screenPointToWorld正在處理中

經過一組變換后，我想畫出滑鼠所在的位置。這與繪圖本身無關，當應用某種變換時，它會在 xyz 中得到重點。對于這篇文章，我只是將問題縮小到最低限度。這是我想要開始作業的代碼：

void setup() {
  size(600, 600, P3D);
}


public void draw() {
    background(0);
    translate(width/2, height/2, -100);
    pushMatrix();
    float rot_y = map(mouseX, 0, width, 0, TWO_PI);
    rotateY(rot_y);
    int dim = min(width, height) / 2;
    noFill();
    stroke(255);
    box(dim);
    

    float z = 0; // or ((PGraphicsOpenGL)g).cameraNear;?
    PVector pos = screenPointToWorld(mouseX, mouseY, z);
    translate(pos.x, pos.y, pos.z);
    box(5); // should appear where the mouse is!

    popMatrix();
}

這是統一的 screenPointToWorld 的模擬： https ://docs.unity3d.com/ScriptReference/Camera.ScreenToWorldPoint.html

我確實找到了這個，這對我有幫助： https ://answers.unity.com/questions/1293942/calculation-behind-camerascreentoworldpoint.html

這些是我的 2 次嘗試：

PVector screenPointToWorld(PVector sp) {
    PGraphicsOpenGL _g = ((PGraphicsOpenGL)g);

    // cam.worldToCameraMatrix?? Not sure about this one
    PMatrix3D final_matrix = new PMatrix3D(_g.modelview);
    final_matrix.apply(_g.projection);
    final_matrix.invert();

    float[] in = new float[4];

    in[0] = sp.x;
    in[1] = sp.y;
    in[2] = sp.z;
    in[3] = 1.0f;  

    /* Map x and y from window coordinates */
    // in[0] = (in[0] - viewport[0]) / viewport[2];
    // in[1] = (in[1] - viewport[1]) / viewport[3];
    in[0] = in[0] / width;
    in[1] = in[1] / height;

    /* Map to range -1 to 1 */
    in[0] = in[0] * 2 - 1;
    in[1] = in[1] * 2 - 1;
    in[2] = in[2] * 2 - 1;

    float[] out = new float[4];

    final_matrix.mult(in, out);

    out[0] /= out[3];
    out[1] /= out[3];
    out[2] /= out[3];
    
    return new PVector(out[X], out[Y], out[Z]);
}

PVector screenPointToWorld2(PVector sp) {
    PGraphicsOpenGL _g = ((PGraphicsOpenGL)g);

    // cam.worldToCameraMatrix?? Not sure about this one
    PMatrix3D worldToCameraMatrix = new PMatrix3D(_g.camera);
    worldToCameraMatrix.invert();

    PMatrix3D world2Screen = new PMatrix3D(_g.projection);
    world2Screen.apply(worldToCameraMatrix);
    
    PMatrix3D screen2World = new PMatrix3D(world2Screen);
    screen2World.invert();

    float[] inn = new float[4];

    inn[0] = 2.0f * (sp.x / width) - 1.0f;
    inn[1] = 2.0f * (sp.y / height) - 1.0f;
    inn[2] = _g.cameraNear;
    inn[3] = 1.0f;  

    float[] pos = new float[4];
    screen2World.mult(inn, pos);

    int X = 0;
    int Y = 1;
    int Z = 2;
    int W = 3;

    pos[W] = 1.0f / pos[W];

    pos[X] *= pos[W];
    pos[Y] *= pos[W];
    pos[Z] *= pos[W];

    return new PVector(pos[X], pos[Y], pos[Z]);
}

但它們是不正確的，我不知道為什么。我希望有人能幫幫忙。

更新：

如果我愿意，我可以在滑鼠位置上畫一個框，這不是問題。目標是讓 screenPointToWorld 按預期作業。這是一個更大的程式的一部分，它不適合在 stackoverflow 帖子中。我很清楚 pushMatrix 和 popMatrix 以及如何使用它們。但是在這種情況下它們沒有用。

uj5u.com熱心網友回復：

以下在我的 Mac 上運行。我使用了您發布的第二個函式 screenPointToWorld。除了將 x,y,z 坐標更改為 PVector 以便可以將其傳遞給 screenPointToWorld 之外，我沒有對代碼做太多事情。我看到一個由滑鼠旋轉的三維框。

