Three.js：将3d位置转换为2d屏幕位置 [英] Three.js: converting 3d position to 2d screen position

问题描述

我有一个位置为（x，y，z）的3D对象。如何计算该对象的屏幕位置（x，y）？

I have a 3D object with the position(x,y,z). How can I calculate the screen position(x,y) of that object?

我已经搜索过它，一个解决方案是我必须找出投影矩阵然后通过该矩阵乘以3D位置点以将其投影到某个2D观察表面（计算机屏幕）上。但是我不知道如何在Three.js中找到这个矩阵。

I have search for it and one solution is that I have to find out the projection matrix then multiply 3D position point by this matrix to project it onto some 2D viewing surface (computer screen). But I have no idea how to find this matrix in Three.js.

我尝试这样的转换函数，但结果不正确

I try a convert function like this but it give incorrect result

function Point3DToScreen2D(point3D){
            var screenX = 0;
            var screenY = 0;
            var inputX = point3D.x - camera.position.x;
            var inputY = point3D.y - camera.position.y;
            var inputZ = point3D.z - camera.position.z;
            var aspectRatio = renderer.domElement.width / renderer.domElement.height;
            screenX = inputX / (-inputZ * Math.tan(camera.fov/2));
            screenY = (inputY * aspectRatio) / (-inputZ * Math.tan(camera.fov / 2));
            screenX = screenX * renderer.domElement.width;
            screenY = renderer.domElement.height * (1-screenY);
            return {x: screenX, y: screenY};
        }

提前感谢。

推荐答案

我最后通过这段代码完成了这项工作：

I make it done by this code at last:

注意：div参数= canvas dom element。

Note: div parameter = canvas dom element.

function toScreenXY( position, camera, div ) {
            var pos = position.clone();
            projScreenMat = new THREE.Matrix4();
            projScreenMat.multiply( camera.projectionMatrix, camera.matrixWorldInverse );
            projScreenMat.multiplyVector3( pos );

            var offset = findOffset(div);

            return { x: ( pos.x + 1 ) * div.width / 2 + offset.left,
                 y: ( - pos.y + 1) * div.height / 2 + offset.top };

        }
function findOffset(element) { 
          var pos = new Object();
          pos.left = pos.top = 0;        
          if (element.offsetParent)  
          { 
            do  
            { 
              pos.left += element.offsetLeft; 
              pos.top += element.offsetTop; 
            } while (element = element.offsetParent); 
          } 
          return pos;
        } 

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