安卓OpenGL之GLES20常用接口解析

ゞ浴缸里的玫瑰 2022-01-28 16:55 546阅读 0赞

## 1.glClearColor ##

//设置SurfaceView的背景颜色为灰色。
    GLES20.glClearColor(0.5f, 0.5f, 0.5f, 0.5f);

//native层接口原型
    public static native void glClearColor(
            float red,				//范围0-1.0f
            float green,			//范围0-1.0f
            float blue,				//范围0-1.0f
            float alpha				//范围0-1.0f
    );

注意：三原色RGB的范围是0-255，而glClearColor的是参数范围是0.0-1.0f，所以按照RGB颜色对照表需要做一个转换（颜色值除以255）。

RGB颜色对照表：  
[https://tool.oschina.net/commons?type=3][https_tool.oschina.net_commons_type_3]

## 2.setLookAtM ##

// Position the eye behind the origin.
            // eye point，视点，眼睛观察的位置
            final float eyeX = 0.0f;
            final float eyeY = 0.0f;
            final float eyeZ = 1.5f;	//值远大，观测的距离就越远，图形显示效果看着就越小
    
            // We are looking toward the distance
            final float lookX = 0.0f;
            final float lookY = 0.0f;
            final float lookZ = -5.0f;
    
            // Set our up vector. This is where our head would be pointing were we holding the camera.
            final float upX = 0.0f;
            final float upY = 1.0f;
            final float upZ = 0.0f;
    
            // Set the view matrix. This matrix can be said to represent the camera position.
            // NOTE: In OpenGL 1, a ModelView matrix is used, which is a combination of a model and
            // view matrix. In OpenGL 2, we can keep track of these matrices separately if we choose.
            // mViewMatrix是一个观察矩阵，又叫视图矩阵，以摄像机或者人眼为中心的坐标
            Matrix.setLookAtM(mViewMatrix, 0, eyeX, eyeY, eyeZ, lookX, lookY, lookZ, upX, upY, upZ);

整理了两个函数发现了一个好用的OpenGL ES2.0的API英文手册。想要知道OpenGL的接口含义直接查看这个API就可以了。  
OpenGL ES2.0的API英文手册：  
[https://www.khronos.org/registry/OpenGL-Refpages/es2.0/][https_www.khronos.org_registry_OpenGL-Refpages_es2.0]

[https_tool.oschina.net_commons_type_3]: https://tool.oschina.net/commons?type=3
[https_www.khronos.org_registry_OpenGL-Refpages_es2.0]: https://www.khronos.org/registry/OpenGL-Refpages/es2.0/