Perspective的矩阵计算方法

高通VR里面的通用透视矩阵计算方法

 static public Matrix4x4 Perspective(float left, float right, float bottom, float top, float near, float far)
 {
     float x = 2.0F * near / (right - left);
     float y = 2.0F * near / (top - bottom);
     float a = (right + left) / (right - left);
     float b = (top + bottom) / (top - bottom);
     float c = -(far + near) / (far - near);
     float d = -(2.0F * far * near) / (far - near);
     float e = -1.0F;
     Matrix4x4 m = new Matrix4x4();
     m[0, 0] = x;
     m[0, 1] = 0;
     m[0, 2] = a;
     m[0, 3] = 0;
     m[1, 0] = 0;
     m[1, 1] = y;
     m[1, 2] = b;
     m[1, 3] = 0;
     m[2, 0] = 0;
     m[2, 1] = 0;
     m[2, 2] = c;
     m[2, 3] = d;
     m[3, 0] = 0;
     m[3, 1] = 0;
     m[3, 2] = e;
     m[3, 3] = 0;
     return m;
 }
 float baseLen = 0.06f;//一般设为0.05~0.08之间
Frustums = new ViewFrustum[2];
Frustums[0].left = -baseLen;
Frustums[0].right = baseLen;
Frustums[0].top = baseLen;
Frustums[0].bottom = -baseLen;
Frustums[0].near = 0.061f;
Frustums[0].far = 1000f;

 _projection = Perspective(frustum.left, frustum.right, frustum.bottom, frustum.top, frustum.near, _camera.farClipPlane);
 public void OnPreCull()
        {
            if (_camera != null)
            {
                //_camera.fieldOfView = 30f;
            _camera.projectionMatrix = _projection;

                //_camera.aspect = 1440/2560f;
            }
        }

此处的值和输出的单眼分辨率比率有关，通常是成正比，因为现在输出的是1:1的图像，所以现在需要将left,right和top,bottom保持一致,否则left/bottom=aspect=width/height;