关于三维物体缩放并转换坐标系的问题

[leefantasy]

3ds文件有自己的一套坐标系，用opgl集成一个场景，导入多个3ds文件，对其进行包围盒视锥裁剪，需要将不同3ds文件中的点转换为统一坐标系下的坐标。

遇到这种情况，首先考虑的是平移操作。这个操作很简单。代码如下：

void C3DModleManager::CalculateRealCoord(t3DModel &TempModel, CS3dVector pos)
{
	float g_max_x = -100000000;
	float g_min_x = 100000000;
	float g_max_y = -100000000;
	float g_min_y = 100000000;
	float g_max_z = -1000000000;
	float g_min_z = 1000000000;
	for (int i=0; i<TempModel.numOfObjects; i++)
	{
		float max_x = -10000000;
		float min_x = 10000000;
		float max_y = -10000000;
		float min_y = 10000000;
		float max_z = -10000000;
		float min_z = 10000000;

		for (int j=0; j<TempModel.pObject[i].numOfVerts; j++)
		{
			CVector3Simple EveryVert = TempModel.pObject[i].pVerts[j];

			TempModel.pObject[i].pVertsGloabal[j].x = TempModel.pObject[i].pVerts[j].x + (pos.x-TempModel.m_Center.x);
			TempModel.pObject[i].pVertsGloabal[j].y = TempModel.pObject[i].pVerts[j].y + (pos.y-TempModel.m_Center.y);
			TempModel.pObject[i].pVertsGloabal[j].z = TempModel.pObject[i].pVerts[j].z + (pos.z-TempModel.m_Center.z);
			
			EveryVert.x = TempModel.pObject[i].pVertsGloabal[j].x;
			EveryVert.y = TempModel.pObject[i].pVertsGloabal[j].y;
			EveryVert.z = TempModel.pObject[i].pVertsGloabal[j].z;

			if(EveryVert.x>g_max_x)
				g_max_x = EveryVert.x;
			if(EveryVert.x<g_min_x)
				g_min_x = EveryVert.x;
			if(EveryVert.y>g_max_y)
				g_max_y = EveryVert.y;
			if(EveryVert.y<g_min_y)
				g_min_y = EveryVert.y;
			if(EveryVert.z>g_max_z)
				g_max_z = EveryVert.z;
			if(EveryVert.z<g_min_z)
				g_min_z = EveryVert.z;
			if(EveryVert.x>max_x)
				max_x = EveryVert.x;
			if(EveryVert.x<min_x)
				min_x = EveryVert.x;
			if(EveryVert.y>max_y)
				max_y = EveryVert.y;
			if(EveryVert.y<min_y)
				min_y = EveryVert.y;
			if(EveryVert.z>max_z)
				max_z = EveryVert.z;
			if(EveryVert.z<min_z)
				min_z = EveryVert.z;
		}
		TempModel.pObject[i].m_BoundaryGlobal.maxx = max_x+1.0;
		TempModel.pObject[i].m_BoundaryGlobal.maxy = max_y+1.0;
		TempModel.pObject[i].m_BoundaryGlobal.maxz = max_z+1.0;
		TempModel.pObject[i].m_BoundaryGlobal.minx = min_x-1.0;
		TempModel.pObject[i].m_BoundaryGlobal.miny = min_y-1.0;
		TempModel.pObject[i].m_BoundaryGlobal.minz = min_z-1.0;
	}
	TempModel.m_BoundaryGlobal.maxx = g_max_x;
	TempModel.m_BoundaryGlobal.maxy = g_max_y;
	TempModel.m_BoundaryGlobal.maxz = g_max_z;
	TempModel.m_BoundaryGlobal.miny = g_min_y;
	TempModel.m_BoundaryGlobal.minz = g_min_z;
}

调用语句为

my3DSCene.m_3DModle.CalculateRealCoord(my3DSCene.m_3DModle.m_ModelList[Index], my3DSCene.m_3DModle.m_ModelList[Index].m_Postion);

在缩放的时候，用如下函数：

void C3DModleManager::CalculateScaleCoord(t3DModel &TempModel, int EditAxis, float fScale)
{
	for (int i=0; i<TempModel.numOfObjects; i++)
	{
		for (int j=0; j<TempModel.pObject[i].numOfVerts; j++)
		{
			switch (EditAxis)
			{
			case 1:
				TempModel.pObject[i].pVerts[j].x = TempModel.pObject[i].pVerts[j].x * fScale;
				break;
			case 2:
				TempModel.pObject[i].pVerts[j].y = TempModel.pObject[i].pVerts[j].y * fScale;
				break;
			case 3:
				TempModel.pObject[i].pVerts[j].z = TempModel.pObject[i].pVerts[j].z * fScale;
				break;
			case 0:
				TempModel.pObject[i].pVerts[j].x = TempModel.pObject[i].pVerts[j].x * fScale; 
				TempModel.pObject[i].pVerts[j].y = TempModel.pObject[i].pVerts[j].y * fScale;
				TempModel.pObject[i].pVerts[j].z = TempModel.pObject[i].pVerts[j].z * fScale;
				break;
			default:
				break;
			}
			
		}
	}
}

之后再将缩放完毕的坐标进行坐标平移转换。

但是问题在于单独进行平移操作，视锥裁剪是正确的。如果进行了缩放之后，再平移，就错误了。我想错误可能是处在缩放的环节。还请高手看看错误在哪里？

[zinking3]

啊，强烈建议你使用向量代数，看着太头晕了

[ryfdizuo]

我想错误可能是处在缩放的环节。还请高手看看错误在哪里？

代码没有细看，缩放后会改变顶点的法向量，缩放后重新单位化试试看，