一段时间以来，我在 OpenGL 中遇到了相机旋转问题。
我尝试通过鼠标移动来旋转相机，但相机只是在闪烁（相机发现的物体在闪烁）。
我初始化相机如下：
Camera::Camera(float x, float y, float z) {
memset(Transform, 0, 16*sizeof(float));
Transform[0] = 1.0f;
Transform[5] = 1.0f;
Transform[10] = 1.0f;
Transform[15] = 1.0f;
Transform[12] = x; Transform[13] = y; Transform[14] = z;
Left=&Transform[0];
Up=&Transform[4];
Forward=&Transform[8];
Position=&Transform[12];
old_x = 0;
old_y = 0;
}
这里的变换是变换矩阵。既然OpenGL是列专业的，那应该是对的吧？
下一部分解释了在绘制框架之前发生了什么。
首先，我用鼠标移动刷新相机，根据最后一个鼠标指针位置的 delta x 和 y，移动值可以是正值或负值：
void Camera::refresh(){
delta_x = UserInputHandler::getMouseMotion()[0];
delta_y = UserInputHandler::getMouseMotion()[1];
}
在下一步中，我将调整场景中的相机。如果鼠标沿 x 或 y 轴移动，我想旋转相机：
void Camera::adjust(){
if(old_x != UserInputHandler::getMousePosition()[0]){
// rotate around y axis
rotateLocal_y(-1.0f*(delta_x));
// save old mouse position
old_x = UserInputHandler::getMousePosition()[0];
}
if(old_y != UserInputHandler::getMousePosition()[1]){
rotateLocal_x(-1.0f*(delta_y));
old_y = UserInputHandler::getMousePosition()[1];
}
// loading the calculated Transform matrix to a viewmatrix
setView();
}
绕 y 轴的旋转是与旋转矩阵和变换矩阵的矩阵相乘：
//rotate a matrix around y axis
void rotateMatrixf_y(float *aMatrix, float angle){
float rotMatrix[] = {cos(angle),0,-1*sin(angle),0, 0, 1, 0, 0, sin(angle), 0, cos(angle), 0, 0, 0, 0, 1};
multMatrixMatrix(aMatrix, rotMatrix);
}
请记住，OpenGL 是主要列，乘法函数是这样创建的：
void multMatrixMatrix(float *m_a, float *m_b){
// column major
float m_c[16] = {m_a[0]*m_b[0]+m_a[4]*m_b[1]+m_a[8]*m_b[2]+m_a[12]*m_b[3], //0
m_a[1]*m_b[0]+m_a[5]*m_b[1]+m_a[9]*m_b[2]+m_a[13]*m_b[3], //1
m_a[2]*m_b[0]+m_a[6]*m_b[1]+m_a[10]*m_b[2]+m_a[14]*m_b[3], // 2
m_a[3]*m_b[0]+m_a[7]*m_b[1]+m_a[11]*m_b[2]+m_a[15]*m_b[3], // 3
m_a[0]*m_b[4]+m_a[4]*m_b[5]+m_a[8]*m_b[6]+m_a[12]*m_b[7], //4
m_a[1]*m_b[4]+m_a[5]*m_b[5]+m_a[9]*m_b[6]+m_a[13]*m_b[7], //5
m_a[2]*m_b[4]+m_a[6]*m_b[5]+m_a[10]*m_b[6]+m_a[14]*m_b[7], // 6
m_a[3]*m_b[4]+m_a[7]*m_b[5]+m_a[11]*m_b[6]+m_a[15]*m_b[7], // 7
m_a[0]*m_b[8]+m_a[4]*m_b[9]+m_a[8]*m_b[10]+m_a[12]*m_b[11], // 8
m_a[1]*m_b[8]+m_a[5]*m_b[9]+m_a[9]*m_b[10]+m_a[13]*m_b[11], //9
m_a[2]*m_b[8]+m_a[6]*m_b[9]+m_a[10]*m_b[10]+m_a[14]*m_b[11], // 10
m_a[3]*m_b[8]+m_a[7]*m_b[9]+m_a[11]*m_b[10]+m_a[15]*m_b[11], // 11
m_a[0]*m_b[12]+m_a[4]*m_b[13]+m_a[8]*m_b[14]+m_a[12]*m_b[15], // 12
m_a[1]*m_b[12]+m_a[5]*m_b[13]+m_a[9]*m_b[14]+m_a[13]*m_b[15], // 13
m_a[2]*m_b[12]+m_a[6]*m_b[13]+m_a[10]*m_b[14]+m_a[14]*m_b[15], // 14