PVector v;

void setup() {
  size(600, 600, P3D);
}

PVector screenPointToWorld(PVector sp) {
  PGraphicsOpenGL _g = ((PGraphicsOpenGL)g);

  // cam.worldToCameraMatrix?? Not sure about this one
  PMatrix3D worldToCameraMatrix = new PMatrix3D(_g.camera);
  worldToCameraMatrix.invert();

  PMatrix3D world2Screen = new PMatrix3D(_g.projection);
  world2Screen.apply(worldToCameraMatrix);

  PMatrix3D screen2World = new PMatrix3D(world2Screen);
  screen2World.invert();

  float[] inn = new float[4];

  inn[0] = 2.0f * (sp.x / width) - 1.0f;
  inn[1] = 2.0f * (sp.y / height) - 1.0f;
  inn[2] = _g.cameraNear;
  inn[3] = 1.0f;

  float[] pos = new float[4];
  screen2World.mult(inn, pos);

  int X = 0;
  int Y = 1;
  int Z = 2;
  int W = 3;

  pos[W] = 1.0f / pos[W];

  pos[X] *= pos[W];
  pos[Y] *= pos[W];
  pos[Z] *= pos[W];

  return new PVector(pos[X], pos[Y], pos[Z]);
}

public void draw() {
  background(0);
  translate(width/2, height/2, -100);
  pushMatrix();
  float rot_y = map(mouseX, 0, width, 0, TWO_PI);
  rotateY(rot_y);
  int dim = min(width, height) / 2;
  noFill();
  stroke(255);
  box(dim);

  float z = 0; // or ((PGraphicsOpenGL)g).cameraNear;?
  v = new PVector(mouseX, mouseY, z);
  PVector pos = screenPointToWorld(v);
  translate(pos.x, pos.y, pos.z);
  box(5); // should appear where the mouse is!

  popMatrix();
}

本次修訂顛倒了方框的順序；小家伙現在首先被要求。翻譯是累積的，所以如果它排在第一位，它將被鎖定到滑鼠坐標。不確定這是否是您希望實作的目標，但您的初始代碼似乎只是試圖更改小盒子的坐標。如果是這種情況，您可能不需要 screenPointToWorld 函式。

void setup() {
  size(800, 800, P3D);
}

void draw() {
  background(0);
  translate(mouseX, mouseY);
  box(5);
  translate(200,200);
  float rot_y = map(mouseX, 0, width, 0, TWO_PI);
  rotateY(rot_y);
  noFill();
  stroke(255);
  box(width/4);
}

uj5u.com熱心網友回復：

這就是目的pushMatrix()和popMatrix()目的。他們讓您應用然后洗掉轉換。如果您正確平衡推送和彈出，您將最終回到螢屏坐標：

public void draw() {
    background(0);
    
    pushMatrix(); // push a new transformation matrix for the big box
      translate(width/2, height/2, -100);
      float rot_y = map(mouseX, 0, width, 0, TWO_PI);
      rotateY(rot_y);
      int dim = min(width, height) / 2;
      noFill();
      stroke(255);
      box(dim);
    popMatrix(); // done with the big box--revert to screen coords

    translate(mouseX, mouseY); // move to the mouse point to draw the small box
    box(5); 
}

uj5u.com熱心網友回復：

如果你愿意，讓它變得困難，但這很容易。

void setup() {
  size(600, 600, P3D);
}

public void draw() {
    background(0);
    translate(width/2, height/2, -100);
    float rot_y = map(mouseX, 0, width, 0, TWO_PI);
    rotateY(rot_y);
    int dim = min(width, height) / 2;
    noFill();
    stroke(255);
    box(dim);
    // Reverse rotation and first translation
    rotateY(-rot_y);
    translate(-width/2, -height/2, 100);
    // Set a new translation so small box will follow cursor
    translate(mouseX,mouseY);
    box(5); // should appear where the mouse is!
}

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