[9] 圆环(Ring)图形的生成算法
顶点数据的生成
1 bool YfBuildRingVertices 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 (slices < 2 || stacks < 3 || !pVerticesBuffer) 15 { 16 return false; 17 } 18 19 Yuint numVertices = slices * stacks; 20 Yuint numTriangles = slices * stacks * 2; 21 22 char* vertexPtr = (char*)pVerticesBuffer + vertexPos; 23 YsVector3* curVertexPtr = NULL; 24 Yuint nOffset = 0; 25 26 Yreal halfHeight = height * 0.5f; 27 Yreal originOffsetY = 0.0f; 28 if (originPose == YE_ORIGIN_POSE_TOP) 29 { 30 originOffsetY = -halfHeight; 31 } 32 else if (originPose == YE_ORIGIN_POSE_BOTTOM) 33 { 34 originOffsetY = halfHeight; 35 } 36 37 Yreal angle, s, c; 38 YsVector3* initVerticesPtr = new YsVector3[slices + 1]; 39 for (Yuint j = 0; j < slices; j++) 40 { 41 angle = YD_REAL_TWAIN_PI * j / slices; 42 s = yf_sin(angle); 43 c = yf_cos(angle); 44 initVerticesPtr[j].x = radius + assistRadius*s; 45 initVerticesPtr[j].y = halfHeight*c + originOffsetY; 46 initVerticesPtr[j].z = 0.0f; 47 } 48 49 for (Yuint i = 0; i < stacks; i++) 50 { 51 angle = YD_REAL_TWAIN_PI * i / stacks; 52 s = yf_sin(angle); 53 c = yf_cos(angle); 54 55 for (Yuint j = 0; j < slices; j++) 56 { 57 nOffset = (i * slices + j) * vertexStriding; 58 curVertexPtr = (YsVector3*)(vertexPtr + nOffset); 59 curVertexPtr->x = initVerticesPtr[j].x * s; 60 curVertexPtr->y = initVerticesPtr[j].y; 61 curVertexPtr->z = initVerticesPtr[j].x * c; 62 } 63 } 64 65 YD_SAFE_DELETE_ARRAY(initVerticesPtr); 66 67 return true; 68 }
三角形索引数据的生成
1 bool YfBuildRingTriIndices 2 ( 3 Yuint slices, 4 Yuint stacks, 5 YeIndexType indexType, 6 Yuint indexStriding, 7 Yuint indexPos, 8 void* pTriIndicesBuffer 9 ) 10 { 11 if (slices < 2 || stacks < 3 || !pTriIndicesBuffer) 12 { 13 return false; 14 } 15 16 Yuint numVertices = slices * stacks; 17 Yuint numTriangles = slices * stacks * 2; 18 if (indexType == YE_INDEX_16_BIT && 19 numVertices > YD_MAX_UNSIGNED_INT16) 20 { 21 return false; 22 } 23 24 // 索引赋值 25 char* indexPtr = (char*)pTriIndicesBuffer + indexPos; 26 Yuint nOffset = 0; 27 if (indexType == YE_INDEX_16_BIT) 28 { 29 YsTriIndex16* triIndexPtr = NULL; 30 for (Yuint i = 0; i < stacks; i++) 31 { 32 for (Yuint j = 0; j < slices; j++) 33 { 34 nOffset = (i*slices + j)*2 * indexStriding; 35 triIndexPtr = (YsTriIndex16*)(indexPtr + nOffset); 36 triIndexPtr->index0 = slices * i + j; 37 triIndexPtr->index1 = slices * i + (j + 1)%slices; 38 triIndexPtr->index2 = slices * ((i + 1) % stacks) + j; 39 40 nOffset += indexStriding; 41 triIndexPtr = (YsTriIndex16*)(indexPtr + nOffset); 42 triIndexPtr->index0 = slices * i + (j + 1)%slices; 43 triIndexPtr->index1 = slices * ((i + 1) % stacks) + (j + 1)%slices; 44 triIndexPtr->index2 = slices * ((i + 1) % stacks) + j; 45 } 46 } 47 } 48 else 49 { 50 YsTriIndex32* triIndexPtr = NULL; 51 for (Yuint i = 0; i < stacks; i++) 52 { 53 for (Yuint j = 0; j < slices; j++) 54 { 55 nOffset = (i*slices + j)*2 * indexStriding; 56 triIndexPtr = (YsTriIndex32*)(indexPtr + nOffset); 57 triIndexPtr->index0 = slices * i + j; 58 triIndexPtr->index1 = slices * i + (j + 1)%slices; 59 triIndexPtr->index2 = slices * ((i + 1) % stacks) + j; 60 61 nOffset += indexStriding; 62 triIndexPtr = (YsTriIndex32*)(indexPtr + nOffset); 63 triIndexPtr->index0 = slices * i + (j + 1)%slices; 64 triIndexPtr->index1 = slices * ((i + 1) % stacks) + (j + 1)%slices; 65 triIndexPtr->index2 = slices * ((i + 1) % stacks) + j; 66 } 67 } 68 } 69 70 return true; 71 }
线框索引数据的生成
1 bool YfBuildRingWireIndices 2 ( 3 Yuint slices, 4 Yuint stacks, 5 YeIndexType indexType, 6 Yuint indexStriding, 7 Yuint indexPos, 8 void* pWireIndicesBuffer 9 ) 10 { 11 if (slices < 2 || !pWireIndicesBuffer) 12 { 13 return false; 14 } 15 16 Yuint numVertices = slices * stacks; 17 Yuint numLines = slices * stacks * 2; 18 if (indexType == YE_INDEX_16_BIT && 19 numVertices > YD_MAX_UNSIGNED_INT16) 20 { 21 return false; 22 } 23 24 // 索引赋值 25 char* indexPtr = (char*)pWireIndicesBuffer + indexPos; 26 Yuint nOffset = 0; 27 if (indexType == YE_INDEX_16_BIT) 28 { 29 YsLineIndex16* lineIndexPtr = NULL; 30 for (Yuint i = 0; i < stacks; i++) 31 { 32 for (Yuint j = 0; j < slices; j++) 33 { 34 nOffset = (i*slices + j) * 2 * indexStriding; 35 lineIndexPtr = (YsLineIndex16*)(indexPtr + nOffset); 36 lineIndexPtr->index0 = slices * i + j; 37 lineIndexPtr->index1 = slices * i + (j + 1)%slices; 38 39 nOffset += indexStriding; 40 lineIndexPtr = (YsLineIndex16*)(indexPtr + nOffset); 41 lineIndexPtr->index0 = slices * i + j; 42 lineIndexPtr->index1 = slices * ((i + 1) % stacks) + j; 43 } 44 } 45 } 46 else 47 { 48 YsLineIndex32* lineIndexPtr = NULL; 49 for (Yuint i = 0; i < stacks; i++) 50 { 51 for (Yuint j = 0; j < slices; j++) 52 { 53 nOffset = (i*slices + j) * 2 * indexStriding; 54 lineIndexPtr = (YsLineIndex32*)(indexPtr + nOffset); 55 lineIndexPtr->index0 = slices * i + j; 56 lineIndexPtr->index1 = slices * i + (j + 1)%slices; 57 58 nOffset += indexStriding; 59 lineIndexPtr = (YsLineIndex32*)(indexPtr + nOffset); 60 lineIndexPtr->index0 = slices * i + j; 61 lineIndexPtr->index1 = slices * ((i + 1) % stacks) + j; 62 } 63 } 64 } 65 66 return true; 67 }
