问过程性纹理uv误差

EN

     Vector2[] CalculateU(float[] leftXMap, float[] rightXMap) {
         int length = leftXMap.Length;
         float totalHeight = (length - 1) * 1;       // distance between two vertices vertically is 1
         float uvheight = totalHeight * uvScale;     // uvScale is 2, purpose is to map a plane's v(vertically), into a range of [0, 0.5]..
         Vector2[] UMap = new Vector2[length * 2];
         for(int i = 0; i < length; i++) {
             float left = leftXMap[i];
             float right = rightXMap[i];
             // make left and right positive.
             while (left < 0) {
                 left += uvheight;
             }
             while(right < 0) {
                 right += uvheight;
             }
             float leftu = (left % uvheight) / uvheight;
             float leftv = (i / (float)(length-1)) / uvScale;
             float rightu = (right % uvheight) / uvheight;
             float rightv = leftv; //(i / (float)length) / 2f;
             UMap[i * 2] = new Vector2(leftu, leftv);
             UMap[i * 2 + 1] = new Vector2(rightu, rightv);

         }
     }