電腦遊戲製作開發設計論壇

[enzopower]

http://thumbsnap.com/s/twzPMokU.jpg



bool CCone::UpdateVertices()
{
CONE_CUSTOMVERTEX* pVertex;
WORD* pIndices;
WORD wVertexIndex = 0;
int nCurrentSegment;

//Lock the vertex buffer
if(FAILED(m_pVertexBuffer->Lock(0, 0, (BYTE**)&pVertex, 0)))
{
LogError("<li>CCone: Unable to lock vertex buffer.");
return false;
}

//Lock the index buffer
if(FAILED(m_pIndexBuffer->Lock(0, m_dwNumOfIndices, (BYTE**)&pIndices, 0)))
{
LogError("<li>CCone: Unable to lock index buffer.");
return false;
}

float rDeltaSegAngle = (2.0f * D3DX_PI / m_nSegments);
float rSegmentLength = 1.0f / (float)m_nSegments;
float ny0 = (90.0f - (float)D3DXToDegree(atan(m_rHeight / m_rRadius))) / 90.0f;

//For each segment, add a triangle to the sides triangle list
for(nCurrentSegment = 0; nCurrentSegment < m_nSegments; nCurrentSegment++)
{
float x0 = m_rRadius * sinf(nCurrentSegment * rDeltaSegAngle);
float z0 = m_rRadius * cosf(nCurrentSegment * rDeltaSegAngle);//<=====這個zo為什麼是用cosf來算:什麼數學原理


pVertex->x = 0.0f;
pVertex->y = 0.0f + (m_rHeight / 2.0f);//<=======為什麼除2.0f來算
pVertex->z = 0.0f;
pVertex->nx = x0;
pVertex->ny = ny0; //
pVertex->nz = z0;
pVertex->tu = 1.0f - (rSegmentLength * (float)nCurrentSegment);
pVertex->tv = 0.0f;
pVertex++;


pVertex->x = x0;
pVertex->y = 0.0f - (m_rHeight / 2.0f);//
pVertex->z = z0;
pVertex->nx = x0;
pVertex->ny = ny0;
pVertex->nz = z0;
pVertex->tu = 1.0f - (rSegmentLength * (float)nCurrentSegment);
pVertex->tv = 1.0f;
pVertex++;

//Set three indices (1 triangle) per segment
*pIndices = wVertexIndex;
pIndices++;
wVertexIndex++;

*pIndices = wVertexIndex;
pIndices++;
wVertexIndex += 2;

if(nCurrentSegment == m_nSegments - 1)
{
*pIndices =1;
pIndices++;
wVertexIndex--;
}
else
{
*pIndices = wVertexIndex;
pIndices++;
wVertexIndex--;
}
}

//Create the bottom triangle fan: Center vertex
pVertex->x = 0.0f;
pVertex->y = 0.0f - (m_rHeight / 2.0f);
pVertex->z = 0.0f;
pVertex->nx = 0.0f;
pVertex->ny = -1.0f;
pVertex->nz = 0.0f;
pVertex->tu = 0.5f;
pVertex->tv = 0.5f;
pVertex++;

//Create the bottom triangle fan: Edge vertices
for(nCurrentSegment = m_nSegments; nCurrentSegment >= 0; nCurrentSegment--)
{
float x0 = m_rRadius * sinf(nCurrentSegment * rDeltaSegAngle);
float z0 = m_rRadius * cosf(nCurrentSegment * rDeltaSegAngle);

pVertex->x = x0;
pVertex->y = 0.0f - (m_rHeight / 2.0f);
pVertex->z = z0;
pVertex->nx = 0.0f;
pVertex->ny = -1.0f;
pVertex->nz = 0.0f;

float tu0 = (0.5f * sinf(nCurrentSegment * rDeltaSegAngle)) + 0.5f;
float tv0 = (0.5f * cosf(nCurrentSegment * rDeltaSegAngle)) + 0.5f;

pVertex->tu = tu0;
pVertex->tv = tv0;
pVertex++;
}

if(FAILED(m_pVertexBuffer->Unlock()))
{
LogError("<li>CCone: Unable to unlock vertex buffer.");
return false;
}

if(FAILED(m_pIndexBuffer->Unlock()))
{
LogError("<li>CCone: Unable to unlock index buffer.");
return false;
}

return true;
}

[babu61509]

Q: 這個zo為什麼是用cosf來算:什麼數學原理 ?
A: 請參考附圖一，原理就是三角函式...

Q: 為什麼除2.0f來算 ?
A: 請參考附圖二，因為坐標原點在中間...