processing - 在处理中渲染近多边形对象的剪裁

Question

我在 Processing 中对 3D 对象建模，遇到一个问题，即当对象离相机太近时，它们的渲染会被剪裁(即不渲染离相机最近的对象位)。这在 P3D 和 OPENGL 模式下都会发生。下图右图说明:

知道如何阻止这种情况发生吗？代码如下，可在 openprocessing.org 在线测试.非常感谢。

void setup() {
  size(600, 400, P3D);
  stroke(0);
  rectMode(CENTER);
  fill(200);

  // initialise camera variables
  scaleY = PI/height;
  scaleX = 2*PI/width;
  camDir = PI/3;
  camElev = PI/2;
  MouseX = width/2;
  MouseY = height/3;
  turnCamera();
  camF_rel = setVector(camDir, camElev);
}

void draw() {
  background(255);

  // CAMERA & CONTROL OPERATIONS
  MouseX = constrain(mouseX, 0, width);
  MouseY = constrain(mouseY, 0, height);
  setCamera();
  camera(camP.x, camP.y, camP.z, camF_abs.x, camF_abs.y, camF_abs.z, 0, 0, -1);

  // DRAW ENVIRONMENT
  // checkered plane
  fill(150,200,255);
  for (int i=-10; i<10; i++) {
    for (int j=-10; j<10; j++) {
      noStroke();
      if ((i+j)%2 == 0) rect(i*50, j*50, 50, 50);
    }
  }
  // vertical line
  noFill();
  stroke(100);
  box(1000);
}


// camera position and focus variables
PVector camP = new PVector(0, 1200, 700); // camera position
PVector camF_abs = new PVector();     // camera focus (absolute position)
PVector camF_rel = new PVector();     // camera focus (relative vector)
float camDir, camElev;                // last camera bearing/elevation angles
float mx, my;                         // last mouse X/Y
float MouseX, MouseY;                 // replicate inbuilt mouse variables
float scaleY;                         // scale mouseY inputs to vertical movement
float scaleX;                         // scale mouseX inputs to horizontal movement
int direction = 0;                    // code for controling movement
float moveSpeed = 10;                 // overall controls responsiveness


// main camera calculation operations
void setCamera() {
  camF_rel = setVector(camDir, camElev);
  if (direction >= 1 & direction <= 4) moveCamera(moveSpeed);
  if (direction >= 5 & direction <= 6) elevCamera(moveSpeed);

  camF_abs = camF_rel.get();
  camF_abs.add(camP);
}


PVector setVector(float dir, float elev){
  //generic function to calculate the PVector based on radial coordinates
  PVector v = new PVector(cos(dir), sin(dir), 0);
  float fz = -sin(elev);
  float fy = sqrt(1-pow(fz, 2));
  v.mult(fy);
  v.z = fz;
  return(v);
}


void moveCamera (float speed) {
  PVector moveto = new PVector();

  // left / right movement
  if (direction%2 == 0) {
    float dir = 0;
    if (direction == 2) dir = camDir + PI/2;  // right
    else                dir = camDir - PI/2;  // left
    PVector v = setVector(dir, 0);
    v.mult(speed);
    camP.add(v);
  }

  // forward / backward movement
  else {
    moveto = camF_rel.get();
    if (direction == 1) moveto.mult(-1); // forward
  }

  moveto.normalize();
  moveto.mult(speed);
  camP.sub(moveto);
}


void turnCamera(){
  float x = MouseX - mx;
  float x_scaled = x * scaleX;
  float y = MouseY - my;
  float y_scaled = y * scaleY;
  camDir += x_scaled;
  camElev += y_scaled;
  mx = MouseX;
  my = MouseY;

}


void elevCamera (float speed) {
  if (direction == 5) {  // lower camera
    camP.z -= speed;               
    camF_abs.z -= speed;
  }
  else {                 // raise camera
    camP.z += speed;               
    camF_abs.z += speed;
  }
}


void keyPressed() {
  if      (keyCode == 38 | key == 'w') direction = 1;  // move forward
  else if (keyCode == 39 | key == 'd') direction = 2;  // move right
  else if (keyCode == 40 | key == 's') direction = 3;  // move backward
  else if (keyCode == 37 | key == 'a') direction = 4;  // move left
  else if (key == 'z')                 direction = 5;  // lower camera
  else if (key == 'x')                 direction = 6;  // raise camera
}


void keyReleased() {
  direction = 0;
}


void mouseMoved() {  // turns the camera
  turnCamera();
}

Answer 1

您可以通过调用 perspective() 来控制近距离和远距离的裁剪距离。在处理中发挥作用。

将这些行添加到您的 setup() 中，问题就消失了:

float fov = PI/3.0;
float cameraZ = (height/2.0) / tan(fov/2.0);
float nearClippingDistance = 0.01; // default is cameraZ/10.0
perspective(fov, float(width)/float(height), nearClippingDistance, cameraZ*10.0);

您可以通过在之前几行之后添加此行来找出草图中的默认近裁剪距离:

println(cameraZ/10.0); // output: 34.6410