[8] 圆面(Round)图形的生成算法

顶点数据的生成

 

bool                        YfBuildRoundVertices
(
    Yreal                   radius, 
    Yreal                   height, 
    Yuint                   slices,
    YeOriginPose            originPose, 
    Yuint                   vertexStriding, 
    Yuint                   vertexPos,
    void*                   pVerticesBuffer
)
{
    if (slices < 3 || !pVerticesBuffer)
    {
        return false;
    }

    Yuint numVertices  = slices + 1;

    char* vertexPtr = (char*)pVerticesBuffer + vertexPos;
    YsVector3* curVertexPtr   = NULL;
    Yuint nOffset = 0;

    // 圆心顶点赋值
    {
        nOffset = 0;   
        curVertexPtr = (YsVector3*)(vertexPtr + nOffset);
        curVertexPtr->x = 0.0f;
        curVertexPtr->y = height;
        curVertexPtr->z = 0.0f;
    }

    Yreal angleXZ;
    Yreal posX, posZ;        
    for (Yuint i = 0; i < slices; i++)
    {
        angleXZ = YD_REAL_TWAIN_PI * i / slices;
        posX = yf_sin(angleXZ);
        posZ = yf_cos(angleXZ);

        nOffset = (i + 1) * vertexStriding; 
        curVertexPtr = (YsVector3*)(vertexPtr + nOffset);
        curVertexPtr->x = radius * posX;
        curVertexPtr->y = height;
        curVertexPtr->z = radius * posZ;
    }

    return true;
} 

 

三角形索引数据的生成

 

bool                        YfBuildRoundTriIndices
(
    Yuint                   slices,
    YeIndexType             indexType,
    Yuint                   indexStriding,  
    Yuint                   indexPos,
    void*                   pTriIndicesBuffer
)
{
    if (slices < 3 || !pTriIndicesBuffer)
    {
        return false;
    }

    Yuint numVertices  = slices + 1;
    Yuint numTriangles = slices;
    if (indexType == YE_INDEX_16_BIT && 
        numVertices > YD_MAX_UNSIGNED_INT16)
    {
        return false;
    }

    // 索引赋值
    char* indexPtr = (char*)pTriIndicesBuffer + indexPos;
    Yuint nOffset = 0;
    if (indexType == YE_INDEX_16_BIT)
    {
        YsTriIndex16* triIndexPtr = NULL;
        for (Yuint i= 0; i < slices; i++)
        {
            nOffset = i * indexStriding;
            triIndexPtr = (YsTriIndex16*)(indexPtr + nOffset);
            triIndexPtr->index0 = 0;
            triIndexPtr->index1 = 1 + i;
            triIndexPtr->index2 = 1 + (i + 1)%slices;
        }
    }
    else
    {
        YsTriIndex32* triIndexPtr = NULL;
        for (Yuint i= 0; i < slices; i++)
        {
            nOffset = i * indexStriding;
            triIndexPtr = (YsTriIndex32*)(indexPtr + nOffset);
            triIndexPtr->index0 = 0;
            triIndexPtr->index1 = 1 + i;
            triIndexPtr->index2 = 1 + (i + 1)%slices;
        }
    }

    return true;
}     

 

线框索引数据的生成

bool                        YfBuildRoundWireIndices
(
    Yuint                   slices,
    YeIndexType             indexType,
    Yuint                   indexStriding,  
    Yuint                   indexPos,
    void*                   pWireIndicesBuffer
)
{
    if (slices < 2 || !pWireIndicesBuffer)
    {
        return false;
    }

    Yuint numVertices = slices + 1;
    Yuint numLines    = slices;
    if (indexType == YE_INDEX_16_BIT && 
        numVertices > YD_MAX_UNSIGNED_INT16)
    {
        return false;
    }

    // 索引赋值
    char* indexPtr = (char*)pWireIndicesBuffer + indexPos;
    Yuint nOffset = 0;
    if (indexType == YE_INDEX_16_BIT)
    {
        YsLineIndex16* lineIndexPtr = NULL;
        for (Yuint i= 0; i < slices; i++)
        {
            nOffset = i * indexStriding;
            lineIndexPtr = (YsLineIndex16*)(indexPtr + nOffset);
            lineIndexPtr->index0 = 1 + i;
            lineIndexPtr->index1 = 1 + (i + 1)%slices;
        }
    }
    else
    {
        YsLineIndex32* lineIndexPtr = NULL;
        for (Yuint i= 0; i < slices; i++)
        {
            nOffset = i * indexStriding;
            lineIndexPtr = (YsLineIndex32*)(indexPtr + nOffset);
            lineIndexPtr->index0 = 1 + i;
            lineIndexPtr->index1 = 1 + (i + 1)%slices;
        }
    }

    return true;
}