the issue.
Say I have my camera and x1 y1 z1 and i have a vector (just a pixel) and x2 y2 z2. How would I figure out the position I draw the x and y if Im drawing it orthagonally?

[lcass]

Just to note the website wasnt about java it was just about the maths behind it, thats all im looking for I can implement the code.

[opiop65]

You mean centering the camera on a pixel? I don't understand.

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[lcass]

Its for 3d programming. I want to find out how to draw the pixel via the cameras perspective.

[lcass]

So really the question should be , how do I get the x and y position the pixel should be drawn in based off of the distance from the object and the objects position(x,y)

[opiop65]

You mean the distance formula?
http://cs.selu.edu/~rbyrd/math/distance/

[lcass]

Nope.
What I mean is say the camera is at x 0 y 0 z 0 and I have an object at x 5 , y 2 z 15 . I want to know how to calculate the position I would draw the object relative to the camera using the coordinates. Note its for 3D movement.

[opiop65]

Ahh I see! If I remember correctly, use this formula:
X = cam.x + radius * cos(rotation.x) * sin(rotation.y)
Y = cam.y + radius * sin(rotation.x)  *  sin(rotation.y)
Z = cam.z +radius * cos(rotation.y)

Please note that the rotation vector should be in radians. Multiply your degrees by PI / 180.

[relminator]

I'm not so sure but do you mean "projection"?

If that's the case, divide the other 2 components by z(or distance).

Here's how it works:

www.rel.phatcode.net/mytutes/3dtutes/chapter1/chapter1.htm

A more in-depth explanation written my a friend of mine:

www.ocf.berkeley.edu/~horie/persp.txt

[lcass]

I'm not so sure but do you mean "projection"?

If that's the case, divide the other 2 components by z(or distance).

Here's how it works:

www.rel.phatcode.net/mytutes/3dtutes/chapter1/chapter1.htm

A more in-depth explanation written my a friend of mine:

www.ocf.berkeley.edu/~horie/persp.txt

When I say pojection I mean orthagonally projected from 3d to 2d.
Also thanks opiop you have even given me the rotation part

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[lcass]

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package lcass.com.graphics; import lcass.com.control.Camera; import lcass.com.core.core; import lcass.com.graphics.objects.vertex; public class RENDER3D {    private core core;    public RENDER3D(core core) {       this.core = core;    }    public void drawvertex(vertex v, Camera c,double rotx,double roty) {           double cz = c.z;       double dist = v.z - cz;       double ax = ((v.x - c.x)+dist) * Math.cos(rotx)* Math.sin(roty);       double ay = ((v.y - c.y)+dist) * Math.sin(rotx)* Math.sin(roty);       double dx = 0;       double dy = 0;       double scale = 512 / dist;             if (dist > 0) {          dx = (ax * (scale / dist)) + (core.WIDTH / 2);          dy = (ay * (scale / dist)) + (core.HEIGHT / 2);       }       System.out.println("dx " + ax + " dy " + dy);       if (dx < core.WIDTH && dy < core.HEIGHT) {          if (dx > 0 && dy > 0) {             core.screen.map[(int) dx][(int) dy] = 0xFF00FF;          }       }    } }

I currently have that it behaves a bit odd though and im not to sure on where I would implement the z variable.
the prefix d is for drawn
prefix a is for adjusted
prefix v is for vertex
prefix c is for camera

[opiop65]

Did you make sure your rotation is converted to radians? That distance variable seems a little sketchy, too because you have it clamped to under zero, the radius really should be positive!

How are you having trouble with the z component?

[lcass]

oop I know how to fix the distance. With the z component I dont know how I would implement it into the code and how I would change the rendering. yep its in radians. When I render it what happens is I use each vector in a shape object which I call square. When I change the rotx roty values the square changes shape into an odd looking rectangle

[opiop65]

Can you post more code and screenshots? And the z component is the sane thing as the others, it just isn't as complex. All you need is the z position of the camera and the rotation on the y axis. Do you not using a z axis in your rendering? Because you would need to for it to be fully controllable in 3D...

[lcass]

Do you have an example of some code I could just see how you render it.

[opiop65]

Yeah, sure. In my voxel engine I use this:

1

cube.createWireFrameCube(-this.getPosition().x + (4 * Math.cos(this.getRotation().x * (Math.PI / 180)) * Math.sin(this.getRotation().y * (Math.PI / 180))), -this.getPosition().y + (4 * Math.sin(this.getRotation().x * (Math.PI / 180)) * Math.sin(this.getRotation().y * (Math.PI / 180))), -this.getPosition().z + (4 * Math.cos(this.getRotation().y * (Math.PI / 180))), 1);

Its honestly just the equation I gave you, with a little extra math to convert it to radians. I take the negative position because my player class was a little screwed up, maybe you should try seeing if that works!

