ios地图sdk | 百度地图api sdk-凯发k8官方旗舰厅

ios sdk开放了opengl绘制功能，开发者可利用opengl的绘制来实现更多复杂的覆盖物绘制。

bmkmapviewdelegate中的-mapview:ondrawmapframe:，地图渲染每一帧画面过程中，以及每次需要重绘地图时（例如添加覆盖物）都会调用此接口。开发者可以在这个接口中进行opengl的绘制。

不需要用户自己创建context和buffer，v5.0.0新增opengl映射矩阵(getprojectionmatrix)和视图矩阵(getviewmatrix)接口，用于3d绘制场景,具体代码请参考baidumap_iossdk_sample bmkopenglespage。

下面代码以在地图上绘制3d立方体为例，介绍如何使用opengl绘制接口。

-(void)init3dshader
{
//顶点着色器
nsstring*vertexshader = @"precision highp float;
    attribute vec3 avertex;
    attribute vec4 acolor;
    uniform mat4 aviewmatrix;
    uniform mat4 aprojectionmatrix;
    uniform mat4 atransformmatrix;
    uniform mat4 ascalematrix;
    varying vec4 color;
voidmain(){
    gl_position = aprojectionmatrix * aviewmatrix *vec4(avertex,1.0);
    color = acolor;
}";
//片段着色器
nsstring*fragmentshader = @"
    precision highp float;
    varying vec4 color;
voidmain(){
    gl_fragcolor = color;
}";
// program对象是可以附加着色器对象的对象
// 创建一个空program并返回一个可以被引用的非零值（program id）
    _program3d =glcreateprogram();
gluint vshader =glcreateshader(gl_vertex_shader);
gluint fshader =glcreateshader(gl_fragment_shader);
glint vlength =(glint)[vertexshader length];
glint flength =(glint)[fragmentshader length];
constglchar*vbyte =[vertexshader utf8string];
constglchar*fbyte =[fragmentshader utf8string];
glshadersource(vshader,1,&vbyte,&vlength);
glshadersource(fshader,1,&fbyte,&flength);
//成功编译着色器对象
glcompileshader(vshader);
glcompileshader(fshader);
//成功地将着色器对象附加到program 对象
glattachshader(_program3d, vshader);
glattachshader(_program3d, fshader);
//成功的链接program 对象之后
gllinkprogram(_program3d);
//查询由program指定的先前链接的程序对象
    _vertexlocation3d  =glgetattriblocation(_program3d,"avertex");
//表示程序对象中特定统一变量的位置
    _viewmatrixlocation3d =glgetuniformlocation(_program3d,"aviewmatrix");
//得到名字为“aprojectionmatrix”在shader中的位置
    _projectionmatrixlocation3d =glgetuniformlocation(_program3d,"aprojectionmatrix");
    _colorlocation3d =glgetattriblocation(_program3d,"acolor");
}

-(void)init3dvertext
{
//创建vertex
    float vertext[]={
0.0,0.0,0.0,
1.0,0.0,0.0,
1.0,1.0,0.0,
0.0,1.0,0.0,
0.0,0.0,1.0,
1.0,0.0,1.0,
1.0,1.0,1.0,
0.0,1.0,1.0,
};
for(int i =0; i <24; i){
// 对标墨卡托坐标
        _vertext[i]= vertext[i]*10000;
}
    short indices[]={
0,4,5,
0,5,1,
1,5,6,
1,6,2,
2,6,7,
2,7,3,
3,7,4,
3,4,0,
4,7,6,
4,6,5,
3,0,1,
3,1,2,
};
for(int i =0; i <36; i){
        _indecies[i]= indices[i];
}
    float colors[]={
1.0f,0.0f,0.0f,1.0f,
0.0f,1.0f,0.0f,1.0f,
0.0f,0.0f,1.0f,1.0f,
1.0f,1.0f,0.0f,1.0f,
0.0f,1.0f,1.0f,1.0f,
1.0f,0.0f,1.0f,1.0f,
0.0f,0.0f,0.0f,1.0f,
1.0f,1.0f,1.0f,1.0f,
};
for(int i =0; i <32; i){
        _color[i]= colors[i];
}
}

-(void)drawframefor3dcube {
if(_program3d ==0){
[self init3dshader];
[self init3dvertext];
}
glboolean depthmask =0;
glgetbooleanv(gl_depth_writemask,&depthmask);
gluseprogram(_program3d);
glenable(gl_depth_test);
if(depthmask ==gl_false){
gldepthmask(gl_true);
}
glenablevertexattribarray(_vertexlocation3d);
glvertexattribpointer(_vertexlocation3d,3,gl_float,false,0, _vertext);
glenablevertexattribarray(_colorlocation3d);
glvertexattribpointer(_colorlocation3d,4,gl_float,false,0, _color);
bmkmappoint center =bmkmappointforcoordinate(cllocationcoordinate2dmake(39.965,116.404));
cgpoint offsetpoint =[self.mapview glpointformappoint:center];
    float *viewmatrix =[self.mapview getviewmatrix];
translatem(viewmatrix,0, offsetpoint.x, offsetpoint.y,0);
    float *projectionmatrix =[self.mapview getprojectionmatrix];
//传值函数，该函数的第一个参数是该变量在shader中的位置，第二个参数是被赋值的矩阵的数目。第三个参数表明在向uniform变量赋值时该矩阵是否需要转置
//vec4类型的变量赋值，我们可以使用gluniform4f或者gluniform4fv。v代表数组
gluniformmatrix4fv(_viewmatrixlocation3d,1,false, viewmatrix);
gluniformmatrix4fv(_projectionmatrixlocation3d,1,false, projectionmatrix);
gldrawelements(gl_triangles,36,gl_unsigned_short, _indecies);
gldisablevertexattribarray(_vertexlocation3d);
gldisablevertexattribarray(_colorlocation3d);
gldisable(gl_depth_test);
gldepthmask(depthmask);
}

/**
 地图渲染每一帧画面过程中，以及每次需要重新绘制地图时(例如添加覆盖物)都会调用此方法
 @param mapview 地图view
 @param status 地图的状态
 */
-(void)mapview:(bmkmapview*)mapview ondrawmapframe:(bmkmapstatus*)status {
[self drawframefor3dcube];
}

效果如图：