页面滚动效果

Question

我想在着色器中创建页面滚动效果。所以我有一个XZ平面点y = 0。现在我假设一个具有R半径和Inf的密室。高度在Y轴上以一定角度旋转时在平面上隐藏。查看图片：

我希望有一个公式，使纸可以结转在给定的XZ方向的领域。

什么我做的是：

float2 currPoint = gl_Vertex.xz; 
float2 normDir = normalize(-1, 0); //direction at which paper will start rolling out. 
float cylRadius = 1.f; 
float dist = sqrt(normDir.x *vi.x * vi.x + normDir.y *vi.y * vi.y); 
float beta = dist/cylRadius; 

float3 outPos = 0; 
outPos.x = currPoint.x + N.x * cylRadius * sin(beta); 
outPos.z = cylRadius * (1 -cos(beta)); 
outPos.y = currPoint.y + N.y * cylRadius * sin(beta); 

但它仅适用于normDir = normalize(-1, 0)的情况下，在其他情况下，结果并不如预期。

Answer 1

我this.My实现是基于帕维尔的翻页执行力度（http://nomtek.com/page-flip-3d/）

这里是HLSL代码。

float DistToLine(float2 pt1, float2 pt2, float2 testPt) 
    { 
     float2 lineDir = pt2 - pt1; 
     float2 perpDir = float2(lineDir.y, -lineDir.x); 
     float2 dirToPt1 = pt1 - testPt; 
     return (dot(normalize(perpDir), dirToPt1)); 
    } 

    float3 Roll(float2 pos) //per vertex 
    { 
     float time = param1.z ; 
     float t = (time); 
     float2 A = float2(0 , 1); //tweak these 4 variables for the direction of Roll 
     float2 B = float2(5.f , 1); // 
     float2 C = float2(1 , 0); // 
     float2 D = float2(0 , 0); // 

     float2 P1 = lerp(B , A , time) ; 
     float2 P2 = lerp(C , D , time) ; ; 
     float2 N = normalize(float2(-(P2-P1).y , (P2-P1).x)); 
     float dist = DistToLine(P1 , P2 , float2(pos.x , pos.y)); 

     float3 vOut; 
     if (dist > 0) 
     { 
      float distFromEnd = DistToLine(C , B , float2(pos.x , pos.y)) ; 
      float R = lerp(.1 , .13 , distFromEnd); 

      float2 p = pos - N * dist; 
      float alpha = dist/R; 
      float sinAlpha = R * sin(alpha); 
      vOut.x = p.x + N.x * sinAlpha; 
      vOut.y = p.y + N.y * sinAlpha; 
      vOut.z = (1 - cos(alpha)) * R; 
     } 
     else 
     { 
      vOut.x = pos.x; 
      vOut.y = pos.y; 
      vOut.z = 0; 
     } 
     return vOut; 
    }