[lcass]

What ill do is upload the code just so you can see the issue

https://drive.google.com/file/d/0B48ywWBymi3OZDcwYjJLQTBQdUE/edit?usp=sharing

[opiop65]

Well, what am I looking at here? I don't know what to look for or anything... Does your camera have a z axis? If it does, than that's what you need for the z component. I don't entirely understand what the problem is here as you haven't explained whats wrong.

[lcass]

OH the z works perfectly its the x changing what happens is instead of rotating it makes it look like you are just walking by the pixel.

[lcass]

And I think I just noticed why this may seem confusing... Im looking for drawing the vectors when the cameras rotation changes not rotating the vectors.

[lcass]

Honestly I have no goddamn clue what the hell is going on with this I want it to rotate around the camera via the y axis it doesnt even make a square it just shoots around the place for no reason....

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package lcass.com.graphics; import lcass.com.control.Camera; import lcass.com.core.core; import lcass.com.graphics.objects.vertex; public class RENDER3D {    private core core;    public RENDER3D(core core) {       this.core = core;    }    public void drawvertex(vertex v, Camera c,double rotx,double roty) {           double cz = c.z;             double dist = Math.abs(v.z - cz);       double tx = v.x - c.x;       double ty = v.y - c.y;       double tz = v.z - c.z;             double nx = tx * Math.cos(roty) - ty * Math.sin(roty);       double ny = tx * Math.sin(rotx) + ty * Math.cos(rotx);       double nz = tz* Math.cos(roty);       double adist = Math.abs(nz-c.z);       double dx = 0;       double dy = 0;       System.out.println(dist);       double scale = 512 /adist;                    dx = (nx) * (scale /adist)+ (core.WIDTH / 2);          dy = (ny)* (scale / adist)+ (core.HEIGHT / 2);                   if (dx < core.WIDTH && dy < core.HEIGHT) {          if (dx > 0 && dy > 0 && nz >=0) {             core.screen.map[(int) dx][(int) dy] = 0xFF00FF;          }       }    } }

[lcass]

Ok so this code works for moving foward backward up down left right but how would I rotate For example minecraft rotation like that turning the camera.

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public class RENDER3D {    private core core;    public RENDER3D(core core) {       this.core = core;    }    public void drawvertex(vertex v, Camera c,double rotx,double roty) {           double cz = c.z;             double dist = Math.abs(v.z - cz);       double tx = v.x - c.x;       double ty = v.y - c.y;       double tz = v.z - c.z;       double dx = 0;       double dy = 0;       double scale = 512 /dist;                    dx = (tx) * (scale /                tz)+ (core.WIDTH / 2);          dy = (ty)* (scale / tz)+ (core.HEIGHT / 2);                   if (dx < core.WIDTH && dy < core.HEIGHT) {          if (dx > 0 && dy > 0 ) {             core.screen.map[(int) dx][(int) dy] = 0xFF00FF;          }       }    } }

[Dxu1994]

No wonder its not rotating, you're not doing anything with your input params rotx and roty.

Take a look at http://www.genesis3d.com/~kdtop/Quaternions-UsingToRepresentRotation.htm , that should get you started.

[lcass]

No wonder its not rotating, you're not doing anything with your input params rotx and roty.

Take a look at http://www.genesis3d.com/~kdtop/Quaternions-UsingToRepresentRotation.htm , that should get you started.

I know that that is the code I was using for moving that worked.

[lcass]

I think instead of sin sin its sin cos also would the radius be     cuberoot(x-xx)2+(y-yy)2+(z-zz)2)  with the 2 being square?

x'=z*sin(yaw)+x*cos(yaw)
y'=y
z'=z*cos(yaw)-x*sin(yaw)

x"=x'
y"=y'*cos(pitch)-z'*sin(pitch)
z"=y'*sin(pitch)+z'*cos(pitch)

x"'=y"*sin(roll)+x"*cos(roll)
y"'=y"*cos(roll)-x"*sin(roll)
z"'=z"

[opiop65]

No, the formula I posted works.

[lcass]

okly just checking

[lcass]

Opiop in your code what is the radius equal to is it   the   sqrt((x*x)+(y*y)+(z*z))  ??

[opiop65]

No, the radius is just half the size of the sphere. So say you want to have your code pick an object 4 tiles ahead of you, you would set the radius to 4. Thats it!

[lcass]

Oh thanks lol I was vizualising it in my head thing this is a bit odd