[18] 螺旋楼梯(Spiral Stairs)图形的生成算法

1 bool YfBuildSpiralStairsVertices  2 (  3  Yreal radius,  4  Yreal assistRadius,  5  Yreal height,  6  Yuint slices,  7  Yuint stacks,  8  YeOriginPose originPose,  9  Yuint vertexStriding, 10  Yuint vertexPos, 11     void* pVerticesBuffer 12 ) 13 { 14     if (stacks < 1 || slices < 3 || !pVerticesBuffer) 15  { 16         return false; 17  } 18     Yuint numVertices  = 2 + stacks * 4; 19     //Yuint numTriangles = stacks * 8;
20
21     char* vertexPtr = (char*)pVerticesBuffer + vertexPos; 22     YsVector3* curVertexPtr = NULL; 23     Yuint nOffset = 0; 24
25     Yreal originOffsetY = 0.0f; 26     if (originPose == YE_ORIGIN_POSE_TOP) 27  { 28         originOffsetY = -height; 29  } 30     else if (originPose == YE_ORIGIN_POSE_CENTER) 31  { 32         originOffsetY = -height * 0.5f; 33  } 34
35     Yreal fStepTexcoord = 1.0f / (stacks - 1); 36     Yreal fStepHeight = height / stacks; 37     Yreal fStepAngle = YD_REAL_TWAIN_PI / slices; 38
39  Yreal angleXZ; 40  Yreal posX, posZ; 41     for (Yuint i = 0; i <= stacks; i++) 42  { 43         angleXZ = i * fStepAngle; 44         posX = yf_sin(angleXZ); 45         posZ = yf_cos(angleXZ); 46
47         nOffset = i * 4 * vertexStriding; 48         curVertexPtr = (YsVector3*)(vertexPtr + nOffset); 49         curVertexPtr->x = radius * posX; 50         curVertexPtr->y = i * fStepHeight + originOffsetY; 51         curVertexPtr->z = radius * posZ; 52
53         nOffset += vertexStriding; 54         curVertexPtr = (YsVector3*)(vertexPtr + nOffset); 55         curVertexPtr->x = assistRadius * posX; 56         curVertexPtr->y = i * fStepHeight + originOffsetY; 57         curVertexPtr->z = assistRadius * posZ; 58
59         if (i == stacks) 60  { 61             continue; 62  } 63
64         nOffset += vertexStriding; 65         curVertexPtr = (YsVector3*)(vertexPtr + nOffset); 66         curVertexPtr->x = radius * posX; 67         curVertexPtr->y = (i+1) * fStepHeight + originOffsetY; 68         curVertexPtr->z = radius * posZ; 69
70         nOffset += vertexStriding; 71         curVertexPtr = (YsVector3*)(vertexPtr + nOffset); 72         curVertexPtr->x = assistRadius * posX; 73         curVertexPtr->y = (i+1) * fStepHeight + originOffsetY; 74         curVertexPtr->z = assistRadius * posZ; 75  } 76
77     return true; 78 }

1 bool YfBuildSpiralStairsTriIndices  2 (  3  Yuint stacks,  4  YeIndexType indexType,  5  Yuint indexStriding,  6  Yuint indexPos,  7     void* pTriIndicesBuffer  8 )  9 { 10     return YfBuildStairsTriIndices( 11  stacks, 12  indexType, 13  indexStriding, 14  indexPos, 15  pTriIndicesBuffer 16  ); 17 } 18
19 bool YfBuildSpiralStairsWireIndices 20 ( 21  Yuint stacks, 22  YeIndexType indexType, 23  Yuint indexStriding, 24  Yuint indexPos, 25     void* pWireIndicesBuffer 26 ) 27 { 28     return YfBuildStairsWireIndices( 29  stacks, 30  indexType, 31  indexStriding, 32  indexPos, 33  pWireIndicesBuffer 34  ); 35 }