Fit 3d box in camera view

Programming Questions

janjacobsv

in Programming Questions • 4 months ago

Hello I am having a problem with fitting 3d objects in my camera view :( can anyone please help?

The basic problem is this:
I have a 3d box(minx,miny,minz,maxx,maxy,maxz)
and a camera looking at the box in the direction (ax,ay,az)
how can I make sure the box fits in the view(width, height)?

thanks!

Replies(3)

tfguy44

Re: Fit 3d box in camera view

4 months ago

What exactly do you mean by "fits"?

I mean, here's a 3D box (done in wireframe) who's front face is the 2D plane that you would normally be drawing on in a 2D sketch. In some sense, it "fits" perfectly inside the sketch window.

final int S = 220;
void setup(){
size(S,S,P3D);
}
void draw(){
background(0);
noFill();
stroke(255);
translate(S/2,S/2,-S/2-1);
scale(S);
box(1);
}

Or are you trying to tell if you can see some box if you're looking in a particular direction?
Or what?

Can you post some code to demonstrate your problem?

janjacobsv

Re: Fit 3d box in camera view

4 months ago

This is the basic problem:
a box somewhere in 3d space and a camera with a looking direction which can change, and a zoom value. What I am looking for is the value of "zoom" so that the box fits exactly in the drawing window.

PVector minVec, maxVec, lookDir;
float zoom;

void setup() {
size (300, 300, P3D );
//bbox values
minVec = new PVector(10, 20, 30 );
maxVec = new PVector(60, 50, 40);
//looking direction, can vary
lookDir = new PVector(0.5, 0.5, 0.3);
zoom = 100;
}

void draw() {
background(255);
//camera, eye values start at center of box and added are looking direction times zoom
camera(60+lookDir.x*zoom, 50+lookDir.y*zoom, 40+lookDir.z*zoom, // eyeX, eyeY, eyeZ
60, 50, 40, // centerX, centerY, centerZ
0, 0, 1); // upX, upY, upZ

fill(150);
translate(60, 50, 40);
box(maxVec.x-minVec.x, maxVec.y-minVec.y, maxVec.z-minVec.z);
}

janjacobsv

Re: Fit 3d box in camera view

4 months ago

Well got it somewhat working,
minVec and maxVec describe a BBox
Press x for a new random viewing direction, the camera kind of keeps the box in the view area. Not perfect, I would like to have the objCentre value move so it would fit the box better in view and have a better fit, but itll do. Any suggestions always welcome.

PVector minVec, maxVec, objCentre, lookDir, viewPlanePoint;
float zoom;

void setup() {
size (300, 300, P3D );

//bbox values
minVec = new PVector(10, 15, 20 );
maxVec = new PVector(50, 45, 40);

objCentre = new PVector();

zoom = 100;
//looking direction, can vary
lookDir = new PVector(.1, .1, .4);
}

void draw() {
background(255);

lookDir.normalize();
viewPlanePoint = new PVector((maxVec.x+minVec.x)/2, ( maxVec.y+minVec.y)/2, ( maxVec.z+minVec.z)/2);

//camera, eye values start at center of box and added are looking direction times zoom
camera( objCentre.x+lookDir.x*zoom, objCentre.y+lookDir.y*zoom, objCentre.z+lookDir.z*zoom, // eyeX, eyeY, eyeZ
objCentre.x, objCentre.y, objCentre.z, // centerX, centerY, centerZ
0, 1, 0); // upX, upY, upZ

//visualise box
pushMatrix();
fill(150, 150, 150, 150);
translate((maxVec.x+minVec.x)/2, ( maxVec.y+minVec.y)/2, ( maxVec.z+minVec.z)/2);
box(maxVec.x-minVec.x, maxVec.y-minVec.y, maxVec.z-minVec.z);
fill(200, 0, 0);
noStroke();
sphere(1);
stroke(0);
popMatrix();

PVector pv = new PVector();
PVector tv = new PVector();
PVector nv = new PVector();
PVector dotv = new PVector();
PVector projPoint = new PVector();
float minX = 1000;
float minY = 1000;
float minZ = 1000;
float maxX = -1000;
float maxY = -1000;
float maxZ = -1000;
for (int i =0; i<8; i++) {
    if (i==0) {
      tv =new PVector(minVec.x, minVec.y, minVec.z);
    }
    else if (i==1) {
      tv =new PVector(maxVec.x, minVec.y, minVec.z);
    }
    else if (i==2) {
      tv =new PVector(minVec.x, maxVec.y, minVec.z);
    }
    else if (i==3) {
      tv =new PVector(minVec.x, minVec.y, maxVec.z);
    }
    else if (i==4) {
      tv =new PVector(minVec.x, maxVec.y, maxVec.z);
    }
    else if (i==5) {
      tv =new PVector(maxVec.x, minVec.y, maxVec.z);
    }
    else if (i==6) {
      tv =new PVector(maxVec.x, maxVec.y, minVec.z);
    }
    else {
      tv =new PVector(maxVec.x, maxVec.y, maxVec.z);
    }
    // get planar projection of boxpoint on camera viewing plane
    PVector.sub(tv, viewPlanePoint, pv);
    float dotp = PVector.dot(pv, lookDir);
    PVector.mult(lookDir, dotp, dotv);
    PVector.sub(tv, dotv, projPoint);

    if (projPoint.x<minX) {
      minX = projPoint.x;
    }
    else if (projPoint.x>maxX) {
      maxX = projPoint.x;
    }

    if (projPoint.y<minY) {
      minY = projPoint.y;
    }
    else if (projPoint.y>maxY) {
      maxY = projPoint.y;
    }

    if (projPoint.z<minZ) {
      minZ = projPoint.z;
    }
    else if (projPoint.z>maxZ) {
      maxZ = projPoint.z;
    }
}
objCentre.x = ((minX+maxX)/2);
objCentre.y = ((minY+maxY)/2);
objCentre.z = ((minZ+maxZ)/2);

float vPlaneCross = dist(minX, minY, minZ, maxX, maxY, maxZ);

//tan cam fov = vPlaneCross / zoom dist
float zoomDist = (vPlaneCross/2)/tan(PI/6);
zoom = zoom+ (1*zoomDist-zoom)/10;
}

void keyPressed()
{
if (key == 'x')
{
    float x =random(-1, 1);
    float y =random(-1, 1);
    float z =random(-1, 1);
    lookDir = new PVector(x, y, z);
}
}

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