问题描述

glGetFloatv不能查询到modelview 矩阵。

这个bug困扰我很久。
我用基于glkit编程，pan手势识别之后程序需要讲对应的顶点坐标计算出来。.

手势这边的代码是这样的：

if ([gestureRecognizer state] == UIGestureRecognizerStateChanged) {
    NSLog(@"pan2");
    CGPoint location = [gestureRecognizer locationOfTouch:0 inView:nil];
    GLKVector3 obj;
    GLfloat winZ=-1.0f;
    **gluGetObjectLocation**( location.x,location.y, winZ,obj);
    initialLine[i].Position=obj;
    initialLine[i].normal=obj;
    i++;
}

里面的函数 gluGetObjectLocation 是下面这样的：

void gluGetObjectLocation(GLfloat screenX,GLfloat screenY,GLfloat winZ,GLKVector3 obj)
{
    NSLog(@"location: %f,%f",screenX,screenY);
    GLfloat winX,winY;
    GLfloat mvmatrix[16]={0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
    GLfloat projmatrix[16];
    GLint viewport[4];
    NSLog(@"modleview matrix1:n,%f,%f,%f,%f,n,%f,%f,%f,%f,n,%f,%f,%f,%f,n,%f,%f,%f,%f,",mvmatrix[0],mvmatrix[1],mvmatrix[2],mvmatrix[3],mvmatrix[4],mvmatrix[5],mvmatrix[6],mvmatrix[7],mvmatrix[8],mvmatrix[9],mvmatrix[10],mvmatrix[11],mvmatrix[12],mvmatrix[13],mvmatrix[14],mvmatrix[15]);
    glGetFloatv(GL_MODELVIEW_MATRIX,mvmatrix);
    glGetFloatv(GL_PROJECTION_MATRIX,projmatrix);
    glGetIntegerv(GL_VIEWPORT,viewport);
    NSLog(@"modleview matrix2:n,%f,%f,%f,%f,n,%f,%f,%f,%f,n,%f,%f,%f,%f,n,%f,%f,%f,%f,",mvmatrix[0],mvmatrix[1],mvmatrix[2],mvmatrix[3],mvmatrix[4],mvmatrix[5],mvmatrix[6],mvmatrix[7],mvmatrix[8],mvmatrix[9],mvmatrix[10],mvmatrix[11],mvmatrix[12],mvmatrix[13],mvmatrix[14],mvmatrix[15]);
    winX=screenX;
    winY=viewport[3]-screenY;
    gluUnProject(winX,winY,winZ,mvmatrix,projmatrix,viewport,obj);
    NSLog(@"obj:%f,%f,%f",obj.x,obj.y,obj.z);
    }

run.我发现glGetFloatv(GL_MODELVIEW_MATRIX,mvmatrix) 不工作.

modleview matrix1 是0, 没错.

modleview matrix2 还是 0, 就不对了.它应该已经读取了值出来，不能再是0.

2014-02-06 00:40:26.088 lianxi[467:70b] Cannot find executable for CFBundle 0x8b7f740 (not loaded)
2014-02-06 00:40:32.171 lianxi[467:70b] pan2
2014-02-06 00:40:32.172 lianxi[467:70b] location: 192.000000,574.500000
2014-02-06 00:40:32.173 lianxi[467:70b] modleview matrix1:
,0.000000,0.000000,0.000000,0.000000,
,0.000000,0.000000,0.000000,0.000000,
,0.000000,0.000000,0.000000,0.000000,
,0.000000,0.000000,0.000000,0.000000,
2014-02-06 00:40:32.173 lianxi[467:70b] modleview matrix2:
,0.000000,0.000000,0.000000,0.000000,
,0.000000,0.000000,0.000000,0.000000,
,0.000000,0.000000,0.000000,0.000000,
,0.000000,0.000000,0.000000,0.000000,
2014-02-06 00:40:32.174 lianxi[467:70b] obj:0.000000,0.000000,0.000000

请帮忙看看，这到底怎么回事啊，头都想痛了。谢谢！

解决方案

刚猪八戒上看到了你的问题。你都没设置这些矩阵拿到的当然都是0