m_a[3]*m_b[12]+m_a[7]*m_b[13]+m_a[11]*m_b[14]+m_a[15]*m_b[15] // 15
};
for(int i = 0; i<16;i++){
m_a[i] = m_c[i];
}
}
此时，矩阵应该没问题并加载到 OpenGL。在adjust()中调用了setView方法：
void Camera::setView() {
float viewmatrix[16]={//Remove the three - for non-inverted z-axis
Transform[0], Transform[4], -Transform[8], 0,
Transform[1], Transform[5], -Transform[9], 0,
Transform[2], Transform[6], -Transform[10], 0,
-(Transform[0]*Transform[12] +
Transform[1]*Transform[13] +
Transform[2]*Transform[14]),
-(Transform[4]*Transform[12] +
Transform[5]*Transform[13] +
Transform[6]*Transform[14]),
//add a - like above for non-inverted z-axis
(Transform[8]*Transform[12] +
Transform[9]*Transform[13] +
Transform[10]*Transform[14]), 1};
}
glLoadMatrixf(viewmatrix);
}
函数在完整场景中调用如下：
int DrawGLScene(GLvoid){ // 这是我们进行所有绘图的地方
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Clear The Screen And The Depth Buffer
glMatrixMode(GL_MODELVIEW);
glLoadIdentity(); // Reset The Current Modelview Matrix
glPushMatrix();
cam.refresh();
cam.adjust();
// distance between object and near plane
glTranslatef(0.0f, 0.0f,-30.0f);
// testwise rotating the drawn object
float rotX,rotY,rotZ;
rotX = -90.0f;
rotZ = 0.0f;
rotY = 0.0f;
MeshNode* aMeshNode = myMeshLoader.getMeshNode();
while(aMeshNode->next){
Mesh aMesh = *aMeshNode->theMesh;
FaceNode* aFaceNode = aMesh.getFirstFaceNode();
while(aFaceNode->next){
Face theFace = *aFaceNode->aFace;
Vertex theFaceVertexA = aMesh.getVertexAt((*theFace.myVertices)[0]);
Vertex theFaceVertexB = aMesh.getVertexAt((*theFace.myVertices)[1]);
Vertex theFaceVertexC = aMesh.getVertexAt((*theFace.myVertices)[2]);
glColor3f(1.0f,1.0f,1.0f);
glBegin(GL_TRIANGLES); // Drawing Using Triangles
// glNormal3f(*theFace.myNormal[0],*theFace.myNormal[1],*theFace.myNormal[2]);
glVertex3f( theFaceVertexA.position[0], theFaceVertexA.position[1], theFaceVertexA.position[2]);
glVertex3f( theFaceVertexB.position[0], theFaceVertexB.position[1], theFaceVertexB.position[2]);
glVertex3f( theFaceVertexC.position[0], theFaceVertexC.position[1], theFaceVertexC.position[2]);
glEnd(); // Finished Drawing The Triangle
aFaceNode = aFaceNode->next;
}
aMeshNode = aMeshNode->next;
}
glPopMatrix();
return TRUE; // Everything Went OK
}
这里我选择 Modelview 矩阵，然后加载单位矩阵。在矩阵推送和弹出之间是相机刷新和调整（包括 setView），然后我为要绘制的对象设置一个变换，然后绘制对象。
就这样。我玩了很多矩阵的推送和弹出操作，查看了翻转码相机教程（http://www.flipcode.com/archives/OpenGL_Camera.shtml），但闪烁仍然存在。有没有人有任何想法可能是错的？